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dc.contributor.authorSmith, P. S.
dc.date.accessioned2020-02-24T20:15:25Z
dc.date.available2020-02-24T20:15:25Z
dc.date.issued2020-01-28
dc.identifier.citationAbdalla, H., Adam, R., Aharonian, F., Ait Benkhali, F., Angüner, E. O., Arakawa, M., … Smith, P. S. (2020). H.E.S.S. detection of very high-energy γ-ray emission from the quasar PKS 0736+017. Astronomy & Astrophysics, 633, A162. https://doi.org/10.1051/0004-6361/201935906 ‌en_US
dc.identifier.issn0004-6361
dc.identifier.doi10.1051/0004-6361/201935906
dc.identifier.urihttp://hdl.handle.net/10150/637078
dc.description.abstractContext. Flat-spectrum radio-quasars (FSRQs) are rarely detected at very high energies (E& x2004;>=& x2004;100 GeV) due to their low-frequency-peaked spectral energy distributions. At present, only six FSRQs are known to emit very high-energy (VHE) photons, representing only 7% of the VHE extragalactic catalog, which is largely dominated by high-frequency-peaked BL Lacertae objects. Aims. Following the detection of MeV-GeV gamma-ray flaring activity from the FSRQ PKS 0736+017 (z& x2004;=& x2004;0.189) with Fermi-LAT, the H.E.S.S. array of Cherenkov telescopes triggered target-of-opportunity (ToO) observations on February 18, 2015, with the goal of studying the gamma-ray emission in the VHE band. Methods. H.E.S.S. ToO observations were carried out during the nights of February 18, 19, 21, and 24, 2015. Together with Fermi-LAT, the multi-wavelength coverage of the flare includes Swift observations in soft X-ray and optical-UV bands, and optical monitoring (photometry and spectro-polarimetry) by the Steward Observatory, and the ATOM, the KAIT, and the ASAS-SN telescopes. Results. VHE emission from PKS 0736+017 was detected with H.E.S.S. only during the night of February 19, 2015. Fermi-LAT data indicate the presence of a gamma-ray flare, peaking at the time of the H.E.S.S. detection, with a flux doubling timescale of around six hours. The gamma-ray flare was accompanied by at least a 1 mag brightening of the non-thermal optical continuum. No simultaneous observations at longer wavelengths are available for the night of the H.E.S.S. detection. The gamma-ray observations with H.E.S.S. and Fermi-LAT are used to put constraints on the location of the gamma-ray emitting region during the flare: it is constrained to be just outside the radius of the broad-line region r(BLR) with a bulk Lorentz factor Gamma& x2004;similar or equal to& x2004;20, or at the level of the radius of the dusty torus r(torus) with Gamma& x2004;similar or equal to& x2004;60. Conclusions. PKS 0736+017 is the seventh FSRQ known to emit VHE photons, and at z& x2004;=& x2004;0.189 is the nearest so far. The location of the gamma-ray emitting region during the flare can be tightly constrained thanks to opacity, variability, and collimation arguments.en_US
dc.language.isoenen_US
dc.publisherEDP SCIENCES S Aen_US
dc.rightsCopyright © H.E.S.S. Collaboration et al. 2020. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.en_US
dc.rights.urihttp://creativecommons.org/licenses/by/4.0
dc.subjectgamma raysen_US
dc.subjectgeneralen_US
dc.subjectastroparticle physicsen_US
dc.subjectrelativistic processesen_US
dc.subjectquasarsen_US
dc.subjectindividualen_US
dc.subjectPKS 0736+017en_US
dc.titleH.E.S.S. detection of very high-energy γ-ray emission from the quasar PKS 0736+017en_US
dc.typeArticleen_US
dc.contributor.departmentUniv Arizona, Steward Observen_US
dc.identifier.journalASTRONOMY & ASTROPHYSICSen_US
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en_US
dc.eprint.versionFinal published versionen_US
dc.identifier.piiaa35906-19
dc.source.journaltitleAstronomy & Astrophysics
dc.source.volume633
dc.source.beginpageA162
refterms.dateFOA2020-02-24T20:15:25Z


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Copyright © H.E.S.S. Collaboration et al. 2020. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Except where otherwise noted, this item's license is described as Copyright © H.E.S.S. Collaboration et al. 2020. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.