The changing look of PKS 2149-306
Abstract
Aims: We study the blazar nature of the high-redshift Flat-Spectrum Radio Quasar PKS 2149-306 (z = 2.345) by investigating its long-term behavior. Methods: We analyzed all publicly available optical-to-X-ray observations performed by XMM-Newton, Swift, and INTEGRAL. Conclusions: PKS 2149-306 is one of four blazars at z>2 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 60-300 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.
Keywords
Cite
@article{arxiv.0902.1789,
title = {The changing look of PKS 2149-306},
author = {V. Bianchin and L. Foschini and G. Ghisellini and G. Tagliaferri and F. Tavecchio and A. Treves and G. Di Cocco and M. Gliozzi and E. Pian and R. M. Sambruna and A. Wolter},
journal= {arXiv preprint arXiv:0902.1789},
year = {2009}
}
Comments
7 pages, 2 figures. A&A accepted for publication