AGILE detection of intense gamma-ray emission from the blazar PKS 1510-089

Free access article

Issue		A&A Volume 491, Number 2, November IV 2008


Page(s)		L21 - L24
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:200810594
Published online		15 October 2008

A&A 491, L21-L24 (2008)
DOI: 10.1051/0004-6361:200810594

Letter

AGILE detection of intense gamma-ray emission from the blazar PKS 1510-089

G. Pucella¹, V. Vittorini^{1, 2}, F. D'Ammando^{1, 3}, M. Tavani^{1, 3}, C. M. Raiteri⁴, M. Villata⁴, A. Argan¹, G. Barbiellini⁵, F. Boffelli^{6, 7}, A. Bulgarelli⁸, P. Caraveo⁹, P. W. Cattaneo⁶, A. W. Chen^{2, 9}, V. Cocco¹, E. Costa¹, E. Del Monte¹, G. De Paris¹, G. Di Cocco⁸, I. Donnarumma¹, Y. Evangelista¹, M. Feroci¹, M. Fiorini⁸, T. Froysland^{2, 3}, F. Fuschino⁸, M. Galli¹⁰, F. Gianotti⁸, A. Giuliani⁹, C. Labanti⁸, I. Lapshov¹, F. Lazzarotto¹, P. Lipari¹¹, F. Longo⁵, M. Marisaldi⁸, S. Mereghetti⁹, A. Morselli¹², L. Pacciani¹, A. Pellizzoni⁹, F. Perotti⁹, P. Picozza¹², M. Prest¹³, M. Rapisarda¹⁴, A. Rappoldi⁶, P. Soffitta¹, M. Trifoglio⁸, A. Trois¹, E. Vallazza⁵, S. Vercellone⁹, A. Zambra¹, D. Zanello¹¹, L. A. Antonelli¹⁵, S. Colafrancesco¹⁵, S. Cutini¹⁵, D. Gasparrini¹⁵, P. Giommi¹⁵, C. Pittori¹⁵, F. Verrecchia¹⁵, L. Salotti¹⁶, M. F. Aller¹⁷, H. D. Aller¹⁷, D. Carosati¹⁸, V. M. Larionov¹⁹, and R. Ligustri²⁰

¹ INAF/IASF-Roma, via del Fosso del Cavaliere 100, 00133 Roma, Italy
e-mail: gianluca.pucella@iasf-roma.inaf.it
² CIFS-Torino, Viale Settimio Severo 3, 10133 Torino, Italy
³ Dip. di Fisica, Univ. di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
⁴ INAF, OATo, via Osservatorio 20, 10025 Pino Torinese (Torino), Italy
⁵ Dip. di Fisica and INFN Trieste, via Valerio 2, 34127 Trieste, Italy
⁶ INFN-Pavia, via Bassi 6, 27100 Pavia, Italy
⁷ Dip. di Fisica Nucleare e Teorica, Univ. di Pavia, via Bassi 6, 27100 Pavia, Italy
⁸ INAF/IASF-Bologna, via Gobetti 101, 40129 Bologna, Italy
⁹ INAF/IASF-Milano, via E. Bassini 15, 20133 Milano, Italy
¹⁰ ENEA-Bologna, via dei Martiri di Monte Sole 4, 40129 Bologna, Italy
¹¹ INFN-Roma “La Sapienza”, Piazzale A. Moro 2, 00185 Roma, Italy
¹² INFN-Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
¹³ Dip. di Fisica, Univ. dell'Insubria, via Valleggio 11, 22100 Como, Italy
¹⁴ ENEA-Roma, via E. Fermi 45, 00044 Frascati (Roma), Italy
¹⁵ ASI-ASDC, via G. Galilei, 00044 Frascati (Roma), Italy
¹⁶ ASI, Viale Liegi 26, 00198 Roma, Italy
¹⁷ Department of Astronomy, University of Michigan, USA
¹⁸ Armenzano, Astronomical Observatory, 06083 Assisi (Perugia), Italy
¹⁹ Astron. Inst., St-Petersburg State University, Russia
²⁰ Circolo AStrofili Talmassons, via Cadorna 57, 33030 Talmassons (Udine), Italy

Received 14 July 2008 / Accepted 5 October 2008

Abstract
Context. We report the detection by the AGILE (Astro-rivelatore Gamma a Immagini LEggero) satellite of an intense gamma-ray flare from the source AGL J1511-0909, associated with the powerful quasar PKS 1510-089, during ten days of observations from 23 August to 1 September 2007.
Aims. During the observation period, the source was in optical decrease following a flaring event monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). The simultaneous gamma-ray, optical, and radio coverage allows us to study the spectral energy distribution and the theoretical models based on the synchrotron and inverse Compton (IC) emission mechanisms.
Methods. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector and the hard X-ray imager Super-AGILE sensitive in the 30 MeV $\div$ 50 GeV and 18 $\div$ 60 keV bands, respectively.
Results. Between 23 and 27 August 2007, AGILE detected gamma-ray emission from PKS 1510-089 when this source was located ~ $50^\circ$ off-axis, with an average flux of $(270 \pm 65)$ $\times$ 10^-8 photons cm^-2 s^-1 for photon energy above 100 MeV. In the following period, 28 August-1 September, after a satellite re-pointing, AGILE detected the source at ~ $35^\circ$ off-axis, with an average flux (E > 100 MeV) of $(195 \pm 30)$ $\times$ 10^-8 photons cm^-2 s^-1. No emission was detected by Super-AGILE, with a 3- $\sigma$ upper limit of 45 mCrab in 200 ks.
Conclusions. The spectral energy distribution is modelled with a homogeneous one-zone synchrotron self Compton (SSC) emission plus contributions by external photons: the SSC emission contributes primarily to the X-ray band, whereas the contribution of the IC from the external disc and the broad line region match the hard gamma-ray spectrum observed.

Key words: gamma rays: observations -- radiation mechanisms: non-thermal -- quasars: individual: PKS 1510-089

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