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Type: Journal article
Title: Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift
Other Titles: Discovery of TeV gamma-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift
Author: Abramowski, A.
de Wilt, P.
Maxted, N.
Rowell, G.
Citation: Astronomy and Astrophysics: a European journal, 2013; 552:1-14
Publisher: E D P Sciences
Issue Date: 2013
ISSN: 0004-6361
Statement of
H.E.S.S. Collaboration, A. Abramowski ... P. deWilt ... N.Maxted ... G. Rowell ... et al.
Abstract: Very high-energy γ-ray emission from PKS 0447−439 was detected with the H.E.S.S. Cherenkov telescope array in December 2009. This blazar is one of the brightest extragalactic objects in the Fermi bright source list and has a hard spectrum in the MeV to GeV range. In the TeV range, a photon index of 3.89 ± 0.37 (stat) ±0.22 (sys) and a flux normalisation at 1 TeV, Φ1 TeV = (3.5 ± 1.1(stat) ± 0.9(sys)) × 10⁻¹³ cm⁻² s⁻¹ TeV⁻¹ were found. The detection with H.E.S.S. triggered observations in the X-ray band with the Swift and RXTE telescopes. Simultaneous UV and optical data from Swift UVOT and data from the optical telescopes ATOM and ROTSE are also available. The spectrum and light curve measured with H.E.S.S. are presented and compared to the multi-wavelength data at lower energies. A rapid flare is seen in the Swift XRT and RXTE data, together with a flux variation in the UV band, at a time scale of the order of one day. A firm upper limit of z < 0.59 on the redshift of PKS 0447−439 is derived from the combined Fermi-LAT and H.E.S.S. data, given the assumptions that there is no upturn in the intrinsic spectrum above the Fermi-LAT energy range and that absorption on the extragalactic background light (EBL) is not weaker than the lower limit provided by current models. The spectral energy distribution is well described by a simple one-zone synchrotron self-Compton scenario, if the redshift of the source is less than z ≲ 0.4.
Keywords: galaxies: active
BL Lacertae objects: individual: PKS 0447-439
radiation mechanisms: non-thermal
gamma rays: galaxies
Description: Reproduced with permission from Astronomy & Astrophysics, © ESO
Rights: © ESO 2013
DOI: 10.1051/0004-6361/201321108
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