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Your search keyword '"E. Ovcharov"' showing total 2 results
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2 results on '"E. Ovcharov"'

1. The Whole Earth Blazar Telescope Campaign on the Intermediate BL Lac Object 3C 66A in 2007-2008

Author

Böttcher, M, Fultz, K, Aller, H. D., Aller, M. F., Apodaca, J, Arkharov, A. A., Bach, U, Bache, R, Berdyugin, A, Buemi, C, Calcidese, P, Carosati, D, Charlot, P, Ciprini, S, PAOLA A., Di, Dolci, M, Efimova, N. V., Forné, SCURRATS E., Frasca, A, Gupta, A. C., HAGEN THORN, V. A., Heidt, J, Hiriart, D, Konstantinova, T. S., Kopatskaya, E. N., Lähteenmäki, A, Lanteri, L, Larionov, V. M., Lecampion, J. F., Leto, P, Lindfors, E, Mihov, E, Marilli, E, Nieppola, E, Nilsson, K, OHLERT E, OVCHAROV J. M., Pääkkönen, P, Pasanen, M, Ragozzine, B, Raiteri, C. M., Ros, J. A., Sadun, A, Sanchez, A, Semkov, E, Sorcia, M, Strigachev, A, Takalo, L, Tornikoski, M, Trigilio, Corrado, Umana, G, Valcheva, A, Villata, M, Volvach, A, J. H., Wu, Zhou, X., Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Brightness, 010308 nuclear & particles physics, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], galaxies: active, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Flux, Astronomy and Astrophysics, Astrophysics, radiation mechanisms: non-thermal, gamma rays: theory, 01 natural sciences, law.invention, Telescope, Space and Planetary Science, law, 0103 physical sciences, Blazar, BL Lacertae objects: individual: 3C 66A, 010303 astronomy & astrophysics, BL Lac object
Abstract

International audience; Prompted by a high optical state in 2007 September, the Whole Earth Blazar Telescope consortium organized an intensive optical, near-IR (JHK) and radio observing campaign on the intermediate BL Lac object 3C 66A throughout the fall and winter of 2007-2008. In this paper, we present data from 28 observatories in 12 countries, covering the observing season from late 2007 July through 2008 February. The source remained in a high optical state throughout the observing period and exhibited several bright flares on timescales of ~10 days. This included an exceptional outburst around 2007 September 15-20, reaching a peak brightness at R~ 13.4. Our campaign revealed microvariability with flux changes up to |dR/dt|~ 0.02 mag hr–1. Our observations do not reveal evidence for systematic spectral variability in the overall high state covered by our campaign, in agreement with previous results. In particular, we do not find evidence for spectral hysteresis in 3C 66A for which hints were found in an earlier campaign in a somewhat lower flux state. We also did not find any evidence for spectral lags in the discrete correlation functions between different optical bands. We infer a value of the magnetic field in the emission region of B~ 19 e 2/7 B τ–6/7 h D 13/7 1 G, where eB is the magnetic field equipartition fraction, τ h is the shortest observed variability timescale in units of hours, and D 1 is the Doppler factor in units of 10. From the lack of systematic spectral variability, we can derive an upper limit on the Doppler factor, D

Published
2009

2. The high activity of 3C 454.3 in autumn 2007. Monitoring by the WEBT during the AGILE detection

Author

C. M. Raiteri, M. Villata, W. P. Chen, W.-S. Hsiao, O. M. Kurtanidze, K. Nilsson, V. M. Larionov, M. A. Gurwell, I. Agudo, H. D. Aller, M. F. Aller, E. Angelakis, A. A. Arkharov, U. Bach, M. Böttcher, C. S. Buemi, P. Calcidese, P. Charlot, F. D'Ammando, I. Donnarumma, E. Forné, A. Frasca, L. Fuhrmann, J. L. Gómez, V. A. Hagen-Thorn, S. G. Jorstad, G. N. Kimeridze, T. P. Krichbaum, A. Lähteenmäki, L. Lanteri, G. Latev, J.-F. Le Campion, C.-U. Lee, P. Leto, H.-C. Lin, N. Marchili, E. Marilli, A. P. Marscher, R. Nesci, E. Nieppola, M. G. Nikolashvili, J. Ohlert, E. Ovcharov, D. Principe, T. Pursimo, B. Ragozzine, A. C. Sadun, L. A. Sigua, R. L. Smart, A. Strigachev, L. O. Takalo, M. Tavani, C. Thum, M. Tornikoski, C. Trigilio, K. Uckert, G. Umana, A. Valcheva, S. Vercellone, A. Volvach, H. Wiesemeyer, INAF - Osservatorio Astrofisico di Torino (OATo), Istituto Nazionale di Astrofisica (INAF), Laboratoire de Physico-Chimie de l'Atmosphère (LPCA), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale, Laboratoire de chimie bactérienne (LCB), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Insitute of Geology China Earthquake Administration Beijing 100029, China (X.X., G.C., W.C.) (INSITUTE OF GEOLOGY), Insitute of Geology, ECE Dept., University of Wisconsin-Madison, Harbin Institute of Technology (HIT), Department of Information Science and Media Studies [Bergen], University of Bergen (UIB), Institute of Geology, Chinese Academy of Sciences [Changchun Branch] (CAS), Linköping University (LIU), Department of Mechanical Engineering, National Chung-Hsing University, Research Center for Environmental Changes, Institute of Earthquake Prediction Research, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université du Littoral Côte d'Opale (ULCO)-Centre National de la Recherche Scientifique (CNRS), Department of Information Science and Media Studies [Bergen] (UiB), University of Bergen (UiB), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Raiteri CM, Villata M, Chen WP, Hsiao WS, Kurtanidze OM, Nilsson K, Larionov VM, Gurwell MA, Agudo I, Aller HD, Aller MF, Angelakis E, Arkharov AA, Bach U, Bottcher M, Buemi CS, Calcidese P, Charlot P, DAmmando F, Donnarumma I, Forne E, Frasca A, Fuhrmann L, Gomez JL, Hagen-Thorn VA, Jorstad SG, Kimeridze GN, Krichbaum TP, Lahteenmaki A, Lanteri L, Latev G, Le Campion JF, Lee CU, Leto P, Lin HC, Marchili N, Marilli E, Marscher AP, Nesci R, Nieppola E, Nikolashvili MG, Ohlert J, Ovcharov E, Principe D, Pursimo T, Ragozzine B, Sadun AC, Sigua LA, Smart RL, Strigachev A, Takalo LO, Tavani M, Thum C, Tornikoski M, Trigilio C, Uckert K, Umana G, Valcheva A, Vercellone S, Volvach A, and Wiesemeyer H

Subjects
Brightness, Swift Gamma-Ray Burst Mission, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Extinction (astronomy), galaxies: active, FOS: Physical sciences, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, galaxies: active -- galaxies: quasars: general -- galaxies: quasars: individual: 3C 454.3, 01 natural sciences, law.invention, Telescope, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], law, 0103 physical sciences, galaxies: quasars: individual: 3C 454.3, Blazar, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics (astro-ph), Astronomy and Astrophysics, Light curve, galaxies: quasars: general, Space and Planetary Science, Satellite
Abstract

The quasar-type blazar 3C 454.3 underwent a phase of high activity in summer and autumn 2007, which was intensively monitored in the radio-to-optical bands by the Whole Earth Blazar Telescope (WEBT). The gamma-ray satellite AGILE detected this source first in late July, and then in November-December 2007. In this letter we present the multifrequency data collected by the WEBT and collaborators during the second AGILE observing period, complemented by a few contemporaneous data from UVOT onboard the Swift satellite. The aim is to trace in detail the behaviour of the synchrotron emission from the blazar jet, and to investigate the contribution from the thermal emission component. Optical data from about twenty telescopes have been homogeneously calibrated and carefully assembled to construct an R-band light curve containing about 1340 data points in 42 days. This extremely well-sampled optical light curve allows us to follow the dramatic flux variability of the source in detail. In addition, we show radio-to-UV spectral energy distributions (SEDs) at different epochs, which represent different brightness levels. In the considered period, the source varied by 2.6 mag in a couple of weeks in the R band. Many episodes of fast (i.e. intranight) variability were observed, most notably on December 12, when a flux increase of about 1.1 mag in 1.5 hours was detected, followed by a steep decrease of about 1.2 mag in 1 hour. The contribution by the thermal component is difficult to assess, due to the uncertainties in the Galactic, and possibly also intrinsic, extinction in the UV band. However, polynomial fitting of radio-to-UV SEDs reveals an increasing spectral bending going towards fainter states, suggesting a UV excess likely due to the thermal emission from the accretion disc., 5 pages, 4 figures, accepted for publication in Astronomy & Astrophysics Letters

Published
2008

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