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Discovery of very high energy γ-ray emission from the BL Lacertae object H 2356-309 with the HESS Cherenkov telescopes

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posted on 2012-10-24, 09:09 authored by F. Aharonian, W. Benbow, D. Berge, K. Bernlöhr, O. Bolz, I. Braun, R. Bühler, S. Carrigan, L. Costamante, K. Egberts, S. Funk, M. Ouchrif, M. Tluczykont, G. Hermann, J. A. Hinton, W. Hofmann, B. Khélifi, C. Masterson, M. Panter, G. Rowell, V. Sahakian, van Eldik C, H. J. Völk, A. G. Akhperjanian, A. R. Bazer-Bachi, V. Borrel, A. Marcowith, M. Beilicke, R. Cornils, G. Heinzelmann, M. Raue, J. Ripken, A. Konopelko, F. Breitling, N. Komin, T. Lohse, S. Schlenker, U. Schwanke, C. Stegmann, C. Boisson, J. M. Martin, H. Sol, A. M. Brown, P. M. Chadwick, le Gallou R, H. J. Dickinson, C. Hadjichristidis, I. J. Latham, T. J. L. McComb, S. J. Nolan, A. Noutsos, K. J. Orford, J. L. Osborne, S. M. Rayner, D. Spangler, M. Ward, I. Büsching, C. Venter, M. Holleran, de Jager OC, B. C. Raubenheimer, L. -. M. Chounet, B. Degrange, G. Dubus, G. Fontaine, B. Giebels, M. Lemoine-Goumard, G. Superina, S. Pita, A. Djannati-Ataï, P. Espigat, A. Lemière, M. Punch, R. Terrier, C. G. Théoret, L. O. Drury, D. Emmanoulopoulos, E. Ferrero, M. Hauser, G. Pühlhofer, A. Jacholkowska, S. J. Wagner, F. Feinstein, Y. A. Gallant, G. Vasileiadis, J. F. Glicenstein, P. Goret, L. Rolland, G. Henri, G. Pelletier, L. Saugé, D. Horns, O. Martineau-Huynh, P. Vincent, de Naurois M, J. -. P. Tavernet, D. Nedbal, L. Rob, A. Reimer, O. Reimer, R. Schlickeiser, F. Spanier, R. Steenkamp, D. Hauser
The extreme synchrotron BL Lac object H 2356-309, located at a redshift of z = 0.165, was observed from June to December 2004 with a total exposure of $\approx$40 h live-time with the HESS (High Energy Stereoscopic System) array of atmospheric-Cherenkov telescopes (ACTs). Analysis of this data set yields, for the first time, a strong excess of 453 $\gamma$-rays (10 standard deviations above background) from H 2356-309, corresponding to an observed integral flux above 200 GeV of I(>200 GeV) = (4.1 $\pm$ 0.5) $\times$ 10-12 cm-2 s-1 (statistical error only). The differential energy spectrum of the source between 200 GeV and 1.3 TeV is well-described by a power law with a normalisation (at 1 TeV) of N0 = (4.1 $\pm$ 0.5) $\times$ 10-13 cm-2 s-1 TeV-1 and a photon index of $\Gamma$ = $3.09\,\pm\,0.24_\mathrm{stat}\,\pm\,0.10_\mathrm{sys}$. H 2356-309 is one of the most distant BL Lac objects detected at very-high-energy $\gamma$-rays so far. Results from simultaneous observations from ROTSE-III (optical), RXTE (X-rays) and NRT (radio) are also included and used together with the HESS data to constrain a single-zone homogeneous synchrotron self-Compton (SSC) model. This model provides an adequate fit to the HESS data when using a reasonable set of model parameters.

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Citation

Astronomy & Astrophysics, 2006, 455 (2), pp. 461-466

Version

  • VoR (Version of Record)

Published in

Astronomy & Astrophysics

Publisher

EDP Sciences for European Southern Observatory (ESO)

issn

0004-6361

eissn

1432-0746

Copyright date

2006

Available date

2012-10-24

Publisher version

http://www.aanda.org/articles/aa/abs/2006/32/aa4732-05/aa4732-05.html

Language

en

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