Volume 496, Number 2, March III 2009
|Page(s)||423 - 428|
|Published online||18 February 2009|
The changing look of PKS 2149-306
INAF/IASF-Bologna, via Gobetti 101, 40129 Bologna, Italy e-mail: email@example.com
2 INAF - Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate, Italy
3 Dipartimento di Scienze, Università dell'Insubria, Como, Italy
4 George Mason University, 4400 University Drive, Fairfax, Va 22030, USA
5 INAF - Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
6 NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA
Accepted: 20 December 2008
Aims. We study the blazar nature of the high-redshift Flat-Spectrum Radio Quasar PKS 2149-306 () by investigating its long-term behavior.
Methods. We analyzed all publicly available optical-to-X-ray observations performed by XMM-Newton, Swift, and INTEGRAL.
Results. PKS 2149-306 is one of four blazars at that have been observed in the hard-X-ray regime with both the BAT and ISGRI instruments. Observations acquired almost 1 year apart in the keV energy band in the object rest frame, exhibit no noticeable change in spectral slope associated with a flux variation of more than a factor of two. Swift data appear to show a roll-off below ~1 keV, which becomes increasingly evident during a ~3-day time-frame, that can be explained as the natural spectral break caused by the Inverse Compton onset. The broad-band spectra allow us to identify two different states. The SED modeling suggests that they can be interpreted by only a change in the bulk Lorentz factor of the jet.
Key words: quasars: individual: PKS 2149-306 / quasars: general / X-rays: galaxies
© ESO, 2009
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