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Ivan Agudo,
Alan P. Marscher,
Svetlana G. Jorstad,
Valeri M. Larionov,
Jose L. Gomez,
Anne Lahteenmaki,
Paul S. Smith,
Kari Nilsson,
Anthony C. S. Readhead,
Margo F. Aller,
Jochen Heidt,
Mark Gurwell,
Clemens Thum,
Ann E. Wehrle, Omar M. Kurtanidze
[show abstract]
[hide abstract]
ABSTRACT: We present observations of a major outburst at centimeter, millimeter,
optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO 0235+164
in 2008. We analyze the timing of multi-waveband variations in the flux and
linear polarization, as well as changes in Very Long Baseline Array (VLBA)
images at 7mm with ~0.15 milliarcsecond resolution. The association of the
events at different wavebands is confirmed at high statistical significance by
probability arguments and Monte-Carlo simulations. A series of sharp peaks in
optical linear polarization, as well as a pronounced maximum in the 7mm
polarization of a superluminal jet knot, indicate rapid fluctuations in the
degree of ordering of the magnetic field. These results lead us to conclude
that the outburst occurred in the jet both in the quasi-stationary core and in
the superluminal knot, both at >12 parsecs downstream of the supermassive black
hole. We interpret the outburst as a consequence of the propagation of a
disturbance, elongated along the line of sight by light-travel time delays,
that passes through a standing recollimation shock in the core and propagates
down the jet to create the superluminal knot. The multi-wavelength light curves
vary together on long time-scales (months/years), but the correspondence is
poorer on shorter time-scales. This, as well as the variability of the
polarization and the dual location of the outburst, agrees with the
expectations of a multi-zone emission model in which turbulence plays a major
role in modulating the synchrotron and inverse Compton fluxes.
03/2013;
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Ivan Agudo,
Alan P. Marscher,
Svetlana G. Jorstad,
Valeri M. Larionov,
Jose L. Gomez,
Anne Lahteenmaki,
Paul S. Smith,
Kari Nilsson,
Anthony C. S. Readhead,
Margo F. Aller,
Jochen Heidt,
Mark Gurwell,
Clemens Thum,
Ann E. Wehrle, Omar M. Kurtanidze
[show abstract]
[hide abstract]
ABSTRACT: We locate the gamma-ray and lower frequency emission in flares of the BL Lac
object AO 0235+164 at >12pc in the jet of the source from the central engine.
We employ time-dependent multi-spectral-range flux and linear polarization
monitoring observations, as well as ultra-high resolution (~0.15
milliarcsecond) imaging of the jet structure at lambda=7mm. The time
coincidence in the end of 2008 of the propagation of the brightest superluminal
feature detected in AO 0235+164 (Qs) with an extreme multi-spectral-range
(gamma-ray to radio) outburst, and an extremely high optical and 7mm (for Qs)
polarization degree provides strong evidence supporting that all these events
are related. This is confirmed at high significance by probability arguments
and Monte-Carlo simulations. These simulations show the unambiguous correlation
of the gamma-ray flaring state in the end of 2008 with those in the optical,
millimeter, and radio regime, as well as the connection of a prominent X-ray
flare in October 2008, and of a series of optical linear polarization peaks,
with the set of events in the end of 2008. The observations are interpreted as
the propagation of an extended moving perturbation through a re-collimation
structure at the end of the jet's acceleration and collimation zone.
12/2011;
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Ivan Agudo,
Alan P. Marscher,
Svetlana G. Jorstad,
Valeri M. Larionov,
Jose L. Gomez,
Anne Lahteenmaki,
Paul S. Smith,
Kari Nilsson,
Anthony C. S. Readhead,
Margo F. Aller, [......],
Mar Roca-Sogorb,
Gary D. Schmidt,
Lorand A. Sigua,
Aimo Sillanpaa,
Leo Takalo,
Brian Taylor,
Merja Tornikoski,
Ivan S. Troitsky,
Alma C. Zook,
Helmut Wiesemeyer
[show abstract]
[hide abstract]
ABSTRACT: We present observations of a major outburst at centimeter, millimeter,
optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO
0235+164. We analyze the timing of multi-waveband variations in the flux and
linear polarization, as well as changes in Very Long Baseline Array (VLBA)
images at 7mm with 0.15 milliarcsecond resolution. The association of the
events at different wavebands is confirmed at high statistical significance by
probability arguments and Monte-Carlo simulations. A series of sharp peaks in
optical linear polarization, as well as a pronounced maximum in the 7 mm
polarization of a superluminal jet knot, indicate rapid fluctuations in the
degree of ordering of the magnetic field. These results lead us to conclude
that the outburst occurred in the jet both in the quasi-stationary "core" and
in the superluminal knot, both parsecs downstream of the supermassive black
hole. We interpret the outburst as a consequence of the propagation of a
disturbance, elongated along the line of sight by light-travel time delays,
that passes through a standing recollimation shock in the core and propagates
down the jet to create the superluminal knot. The multi-wavelength light curves
vary together on long time-scales (months/years), but the correspondence is
poorer on shorter time-scales. This, as well as the variability of the
polarization and the dual location of the outburst, agrees with the
expectations of a multi-zone emission model in which turbulence plays a major
role in modulating the synchrotron and inverse Compton fluxes.
05/2011;
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M. Angela Osterman,
H. Richard Miller,
Amy M. Campbell,
Kevin Marshall,
John P. McFarland,
Hugh Aller,
Margo Aller,
Robert E. Fried, Omar M. Kurtanidze,
Maria G. Nikolashvili,
Merja Tornikoski,
and Esko Valtaoja
[show abstract]
[hide abstract]
ABSTRACT: PG 1553+11 was the target of a coordinated 3 week multiwavelength campaign during 2003 April and May. A significant X-ray flare was observed during the second half of this campaign. Although no optical flare was recorded during the X-ray campaign, optical observations obtained immediately prior to the campaign displayed a flux higher than that recorded during the campaign. An optical flare was observed a few days after the end of the X-ray campaign and may be related to the X-ray flare. Radio observations were made at three frequencies, with no significant changes in flux detected near the times of the optical and X-ray flares. The spectral energy distributions and flux ratios in different wave bands observed for this object are compared to other X-ray-selected blazars to demonstrate that PG 1553+11 is an extreme member of this group.
The Astronomical Journal 12/2007; 132(2):873. · 4.03 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present optical R band photometry of nine X-ray selected BL Lac objects: 1ES 0229+200, 1ES 0323+022, 1ES 502+675, 1ES 0647+250, 1ES 0806+524, 1ES0927+500, 1ES 1028+511, 1ES 1959+650, 1ES2344+514.Variability on long time scales within one magnitude in R band was found for all of the observed objects, except 1ES 0229+200 and 1ES0927+500. Largest variation was detected for 1ES 0502+675 and equals to 1.07 mag. Only few objects show statistically significant variation on intra-day scale.
Proceedings of the International Astronomical Union 07/2006; 2:399 - 400.
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[show abstract]
[hide abstract]
ABSTRACT: We give a brief summary of the ongoing Abastumani Blazar Monitoring Program started in the May of 1997. More than 45000 frames are obtained during 507 nights of observation for about 50 target objects, among them X-ray, γ-ray and Optical Blazars. All observations were done in the BVRI bands using ST-6 CCD based Photometer attached to the Newtonian focus of 70-cm meniscus telescope. Image reductions have been done using different software packages of image reduction systems such as IRAF, MIDAS and STARLINK. Most objects under study show light variations in optical band over one magnitude. Largest one was observed for AO 0235+116−4.0 mag in R band. © 2001 American Institute of Physics.
AIP Conference Proceedings. 10/2001; 587(1):333-337.
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[show abstract]
[hide abstract]
ABSTRACT: We present preliminary results of the optical observations of BL Lacertae during the period from Aug 1997 to Aug 1998 carried out with ST-6 CCD Camera attached to the Newtonian focus of the 70-cm meniscus telescope of the Abastumani Observatory. The aim of these observations is to study the long-term, intranight and intrahour variability of BL Lacertae. They were studied on the bases of 172 nights of observations, while the long-term variability during 183 nights. The maximum variation is observed in B band and equals to 3.00 (rms = 0.03). The variations in the V and R bands are within 2.71 (0.02) and 2.53 (0.01), respectively. This means that variations are larger at shorter wavelength or the object become bluer in the active phase. It were also demonstrated that BL Lacertae shows the short time scale variability in R band within 0.30 (0.02) and 0.10 (0.01). © 2001 American Institute of Physics.
AIP Conference Proceedings. 10/2001; 587(1):338-342.
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[show abstract]
[hide abstract]
ABSTRACT: The results on the deep low dispersion (1250 A/mm at H fl , 30 ffi ! l ! 165 ffi , 195 ffi ! l ! 210 ffi , jbj ! 5 ffi ; 7000 A/mm at A band, 50 ffi ! l ! 115 ffi , b=0 ffi , b=Sigma3.5 ffi ) spectral surveys of the MILKY WAY are presented. More than 2250 carbon stars were identified among them 1440 new ones. The C/M5 + ratio increases from 0.02 to 0.3 when longitude varies from 30 ffi to 210 ffi . On the basis of A GENERAL CATALOG OF GALACTIC COOL CARBON STARS the surface distribution of carbon stars has been studied. I. INTRODUCTION Theoretical models for AGB stars indicate that the Carbon Star (CS) phase may last up to 10 6 years which is strongly limited by rapid mass loss rates up to 10 Gamma4 M fi yr Gamma1 (Kleinmann 1989). This lifetime is consistent with the analysis of Claussen et al. (1987), who used the space distribution of high luminosity CS and their main sequence progenitors to argue that the lifetime of CS lies between 10 5 and 10 ...
04/1997;
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[show abstract]
[hide abstract]
ABSTRACT: We present the results of optical observations of BL Lacertae from August 1997 to November 2001 carried out with ST-6 CCD Camera attached to the Newtonian focus of the 70-cm meniscus telescope of Abastumani Observatory. The long-term, intraday and intrahour variabilities of BL Lacertae were studied on the bases of 317 and 259 nights, respectively. The variability pattern shown by BL Lacertae is very complex. The maximum amplitude of the long-term variability in the B band equals 3m.0 (rms=0.03). The variation in the V and R bands are within 2m.71 (0.02) and m.53 (0.01), respectively. This means that variations are larger at shorter wavelength or the object become bluer in the active phase. It were also demonstrated that BL Lacertae shows intraday variability within 0.30 (0.02), while intrahour variability within 0.10 (0.01) magnitudes.
Nuclear Physics B - Proceedings Supplements 132:205-208. · 0.88 Impact Factor
