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http://hdl.handle.net/20.500.12386/26015
Title: | High-energy properties of the high-redshift flat spectrum radio quasar PKS 2149-306 | Authors: | D'AMMANDO, FILIPPO ORIENTI, Monica |
Issue Date: | 2016 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 455 | Issue: | 2 | First Page: | 1881 | Abstract: | We investigate the γ-ray and X-ray properties of the flat spectrum radio quasar PKS 2149-306 at redshift z = 2.345. A strong γ-ray flare from this source was detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope satellite in 2013 January, reaching on January 20 a daily peak flux of (301 ± 36) × 10<SUP>-8</SUP> ph cm<SUP>-2</SUP> s<SUP>-1</SUP> in the 0.1-100 GeV energy range. This flux corresponds to an apparent isotropic luminosity of (1.5 ± 0.2) × 10<SUP>50</SUP> erg s<SUP>-1</SUP>, comparable to the highest values observed by a blazar so far. During the flare the increase of flux was accompanied by a significant change of the spectral properties. Moreover significant flux variations on a 6-h time-scale were observed, compatible with the light crossing time of the event horizon of the central black hole. The broad-band X-ray spectra of PKS 2149-306 observed by Swift-XRT and NuSTAR are well described by a broken power-law model, with a very hard spectrum (Γ<SUB>1</SUB> ∼ 1) below the break energy, at E<SUB> break</SUB> = 2.5-3.0 keV, and Γ<SUB>2</SUB> ∼ 1.4-1.5 above the break energy. The steepening of the spectrum below ∼3 keV may indicate that the soft X-ray emission is produced by the low-energy relativistic electrons. This is in agreement with the small variability amplitude and the lack of spectral changes in that part of the X-ray spectrum observed between the two NuSTAR and Swift joint observations. As for the other high-redshift FSRQ detected by both Fermi-LAT and Swift-BAT, the photon index of PKS 2149-306 in hard X-ray is 1.6 or lower and the average γ-ray luminosity higher than 2 × 10<SUP>48</SUP> erg s<SUP>-1</SUP>. | URI: | http://hdl.handle.net/20.500.12386/26015 | URL: | https://academic.oup.com/mnras/article/455/2/1881/1121821 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stv2452 | Bibcode ADS: | 2016MNRAS.455.1881D | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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