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Post Info TOPIC: BL Lac S5 0716+714
Blobrana


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Posts: 131433
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S5 0716+714
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Title: Radio to gamma-ray variability study of blazar S5 0716+714
Authors: B. Rani (1), T. P. Krichbaum (1), L. Fuhrmann (1), M. Boettcher (2,3), B. Lott (4), H. D. Aller (5), M. F. Aller (5), E. Angelakis (1), U. Bach (1), D. Bastieri (6,7), A. D. Falcone (8), Y. Fukazawa (9), K. E. Gabanyi (10,11), A. C. Gupta (12), M. Gurwell (13), R. Itoh (9), K. S. Kawabata (14), M. Krips (15), A. A. Lähteenmäki (16), X. Liu (17), N. Marchili (1,7), W. Max-Moerbeck (18), I. Nestoras (1), E. Nieppola (16), G. Quintana-Lacaci (19,20), A. C. S. Readhead (18), J. L. Richards (21), M. Sasada (14,22), A. Sievers (19), K. Sokolovsky (1,23), M. Stroh (8), J. Tammi (16), M. Tornikoski (16), M. Uemura (14), H. Ungerechts (19), T. Urano (9), J. A. Zensus (1) ((1) Max-Planck-Institut für Radioastronomie (MPIfR), Germany, (2) Astrophysical Institute, Ohio University Athens, (3) Centre for Space Research, North-West University, Potchefstroom Campus, South Africa, (4) Université Bordeaux 1, CNRS/IN2p3, Centre d'Etudes Nucláires de Bordeaux Gradignan, France, (5) Astronomy Department, University of Michigan, Ann Arbor (6) Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Italy, (7) Dipartimento di Fisica e Astronomia, Università di Padova, Italy, (8) Dept. of Astronomy and Astrophysics, Penn State University, University Park, (9) Department of Physical Sciences, Hiroshima University, (10) FÖMI Satellite Geodetic Observatory, Hungary, (11) Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Hungary, (12) Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, India, (13) Harvard-Smithsonian Centre for Astrophysics, Cambridge, (14) Hiroshima Astrophysical Science Centre, Hiroshima University, (15) IRAM, 300 rue de la piscine, France, (16) Aalto University Metsähovi Radio Observatory, Finland, (17) Xinjiang Astronomical Observatory, Chinese Academy of Sciences, P.R. China, (18) Cahill Centre for Astronomy and Astrophysics, California Institute of Technology, (19) Instituto de Radioastronomía Milimétrica (IRAM), Granada, Spain, (20) CAB, INTA-CSIC, Ctra. de Torrejón a Ajalvir, Madrid, Spain, (21) Purdue University, Department of Physics, (22) Department of Astronomy, Kyoto University, (23) Astro Space Centre of Lebedev Physical Institute, Moscow, Russia)

We present the results of a series of radio, optical, X-ray and gamma-ray observations of the BL Lac object S50716+714 carried out between April 2007 and January 2011. The multi-frequency observations were obtained using several ground and space based facilities. The intense optical monitoring of the source reveals faster repetitive variations superimposed on a long-term variability trend at a time scale of ~350 days. Episodes of fast variability recur on time scales of ~ 60-70 days. The intense and simultaneous activity at optical and gamma-ray frequencies favours the SSC mechanism for the production of the high-energy emission. Two major low-peaking radio flares were observed during this high optical/gamma-ray activity period. The radio flares are characterised by a rising and a decaying stage and are in agreement with the formation of a shock and its evolution. We found that the evolution of the radio flares requires a geometrical variation in addition to intrinsic variations of the source. Different estimates yield a robust and self-consistent lower limits of \delta > 20 and equipartition magnetic field B_eq > 0.36 G. Causality arguments constrain the size of emission region \theta < 0.004 mas. We found a significant correlation between flux variations at radio frequencies with those at optical and gamma-rays. The optical/GeV flux variations lead the radio variability by ~65 days. The longer time delays between low-peaking radio outbursts and optical flares imply that optical flares are the precursors of radio ones. An orphan X-ray flare challenges the simple, one-zone emission models, rendering them too simple. Here we also describe the spectral energy distribution modelling of the source from simultaneous data taken through different activity periods.

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Blobrana


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Posts: 131433
Date:
BL Lac S5 0716+714
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Title: Seven-Year Multi-Colour Optical Monitoring of BL Lacertae Object S5 0716+714
Authors: Yan Dai, Jianghua Wu, Zong-Hong Zhu, Xu Zhou, Jun Ma, Qirong Yuan, Lingzhi Wang

We have monitored the BL Lac object S5 0716+714 in five intermediate optical wavebands from 2004 September to 2011 April. Here we present the data that include 8661 measurements which represents one of the largest databases obtained for an object at optical domain. A simple analysis of the data indicates that the object was active in most time, and intraday variability was frequently observed. In total, the object varied by 2.614 magnitudes in the i band. Strong bluer-when-brighter chromatism was observed on long, intermediate, and short timescales.

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Blobrana


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The BL Lac object PKS 0716+714 is in outburst.

Magnitude 12.7 V on the 13th September 18, 2012

Position (J2000): R.A. 07 21 53.44846  |  Dec. +71° 20' 36.3634''



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Blobrana


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Title: Multiwavelength Intraday Variability of the BL Lac S5 0716+714
Authors: Alok C. Gupta, T. P. Krichbaum, P. J. Wiita, B. Rani, K. V. Sokolovsky, P. Mohan, A. Mangalam, N. Marchili, L. Fuhrmann, I. Agudo, U. Bach, R. Bachev, M. Böttcher, K. E. Gabanyi, H. Gaur, K. Hawkins, G. N. Kimeridze, O. M. Kurtanidze, S. O. Kurtanidze, C. -U. Lee, X. Liu, B. McBreen, R. Nesci, G. Nestoras, M. G. Nikolashvili, J. M. Ohlert, N. Palma, S. Peneva, T. Pursimo, E. Semkov, A. Strigachev, J. R. Webb, H. Wiesemeyer, J. A. Zensus

We report results from a 1 week multi-wavelength campaign to monitor the BL Lac object S5 0716+714 (on December 9-16, 2009). In the radio bands the source shows rapid (~ (0.5-1.5) day) intra-day variability with peak amplitudes of up to ~ 10 %. The variability at 2.8 cm leads by about 1 day the variability at 6 cm and 11 cm. This time lag and more rapid variations suggests an intrinsic contribution to the source's intraday variability at 2.8 cm, while at 6 cm and 11 cm interstellar scintillation (ISS) seems to predominate. Large and quasi-sinusoidal variations of ~ 0.8 mag were detected in the V, R and I-bands. The X-ray data (0.2-10 keV) do not reveal significant variability on a 4 day time scale, favouring reprocessed inverse-Compton over synchrotron radiation in this band. The characteristic variability time scales in radio and optical bands are similar. A quasi-periodic variation (QPO) of 0.9 - 1.1 days in the optical data may be present, but if so it is marginal and limited to 2.2 cycles. Cross-correlations between radio and optical are discussed. The lack of a strong radio-optical correlation indicates different physical causes of variability (ISS at long radio wavelengths, source intrinsic origin in the optical), and is consistent with a high jet opacity and a compact synchrotron component peaking at ~= 100 GHz in an ongoing very prominent flux density outburst. For the campaign period, we construct a quasi-simultaneous spectral energy distribution (SED), including gamma-ray data from the FERMI satellite. We obtain lower limits for the relativistic Doppler-boosting of delta >= 12-26, which for a BL\,Lac type object, is remarkably high.

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Blobrana


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Title: Intra-day variability observations of S5 0716+714 over 4.5 years at 4.8 GHz
Authors: X. Liu, H.-G. Song, N. Marchili, B.-R. Liu, J. Liu, T. P. Krichbaum, L. Fuhrmann, J. A. Zensus

We aim to search for evidence of annual modulation in the time scales of the BL Lac object S5 0716+714. The intra-day variability (IDV) observations were carried out monthly from 2005 to 2009, with the Urumqi 25m radio telescope at 4.8 GHz. The source has shown prominent IDV as well as long-term flux variations. The IDV time scale does show evidence in favour of an annual modulation, suggesting that the IDV of 0716+714 is dominated by interstellar scintillation. The source underwent a strong outburst phase between mid-2008 and mid-2009; a second intense flare was observed in late 2009, but no correlation between the total flux density and the IDV time scale is found, implying that the flaring state of the source does not have serious implications for the general characteristics of its intra-day variability. However, we find that the inner-jet position angle is changing throughout the years, which could result in an annual modulation noise in the anisotropic ISS model fit. There is also an indication that the lowest IDV amplitudes (rms flux density) correspond to the slowest time scales of IDV, which would be consistent with an ISS origin of the IDV of 0716+714.

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Blobrana


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Title: A Quasi-Periodic Oscillation of ~ 30 Minutes in the X-ray Light Curve of the BL Lac S5 0716+714
Authors: Alok C. Gupta (1), Paul J. Wiita (2,3), Jeewan C. Pandey (1), A. K. Srivastava (1) ((1) ARIES, Nainital, India; (2) Princeton, NJ, USA; (3) GSU, Atlanta, USA)
(Version v2)

We withdraw our claim that a component in an XMM-Newton satellite light curve of the BL Lacertae object S5 0716 + 714 shows quasi-periodic oscillations (QPOs) of ~30 minutes. Although both our original periodogram and wavelet analyses gave consistent results, the data do not lead to a statistically significant result once red-noise at low frequencies is properly taken into account for periodogram analyses.

Source  arXiv



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