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https://hdl.handle.net/2440/37502
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Type: | Journal article |
Title: | Evidence for VHE γ-ray emission from the distant BL Lac PG 1553+113 |
Other Titles: | Evidence for VHE gamma-ray emission from the distant BL Lac PG 1553+113 |
Author: | Aharonian, F. Akhperjanian, A. Bazer-Bachi, A. Beilicke, M. Benbow, W. Berge, D. Bernlohr, K. Boisson, C. Bolz, O. Borrel, V. Braun, I. Breitling, F. Brown, A. Buhler, R. Carrigan, S. Chadwick, P. Chounet, L. Cornils, R. Costamante, L. Degrange, B. et al. |
Citation: | Astronomy and Astrophysics: a European journal, 2006; 448(2):L19-L23 |
Publisher: | E D P Sciences |
Issue Date: | 2006 |
ISSN: | 0004-6361 1432-0746 |
Statement of Responsibility: | F. Aharonian...G. Rowell...et al. |
Abstract: | The high-frequency peaked BL Lac PG 1553+113 was observed in 2005 with the HESS stereoscopic array of imaging atmospheric-Cherenkov telescopes in Namibia. Using the HESS standard analysis, an excess was measured at the 4.0σ level in these observations (7.6 hours live time). Three alternative, lower-threshold analyses yield >5σ excesses. The observed integral flux above 200 GeV is (4.8 ± 1.3stat ± 1.0syst) × 10 -12 cm-2 s-1, and shows no evidence for variability. The measured energy spectrum is characterized by a very soft power law (photon index of Γ = 4.0 ± 0.6). Although the redshift of PG 1553+113 is unknown, there are strong indications that it is greater than z = 0.25 and possibly larger than z = 0.78. The observed spectrum is interpreted in the context of VHE γ-ray absorption by the Extragalactic Background Light, and is used to place an upper limit on the redshift of z < 0.74. © ESO 2006. |
Rights: | © The European Southern Observatory 2006 |
DOI: | 10.1051/0004-6361:200600010 |
Published version: | http://dx.doi.org/10.1051/0004-6361:200600010 |
Appears in Collections: | Aurora harvest 6 Physics publications |
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