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Published February 10, 2010 | Published
Journal Article Open

PKS 1502+106: A New and Distant Gamma-ray Blazar in Outburst Discovered by the Fermi Large Area Telescope

Abdo, A. A.
Ackermann, M.
Ajello, M. ORCID icon
Atwood, W. B.
Axelsson, M.
Baldini, L.
Ballet, J.
Barbiellini, G.
Bastieri, D.
Baughman, B. M.
Bechtol, K.
Bellazzini, R.
Berenji, B.
Bloom, E. D.
Bogaert, G.
Bonamente, E.
Borgland, A. W.
Bregeon, J.
Brez, A.
Brigida, M.
Bruel, P.
Burnett, T. H.
Caliandro, G. A.
Cameron, R. A.
Caraveo, P. A.
Casandjian, J. M.
Cavazzuti, E.
Cecchi, C.
Çelik, Ö.
Chekhtman, A.
Cheung, C. C.
Chiang, J.
Ciprini, S.
Claus, R.
Cohen-Tanugi, J.
Conrad, J
Cutini, S.
Dermer, C. D.
De Angelis, A.
De Palma, F.
Digel, S. W.
Do Couto e Silva, E.
Drell, P. S.
Dubois, R.
Dumora, D.
Farnier, C.
Favuzzi, C.
Fegan, S. J.
Ferrara, E. C.
Focke, W. B.
Frailis, M.
Fuhrmann, L.
Fukazawa, Y.
Funk, S.
Fusco, P.
Gargano, F.
Gasparrini, D.
Gehrels, N.
Germani, S.
Giebels, B.
Giglietto, N.
Giordano, F.
Giroletti, M.
Glanzman, T.
Godfrey, G.
Grenier, I. A.
Grondin, M. -H.
Grove, J. E.
Guillemot, L.
Guiriec, S.
Hanabata, Y.
Harding, A. K. ORCID icon
Hayashida, M.
Hays, E.
Hughes, R. E.
Jóhannesson, G.
Johnson, A. S.
Johnson, R. P.
Johnson, W. N.
Kadler, M.
Kamae, T.
Katagiri, H.
Kataoka, J.
Kerr, M.
Knödlseder, J.
Kocian, M. L.
Kuehn, F.
Kuss, M.
Lande, J.
Latronico, L.
Lemoine-Goumard, M.
Longo, F.
Loparco, F.
Lott, B.
Lovellette, M. N.
Lubrano, P.
Madejski, G. M.
Makeev, A.
Marelli, M.
Massaro, E.
Max-Moerbeck, W. ORCID icon
Mazziotta, M. N.
McConville, W.
McEnery, J. E.
Meurer, C.
Michelson, P. F.
Mitthumsiri, W.
Mizuno, T.
Moiseev, A. A.
Monte, C.
Monzani, M. E.
Morselli, A.
Moskalenko, I. V.
Murgia, S.
Nolan, P. L.
Norris, J. P.
Nuss, E.
Ohsugi, T.
Omodei, N.
Orlando, E.
Ormes, J. F.
Ozaki, M.
Paneque, D.
Panetta, J. H.
Parent, D.
Pavlidou, V.
Pearson, T. J. ORCID icon
Pelassa, V.
Pepe, M.
Pesce-Rollins, M.
Piron, F.
Porter, T. A.
Rainò, S.
Rando, R.
Razzano, M.
Razzaque, S.
Readhead, A. ORCID icon
Reimer, A.
Reimer, O.
Reposeur, T.
Richards, J. L.
Ritz, S.
Rochester, L. S.
Rodriguez, A. Y.
Romani, R. W. ORCID icon
Roth, M.
Ryde, F.
Sadrozinski, H. F.-W.
Sanchez, D.
Sander, A.
Saz Parkinson, P. M.
Scargle, J. D.
Sgrò, C.
Shaw, M. S.
Siskind, E. J.
Smith, D. A.
Smith, P. D.
Spandre, G.
Spinelli, P.
Stevenson, M.
Strickman, M. S.
Suson, D. J.
Tajima, H.
Takahashi, H.
Tanaka, T.
Thayer, J. B.
Thayer, J. G.
Thompson, D. J.
Tibaldo, L.
Tibolla, O.
Torres, D. F. ORCID icon
Tosti, G.
Tramacere, A.
Ubertini, P.
Uchiyama, Y.
Usher, T. L.
Vasileiou, V.
Vilchez, N.
Vitale, V.
Waite, A. P.
Wang, P.
Winer, B. L.
Wood, K. S. ORCID icon
Yasuda, H.
Ylinen, T.
Zensus, J. A.
Ziegler, M.
Angelakis, E. ORCID icon
Hovatta, T. ORCID icon
Hoversten, E.
Ikejiri, Y.
Kawabata, K. S.
Kovalev, Y. Y. ORCID icon
Kovalev, Yu. A.
Krichbaum, T. P.
Lister, M. L. ORCID icon
Lähteenmäki, A.
Marchili, N.
Ogle, P. ORCID icon
Pagani, C.
Pushkarev, A. B. ORCID icon
Sakimoto, K.
Sasada, M.
Tornikoski, M. ORCID icon
Uemura, M.
Yamanaka, M.
Yamashita, T.
FERMI LAT Collaboration


The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope discovered a rapid (~5 days duration), high-energy (E > 100 MeV) gamma-ray outburst from a source identified with the blazar PKS 1502+106 (OR 103, S3 1502+10, z = 1.839) starting on 2008 August 5 (~23 UTC, MJD 54683.95), and followed by bright and variable flux over the next few months. Results on the gamma-ray localization and identification, as well as spectral and temporal behavior during the first months of the Fermi all-sky survey, are reported here in conjunction with a multiwaveband characterization as a result of one of the first Fermi multifrequency campaigns. The campaign included a Swift ToO (followed up by a 16 day observation on August 7-22, MJD 54685-54700), VLBA (within the MOJAVE program), Owens Valley Radio Observatory (OVRO) 40 m, Effelsberg-100 m, Metsähovi-14 m, RATAN-600, and Kanata-Hiroshima radio/optical observations. Results from the analysis of archival observations by INTEGRAL, XMM-Newton, and Spitzer space telescopes are reported for a more complete picture of this new gamma-ray blazar. PKS 1502+106 is a sub-GeV peaked, powerful flat spectrum radio quasar (luminosity at E > 100 MeV, L_γ, is about 1.1 × 10^(49) erg s^(–1), and black hole mass likely close to 10^9 M_⊙), exhibiting marked gamma-ray bolometric dominance, in particular during the asymmetric outburst (L_γ/L_(opt) ~ 100, and 5 day averaged flux F_(E > 100 MeV) = 2.91 ± 1.4 × 10^(–6) ph cm^(–2) s^(–1)), which was characterized by a factor greater than 3 of flux increase in less than 12 hr. The outburst was observed simultaneously from optical to X-ray bands (F_(0.3 – 10 keV) = 2.18^(+0.15)_(–0.12) × 10^(–12) erg cm^(–2) s^(–1), and hard photon index ~1.5, similar to past values) with a flux increase of less than 1 order of magnitude with respect to past observations, and was likely controlled by Comptonization of external-jet photons produced in the broad-line region (BLR) in the gamma-ray band. No evidence of a possible blue bump signature was observed in the optical-UV continuum spectrum, while some hints for a possible 4 day time lag with respect to the gamma-ray flare were found. Nonetheless, the properties of PKS 1502+106 and the strict optical/UV, X-, and gamma-ray cross-correlations suggest the contribution of the synchrotron self-Compton (SSC), in-jet, process should dominate from radio to X-rays. This mechanism may also be responsible for the consistent gamma-ray variability observed by the LAT on longer timescales, after the ignition of activity at these energies provided by the BLR-dissipated outburst. Modulations and subsequent minor, rapid flare events were detected, with a general fluctuation mode between pink-noise and a random-walk. The averaged gamma-ray spectrum showed a deviation from a simple power law, and can be described by a log-parabola curved model peaking around 0.4-0.5 GeV. The maximum energy of photons detected from the source in the first four months of LAT observations was 15.8 GeV, with no significant consequences on extragalactic background light predictions. A possible radio counterpart of the gamma-ray outburst can be assumed only if a delay of more than three months is considered on the basis of opacity effects at cm and longer wavelengths. The rotation of the electric vector position angle observed by VLBA from 2007 to 2008 could represent a slow field ordering and alignment with respect to the jet axis, likely a precursor feature of the ejection of a superluminal radio knot and the high-energy outburst. This observing campaign provides more insight into the connection between MeV-GeV flares and the moving, polarized structures observed by the VLBI.

Additional Information

© 2010 The American Astronomical Society. Received 2009 July 29; accepted 2009 December 21; published 2010 January 22. This research is based on observations obtained with the Fermi Gamma-ray Space Telescope. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat `a l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucl´eaire et de Physique des Particules in France, the Agenzia Spaziale Italiana (ASI) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK), and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council, and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica (INAF) in Italy and the Centre National d' ´ Etudes Spatiales in France. S.C. acknowledges funding by grant ASI-INAF n.I/047/8/0 related to Fermi on-orbit activities. This research has made use of the NASA/IPAC NED database (JPL CalTech and NASA, USA), the HEASARC database (LHEA NASA/GSFC and SAO, USA), the Smithsonian/ NASA's ADS bibliographic databases, and the SIMBAD database (CDS, Strasbourg, France). This work includes observations obtained with the NASA Swift gamma-ray burst Explorer. This work includes observations obtained with the Spitzer Space Telescope (operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA). This work includes observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. This work has made use of observations obtained with the Owens Valley Radio Observatory. The monitoring program at the Owens Valley Radio Observatory is supported by NASA award No. NNX08AW31G, and NSF award No. AST-0808050. This research has made use of observations from the MOJAVE database that is maintained by the MOJAVE team. The MOJAVE project is supported under National Science Foundation grant 0807860- AST and NASA-Fermi grant NNX08AV67G. The National Radio Astronomy Observatory (NRAO VLBA) is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research has made use of observations obtained with the 100 m telescope of the MPIfR (Max-Planck-Institut f¨ur Radioastronomie) at Effelsberg, Germany. This research has made use of observations from the RATAN-600 that is partly supported by the Russian Foundation for Basic Research (projects 01-02-16812, 05-02- 17377, and 08-02-00545). This work has made use of observations obtained with the 14 m Mets¨ahovi Radio Observatory, a separate research institute of the Helsinki University of Technology. The Mets¨ahovi team acknowledges the support from the Academy of Finland. This work has made use of observations obtained with the TRISPEC instrument on the Kanata telescope that is operated by Hiroshima University, Japan. Y.Y.K. is a Research Fellow of the Alexander von Humboldt Foundation. The LAT team and multifrequency collaboration extend thanks to the anonymous referee who made very useful comments. Facilities: Fermi, Swift, VLBF, XMM, Spitzer, INTEGRAL

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