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

Aharonian, F; Akhperjanian, AG; Bazer-Bachi, AR; Beilicke, M; Benbow, W; Berge, D; Bernlohr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, AM; Buhler, R; Busching, I; Carrigan, S; Chadwick, PM; Chounet, LM; Cornils, R; Costamante, L; Degrange, B; Dickinson, HJ; Djannati-Atai, A; Drury, LO; Dubus, G; Egberts, K; Emmanoulopoulos, D; Espigat, P; Feinstein, F; Ferrero, E; Fontaine, G; Funk, S; Gallant, YA; Giebels, B; Glicenstein, JF; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, JA; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; de Jager, OC; Khelifi, B; Komin, N; Konopelko, A; Latham, IJ; Le Gallou, R; Lemiere, A; Lemoine-Goumard, M; Lohse, T; Martin, JM; Martineau-Huynh, O; Marcowith, A; Masterson, C; McComb, TJL; de Naurois, M; Nedbal, D; Nolan, SJ; Noutsos, A; Orford, KJ; Osborne, JL; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Puhlhofer, G; Punch, M; Raubenheimer, BC; Raue, M; Rayner, SM; Reimer, A; Reimer...

Abstract

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.

Citation

Aharonian, F., Akhperjanian, A., Bazer-Bachi, A., Beilicke, M., Benbow, W., Berge, D., …Ward, M. (2006). Discovery of very high energy γ-ray emission from the BL Lacertae object H 2356-309 with the HESS Cherenkov telescopes. Astronomy & Astrophysics, 455(2), 461-466. https://doi.org/10.1051/0004-6361%3A20054732

• Journal Article Type: Article
• Publication Date: 2006-08
• Journal: Astronomy and astrophysics.
• Print ISSN: 0004-6361
• Electronic ISSN: 1432-0746
• Publisher: EDP Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 455
• Issue: 2
• Pages: 461-466
• DOI: https://doi.org/10.1051/0004-6361%3A20054732
• Keywords: gamma rays : observations; galaxies : active; galaxies : BL Lacertaeobjects : individual : H2356-309ACTIVE GALACTIC NUCLEI; LAC OBJECTS; X-RAY; BLAZAR SEQUENCE; HOSTGALAXIES; PKS 2155-304; RADIATION; SYSTEM; RADIO; MARKARIAN-421
• Public URL: https://durham-repository.worktribe.com/output/1545482