AGILE detection of a rapid γ-ray flare from the blazar PKS 1510-089 during the GASP-WEBT monitoring

Journal
ASTRONOMY & ASTROPHYSICS
Date Issued
2009
Author(s)
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Pucella, G.
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Donnarumma, I.
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Longo, F.
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Barbiellini, G.
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Boffelli, F.
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Cattaneo, P.W.
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Chen, A.W.
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Cocco, V.
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Di Cocco, G.
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Ferrari, A.
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Froysland, T.
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Galli, M.
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Lapshov, I.
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Lipari, P.
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Morselli, A.
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Perotti, F.
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Picozza, P.
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Prest, M.
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Rapisarda, M.
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Rappoldi, A.
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Sabatini, S.
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Vallazza, E.
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Zambra, A.
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Zanello, D.
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Agudo, I.
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Aller, M.F.
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Aller, H.D.
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Arkharov, A.A.
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Bach, U.
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Benitez, E.
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Berdyugin, A.
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Blinov, D.A.
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Chen, W.P.
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Dultzin, D.
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Fuhrmann, L.
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Gómez, J.L.
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Gurwell, M.A.
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Jorstad, S.G.
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Heidt, J.
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Hiriart, D.
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Hsiao, H.Y.
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Kimeridze, G.
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Konstantinova, T.S.
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Kopatskaya, E.N.
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Koptelova, E.
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Kurtanidze, O.
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Larionov, V.M.
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Lindfors, E.
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Lopez, J.M.
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Marscher, A.P.
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McHardy, I.M.
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Melnichuk, D.A.
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Mommert, M.
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Mujica, R.
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Nilsson, K.
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Pasanen, M.
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Roca-Sogorb, M.
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Sorcia, M.
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Takalo, L.O.
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Taylor, B.
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Troitsky, I.S.
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Colafrancesco, S.
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Cutini, S.
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Gasparrini, D.
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Preger, B.
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Santolamazza, P.
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Giommi, P.
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Salotti, L.
DOI
10.1051/0004-6361/200912560
Abstract
We report the detection by the AGILE satellite of a rapid gamma-ray flare from the powerful gamma-ray quasar PKS 1510-089, during a pointing centered on the Galactic Center region from 1 March to 30 March 2008. This source has been continuosly monitored in the radio-to-optical bands by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). Moreover, the gamma-ray flaring episode triggered three ToO observations by the Swift satellite in three consecutive days, starting from 20 March 2008. In the period 1-16 March 2008, AGILE detected gamma-ray emission from PKS 1510-089 at a significance level of 6.2-sigma with an average flux over the entire period of (84 +/- 17) x 10^{-8} photons cm^{-2} s^{-1} for photon energies above 100 MeV. After a predefined satellite re-pointing, between 17 and 21 March 2008, AGILE detected the source at a significance level of 7.3-sigma, with an average flux (E > 100 MeV) of (134 +/- 29) x 10^{-8} photons cm^{-2} s^{-1} and a peak level of (281 +/- 68) x 10^{-8} photons cm^{-2} s^{-1} with daily integration. During the observing period January-April 2008, the source also showed an intense and variable optical activity, with several flaring episodes and a significant increase of the flux was observed at millimetric frequencies. Moreover, in the X-ray band the Swift/XRT observations seem to show an harder-when-brighter behaviour of the source spectrum. The spectral energy distribution of mid-March 2008 is modelled with a homogeneous one-zone synchrotron self Compton emission plus contributions from inverse Compton scattering of external photons from both the accretion disc and the broad line region. Indeed, some features in the optical-UV spectrum seem to indicate the presence of Seyfert-like components, such as the little blue bump and the big blue bump.
Volume
508
Issue
1
Start page
181-189
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