期刊
ASTRONOMY & ASTROPHYSICS
卷 554, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201321135
关键词
gamma rays: galaxies; quasars: individual: PKS 1510-089; infrared: diffuse background
资金
- Namibian authorities
- University of Namibia
- German Ministry for Education and Research (BMBF)
- Max Planck Society
- German Research Foundation (DFG)
- French Ministry for Research
- CNRS [IN2P3]
- Astroparticle Interdisciplinary Programme of the CNRS
- UK Science and Technology Facilities Council (STFC)
- IPNP of the Charles University
- Czech Science Foundation
- Polish Ministry of Science and Higher Education
- South African Department of Science and Technology
- National Research Foundation
- International Max Planck Research School (IMPRS) for Astronomy & Cosmic Physics at the University of Heidelberg
- Science and Technology Facilities Council [PP/E001319/1, ST/K000861/1, ST/I001573/1] Funding Source: researchfish
The quasar PKS 1510-089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E >= 0.1 TeV) emission. VHE gamma-rays were detected with a statistical significance of 9.2 standard deviations in 15.8 h of H. E. S. S. data taken during March and April 2009. A VHE integral flux of I(0.15 TeV < E < 1.0TeV) = (1.0 +/- 0.2(stat) +/- 0.2(sys)) x 10(-11) cm(-2) s(-1) is measured. The best-fit power law to the VHE data has a photon index of G = 5.4 +/- 0.7(stat) +/- 0.3(sys). The GeV and optical light curves show pronounced variability during the period of H.E.S.S. observations. However, there is insufficient evidence to claim statistically significant variability in the VHE data. Because of its relatively high redshift, the VHE flux from PKS 1510-089 should suffer considerable attenuation in the intergalactic space due to the extragalactic background light (EBL). Hence, the measured gamma-ray spectrum is used to derive upper limits on the opacity due to EBL, which are found to be comparable with the previously derived limits from relatively-nearby BL Lac objects. Unlike typical VHE-detected blazars where the broadband spectrum is dominated by nonthermal radiation at all wavelengths, the quasar PKS 1510-089 has a bright thermal component in the optical to UV frequency band. Among all VHE detected blazars, PKS 1510-089 has the most luminous broad line region. The detection of VHE emission from this quasar indicates a low level of gamma - gamma absorption on the internal optical to UV photon field.
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