AGILE detection of extreme gamma-ray activity from the blazar PKS 1510-089 during March 2009

作者：D'Ammando F^*; Raiteri C M; Villata M; Romano P; Pucella G; Krimm H A; Covino S; Orienti M; Giovannini G; Vercellone S; Pian E; Donnarumma I; Vittorini V; Tavani M; Argan A; Barbiellini G; Boffelli F; Bulgarelli A; Caraveo P; Cattaneo P W; Chen A W; Cocco V; Costa E; Del Monte E; De Paris G; Di Cocco G; Evangelista Y; Feroci M; Ferrari A; Fiorini M; Froysland T; Frutti M; Fuschino F; Galli M; Gianotti F; Giuliani A

来源：Astronomy & Astrophysics, 2011, 529: A145.

DOI：10.1051/0004-6361/201016128

• radiation mechanisms: non-thermal
• galaxies: active
• gamma rays: general
• quasars: general
• quasars: individual: PKS 1510-089

We report on the extreme gamma-ray activity from the flat spectrum radio quasar (FSRQ) PKS 1510-089 observed by the AGILE satellite in March 2009. In the same period a radio-to-optical monitoring of the source was provided by the GASP-WEBT and REM facilities. In the radio band we made use also of multi-epoch 15-GHz Very Long Baseline Array data from the MOJAVE Program to get information on the parsec-scale structure. Moreover, several Swift target of opportunity observations were triggered, adding important information on the source behaviour from optical/UV to hard X-rays. We paid particular attention to the calibration of the Swift/UVOT data to make it suitable to the blazars spectra. Simultaneous observations from radio to gamma rays allowed us to study in detail the correlation among the emission variability at different frequencies and to investigate the mechanisms at work during this high activity state of the source.
In the period 9-30 March 2009, AGILE detected gamma-ray emission from PKS 1510-089 at a significance level of 21.5-sigma with an average flux over the entire period of (311 +/- 21) x 10(-8) photons cm(-2) s(-1) for photon energies above 100 MeV, and a peak level of (702 +/- 131) x 10(-8) photons cm(-2) s(-1) on daily integration. The activity detected in gamma rays occurred during a period of increasing activity from near-infrared to UV, as monitored by GASP-WEBT, REM and Swift/UVOT. A flaring episode on 26-27 March 2009 was detected from near-IR to UV, suggesting that a single mechanism is responsible for the flux enhancement observed at the end of March. By contrast, Swift/XRT observations seem to show no clear correlation of the X-ray fluxes with the optical and gamma-ray ones. However, the X-ray observations show a harder photon index (Gamma(x) similar or equal to 1.3-1.6) with respect to most FSRQs and a hint of harder-when-brighter behaviour, indicating the possible presence of a second emission component at soft X-ray energies. Moreover, the broad band spectrum from radio-to-UV confirmed the evidence of thermal features in the optical/UV spectrum of PKS 1510-089 also during high gamma-ray state. On the other hand, during 25-26 March 2009 a flat spectrum in the optical/UV energy band was observed, suggesting an important contribution of the synchrotron emission in this part of the spectrum during the brightest gamma-ray flare, therefore a significant shift of the synchrotron peak.

• 出版日期2011-5
• 单位中央民族大学