Name of the Speaker(s): A. Alberdi1, L. Lara2,
J.M. Marcaide3, A. Kemball4, K. Leppanen5,
A. Patnaik6, R. Porcas6
1 IAA, CSIC, Granada, Spain
LAEFF, Madrid, Spain
2 IRA, Bologna, Italia
3 Univ. Valencia, Valencia, Spain
4 NRAO, Socorro, NM, USA
5 JIVE, Dwingeloo, Holland
6 MPIfR, Bonn, Germany
Title of the communication: DUAL HIGH FREQUENCY POLARIZATION VLBI IMAGES
OF 3C395.
Preliminary abstract:
The radio source 3C395 (1901+319), identified with a 17th magnitude quasar at
a redshift z=0.635, presents a core-jet radio structure which consists, on
milliarcsecond scales, of two components (A and B) in a position angle of 118
degrees separated 15 milliarcseconds and stationary with respect to each
other. 3C395 exhibits strong variability in its total flux density which is
the result of the activity in component A, generally identified with the
compact core of the radio source. Component B can be explained as the result
of a local bend in the jet towards the observer. A third weaker component (C)
is located between components A and B. Component C, previously reported as
superluminal, appears also stationary since 1990.
We have carried out simultaneous VLBI polarimetric observations of 3C395 at
8.4 and 15 GHz. We find that component A is resolved in a complex core-jet
structure with at least two sub-components, with three different orientations
of the polarization vectors along the A-region jet, and with curvatures in the
inner parts of the jet structure. The rotation of the polarization vectors
along the jet could be due to kinks in the jet trajectory itself, to
compressive shocks which enhance the component of the magnetic field
perpendicular to the jet direction, or to transitions from optically thick to
optically thin regimes and viceversa. The relative orientation of the
polarization vectors are similar at 8.4 and 15 GHz, except at the westernmost
edge coincident with the region identified with the most compact sub-component
(probably, the true core). In addition, these observations show that the
degree of polarization increases with the frequency, probably due to
opacity effects.
In addition, we present VLBI polarization images of the parsec-scale
radio-jets of other compact active galactic nuclei, used as calibrators of the
3C395 data.
Short talk: Session 2
Name of the Speaker(s): Stefan Appl
Institution: Observatoire de Strasbourg
Title of the communication:
Relativistic Accretion Discs and Magnetized Jets
Preliminary abstract:
The structure of stationary transsonic accretion discs around rotating
black holes is calculated. The discs possess ion temperatures in the
range $10^{11} - 10^{12}$ K. Disks around rapidly rotating black holes
are hotter and deposit less angular momentum onto the central object
than those around non-rotating black holes.
A model for stationary collimated relativistic MHD jets is presented.
It provides a consistent kinematical and magnetic structure.
Relations between the mass flux, Lorentz factor, Mach numbers
are given. Relativistic MHD jets are shown to be more stable
than their hydrodynamic counterparts.
Long talk: Session 12b
Name of the Speaker(s): M.K.Babadzhanyants
Institution: Astronomical Institute of St.-Petersburg University, Russia
Title of the communication:
The difference between spectral indices of
"slow"- and "short"-time optical-IR outbursts of
quasar 3C 345.
Preliminary abstract:
Own long-term UBV observations of quasar 3C 345 together with other
available optical-IR multibands data were analyzed. It is shown that
the sources responsible for f-flares (weeks of duration) have sufficiently
flatter spectra than ones responsible for s-flares (nearly 2 yrs of
duration). Optical spectral indices: alpha(f)=-0.8 and alpha(s)=-1.7.
This difference is one of the reasons for appearance of opposite
correlations between observational spectral slope and flux density
revealed for 3C 345.
Poster
Name of the Speaker(s): E.T.Belokon'
Institution: Astronomical Institute of St.-Petersburg University
Title of the communication:
Quasar 3C 345: similarity in behavior of optical
polarization during the flares connected with
the ejection of superluminal jet components.
Preliminary abstract:
We present the results of optical polarimetric observation of quasar
3C 345 made during 1983-1993. The analysis of these data together with
all observations published earlier revealed close similarity in
behavior of optical polarization during two large s(slow)-flares
occurred in 1982-1983 and 1991-1992. In particular there are some
evidences for the systematic rotation of position angle with similar
velocities (50 and 35 deg./100 days) since the beginning up to the end
of the flares. In both cases its ending value (theta=90deg) coincides
with the position angle of parsec scale radio jet. Earlier the comparison
of VLBI data and total optical light curve suppose the connection between
s-flares and the ejection of superluminal components of 3C 345 parsec scale
radiojet.
Short talk: Session 4
Name of the Speaker(s):Holger Bock
Institution: Landessternwarte Heidelberg
Title of the communication: Spectral index variations of Blazars
Preliminary abstract:
From our previous research we know the IDV
phenomenon to be typical of the Blazar
class. In order to study the radiation
processes in the optical thin part of the
spectrum, we investigated a sample of
northern, highly variable blazars for
variations of the spectral indices with
time scales of about 1 hour.
Our results from UBVRI-observations of
3C66A, 0716+71, OJ 287, 0954+65 and
Mkn 421 will be presented.
Poster
Name of the Speaker(s):Bogovalov Sergei Vladimirovich
Institution: Moscow Engineering Physics Institute
Title of the communication: Acceleration of relativistic plasma at
the ejection by fast rotating magnetized object.
Preliminary abstract:
I intend to discuss the results of
an analytical and numerical analysis of a 3-dimensional axisymmetrical
time dependent plasma flow in the magnetosphere of a
fast rotating magnetized
object. Analytical approximate solution of the stationary
plasma flow in the magnetosphere of rotator is obtained. Plasma is not
accelerated and is not collimated in the limit of the fast mode surface
in this flow even at fast rotation of the central object when the light
cylinder is placed deeply inside the subsonic region. Numerical
simulations of the time dependent version of this problem confirm this
picture. Simultaneously they show that this stationary flow is not stable.
Evidence that plasma is accelerated due to the instability of the flow is
obtained.
Name of the Speaker(s): Paul Boltwood
Institution: None
Title of the communication: To be decided
Preliminary abstract:
Not presented yet
Poster
Name of the Speaker(s): Marco Bondi
Institution: Istituto di Radioastronomia
Title of the communication:
FR I and FR II radio sources in the 1 Jy
sample of BL Lac objects
Preliminary abstract:
We present the final results from
multifrequency VLA observations aimed to
investigate the polarization properties
and the amount of extended emission in
about 20 BL Lac objects selected from
the 1 Jy sample (Stickel et al. 1991).
Poster
Name of the Speaker(s): Marco Bondi
Institution: Istituto di Radioastronomia
Title of the communication:
A 15 years monitoring program at 408 MHz.
Preliminary abstract:
We present the final results from a
15 years monitoring program carried out
at 408 MHz with the East-West arm of the
Bologna interferometer. The monitoring
concerned 125 radio sources measured
approximately once a month.
Poster
Name of the Speaker(s): Marco Bondi
Institution: Istituto di Radioastronomia
Title of the communication:
VLBA observations of low luminosity radio
selected BL Lac objects and flat spectrum
radio galaxies.
Preliminary abstract:
We present VLBA observations at 6 cm on a
sample of 14 objects selected from the
200 mYj sample (Marcha 1994) of flat
spectrum radio galaxies: 8 of them are BL
Lac objects or candidates , and 6 are
radio galaxies.The specific aim of these
observations is to look for structural
differences in the cores of BL Lac objects
and flat spectrum radio galaxies which
might arise, for example, from different
viewing angles
Poster
Name of the Speaker(s): Jorge Casares
Institution: Oxford University
Title of the communication: Misalignment effects in BL Lac objects
Preliminary abstract:
We present Doppler images of accretion
disks in 4 black hole binaries with
dynamical evidence. Common properties
are summarized.
Short talk: Session 8a
Name of the Speaker(s): Sonia Anton Castillo
Institution: Complexo II da Univ. de Lisboa
Av. Prof. Gama Pinto, 2
1699 Lisboa
Title of the communication:
To be communicated
Preliminary abstract:
To be communicated
Withdrawn
Name of the Speaker(s): Annalisa CELOTTI
Institution: SISSA/ISAS
Title of the communication: Jets and accretion processes in Active
Galactic Nuclei: further clues
Preliminary abstract:
We present evidence in favour of a strong link between
the luminosity radiatively dissipated in the central engine of radio--loud
Active Galactic Nuclei and the kinetic power in their jets. This piece of
evidence is based on the relation we find between the luminosity in broad
emission lines and the kinetic power in pc--scale radio jets, for a sample
of radio--loud quasars for which suitable data are available in the
literature. A strong magnetic field in equipartition with the radiation
field could be responsible for regulating both processes. BL Lac objects
seem to follow a similar behaviour, but with a comparatively fainter broad
line emission.
Short talk: Session 14.
Name of the Speaker(s): Krzysztof Tadeusz Chyzy
Title of the communication: Jet and radio lobe analytical modelling
Preliminary abstract:
An approximate approach to the modelling of jet and large-scale
structure evolution of powerful extragalactic radio sources will be presented.
It is assumed that two plasma jets propagate from the core through the
ambient medium, create a shock front at the jet head and deposit constant
fractions of the jet energy into a lobe in the forms of cosmic ray electrons
and ions, thermal particles and magnetic fields. The whole forming lobe is
approximated by a range of adjacent volume elements that evolve individually
and sideways only. From the pressure and energy balance geometrical
properties of this evolution are found as well as energy and synchrotron
luminosity of the entire lobe. Classical and relativistic description of the
jet propagation and various physical parameters in the jet and the lobe will
be discussed in the framework of the presented model.
Poster
Name of the Speaker(s):Oliver DREISSIGACKER
Institution: Landessternwarte Heidelberg
Title of the communication: Modelling Blazar Broad Band Spectra
Preliminary abstract:
Our 'lighthouse' model, combined with advanced
spectra calculations allow not only to model
Blazar lightcurves in the optical and higher
energy regimes, but also put constraints on
jet parameters as * density * volume * max.
energy * magnetic field and * bulk speed.
Also, statements about time lags between the
different spectral branches become possible.
Poster
Name of the Speaker(s):DEBORAH DULTZIN-HACYAN
Institution: INSTITUTO DE ASTRONOMIA
UNAM APDO. 70-264
Title of the communication:
IS BLAZAR ACTIVITY ALSO INDUCED BY
INTERACTIONS?. THE CASE OF OJ287
Preliminary abstract:
On the basis of recent observations
of the nearby environment of blazars, the
evidence indicating that this type of
activity might be triggered by
interactions is analyzed. The particular
case of the underlying nebulosity and
nearby environment of the blazar OJ287 is
discussed in detail.
Poster
Name of the Speaker(s): D. Dultzin-Hacyan, L.O. Takalo, E. Benitez,
A. Sillanpaa, T. Pursimo, H. Lehto, J.A. de Diego
Institution:
Instituto de Astronomia, UNAM, Apdo. Postal, 70-264,
04510 Mexico D.F., Mexico
Tuorla Observatory, Tuorla, FIN-21500 Piikkio, Finland
Title of the communication: Microvariability in OJ 287 during a flare
Preliminary abstract:
We present microvariability observations of OJ 287, taken during a
small flare in January 1994. We can follow the behaviour of OJ 287
during the whole flare. The event has a synchrotron flare shape, with a
steep ingress and slower egress, and a double peak structure most
likely due to two similar flares occuring a day apart. Microvariability
is observed on top of this flare during five nights, out of ten. Two
types of microvariability events can be identified: smaller flares and
smoother sinusoidal variations. The time scales are of the order of
minutes to hours. We do not find any periodical or quasi-periodical
variations. A brief discussion on the possible mechanisms responsible
for the different scales and types of variability is given.
Poster
Name of the Speaker(s): Yuri Efimov
Institution: Crimean Astrophysical Observatory
Title of the communication:
Blazar's polarimetry at the Crimean Astrophysical Observatory
Preliminary abstract:
Photopolarimetry of four blazars
(OJ 287, 3C66A, S5 0716+71, Mrk 421) in UBVRI bands was made at the
Crimean Astriphysical Observatory in the course of the international
campaigne OJ-94. The mostly important was the detection of the
continuous rotation of the pozition angle of polarization in OJ 287
during its outburst in winter 1994/1995. This rotation may be considered
as direct indication on the helical structure of the magnetic field
of the jet in OJ 287. The rapid variations of the brightness of the
object in 1995/1996 may be due to the multicomponent structure of the
jet. The others object also show complicated time variations of the
polarization parameters. The degree of polarization of 3C66A which was
in bright stage was at the level of 25-30%.
Name of the Speaker(s): Fargion Daniele
Institution: Physics Dept Rome Univ.1
Title of the communication:
GRBs as Precessing Gamma Jets
PSRs blazing from binary systems in extended
galactic halo
Preliminary abstract:
The GRBs problem may be well understood as a sudden signal originated by a precessing Gamma Jet, born by a compact NS or BH in a binary system
located in an extended halo.
The Gamma Jet is due to the Inverse Compton Scattering of electron Jet onto thermal photon of the companion object.
The GRB non equilibrium spectra is well reproduced by the model either in total intensity as well as in its time evolution behaviour.
The nature and the evidence of the Precessing Gamma Jets (GJ) candidature may be found among the other within superluminal sources, SGRs, Egg Nebula,
SN1987A twin rings.
Short talk: Session 7.
Name of the Speaker(s): David J. Fegan
Institution: Physics Department, University College Dublin
Title of the communication:
Dramatic Outbursts of TeV photons from Markarian 421
Preliminary abstract:
In its relatively quiescent state, the TeV flux of
gamma rays from Mrk421 is about 0.5 gammas per minute
above an energy threshold of 0.35 TeV. On May 7th 1996
a dramatic flare was observed whereby the flux increased
by a factor of thirty at the peak becoming, for a
duration of two hours, the brightest TeV gamma ray
source ever observed. A second flare of lesser intensity
was observed on May 15th 1996 with duration less than one
hour. The highly Doppler boosted outbursts are indicative
of very compact emissionn regions perhaps smaller than the
solar system.
Short talk: Session 6.
Name of the Speaker(s): Forster, James R.
Institution: Hat Creek Radio Observatory
Title of the communication: High-Resolution Image of M87 at 3mm
Preliminary abstract:
A new radio image of M87 at 3mm wavelength
(90 GHz) made with the BIMA telescope is
presented. The high dynamic range image
has a resolution of 0.5 arcsec and is
sensitive to structure up to 1 arcmin in
extent. The episodic nature of
relativistic particle injection from the
nucleus is discussed in light of recent
high-resolution radio observations.
Short talk: Session 2.
Name of the Speaker(s):Fossati G., Celotti A., Ghisellini G. and Maraschi L.
Institution: International School for Advenced Studies, Trieste
Title of the communication: On the relation between radio selcted and
x-ray selecte BL Lacertae objects
Preliminary abstract:
We discuss alternative interpretations of the differences
in the Spectral Energy Distributions (SEDs) of BL Lacs found
in flux limited Radio or X-ray surveys.
Using a Montecarlo approach we compare the predictions of the two
proposed scenarios, the first based on orientation, the second on
different cut off energies, with the observed properties of BL Lacs
in the complete radio sample of Stickel et al. (1991)and in the
complete X-ray sample of Perlman et al. (1996).
We find that both models reproduce reasonably well a number but
not ALL the observed properties of the samples. In particular in
both models the redshift distributions conflict with the observed ones.
We then explore an alternative approach based on the idea that a
physical parameter should govern the shape of the SEDs. Assuming an
empirical relation between spectral shape and luminosity
we show that the properties of the two surveys can be reproduced
with only minor discrepancies.
Short talk: Session 8.
Name of the Speaker(s): Denise C. Gabuzda
Institution: Astro Space Center, Moscow
Title of the communication: The Parsec-scale Magnetic Field Structures of Blazars.
Preliminary abstract:
VLBI polarization observations have shown
that the characteristic magnetic field structures for different types of
blazars -- BL Lacertae objects and quasars, for example -- are systematically
different. This suggests that some fundamental physical parameters for the
jets -- and quite possibly for the central accretion -- in these sources
are considerably different. New VLBI polarization images for sources from a
complete sample of BL Lacertae objects and images for intraday variable blazars
will be presented and discussed in the context of qualitative models offering
a connection between the optical and compact radio properties of blazars with
prominent and weak emission lines.
Short talk: Session 2.
Name of the Speaker(s): Galama, T.J.
Institution: University of Amsterdam,
Kruislaan 403,
NL-1098SJ Amsterdam,
The Netherlands
Title of the communication:
Monitoring of the galactic superluminal source
GRS 1915+105, and mapping of its immediate
surroundings, at 21 cm.
Preliminary abstract:
Preliminary? results on monitoring of the galactic superluminal source
GRS 1915+105, at 1.4 GHz (21 cm) with the WSRT, to establish the nature
and existence of the oscillations reported by G. Pooley at 15 GHz (2 cm)
in a recent IAU circular (No. 6269), and mapping of its immediate
surroundings, to look for lobe structure, that could indicate yet outflow
in the past.
Poster
Name of the Speaker(s): Ramon Nartallo1,
Walter K. Gear2
1 Queen Mary & Westfield College, Univ. London
2 Royal Observatory Edinburgh
Title of the communication: MM/Submillimetre Polarisation Properties
of BL Lac Objects and Quasars
Preliminary abstract:
Results of a monitoring campaign of the polarisation properties of a sample of BL Lac objects and Quasars carried out at 1.1mm with the JCMT.
We establish a comparison between the two types of sources and look at the variability of individual objects.
Long talk: Session 2.
Name of the Speaker(s): Markos Georganopoulos
Institution: Boston University
Astronomy Department
Title of the communication:
Comparison of the accelerating inner jet
model to blazar observations.
Preliminary abstract:
The accelerated inner jet model is briefly
described and a comparison to the obervations
is attempted. The optically thin synchrotron
steady-state model spectra are used in an
effort to explain the dichotomy between
the radio and X-ray selected BL Lacs. The
emerging picture suggests that the observed
properties of a blazar are defined by both the
jet orientation and the intrisic properties
of the object.
Short talk: Session 12.
Name of the Speaker(s): Dr. Jose L. Gomez
Institution:Department of Astronomy
Boston University
Title of the communication: Time-Variable Synchrotron Emission from
Hydrodynamic Relativistic Jets
Preliminary abstract:
We present numerical simulations of the
synchrotron emission from hydrodynamic
relativistic jets, which can be compared
directly with actual VLBI observations.
The generation and evolution of shock
waves along the jet are studied through
the introduction of perturbations in the
beam initial conditions. The association
of such shocks with superluminal
components in VLBI maps is analyzed
through multi-epoch and multifrequency
radio images obtained from the
hydrodynamic simulations.
Long talk: Session 14.
Name of the Speaker(s): Jose Nicolas Gonzalez Perez
Institution: Instituto de Astrofisica de Canarias
Title of the communication: Is microvariability in OJ287
seen more frequently during flares?
Preliminary abstract:
In the last 3 years the light curve of
OJ287 has shown a large degree of
activity. We present a comparison between
the rapid variability observed in the low
and high states in order to determine if
this BL object exhibits more and faster
variablity during flares. If this is
the case, al least a part of
microvariability is related to the
mechanism that produces the flares, despite the two order
of magnitude difference in
typical time scales between microvariability and flares.
Poster
Name of the Speaker(s): Jose Nicolas Gonzalez Perez
Institution: Instituto de Astrofisica de Canarias
Title of the communication: Multiband microvariability in OJ287 and
other blazars.
Preliminary abstract:
OJ287 and other blazars have been monitored
simultaneously on a number of nights in the optical and near infrared
from the Canary Islands' Observatories. Here we present the
preliminary results on the spectral behaviour of the rapid variability
in this range of wavelengths.
Poster
Name of the Speaker(s): Jose Nicolas Gonzalez Perez
Institution: Instituto de Astrofisica de Canarias
Title of the communication: BVRI photometry of stars in the fields of
OJ287, 3C66A and 3C345.
Preliminary abstract:
We present CCD BVRI photometry of stars in the field of OJ287,
3C66A and 3C345. These stars are suitable for use as photometric comparisons
stars for monitoring the variability of optical continuum of these AGNs.
Name of the Speaker(s): Vasilii Gvaramadze
Institution: Abastumani Astrophysical
Observatory, Tbilisi, Republic of Georgia
Title of the communication:
A model of unsteady jet formation
Preliminary abstract:
We propose a model of unsteady jet formation in a system
consisting of a black hole and a magnetized accretion disk.
Accumulation and/or generation of strong large-scale magnetic
fields in the inner part of the accretion disk play a key role
in accretion instabilities, which lead to the sudden destruction
and subsequent collapse of the accretion funnel. In this
cataclismic process a strong energy concentration occurs on the
disk's symmetry axis, that leads to the ejection of a pair of
blobs moving in opposite directions perpendicular to the disk's
plane. Frequent and unidirected ejections of blobs may mimic
quasi-steady outflows.
Poster
Name of the Speaker(s): Hagen-Thorn Vladimir A.
Title of the communication: Variable sources in AGNs
Preliminary abstract:
Photometric variability is one of the main manifestations of nuclear activity.
Variable point sources located at the very nucleus are evidently responsible
for such activity. Multicolour observations of variability allow to obtain some
information on spectral energy distribution of these sources even without
knowledge of their contribution to total observed fluxes. The method of analysis will be briefly discussed and some results important for establishing the nature of the sources will be given for a number of famous blazars.
Poster
Name of the Speaker(s): M. Hanasz, H. Sol
Institution: Observatoire de Paris-Meudon
Title of the communication: The Kelvin-Helmholtz instability of
stratified jets
Preliminary abstract:
The recent development of tomographic analysis of radio data shows
the presence of sheaths around several extragalactic jets. We have studied the
Kelvin-Helmholtz instability of such stratified jets, describing them as inner
relativistic beams embedded in slower plasma envelopes. We find that the para-
meters of the envelope generally determine the Kelvin-Helmholtz properties of
the jet which thus appears isolated from any ambient external medium.
Short talk: Session 12.
Name of the Speaker(s): Heidt, Jochen
Institution: Landessternwarte Heidelberg (Germany)
Title of the communication: Host galaxies and cluster environment of radio-loud AGN
Preliminary abstract:
We present the first results of an extensive study of the properties
of the host galaxies and cluster environment of radio-loud AGN. Our sample
consist of approx. 100 AGNs, including several subsamples of radio-selected BL
Lac objects, QSOs and FR I and II radio galaxies taken from the 1 Jy catalogue
as well as the EMSS sample of x-ray selected BL Lac objects.
Long talk: Session 10.
Name of the Speaker(s):Philip Hughes
Institution: Astronomy Dept.
University of Michigan
Title of the communication: Simulations of Relativistic
Extragalactic Jets
Preliminary abstract:
We present new simulations of relativistic
extragalactic jets, in particular
exploring the pattern of shocks within
diverging flows using extremely long
grids to accommodate the very large
wavelength of such structures. We also
present radiation transfer calculations
incorporating time delay effects.
Withdrawn
Name of the Speaker(s):Eriko Idesawa
Institution: Makishima-group, Department of Physics, School of Science,
University of Tokyo, 7-3-1 Hongou, Bunkyo-ku, Tokyo 113, Japan
Title of the communication:
X-Ray Observation of the BL Lac Object OJ287 with ASCA
Preliminary abstract:
We present ASCA observation results of OJ287 in November 1994.
Observed X-ray flux was fainter than those from previous observations.
The X-ray spectrum is described well with a single power law model,
although, convex broken power law model is also acceptable.
The slope is flatter than those previously reported,
and X-rays exceeds the extrapolation from radio/IR/optical/UV spectrum.
This suggests strongly that X-rays include an additional component to
radio to UV single synchrotron emission.
It is likely that the X-rays from OJ287 contain synchrotron-self-Compton emission.
A few hours scale variability was also detected with a
soft-lagged behavior known as a characteristic of synchrotron emission.
Short talk: Session 8.
Name of the Speaker(s): Chris Impey
Institution: Steward Observatory, University of Arizona
Title of the communication:
Quasars and Blazars Across the Electromagnetic Spectrum
Preliminary abstract:
A statistical analysis of 1 Jy radio sources shows that compact radio emission is
correlated with evidence of strong synchrotron emission at far infrared and optical
wavelengths. Soft X-rays originate in a different spectral component. The apparent
fraction of highly polarized quasars diminishes with increasing redshift, due simply
to dilution from the component believed to be a high temperature accretion disk,
redshifted to optical wavelengths. BL Lac objects are systematically missing this
hot component. These results are consistent with the same bulk relativistic Lorentz
factor for emission at radio and optical wavelengths. Radio sources detected in
gamma rays by EGRET are mostly blazars with strong radio emission and evidence for
bulk relativistic motion. The mechanism for upscattering photons to gamma ray
energies is still uncertain, since the EGRET detections are not notably compact
in their radio emission. Flat spectrum radio sources contribute around 50% of the
diffuse gamma ray background.
Withdrawn.
Name of the Speaker(s): Khujadze George
Institution: Abastumani Astrophysical Observatory (Georgia)
Title of the communication: GENERAL-RELATIVISTIC MODEL OF MAGNETICALLY
DRIVEN JET.
Preliminary abstract:
Powerful bipolar outflows appear to be common features of a wide class of
astrophysical objects are studied in our work. In our work we investigate
originate and propagation general-relativistic magnetically driven jets.
High compactness and huge energy output, which characterizes some (maybe,
the most interesting) concrete kinds of objects featuring bipolar (or,unipolar)
outflows (such as AGNs and quasars), may be explained if one assumes that they
are produced in result of accretion onto the rotating supermassive black hole.
It seems evident that a consideration of the innermost part of such outflows,
in the close neighbourhood of the black hole must be performed in the framework
of general-relativistic magnetohydrodynamics (MHD). Such treatment enables us
to take into account properly the influence of strong gravitational and
electromagnetic fields onto the structure of the jet.
Since 3+1 formulation of black hole electrodynamics is the most convenient
mathematical apparatus for such purposes, in the present study we shall
establish our consideration on it. It must be noted that our basic equations
contain as "special-relativistic" effects (gamma factors and all that) as also
purely gravitational effects related to the curving of absolute space and
"frame dragging".
Name of the Speaker(s): Kidger, Mark R.
Institution: I.A.C (Spain)
Title of the communication: Ten years of infrared and optical monitoring
of blazars in the Canary Islands.
Preliminary abstract:
Near infrared (JHK) monitoring of a sample of blazars started
with the 1.5m telescope in Teide Observatory (Tenerife) in 1988
and has continued ever since, whilst visible monitoring with
various telescopes in El Roque de los Muchachos Observatory and,
later, Teide Observatory, has been carried out since
1986. The observations show a range of phenomena, including
major outbursts and microvariability. Sample light curves of various
blazars including OJ287, 3c345, 3c279 and 3c66 will be
presented. Some of these objects show major changes in their
spectral energy distribution at different levels of activity.
Name of the Speaker(s): Kidger, Mark R. & Takalo, L.O. (for the OJ-94 Team)
Institution: I.A.C (Spain), Tuorla Observatory
Title of the communication: The light curves of OJ287 and 3C66a:
1993-1996
Preliminary abstract:
We present the results of monitoring of OJ287 and 3c66a at frequencies from
4.5 GHz through to the ultraviolet obtained by the OJ-94 Collaboration. The
two blazars have been studied in detail by a collaborative effort involving
observers from eleven countries and four continents. A total of more than
ten thousand individual integrations have been made at 20 frequencies. The
best light curve coverage of both objects is obtained in V and R: in each of
these bands we have more than 2000 points for OJ287 and more than 1000 for
3c66a, making these the most complete and detailed light curves ever obtained
for any extragalactic object. The OJ287 light curve shows two major outbursts,
one in November 1994 and a second in November 1995, both corresponding closely
with predictions on the basis of a possible 11.5 year cycle; the radio light
curves and x-ray observations, however, show very low fluxes at the same time
that the optical, infrared and uv were at their highest level since 1985. The
light curve of 3c66a, in contrast, shows a single, unprecedented outburst
which appears to have initiated around 1990 and which has provided continuous
maxima since intensive monitoring began in Autumn 1993. We provide some initial
analysis of both light curves in terms of the binary black hole and
relativistic jet models.
Name of the Speaker(s): Yuri A. Kovalev
Institution: Astro Space Center,
Profsoyuznaya street 84/32,
Moscow 117810,
Russia
Title of the communication:
Multifrequency 1-22 GHz Spectra Monitoring
of Blazars and Jets in 1995-1996
Preliminary abstract:
New results for measurements of a sample for about
170 objects, selected from the VLBI survey (Preston et al.,1985),
are presented. Monitoring observations have been done
at 31, 13, 7.6, 3.9, 2.7 and 1.4 cm for the each spectrum
quasi simultaneously (with accuracy up to a minute)
at the radio telescope RATAN-600 during up to
5 sets from August, 1995, to June, 1996, to study
a spectra variability of blazars and other AGNs.
A model analysis shows that the main deposit
to the majority of obtained spectra of the sources
may give the emission of compact jets on the
milli-arcsecond scales.
Poster
Name of the Speaker(s): Yuri Y. Kovalev (junior)
Institution: Sternberg Astronomical Institute,
Universitetskij pr. 13,
119899 Moscow,
Russia
Title of the communication:
A STATISTICAL ANALYSIS OF 1995-1996 MULTIFREQUENCY
SPECTRA OBSERVATIONS FOR QUASARS AND BLAZARS
Preliminary abstract:
There are analyzed the results of up to 5 sets of instantaneous
multifrequency spectra observations at the wavelengths of 31, 13, 7.6, 3.9,
2.7 and 1.4 cm, carried out at the RATAN-600 from August, 1995 to Juny,
1996 for a sample of 170 extragalactic radio sources (blazars and quasars).
The statistical distributions and correlations for the turnover flux,
turnover frequency, spectral width as well as spectral indices in 5
frequency bands are analyzed. Results are similar for the spectra at all
epochs, studied independently. In contrast with the other bands, a strong
decreasing of the spectral indices in the band of 11.1-21.7 GHz with the
flux density at 2.3 GHz is obtained. A correlation between turnover flux
and turnover frequency is absent. Obtained results testify in favor of a
hypothesis on a common physical nature for quasars and BL Lac objects!
Poster
Name of the Speaker(s): Hidetoshi Kubo
Institution: University of Tokyo
Title of the communication:
X-ray observations of blazars with ASCA
Preliminary abstract:
We have analyzed 15 blazars observed with ASCA since the launch in 1993.
A half of the observations were conducted in the multiwavelength campaigns.
GeV gamma-ray emission has been detected from 9 of them.
The synchrotron process by the relativistic electrons and
the Comptonization of the synchrotron photons are thought to be
the important radiation processes from blazars.
The X-ray band is the "bridge" between the synchrotron and Compton spectrum.
Therefore X-ray observation is crucial to study
the mechanism of emission extending up to GeV or TeV gamma-rays.
In this paper we present the observed properties of blazars in keV regime
and its relation to other wavelength.
Short talk. Session 8b.
Name of the Speaker(s): Wolfgang Kundt
Institution: Bonn University
Title of the communication: THE (STELLAR-MASS) BLACK-HOLE CANDIDATES (BHCs)
Preliminary abstract:
are observationally defined as the class of (> 15) binary X-ray sources whose
compact component has a mass exceeding several M(sun). Their best-known repre-
sentatives are Cyg X-1, LMC X-1, A 0620-00, Nova Muscae, and the superluminal
jet sources GRS 1915+105 and GRO J1655-40.
The properties of the BHCs differ remarkably little from those of establish-
ed neutron-star sources: they show often: (1) polarized optical emission, (2)
high-low state bimodality, (3) Li absorption (like in Cen X-4), (4) X-ray dip-
ping, (5) X-ray intensity flickering and QPO (like the LMXBs of high neutron-
star spinrate), (6) formation of radio jets (i.e. of relativistic pair plasma),
and (7) transient period lengthening (like during 'superhumps' of the cataclys-
mic variables).
Moreover, the BH interpretation is hard put by the following further proper-
ties: (8) their X-ray lightcurves tend to peak near the Eddington luminosity of
(no more than) one solar mass, and (9) mostly fall below some 10^32 erg/s dur-
ing quiescence, (in conflict with accretion-disk theory). (10) The spectral
power during high state can peak above 1 MeV, (with an equivalent black-body
area of < 10^2 cm^2 !). And an extended, variable, luminous windzone is signal-
led by (11) strong (Balmer) emission lines, (12) noisy LOS line velocities, and
(13) noisy optical light curves which - even during quiescence (of A 0620-00 &
Nova Muscae) - lack reflection symmetry about the two orbital minima.
Due to the Eddington hurdle, disks around neutron stars differ from those
around white dwarfs in being able to store almost all the matter transferred
from their companion, occasionally as much as several M(sun). Once the disk
mass approaches stellar values, a compact binary can appear first as a super-
Eddington source, then as a 'supersoft (X-ray) source', and finally as a BHC.
Long talk: Session 8a.
Name of the Speaker(s): Anne Lahteenmaki
Institution: Metsahovi Radio Research Station
Title of the communication: Doppler boosting factors and viewing angles
for different classes of AGN derived from continuum and VLBI observations
Preliminary abstract:
Two intrinsic parameters determining the appearance of an AGN are the speed of
the jet flow and the viewing angle. These can be calculated if the apparent
superluminal speed and the Doppler boosting factor D are known. D is usually
estimated from the SSC X-ray flux, but the derived values are notoriously
uncertain. We explore alternative ways of estimating D from total
flux density variations associated with the creation of new VLBI components,
and use the derived values to calculate the intrinsic Lorentz factors and
viewing angles of various classes of AGN. The resulting source parameters are
compared with those based on SSC calculations. We argue that the values
derived from flux density variations are much more accurate and realistic than
the SSC-derived ones usually presented.
Short talk: Session 2.
Name of the Speaker(s): Lainela, Markku
Institution: Tuorla Observatory
Vaisalantie 20,
FIN-21500 Piikkio,
Finland
Title of the communication: Decomposing radio outbursts of AGN by
using a simple fitting method
Preliminary abstract:
The excellent high radio frequency light
curves of Metsähovi monitoring program
give us unique opportunity to study the
time variability of AGN in detail. We are
using a simple fitting method to decompose
the light curves to the separate outbursts.
The method can be used for predicting new
VLBI components or new gamma outbursts.
Poster
Name of the Speaker(s):
Lainela Markku
Institution: Tuorla Observatory
Vaisalantie 20,
FIN-21500 Piikkio,
Finland
Title of the communication: The 65 days period in 3C66A
Preliminary abstract:
3C66A was selected for OJ-94 project as a
comparison object for OJ 287. The reason
was that 3C66A had not shown very rapid
variability and was a good candidate for
calibration source. However, after more
detail observations it turns out that the
variability of 3C66A is very interesting
itself. Here we present the first evidences
of the 65 days period in 3C66A.
This research is supported by NASA, and is part of a larger collaboration undertaking
multiwaveband observations of gamma-ray bright blazars.
Poster
Name of the Speaker(s): Leppanen, Kari
Institution: Joint Institute for VLBI in Europe
Postbus 2
7990 AA Dwingeloo
Title of the communication: Shocks still going strong in quasar jets?
-first results from new high-resolution
radio-polarization images
Preliminary abstract:
Linear polarization images of seven
bright quasars obtained from a recent 22
GHz VLBA observation are presented. The
first results from an analysis of the
core-jet magnetic field structure will
be described and discussed in the context
of the predictions by relativistic shock
models. The question whether quasars jets
are intrinsically different from BL Lac
jets, as suggested by 5 GHz polarization
observations, may be addressed.
Short talk: Session 2.
Name of the Speaker(s): Galina Lipunova
Institution: Relativistic Astrophysics Dept., room 31,
Sternberg Astronomical Institute,
Universitetskij pr., 13,
Moscow 119899, Russia
Title of the communication:
The electromagnetic burst shape
from collapsing magnetized star.
Preliminary abstract:
The shape of magneto-dipole losses is investigating.For the first time,
within the limits of the simple model, the burst like-type radiation is
obtained both for a direct collapse and for a case of formation of
a fast-rotating, self-gravitating object colled spinar, taking into
account the main relativistic effect - the desappearance of magnetic
field during the collapse to the black hole. The burst dependence on
radius is analytically derived and the burst dependence on time for
an infinitely far observer is simulated.
The most interesting is the possibility of acceleration of
particles up to Plank energies in the vicinity of the supermassive
spinars. Astrophysical applications to the merging
neutron stars, AGN and QSOs are briefly discussed.
Poster
Name of the Speaker(s): Dr S. G. Lucek
Institution: Imperial College (United Kingdom)
Title of the communication: Magnetohydrodynamic Jet formation
Preliminary abstract: (please see attatched note for more
details)
2 and 3 D numerical solutions for the time-dependent, ideal MHD, equations
suggest that jets may be readily formed by a number of different processes. Two
related processes are examined here, i) the rotation of an accretion disk in a
magnetic field and ii) the pinching of a wind from a stationary disk by an
azimuthal magnetic field. In the first case, the accretion disk loses angular
momentum and falls into a gravitational well, building up the pressure near the
centre of the well, which ejects a jet along the rotation axis. The jet is
collimated partly by hydrodynamic funnelling and partly by the axial component
of the magnetic field, which is compressed and amplified by the infall of the
disk. In the second case, idealised calculations of the generic problem of
collimation by an azimuthal field indicate that, whilst a jet is readily
formed, it is prone to large m=1 (kink) instabilities which disrupt the jet.
Long talk: Session 14.
Name of the Speaker(s): Rohan Mahadevan
Institution:
Title of the communication: Scaling Laws for Advection Dominated Flows: Applications to
Low Luminosity Galactic Nuclei.
Preliminary abstract:
We present analytical scaling laws for self--similar
advection dominated flows.
The spectra
from these systems range from 10$^{8}$ -- 10$^{20}$ Hz,
and are determined by considering cooling
of electrons through synchrotron,
bremsstrahlung, and Compton processes.
We show that the spectra can be quite accurately reproduced without
detailed numerical calculations, and that there is a strong
testable correlation between the radio and X-ray fluxes from these
systems. We describe how different
regions of the spectrum scale with the mass of the accreting
black hole, $M$, the accretion rate of the gas, $\dot{M}$,
and the equilibrium temperature of the electrons, $T_e$. We show
that the universal radio spectral index of 1/3 observed in
most elliptical galaxies (Slee et al. 1994) is a natural
consequence of self--absorbed synchrotron radiation from these
flows. We also
give expressions for the total luminosity of these
flows, and the critical accretion rate,
$\dot{M}_{\rm crit}$, above which the advection solutions
cease to exist. We find that for most cases of interest
the equilibrium
electron temperature is fairly insensitive to $M$, $\dot{M}$, and
parameters in the model. We apply these results to
low luminosity black holes in galactic nuclei. We show
that the problem posed by Fabian & Canizares (1988)
of whether bright elliptical galaxies host
dead quasars is resolved,
as pointed out recently by Fabian & Rees (1995),
by considering advection--dominated flows.
Short talk: Session 14.
Name of the Speaker(s): Michael Maisack
Institution: Insitut fur Astronomie und Astrophysic, Tubingen
Title of the communication: Multiwavelength monitoring of a blazar field
Preliminary abstract:
The field around the EGRET detected blazar W Comae (1219+285) was monitored
from radio through gamma rays in Jan/Feb 1996 covering radio through gamma
rays. 1291+285 and 1222+216 (an EGRET and Comptel source) were found to be in
an outburst. We present the results of the multi-frequency observations and
discuss possible constraints on blazar emission models. The data include radio,
optical, IUE, XTE and EGRET obs.
Long talk: Session 6.
Name of the Speaker(s): Michael Maisack, J.Wilms, J.Dove, M.Begelman
Institution: Insitut fur Astronomie und Astrophysic, Tubingen
Title of the communication: An accretion disk model for the broad-band high
energy spectrum of Cyg X-1
Preliminary abstract:
The X-ray spectrum of Cyg X-1 and other BHC has often been modelled by thermal
Comptonisation and/or Compton reflection. However, observations in different
energy bands have given different model parameters. We collect data covering
the range 1 keV - 1 MeV and discuss them in the light of a self-consistent
accretion disk corona model.
Poster
Name of the Speaker(s): Michael Maisack, F. Rother, R. Staubert
Institution: Insitut fur Astronomie und Astrophysic, Tubingen
Title of the communication: The broad-band spectra of blazars
Preliminary abstract:
We have analysed ROSAT PSPC spectra of flat spectrum radio sources and
collected multifrequency data for the available sample. We discuss the
broad-band indices of sources detected with EGRET and compare them to those
of sources not seen by EGRET. Additionally we try to derive constraints on
the X-ray thru gamma-ray spectra of these objects (indicies and break energies)
by extrapolating spectra from the ROSAT energy range with broken power laws
and testing whether these spectra reproduce the Comptel and EGRET detections
and spectral parameters.
Poster
Name of the Speaker(s): Vigen Malumian
Title of the communication: Detection of Radio Halo of Markarian 421 with
the RATAN -600 (co-author G. Ohanian)
Preliminary abstract:
A radio halo of Markarian 421 was detected with the radio telescope
RATAN-600 at 3.95 Ghz. The half power angular size of these extended
component of the radio emission is 2.7 +- 0.5 minutes of arc, flux density is
242 + 40 mJn. The radio halo of Mark 421 has been previously detected
with the synthesis rado telescopes.
Poster
Name of the Speaker(s): MANOLAKOU KONSTANTINA
Institution: ARISTOTLE UNIVERSITY of THESSALONIKI
DEPARTMENT of PHYSICS
SECTION of ASTROPHYSICS, ASTRONOMY and MECHANICS
Title of the communication:
PARTICLE ACCELERATION IN A STRONGLY
TURBULENT PLASMA
Preliminary abstract:
We present a model for stochastic electron
acceleration inside the body of a strongly
turbulent jet. We use spatiotemporal intermittency
in the acceleration procces and the electrons are
subject to synchrotron losses.
Assuming that non-linear structures with a spectrum
of sizes, will interact with the electrons injected from
the compact object, we estimate numerically the evolution of
an electron energy distribution function and the spectral
index of the synchrotron emission. We also assume canonical values
for the structure of the jet (ex. ambient magnetic field,
velocity of the flow of the jet, dimensions of the jet, etc).
Poster
Name of the Speaker(s): Maria Marcha
Institution: University of Lisbon
Title of the communication: In Search of Transitional Objects
Preliminary abstract:
Recent years have seen great productivity in the elaboration of
unified models for Active Galactic Nuclei (AGN). However, there are still
several unanswered questions concerning the relationships between the
different types of AGN. In particular, the ones that concern us here are
those related to the lower luminosity radio-loud objects, often referred
to as Fanaroff & Riley I galaxies (FR I). Among these fall the BL Lac
objects, an enigmatic type of flat radio spectrum AGN whose peculiar
properties include the generally featureless optical continuum and a
usually high and variable polarisation. Several studies have suggested
that BL Lacs are beamed versions of FR I galaxies. But do all FR I's
hold BL Lac nuclei? Although the present unification schemes establish
broad relationships bewteen different classes of AGN, it is important to
investigate the still existing gaps. One way of doing this is to look
for objects with observational properties that lie somewhere in between
classes. Such is the aim of this communication.
Short talk: Session 11.
Name of the Speaker(s): Marchenko S.G., Hagen-Thorn V.A.,Takalo L.O.,
Sallanpaa A., Pursimo T.
Institution:
Title of the communication: THE VARIABLE SOURCES RESPONSIBLE FOR
THE PHOTOMETRIC BEHAVIOUR
OF OJ~287 IN THE IR-OPTICAL-UV REGION DURING 1994-1995.
Preliminary abstract:
The investigations of multicolour observations of OJ~287 in the IR-optical-
UV region in the frame of OJ-94 project were carried out. The colour
indexes of variable source responsible for the outburst 1994-1995 have been
obtained. The relative spectral energy distribution of the variable
source in the IR-optical-UV region has been found. The comporison of
colour indexes of variable sources responsible for the outbursts 1971-1972,
1983-1984, 1994-1995 is shown that there is a good correlation between
amplitude of outburst and colour indexes of variable sources.
Poster
Name of the Speaker(s):Alan P. Marscher
Institution:>Dept. of Astronomy
Boston University
Title of the communication: Models for Blazars (Key Note talk)
Preliminary abstract:
I will review current models for blazars,
concentrating on the sub-parsec scale
region of the jet. Multiwavelength
monitoring observations show that the
emission site is stratified according to
waveband. I will show how the observations
constrain the geometry of this
stratification. I will also discuss models
for explaining the observed light curves of
blazars and try to draw an overall picture
of a blazar that is consistent with the
observations.We present new simulations of relativistic
extragalactic jets, in particular
exploring the pattern of shocks within
diverging flows using extremely long
grids to accommodate the very large
wavelength of such structures. We also
present radiation transfer calculations
incorporating time delay effects.
Key Note talk.
Name of the Speaker(s):Alan P. Marscher
Institution:>Dept. of Astronomy
Boston University
Title of the communication: VLBI Images of Gamma-Ray Bright Blazars
Preliminary abstract:
The author, with A.E. Wehrle and W. Xu (IPAC), J. Mattox (Boston U.), and S. Bloom (NASA/GSFC),
has observed roughly 40 of the EGRET detected blazars with the VLBA at 22 and 43 GHz (some at
8.4 GHz as well), starting in Nov 1993. For many of these objects, we have data obtained at
two or more epochs. The most interesting images will be shown. Some of the blazars have
prominent jets, while others show only faint secondary components or no non-core structure at
all.
We intend to continue the project for 1-2 more years so that we can measure the apparent
velocities of separation of the knots from the cores.
Poster
Name of the Speaker(s):Jose M. Marti
Institution:UNIVERSIDAD DE VALENCIA
Title of the communication: (preliminary) Models of Relativistic Jets
Preliminary abstract:
The properties of relativistic jets
(aspect, dynamics, propagation) are
studied on the basis of recent
high-resolution hydrodynamical
simulations.
Long Talk: Session 14.
Name of the Speaker(s):JOSEP MARTI
Institution: Service d'Astrophysique, CE-Saclay
Title of the communication: Radio Observations of Galactic Bulge
Hard X-ray Sources detected by SIGMA
Preliminary abstract:
We present the current status of a VLA
multi-epoch observation program of
hard X-ray sources detected by the
coded mask telescope SIGMA. The target
sources are mainly located in the
galactic bulge and they are likely to
be binary systems containing
a compact companion, either black hole
or neutron star. Our goal is to identify
the radio counterpart of these objects
and to measure its position with arcsecond
accuracy in order to allow further studies.
Long talk. Session 14
Name of the Speaker(s): E. Martin
Institution: Instituto de Astrofisica de Canarias (Spain)
Title of the communication: Lithium in black hole binaries
Preliminary abstract:
Lithium is believed to have been one of the 4 elements created
by Big Bang nucleosynthesis. Hence, knowledge of its primordial
abundance and understanding of its Galactic evolution is of
great cosmological interest. In 1992, we reported an unexpected
lithium detection in the secondary of the black hole V404 Cyg,
which has been followed by several detections in other similar
systems. We will give an updated review of the observations
and discuss an scenario of lithium creation during
accretion events onto a black hole.
Short talk: Session 8a.
Name of the Speaker(s): Enrico MASSARO
Institution: Istituto Astronomico, Universita' La Sapienza,
via G. M. Lancisi 29,
I-00161 ROMA (Italy)
Title of the communication:
Narrow Band Photometry between 700 and 1000 nm of some bright BL Lac objects.
E. Massaro, M.Maesano, F. Montagni, R. Nesci and F. D' Alessio
Preliminary abstract:
We present the results of a narrow band
photometric research program in the wavelength
interval 700-1000 nm, started at the beginning
of 1996. The main goal of this project is the
study of the changes of the continuum spectral
distribution of some bright BL Lac objects in different
luminosty states. The filters used are those of the 13
colours Arizona photometric system, and, in the
interval under considerations have the effective wavelengths
of 720, 800, 860, and 980 nm.
Poster
Name of the Speaker(s): Enrico MASSARO
Institution: Istituto Astronomico, Universita' La Sapienza,
via G. M. Lancisi 29,
I-00161 ROMA (Italy)
Title of the communication:
Secular luminosity trends of BLLac objects:
the case of OQ 530 (1418+546).
E. Massaro, T. Aniello, M. Maesano, F. Montagni, R. Nesci
Preliminary abstract:
We present an update of the early historical light curve of OQ 530 based on literature and new photometric data.
These measurements confirm the decreasing trend of the source luminosity, which has reached in spring 1996 B values
around 16.5, about 1 - 1.5 mag brighter than the setimated host galaxy value. The average decreasing rate, over a 90
year interval, is 0.04 mag/year, but i could be even greater (up to 0.08 mag/year) in the last 25 years. Variations
on much shorter time scales (weeks to months) with an overall amplitude of about 3 mag are evident in the first part
of the light curve but in the more recent data this amplitude could be reduced to about 2 mag.
Some considerations on the physical mecahnisms responsible for this long term behaviour are discussed.
Poster
Name of the Speaker(s): Julie McEnery
Institution: Physics Department,
University College Dublin
Title of the communication: Time Variability of the TeV Gamma-Ray
Emission from Markarian 421
Preliminary abstract:
Markarian 421, the closest blazar, has been extensively monitored at TeV energies by the Whipple collaboration.
This object has exhibited variability at TeV gamma-ray energies on a range of timescales from hours to months.
The results of a search for hourscale variability during the 1995 and 1996 observing seasons will be
presented along with a discussion of the temporal properties of the very high energy
emission at longer timescales.
Short talk: Session 6.
Name of the Speaker(s): Julie McEnery
Institution: Physics Department,
University College Dublin
Title of the communication: A search for correlated optical and TeV gamma ray emission from Markarian 421
Preliminary abstract:
The BL Lac object Markarian 421 has been simultaneously monitored by
the Whipple Observatory's 48 inch optical telescope and 10 meter gamma ray
telescope during January, April and May 1996. A possible weak correlation
between optical and TeV gamma ray emission was observed during a strong
outburst from Markarian 421 in April 1995. In May 1996 two dramatic hourscale
outbursts were observed at TeV energies by the Whipple Cerenkov Imaging
Telescope. Results from this years optical campaign and a search for
correlations with the TeV gamma ray emission will be presented.
Poster
Name of the Speaker(s): Joseph S. Miller
Institution: Lick Observatory
University of California Santa Cruz
Santa Cruz, CA 95064
Title of the communication:
The Hosts and Environments of QSOs
Preliminary abstract:
A variety of galaxy types and environments
are found associated with QSOs. Recent
data indicates that mergers and interactions
are a very important aspect of the active
galaxy phenomenon. Recent Keck data on
associated galaxies will be presented.
Long talk: Session 11.
Name of the Speaker(s): H. Richard Miller
Institution: Dept. of Physics and Astronomy
Georgia State University
Atlanta, GA 30303
Title of the communication:
THE CHARACTER OF MICROVARIABILITY FOR RADIO-SELECTED
VERSUS X-RAY-SELECTED BL LAC OBJECTS
Preliminary abstract:
A sample of twenty-six blazars have been studied
in an effort to investigate possible differences in the character of the optical variability exhibited by these objects on timescales ranging from minutes to hours. A comparison of the distribution of variability amplitudes for radio-selected BL Lacs (RBLs) with a similar distribution for the X-ray-selected BL Lacs (XBLs) demonstrates the presence of a large-amplitude component for the RBLs which is not detected for the XBLs. The distributions of variability amplitudes for the RBLs and XBLs were found to be extremely unlikely to have been drawn from the same parent population. Thus, the large-amplitude variations are probably unique to the RBLs. This is consistent with the picture proposed by Urry and Padovani (1995) that suggests that the RBLs are more narrowly beamed than are the XBLs.
Short talk: Session 4.
Name of the Speaker(s): Felix Mirabel
Institution: Service d'astrophysique. Centre d'Etudes de Saclay (France)
Title of the communication: MICROQUASARS IN OUR GALAXY
Preliminary abstract:
I will review the multiwavelength approach to galactic gamma-ray sources
which lead to the diecovery of relativistic jets from collapsed objects.
Invited review: Session 7.
Name of the Speaker(s):Rafal MODERSKI
Institution: Nicolaus Copernicus Astronomical Center
Polish Academy of Sciences
Title of the communication: Evolution of Supermassive Black Hole in AGNs
Preliminary abstract:
We present our numerical study
of the evolution of the supermassive black hole (BH) in the
center of active galactic nuclei (AGN).
Two processes are taken into account:
acretion of matter from geometrically thin
accretion disk and electromagnetic extraction of energy of
the black hole by Blanford-Znajek process. Evolutions of
BH's spin and mass, disk luminosity and power
extracted are presented. Obtained results may explain
observed dichotomy in jet activity of AGNs.
Short talk: Session 14.
Name of the Speaker(s): Anita Muecke
Institution: Max-Planck-Inst. f. Extraterr. Physik
Title of the communication:
Correlation Analysis of Radio- and Gamma ray lightcurves
Preliminary abstract:
We investigated gamma ray data of variable
AGN seen by EGRET together with multi-
frequency monitoring radio observations of
FSRQ at the 100-m-Effelsberg Telescope
which have been performed in parallel to
the CGRO all-sky survey.
We concentrate our statistical analysis on
searching for a systematic connection in
the variability behaviour of the blazars.
The current status of this study is
presented.
Poster
Name of the Speaker(s): Reshmi Mukherjee
Institution: NASA, Goddard Space Fight Center,
Code 661, Bldg 2
Greenbelt MD 20771
Title of the communication:
EGRET Observations of High Energy
Gamma-ray Emission from Blazars
Preliminary abstract:
The Energetic Gamma Ray Experiment Telescope (EGRET)
on the Compton Gamma Ray Observatory (CGRO) has so far
detected about 60 blazars, around 50 of which are high
confidence detections. A summary of the observations
including flux variations and spectra of the blazars will
be presented. Multiwavelength data for some selected
blazars will also be presented. The high luminosities and
rapid time variations seen in the gamma-ray data indicate
that gamma-rays are an important component of the relativistic
jet thought to characterize blazars.
Long talk: Session 6.
Name of the Speaker(s): Ramon Nartallo1,
Walter K. Gear2
1 Queen Mary & Westfield College, Univ. London
2 Royal Observatory Edinburgh
Title of the communication: MM/Submillimetre Polarisation Properties
of BL Lac Objects and Quasars
Preliminary abstract:
Results of a monitoring campaign of the polarisation properties of a sample of BL Lac objects and Quasars carried out at 1.1mm with the JCMT.
We establish a comparison between the two types of sources and look at the variability of individual objects.
Long talk: Session 2.
Name of the Speaker(s):Kari Nilsson
Institution: Tuorla Observatory
FIN-21500 Piikkio
Finland
Title of the communication:
Preliminary abstract:
To be sent.
Poster
Name of the Speaker(s):Atsuo T. Okazaki
Institution: Astronomical Institute, University of Amsterdam
Title of the communication: Global DIsk Oscillations and
Line Profile Variabilities
Preliminary abstract:
We study three dimensional structure of
global eccentric (m=1) oscillations of
accretion disks in active galactic nuclei.
To examine characteristics of eccentric modes,
we consider linear adiabatic m=1 oscillations
in geometrically thin, polytropic disks.
We find that there exist odd (z-antisymmetric)
eccentric modes as well as even (z-symmetric)
eccentric modes.
Structure of these modes and expected
variabilities are discussed.
Poster
Name of the Speaker(s): Victor Oknyanskij
Institution: Sternberg State Astronomical Institute
Title of the communication:
VARIABLE RADIO ECHO FROM A JET IN Q0957+561
Preliminary abstract:
QSO 0957+561 is the famous double quasar which is a generally eccepted
case of gravitational lensing. Radio-optical correlation in the
Q0957+561 was first preliminary reported by Oknyanskij & Beskin (1993,
here after OB). OB used a clear idea to take into account the
known gravitational lensing time delay to get combined radio and optical
light curves and then to use them for determination of the
possible radio-from-optical time delay. It was found this way that radio
variations (5 MHz) followed optical ones by about 6.4 years with high
level of correlation (~0.87). Using new radio data (Haarasma et al.
1996), I have got nearly the same value of the optical-to-radio delay as
it had been found before. New data give opportunities for
physical constrains on the radio source: velocity, size,
location. I have made a conclusion that the variable radio source
is ejected from the central part of the QSO compact region.
Perhaps, Q0957+561 is physically related to Blazar type objects, but it
has different orientation relative to the line of sight.
Short talk: Session 2.
Name of the Speaker(s): PAOLO PADOVANI
Instiution: Dipartimento di Fisica, II Universita' di Roma (Italy)
Title of the communication: THE RELATION BETWEEN X-RAY AND RADIO SELECTED
BL LACS
Preliminary abstract:
We are at present at a turning point in our understanding of the relation
between BL Lacertae objects selected in the radio (RBLs) and X-ray (XBLs)
bands. First, it is clear that this terminology is not physical, as it is not
based on intrinsic properties but on the selection band. Second, the widely
discussed possibility that XBLs are viewed significantly off the beaming axis
and therefore represent a class of objects intermediate between RBLs and
Fanaroff-Riley type I radio galaxies (the putative parent population) is being
challenged. I will describe our recent results in this field, with particular
emphasis on the ROSAT spectra of XBLs and RBLs and our proposed alternative
interpretation of the relationship between the two classes.
Short talk: Session 14.
Name of the Speaker(s): Pariev Vladimir
Institution: Radioastromomy Department of P.N.Lebedev Physical Institute (Russia)
Title of the communication: Hydrodynamic accretion onto rapidly rotating
Kerr black hole
Preliminary abstract:
Bondi type hydrodynamic accretion of the surrounding matter onto Kerr black
hole with an arbitrary rotational parameter is considered. The black hole is
supposed to be at rest with respect to matter at infinity. The flow is
adiabatic and has no angular momentum. The fact that usually in astrophysics
substance far from the black hole has nonrelativistic temperature introduces
small parameter to the problem and allows to search for the solution as a
perturbation to the accretion of a cold, that is dust--like, matter. The
equations thus obtained are solved analytically. The conditions of the
regularity of the solution at the sonic surface and at infinity allow to
specify unique solution, to find the shape of the sonic surface and to
determine the corrections to Bondi accretion rate.
Poster
Name of the Speaker(s): Pariev Vladimir
Institution: Radioastromomy Department of P.N.Lebedev Physical Institute (Russia)
Title of the communication: Stability of a relativistic rotating
electron-positron jet and superluminal motion of knots.
Preliminary abstract:
The linear stability of a hydrodynamic relativistic flow of magnetized plasma
is investigated in force-free approximation. Numerical calculations showed
that modes having reasonable values of azimuthal wavenumber $m$ and radial
number $n$ are stable and have attenuation increment $\gamma$ small. The
dispersion curves $\omega =\omega (k_\parallel)$ have a minimum for
$k_{{\parallel}_0}\simeq 1/R$ ($R$ is the jet radius ). This results in
accumulation of perturbations inside the jet with wavelength of the order of
the jet radius. The wave crests of the perturbation pattern formed in such a
way move along the jet with the velocity exceeding light speed. If one has
relativistic electrons emitting synchrotron radiation inside the jet, than
this pattern will be visible. This provide us with the new type of
superluminal source. If the jet is oriented close to the line of sight, than
the observer will see knots moving backward to the core.
Poster
Name of the Speaker(s): M. Peracaula, J.M. Paredes, J Marti
Institution: Facultat de Fisiques
Universitat de Barcelona
Title of the communication: Multifrequency study of the X-ray binary
system LSI+61 603.
Preliminary abstract:
We analize the properties of the emission
comming form the X-ray binary system LSI+61 603
at the following wavelengths: submm, mm,
cm, optical, infrared and X-ray. A comparative
study is done.
Short talk: Session 8a.
Name of the Speaker(s):Martin Pohl
Institution: MPE
Title of the communication: The average gamma-ray spectrum of AGN
Preliminary abstract:
Part of the gamma-ray production models
for AGN predict cut-offs around 5-10 GeV
due to the onset of the Klein-Nishina
cut-off. We derive the average gamma-ray
spectrum for different classes of AGN
and show that there is no trend of a
cut-off. The implications of this finding
are discussed.
Short talk: Session 6.
Name of the Speaker(s):Tapio Pursimo
Institution: Tuorla Observatory
Title of the communication: DESCRIPTION OF THE OJ-94 PROJECT ARCHIVE
Preliminary abstract:
The OJ-94 project archive contains data mainly on two objects, OJ287
and 3C66A. The wavelength coverage is from gigahertz frequencies up to
X-rays. The temporal resolution varies from one X-ray observation
to V-band lightcurve with a few thousand datapoints.
All the data is in one format, which helps
multifrequency studies.
The quality of the optical data and problems combining data from
different telescopes are discussed.
We will also comment on our experience and problems in collecting
and maintaining large data archive.
Long talk: Session 4.
Name of the Speaker(s):Tapio Pursimo, Aimo Sillanpaa, Leo Takalo,
Kari Nilsson and Jochen Heidt
Institution: Tuorla Observatory
Title of the communication: HIGH RESOLUTION IMAGING OF BL LAC OBJECTS AT NOT
Preliminary abstract:
We present first results of a high resolution imaging study of radio selected
BL Lac-objects from the 1 Jy sample. Our sample contains 30 objects
($\delta$$>$-20$^\circ$) observable at the Nordic Optical Telescope (NOT).
The main goals of this project are:
- Detection of previously unknown host galaxies.
- Study of their morphology (are all BL Lac hosts ellipticals?)
- Probing the AGN activity - interaction scenario
- Searching for BL Lac objects,which are affected by
gravitational microlensing
- Study of the cluster environment and comparison with those of FR I and II
radio galaxies
During the first observing run in October 1995, we could obtain deep images of
13 objects, under good or excellent seeing conditions (FWHM
0$^{\prime \prime}$.5-0$^{\prime \prime}$.9). We will show several examples of
BL Lac objects with close companions and their host galaxiesand present a
previously unknown microlensing candidate.
Poster
Name of the Speaker(s): Travis A. Rector
Institution: Center for Astrophysics and Space Astronomy
CU Campus Box 389,
University of Colorado
Boulder, CO 80309-0389
Title of the communication:
Multiwavelength Studies of Radio-Selected
BL Lacertae Objects
Preliminary abstract:
Due to their rarity, there are only two statistically-complete samples of BL Lacs:
the 1 Jy radio-selected sample (RBLs) and the EMSS X-ray-selected sample (XBLs).
The "beaming hypothesis" suggests that RBLs are highly-beamed Fanaroff-Riley
class I radio galaxies, while XBLs are viewed further from the jet axis. However,
several differences exist between the two samples which are not easily explained
by the beaming hypothesis; and alternate theories have been proposed (e.g. the
"high-energy cutoff" model). XBLs have been studied in detail; however, RBLs are
not as yet well studied. I will present results from radio and optical
observations, part of a multiwavelength study which will define the properties
of the RBL sample and will allow testing of the beaming hypothesis and alternate
theories. If these results are consistent with the beaming hypothesis, limits will
also be placed upon physical and beaming parameters of jets within BL Lacs.
Short talk. Session 12a
Name of the Speaker(s): Stanislaw Rys
Title of the communication: To be decided
Preliminary abstract:
I will present the analysis of the map of
VLBI jet with small set of a physical assumptions.
I show that only few mathematical assumption about
function describing the jet is needed. Physical
interpretation of the jet parameters in the
actual structures will be suggested.
Short talk: Session 12.
Name of the Speaker(s): Craig Robinson
Institution: ES-84, NASA/MSFC,
Huntsville, AL 35812
U.S.A.
Title of the communication:
Results from the Multiwavelength
Campaign on the Galactic Jet Source
GRO J1655-40 and BATSE Observations
of Suspected Black Hole Binaries
Preliminary abstract:
GRO J1655-40 is one of only two known
Galactic sources with superluminal
jets. Results will be presented from
the simultaneous multiwavelength observations
in March 1996 with ROSAT, ASCA and CGRO, monitoring
by the VLA and MOST, and near-continuous coverage
from 6 optical observatories. These observations
will finally provide information to constrain the
physical nature of this system and limit theoretical
models. A more general discussion on the up-to-date
results from BATSE/CGRO on the study of the physics of
black hole binaries can also be presented.
Long talk: Session 7.
Name of the Speaker(s):J.M. Rodriguez Espinosa
Institution: IAC
Title of the communication:
ISO observations of Seyfert galaxies
Preliminary abstract:
ISO is currently observing a sample of
Seyfert galaxies out to 200 micron.
Spectral energy distributions for
some Seyferts will be shown and the origin
of the far IR emission from these objects
will be discussed.
Short talk: Session 10.
Name of the Speaker(s): Gustavo E. Romero
Institution: Instituto Argentino de Radioastronomia
Title of the communication: Rapid Variability Observations of
Southern Extragalactic Radio Sources from Argentina: Review and Prospects
Preliminary abstract:
A brief review of the main results obtained with the 30-m single dish
IAR telescope in the search for rapid radio variability of southern blazars
is presented. The temporal resolution of the observations ranges from a
few hours to weeks. Along several observational campaigns very peculiar
behaviours have been detected in sources like PKS 0521-365, PKS 0537-441,
PKS 2155-152, and many others. Possible interpretations are briefly
discussed, including both intrinsic models and propagation effects along
the radiation path (gravitational microlensing and refractive
interestellar scintillation). Prospects for future researh of southern
blazars are also discussed.
Poster
Name of the Speaker(s): Gustavo E. Romero
Institution: Instituto Argentino de Radioastronomia (Argentina)
Title of the communication: Search for Variability in Selected Southern
Blazars
Preliminary abstract:
We present results in the search for variability in the southern
extragalactic radio sources PKS 1610-77, Cen A, and PKS 1830-21. The first
source has displayed large variations in its flux density over time scales
of months overlapped with short-term flicker probably originated in
refractive effects of the local ISM. Cen A and the gravitational
lensed system PKS 1830-21 were studied at different temporal resolutions
ranging from intraday to intermonth sampling. Results are discussed in
their respective contexts.
Poster
Name of the Speaker(s): Andreasyan Ruben
Institution: Byurakan Astrophysical Observatory
Title of the communication:
Formation of dipole shape magnetic fields and Jets in central
regions of active galaxies.
Preliminary abstract:
The model of formation of large-scale
dipole shape magnetic fields and radio (or/and optical) Jets
in central regions of active galaxies is studied.
Existence of rapidly rotating gas in these regions and
plasma flow from the centre is proposed. In such media the
Biermann "battery" effect acts, and the dipole magnetic
fields are amplified up to several hundreds of microgauss.
Formation of Jets is explained by motion of re-
lativistic or thermal plasma in the dipole magnetic fields.
Poster
Name of the Speaker(s): Alberto C. Sadun
Title of the communication: Chaos Analysis of the Light
Curve of the Blazar OJ 287.
Preliminary abstract:
Flux variability of the blazar OJ 287 has been analyzed using principally the OJ-94 project
data. This analysis uses a myriad of nonlinear techniques. Besides conventional methods,
such as looking at the autocorrelation function, phase space plots for attractors, the
correlation dimension as a measure of underlying structure, and using maximum entropy
to uncover dominant frequencies, some less conventional techniques are employed as well.
In particular, the twin techniques of singular value decomposition (for noise removal) and
model fits to dynamical behavior are used to great effect. Strange attractors are found and
correlations are established. The results thus obtained are discussed, and constraints are
given for further theoretical consideration.
Long talk: Session 4.
Name of the Speaker(s): Alberto C. Sadun1,
P. Boltwood 2
Institution:1Agnes Scott College, 2Boltwood Observatory
Title of the communication:
The Nature of Microvariability--A Chaos Analysis
Preliminary abstract:
A number of blazars have exhibited microvariability, yet even in the same source
there can be periods of great activity and lesser activity. And, the microvariability does
not show any obvious or characteristic form. Thus far, a number of speculative models
have been proposed to account for such microvariability, but they have not been too
specific. By characterizing the light curve one should be able to discriminate better among
the models, constrain them further, and provide better detail for them.
One approach is a nonlinear one. More specifically, if one can use the tools of
chaos analysis, such light curves can be measured and characterized. Principle among the
various techniques, we have found that the measurement of the fractal dimension
correlates well to the activity of the blazars. This paper seeks to characterize a set of light
curves all taken from one object alone, that of OJ 287.
Poster
Name of the Speaker(s): Alberto C. Sadun1,
A. D. Nair2
Institution: 1Agnes Scott College,
2University of Florida
Title of the communication:
Nonlinear Analysis of the Light Curve of 3C 345
Preliminary abstract:
Flux variability of the AGN 3C 345 has been analyzed using data from many sources
covering a large span of time. This analysis uses a myriad of nonlinear techniques.
Besides the more conventional methods such as the use of autocorrelation function,
phase space plots to search for attractors, calculation of Lyapunov exponents to look at
rates of divergence of phase space trajectories, and fractal dimension as a measure of
underlying structure, less conventional techniques are employed as well. In particular,
singular value decomposition is used for noise removal, and model fits to dynamical
behavior are made. Discrete wavelet transforms are calculated and plotted, and the light
curve is deconstructed and reconstructed in various ways to search for further evidence of
non-stochastic behavior. The results obtained are discussed, and a full theoretical
discussion follows.
Poster
Name of the Speaker(s): M. Salvati (1), F. Pacini (1,2), M. Spada (2)
(1) Osservatorio Astrofisico di Arcetri, Firenze
(2) Dipartimento di Astronomia e Scienza dello Spazio, Universita' di Firenze
Title of the communication: Time-dependent radiative transfer in jets
Preliminary abstract:
We have developed a computer code which incorporates to various degrees of
accuracy the dynamics of a relativistic jet, the evolution of the particle
and field components, and the radiative processes thought to be relevant
to the high energy emission of blazars. Our main goal is to investigate the
spectral evolution during a change of the level of activity. Preliminary
results indicate that the inverse Compton light curve has narrower peaks
than the synchrotron light curve, although the time of maximum is the same.
The flares are best modelled as bursts of energetic particles, uncorrelated
or even anticorrelated with the strength of the magnetic field.
Poster
Name of the Speaker(s): Fabio Scardigli
Institution: University of Milano. Italy.
Title of the communication:
The Black Hole Entropy
Preliminary abstract:
The Bekenstein Hawking entropy is recovered via a model based on the
quantum spacetime foam
Poster
Name of the Speaker(s):Michael Schubnell
Institution: University of Michigan
Title of the communication: Multiwaveband Observations of the Blazar Markarian 421
Preliminary abstract:
The BL Lac object Markarian 421 will be monitored by XTE during an extensive
multiwaveband campaign over a period of 36 days in March and April 1996. The
correlation between the X-ray and high-energy emission was indicated by the
recent observation of a strong outburst from Mrk 421 with the ASCA satellite
and the Whipple gamma-ray telescope in April 1995. The XTE observations of
Mrk 421 during spring 1996 emphasize on narrowly spaced pointing intervals
which will allow to measure day-scale variability over a reasonably long
period. Mrk 421 will be observed on average eight times per day during the
5 week program. This campaign will, in conjunction with observations at other
wavelengths (UV, optical), provide an excellent opportunity to study correlated
emission from this object.
Short talk: Session 14.
Name of the Speaker(s): N.M.Shakhovskoy and Yu.S.Efimov
Institution: CRIMEAN ASTROPHYSICAL OBSERVATORY (Ukraine)
Title of the communication:
Helical structure of magnetic fields in blazar's jets
revealed by optical polarization observations.
Preliminary abstract:
In terms of blazars shock-jet model the long sets of polarization
observations may reveal the type of magnetic field structure in jets.
One types of structure is helical field. The best example of field this
type give UBVRI polarization observations of OJ 287 obtained in Crimean
Observatory at its strong outburst in 1994-95. These observations show the
cyclic variations of observed position angles indicating the continuous
clockwise rotation of polarization plane of variable source with the speed
about 5 deg/day during 165 days. This is an evidence of the presence of
the helical magnetic field in the jet. The others cases of sporadic cyclic
variations of optical polarization in blazars we had found for OJ 287 in
its quiescent state in 1975, April (with the same direction of rotation)
and for PKS 0735+16 at the time of its strong outburst in 1977.
Short talk: Session 3.
Name of the Speaker(s): Dr. Joachim Siebert
Institution:Max-Planck Institut f\"ur extraterrestrische Physik
Title of the communication:
X-ray properties of the Parkes sample of
flat-spectrum radio sources
Preliminary abstract:
We investigate the X-ray properties of a
complete sample of about 300 flat-spectrum radio sources from the Parkes
catalog using the ROSAT All-Sky Survey and public pointed observations. First
results of this study will be presented.
Poster
Name of the Speaker(s):Marek Sikora
Institution: N. Copernicus Astronomical Center
Polish Academy of Sciences
Title of the communication: Do we have the theory of gamma-ray blazars?
Preliminary abstract:
We show that the high energy spectra of
gamma-ray loud
blazars cannot be explained by any simple
version of existing models.
The ``differential'' pair models fail to
reproduce flat X-ray spectra, the hadronic
models fails to reproduce steep gamma-ray
spectra, the synchrotron-self-Compton
models require too low magnetic energy
densities, and
the external-radiation-Compton models
predict too much soft X-rays.
We argue that soft X-ray excesses, which
are predicted by us to accompany hard
X-ray and gamma-ray spectra in all models,
can be avoided only in a case of efficient
collective plasma processes keeping
electrons at relativistic temperatures,
or negligible pair production in a jet.
Withdrawn
Name of the Speaker(s): M. Sikora, H. Sol, M.C. Begelman, G. Madejski
Institution: N. Copernicus Astronomical Center
Polish Academy of Sciences
Title of the communication: Radiation drag in relativistic jets of active galactic nuclei
Preliminary abstract:
Using a radiation tensor formalism, we study the radiation drag
acting on a relativistic jet propagating through the dense radiation field
expected in the vicinity of active galactic nuclei. The efficiency of the drag
is discussed in details, depending on the properties of the radiation field
and especially on the internal parameters of the jet described as a mixture of
a cold and a relativistic plasma components.
Withdrawn
Name of the Speaker(s): A. Sillanpaa et al.
Institution: Tuorla Observatory
FIN-21500 Piikkio
Finland
Title of the communication: The optical light curves of blazar OJ 287 based on the OJ-94 project data.
Preliminary abstract:
A large monitoring project, OJ-94, was set up with the aim of monitoring
blazar OJ 287 during the predicted outburst (in fall 1994, Sillanpaa
et al., 1988, ApJ 325, 628). This outburst was also observed almost at the
predicted time, Nov. 95. Another aim of the project was to collect a large
data base of a small sample of blazars. The project is still continuing.
Here we will present preliminary updated light curves of OJ 287.
Long talk: Session 4.
Name of the Speaker(s): A. Sillanpaa et al.
Institution: Tuorla Observatory
FIN-21500 Piikkio
Finland
Title of the communication: Some examples of the extremely close environments of BL Lac objects.
Preliminary abstract:
Our ongoing programmes taking very deep images of different types of BL Lac
objects with the Nordic Optical Telescope on La Palma have continued more
than two years. In many cases we have observations with sub-arcsecond
seeing and in some cases also with almost sub-half-arcsecond seeing.
Some of the objects show extremely close companions. Preliminary
results of these environments will be shown.
Poster
Name of the Speaker(s): Helene Sol
Institution: Observatoire de Paris-Meudon
Title of the communication: Particle beams in close AGN surroundings
Preliminary abstract:
Interaction of energetic particle beams with ambient gas and radiation fields
in close surroundings of AGN will be discussed, with an application to compact radio sources and blazars
Poster
Name of the Speaker(s): RUGGERO STANGA
Institution: DIP. ASTRONOMIA UNIVERSITA` DI FIRENZE
L. ENRICO FERMI 5
FIRENZE ITALIA
Title of the communication:
To be communicated
Preliminary abstract:
To be communicated
Poster
Name of the Speaker(s): Wolfgang Steffen
Institution: University of Manchester,
Dept. of Physics and Astronomy,
Oxford Rd., Manchester M13 9PL
Title of the communication:
Formation of the Narrow Line Region in
Seyfert Galaxies:
Non-adiabatic Hydrodynamic Simulation
of the Jet/ISM interaction.
Preliminary abstract:
We present hydrodynamic simulations of the
non-adiabtic interaction of Jets in the
Narrow Line Region in Seyfert Galaxies.
The simulations show that association of
Narrow Line Region Clouds and Radio Jets
in Seyfert Galaxies can be explained by the
interaction of Jets and their Cocoon with
the Ambient Medium. NLR Clouds form due to
the Cooling of swept-up Gas. We present
Simulated Maps of Optical Line and Radio
Emission and compare them with Observations
obtained with HST and Radio Interferometres.
Poster
Name of the Speaker(s): Jacques J Steyaert
Institution: Institute of Nuclear Physics, UCL
Title of the communication: AGN and Quasar Energetics from
Nuclear Reactions in Gaseous Phase.
Preliminary abstract:
We try to avoid the BH and DM hypothesis.
Nuclear Reactions of a peculiar type
taking place in gaseous phase could explain
the huge energies. Velocities from 72 km/s
up to 30 000 km/s (3He + 3He) are produced.
The underlying bold hypothesis is that nuclear
reactions products give their velocities
to pre-galaxies. Burbidge observation is
thus "explained". Radio-loud AGNs would
correspond to electron production; radio-mute
to neutrino (nu) production. Flat rotation velocities
of 220 km/s would be from H + H -> D + nu.
Poster
Name of the Speaker(s):L.O. Takalo
Institution: Tuorla Observatory,
FIN-21500 Piikkio,
Finland
Title of the communication: Spectral variability in 3C66A observed during a multifrequency monitoring campaign.
Preliminary abstract:
BL Lac object 3C66A has been monitord for three years during the
OJ-94 project. It has been seen about one magnitude brighter than
its historical light curve indicates. The light curves show
continuous variability from time scales of tens of minutes to
weeks. Here we will present results from this monitoring,
concentrating on the spectral variability and its correlations with
objects brightness.
Poster
Name of the Speaker(s): L.O. Takalo, A., Sillanp\"a\"a, T. Pursimo, S. Katajainen, K. Nilsson,
P. Hein\"am\"aki, H. Pietil\"a, M. Hanski
Institution: Tuorla Observatory,
FIN-21500 Piikkio,
Finland
Title of the communication: Monitoring of Blazars at Tuorla Observatory.
Preliminary abstract:
We present preliminary result from monitoring a sample
of blazars at Tuorla Observatory. We have a Peltier cooled CCD, with
V-filter on the one meter telescope. Since last fall we have observed
during 85 nights. A total of 3000 observations on 20 objects have
been collected. A lot of these observations have been made in connection
with international multifrequency campaigns that have included
satellite observations by EGRET, ROSAT, IUE and XTE.
We will describe our telescope and detector systems
and show some preliminary results.
Name of the Speaker(s): Merja Tornikoski
Institution: Metsahovi Radio Research Station, Finland
Title of the communication:
Statistical analysis of a complete sample of Southern AGN
Preliminary abstract:
In 1989-1994 we have made observations of a complete sample of
Southern blazars with the Swedish-ESO Submillimetre Telescope,
SEST, in Chile. Together with data obtained at other frequency
bands, mainly gathered from literature, these data can be used
to study the classification of sources by advanced statistical
methods. We have used Principle Components Analysis and Cluster
Analysis to study the parameter space and classification of AGN,
for example to try to determine if the division into BL Lac objects,
high polarization quasars and low polarization quasars is supported by
these observations.
Poster
Name of the Speaker(s): Mr. Yurij M. Toropin
Institution: Russia 119899, Moscow, Universitetskij Pr. 13,
Sternberg Astronomical Institute,
Department of Astrophysics and Stellar Astronomy (room 52)
Title of the communication: Simulation of Jets Formation during
External Accretion to Magnetised Disks.
Preliminary abstract:
A process of a supersonic accretion of matter to a
central massive object with a surrounding disk is
investigated numerically in non-relativistic approximation.
Ordered poloidal magnetic field penetrates the disk. Results
of 2,5D MHD simulations show that a well collimated supersonic
outflow (jet) is formed alonf a magnetic field lines parrallel
to rotation axis of the system. Significant part of accreting
matter (~10%) is pushed out by the gas pressure gradient from
the vicinity of the disk and the central object. The outflow
is proceeded at a quasi-steady regime. A system of oblique shock
waves formed knotty structure inside the outflow. At the advanced
phase of our simulation the supersonic accretion inflow from
directions near an equatorial plane of the disk and the supersonic
outflow along the rotational axis of the disk are combined.
Short talk: Session 12.
Name of the Speaker(s): Gino Tosti
Institution: Perugia University Observatory
Title of the communication:
Infrared (5-20 microns)Blazar observations
from Antartica: a future prospective
Preliminary abstract:
We present the most recent development of
a project aimed to install a Infrared
Robotic Telescope on the Antartica
plateau. The project is supported
by the Italian National Plan for Research
in Antartica. The 0.8 m Telescope will
be equipped with a new generation
Infrared camera operating between
5-20 microns.
Some of the scientific programs on Blazar
that could be performed with
this system are discussed.
Name of the Speaker(s): Gino Tosti
Institution: Astronomical Observatory of Perugia
Title of the communication:
Automatic Optical Monitoring of Blazar at
Perugia Observatory
Preliminary abstract:
We report a summary of three years of CCD optical monitoring
of a sample of about 30 blazars. The program is carried out
with an Automatic Imaging Telescope which is
able to observe every time the sky is clear.
For a subset of the objects currently under monitoring,
we present the light curves
obtained during October 1995 to
evidentiate the differences in the behavoir of the flaring activity
between X-selected and Radio-selected BL Lac objects.
Poster
Name of the Speaker(s): Gino Tosti, M. Fiorucci, M. Villata et al
Institution: Astronomical Observatory of Perugia
Title of the communication:
Optical Monitoring of the gamma-loud blazar
S4 0954+658
Preliminary abstract:
We here present the preliminary results of an intensive
BVRI CCD optical monitoring of the gamma-loud blazar
S4 0954+658 which was carried out at the
Perugia and Torino Astronomical Observatories
in the period December 1994-May 1995. During our monitoring the
source was very active showing variability with time
scale from days to months.Further we detected intranight
spectral index variations on February 4/5th 1995 and February 11th 1995.
Short talk: Session 3.
Name of the Speaker(s): Gino Tosti, M. Fiorucci, N. Rizzi, E. Massaro, M. Villata et al.
Institution: Astronomical Observatory of Perugia
Title of the communication:
Light curve of W COM during 1994-1996
Preliminary abstract:
We report the preliminary results of CCD BVRI monitoring of W Com from
March 1994 to June 1996. The observations were carried out at Perugia,
Roma and Torino Astronomical Observatories. In this period the mean magnitude
of the source was the higher observed in the last 20 years. Two
major outbursts, showing complex structures and peaked in March 1995 and
February 1996 respectively, are visible in the light curve.
In the historical light curve of W Com
the 1940, 1968, and 1995-1996 outbursts are spaced of about
28 years, supporting the idea of the existence, in this source, of a
quasi-periodic fluctuation.
Poster
Name of the Speaker(s): Aldo Treves
Institution: SISSA
Title of the communication:
Host galaxies of three radio selected BL Lac objects :
Comparison of HST and ground based imaging
Preliminary abstract:
We present images of three BL Lac objects investigated using the
Hubble Space Telescope with the WFPC2 camera.
For 1823+56,and 2254+07 a surrounding nebulosity is detected
while for 0814+49 no extended emission is revealed.
The derived properties of the host galaxies lead to
question the redshift reported for 0814+49 and
possibly for 1823+56.
The results are compared with high quality ground based images
collected at NOT, ESO-NTT and retrieved from CFHT archive.
The agreement between HST and ground based data
is remarkably good on the largest scales, while
the superiority of HST is evident close to the nucleus.
Long talk. Session 11
Name of the Speaker(s): Fausto VAGNETTI
Institution: Tor Vergata Astrophysics,
Dipartimento di Fisica,
Universita` di Roma Tor Vergata,
via della Ricerca Scientifica,
I-00133 Roma
Title of the communication:
Blazars, Quasars, and Radio Galaxies
within the Evolutionary Unified Scheme.
Preliminary abstract:
The expected distributions of jet
asymmetry and of superluminal motions
are discussed in the framework of the
Evolutionary Unified Scheme.
Specific predictions can be made for the
different classes of sources, based on
the changing balance between nuclear
(isotropic and anisotropic) and galactic
radiative components.
Poster
Name of the Speaker(s): Esko Valtaoja
Institution: Metsahovi Radio Research Station
Title of the communication: Multifrequency monitoring campaigns
(invited review)
Preliminary abstract:
I will review the history, the present
status and the future prospects of multi-
frequency observations of active galactic
nuclei. I will argue that new breakthroughs
in AGN research are more likely to come
from coordinated observations and extended
monitoring efforts with existing facilities
than from new telescopes and observational
techniques. On the one hand,large amounts
of data are needed for statistically valid
conclusions about AGN behavior, on the other,
only simultaneous multifrequency data can
differentiate between possible models.
Invited review. Session 15
Name of the Speaker(s): Lourdes VICENTE
Institution: (DARC) Observatoire de Meudon
Title of the communication: Misalignment effects in BL Lac objects
Preliminary abstract:
A large fraction of extragalactic radio sources show strong misalignment between the VLBI and VLA structure. From our sample of 155 objects, 37\% of the sources present an apparent misalignment larger than 45 deg and up to 71 \% for the subsample of BL LAc objects. The secondary peak near 90 deg in the apparent $\Delta PA$ distribution reported in litterature
is difficult to fit with single population simple bend models, especially for BL Lac and intermediate redshift sources. This distribution is significantly different for BL Lacs and quasars. Consideration of different types of phenomena which might be responsible for misalignment lead us to suggest the existence of twisted accretion disks in the central engines
of highly distorted radio sources (Appl,Sol and Vicente, 1996, A\&A 310, 419). Double jet models describe jets as a stratified structure with an inner relativistic beam surrounded by a slower collimated wind. In the context of such models, the presence of highly twisted accretion disks can lead to propagation of the inner jet through a transverse magnetic field.
We study this scenario as a possible explanation for the particular magneticfield configuration observed in BL Lac objects, perpendicular to the VLBI jet (Sol and Vicente, 1996, preprint).
Name of the Speaker(s): Vicente, L., Charlot., and Sol, H.
Institution: (DARC) Observatoire de Meudon
Title of the communication: VLBI maps of a sample of blazars
from geodetic data
Preliminary abstract:
Multi-epoch VLBI maps of nine blazars have been produced from 8.4 and
2.3~GHz geodetic data acquired by the Crustal Dynamics Program. We discuss the
parsec-scale structure of these blazars, some of which have not been previously
mapped with VLBI. Apparent jet component velocities and spectral indices are
estimated. A detailed study of the BL~Lac object OJ287 is presented, based on
ten successive 8.4~GHz maps at intervals of a few months. This intensive
monitoring suggests that the radio knots in the VLBI jet of OJ287 move along
a helical trajectory.
Poster
Name of the Speaker(s): M. Villata1, C. M. Raiteri1,
A. Sillanp\"a\"a2, L.O. Takalo2
1 Osservatorio Astronomico di Torino, Pino Torinese, Italy
2 Tuorla Obsservatory, Tuorla, Finland
Title of the communication: A beaming model for the OJ 287 periodic optical outbursts.
Preliminary abstract:
We present a model describing the quasi periodic outbursts in blazar OJ 287.
The model consists of a pair of supermassive black holes in a binary system,
both of them originating a jet. The combination of a long term precession of
the jet axes appropriately oriented with respect to the orbital axis with the
bending of the jets due to interaction of their magnetized plasma with the
ambient medium gives rise to a time-dependent orientation of the emitting
outflows. The observed periodic outbursts are due to relativistic beaming
effect when part of the emission of the bent jets is beamed in our direction.
The theoretical light curve, for a given choice of model parameters, describes
the observational data very well, and predicts the future behaviour.
Poster
Name of the Speaker(s):Dr. James R. Webb
Institution: Dept. of Physics
Florida International University
Title of the communication: Multifrequency Variability of Selected
Blazars: The Target of Opportunity Approach
Preliminary abstract:
We have been studying the outbursts of
Blazars by collecting multifrequency data from
gamma-rays through radio via a number of Target of
Opportunity programs. We utilize CGRO, IUE, ASKA and
many ground-based instruments to study the
multifrequency variability of Blazars during outbursts.
We then fit the multifrequency spectra we observe
using varions models (jets+disks) in order to
determine which parameters are important
during the outbursts. Our target objects include:
3C 345, OJ 287, PKS 1156+295 and BL Lac.
Withdrawn
Name of the Speaker(s): Kaj Wiik, Esko Valtaoja, Kari Leppänen
Institution: Kaj Wiik, Metsähovi Radio Research Station
Esko Valtaoja, Metsähovi Radio Research Station
Kari Leppänen, JIVE
Title of the communication:
Comparison of total flux and VLBI properties of a sample of
15 AGN at 22 GHz
Preliminary abstract:
A sample of 15 bright AGN has been observed at 22 GHz with two epoch
global VLBI observations. The sample consists of all sources in the
complete 2 Jy catalogue of Valtaoja et al. (1992) previously
unobserved at 22 GHz VLBI. We have begun to investigate how much
structural information can be derived just from continuum monitoring
and how to use total flux density observations to complement VLBI
observations. We present the results from the two VLBI epochs and
compare the source parameters obtained from the VLBI observations and
total flux density observations.
Short talk. Session 2
Name of the Speaker(s):Paul J. Wiita
Institution: Dept. Physics and Astronomy
Georgia State University
Atlanta GA 30303-3083
Title of the communication: Polarization Variability from Accretion
Disks
Preliminary abstract:
Instabilities operating in the inner parts
of accretion disks around black holes in
both AGN and X-ray binaries will cause
rapid fluctuations in luminosity. Some of
these components will be polarized, and we
investigate the energy-dependent polariza-
tion variability from such disk systems.
In the X-ray band, even electron scattering
can produce strong changes in both the
fraction of polarized radiation and the
polarization angle. These can provide a
unique signature of black holes.
Short talk. Session 4
Name of the Speaker(s): Susan Wright
Institution: University of Southampton, UK
Title of the communication:
Host Galaxies of Optically Violently
Variable Quasars
Preliminary abstract:
Unified schemes for radio-loud active galaxies suggest that the different
observed classes arise from one basic phenomenon, with the orientation of
the line of sight with respect to a relativistic jet determining the type
of object seen. In this scheme, optically violently variable (OVV) quasars
would be those systems seen end-on (ie down the jet), while those seen
edge-on would be Fanaroff-Riley type II (FRII) radio galaxies. If OVVs
and FRIIs are intrinsically the same and just viewed from different angles
then we would expect their host galaxies to be similar. We have obtained
deep optical and near-infrared images of a number of OVV quasars to study
the morphology of their host galaxies in order to test the proposed
unified schemes. Modelling of our data suggests that the host galaxies
of OVVs and FRIIs are indeed similar, consistent with unification.
Short talk: Session 10.
Name of the Speaker(s): YAMASHITA, Akiko
Institution: The Institute of Space and Astronautical Science (Tokio, Japan)
Title of the communication: ASCA observation of the broad line radio galaxy 3C445
Preliminary abstract:
We report a ASCA observation of the broad line radio galaxy 3C445
with radio jets. The X-ray spectrum of 3C 445 consists of an
absorbed power law component, a line feature at 6.4 keV (rest frame),
and at least one soft component. These spectral features are similar
to those of (type 2) Seyfert galaxies. This may give a step to
investigate the environments of radio loud objects, especially the blazars.
Short talk. Session 12a.