Multi-wavelength Observations of H 2356-309
Abstract
AIMS: The properties of the broad-band emission from the high-frequency peaked BL Lac H 2356-309 (z=0.165) are investigated. METHODS: Very High Energy (VHE; E > 100 GeV) observations of H 2356-309 were performed with the High Energy Stereoscopic System (HESS) from 2004 through 2007. Simultaneous optical/UV and X-ray observations were made with the XMM-Newton satellite on June 12/13 and June 14/15, 2005. NRT radio observations were also contemporaneously performed in 2005. ATOM optical monitoring observations were also made in 2007. RESULTS: A strong VHE signal, ~13 sigma total, was detected by HESS after the four years HESS observations (116.8 hrs live time). The integral flux above 240 GeV is I(>240 GeV) = (3.06 +- 0.26 {stat} +- 0.61 {syst}) x 10^{-12} cm^{-2} s^{-1}, corresponding to ~1.6% of the flux observed from the Crab Nebula. A time-averaged energy spectrum is measured from 200 GeV to 2 TeV and is characterized by a power law (photon index of Gamma = 3.06 +- 0.15 {stat} +- 0.10 {syst}). Significant small-amplitude variations in the VHE flux from H 2356-309 are seen on time scales of months and years, but not on shorter time scales. No evidence for any variations in the VHE spectral slope are found within these data. The XMM-Newton X-ray measurements show a historically low X-ray state, characterized by a hard, broken-power-law spectrum on both nights. CONCLUSIONS: The broad-band spectral energy distribution (SED) of the blazar can be adequately fit using a simple one-zone synchrotron self-Compton (SSC) model. In the SSC scenario, higher VHE fluxes could be expected in the future since the observed X-ray flux is at a historically low level.
Keywords
Cite
@article{arxiv.1004.2089,
title = {Multi-wavelength Observations of H 2356-309},
author = {HESS Collaboration and A. Abramowski and F. Acero and F. Aharonian and A. G. Akhperjanian and G. Anton and U. Barres de Almeida and A. R. Bazer-Bachi and Y. Becherini and B. Behera and W. Benbow and K. Bernloehr and A. Bochow and C. Boisson and J. Bolmont and V. Borrel and J. Brucker and F. Brun and P. Brun and R. Buehler and T. Bulik and I. Buesching and T. Boutelier and P. M. Chadwick and A. Charbonnier and R. C. G. Chaves and A. Cheesebrough and J. Conrad and L. -M. Chounet and A. C. Clapson and G. Coignet and L. Costamante and M. Dalton and M. K. Daniel and I. D. Davids and B. Degrange and C. Deil and H. J. Dickinson and A. Djannati-Atai and W. Domainko and L. O'C. Drury and F. Dubois and G. Dubus and J. Dyks and M. Dyrda and K. Egberts and P. Eger and P. Espigat and L. Fallon and C. Farnier and S. Fegan and F. Feinstein and M. V. Fernandes and A. Fiasson and A. Foerster and G. Fontaine and M. Fuessling and S. Gabici and Y. A. Gallant and L. Gerard and D. Gerbig and B. Giebels and J. F. Glicenstein and B. Glueck and P. Goret and D. Goering and D. Hampf and M. Hauser and S. Heinz and G. Heinzelmann and G. Henri and G. Hermann and J. A. Hinton and A. Hoffmann and W. Hofmann and P. Hofverberg and M. Holleran and S. Hoppe and D. Horns and A. Jacholkowska and O. C. de Jager and C. Jahn and I. Jung and K. Katarzynski and U. Katz and S. Kaufmann and M. Kerschhaggl and D. Khangulyan and B. Khelifi and D. Keogh and D. Klochkov and W. Kluzniak and T. Kneiske and Nu. Komin and K. Kosack and R. Kossakowski and G. Lamanna and J. -P. Lenain and T. Lohse and C. -C. Lu and V. Marandon and A. Marcowith and J. Masbou and D. Maurin and T. J. L. McComb and M. C. Medina and J. Mehault and R. Moderski and E. Moulin and M. Naumann-Godo and M. de Naurois and D. Nedbal and D. Nekrassov and N. Nguyen and B. Nicholas and J. Niemiec and S. J. Nolan and S. Ohm and J-F. Olive and E. de Ona Wilhelmi and B. Opitz and K. J. Orford and M. Ostrowski and M. Panter and M. Paz Arribas and G. Pedaletti and G. Pelletier and P. -O. Petrucci and S. Pita and G. Puehlhofer and M. Punch and A. Quirrenbach and B. C. Raubenheimer and M. Raue and S. M. Rayner and O. Reimer and M. Renaud and R. de los Reyes and F. Rieger and J. Ripken and L. Rob and S. Rosier-Lees and G. Rowell and B. Rudak and C. B. Rulten and J. Ruppel and F. Ryde and V. Sahakian and A. Santangelo and R. Schlickeiser and F. M. Schoeck and A. Schoenwald and U. Schwanke and S. Schwarzburg and S. Schwemmer and A. Shalchi and I. Sushch and M. Sikora and J. L. Skilton and H. Sol and L. Stawarz and R. Steenkamp and C. Stegmann and F. Stinzing and A. Szostek and P. H. Tam and J. -P. Tavernet and R. Terrier and O. Tibolla and M. Tluczykont and K. Valerius and C. van Eldik and G. Vasileiadis and C. Venter and L. Venter and J. P. Vialle and A. Viana and P. Vincent and M. Vivier and H. J. Voelk and F. Volpe and S. Vorobiov and S. J. Wagner and M. Ward and A. A. Zdziarski and A. Zech and H. -S. Zechlin},
journal= {arXiv preprint arXiv:1004.2089},
year = {2015}
}
Comments
11 pages; 13 figures; Accepted for publication in Astronomy & Astrophysics; Figure 8 (SED) updated from V1 to have erroneously plotted optical point (without host galaxy subtracted) removed.