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Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author , MAGIC Collaboration
dc.contributor.author , for the Fermi-LAT Collaboration
dc.date.accessioned 2018-10-16T08:56:08Z
dc.date.available 2018-10-16T08:56:08Z
dc.date.issued 2018-09-01
dc.identifier.citation MAGIC Collaboration & for the Fermi-LAT Collaboration 2018 , ' Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state ' , Astronomy and Astrophysics , vol. 617 , A30 . https://doi.org/10.1051/0004-6361/201832624 en
dc.identifier.issn 0004-6361
dc.identifier.issn 1432-0746
dc.identifier.other PURE UUID: aa9801f9-1350-46d2-96a8-7bdddfb1d4fc
dc.identifier.other PURE ITEMURL: https://research.aalto.fi/en/publications/detection-of-the-blazar-s4-095465-at-veryhighenergy-with-the-magic-telescopes-during-an-exceptionally-high-optical-state(aa9801f9-1350-46d2-96a8-7bdddfb1d4fc).html
dc.identifier.other PURE LINK: http://www.scopus.com/inward/record.url?scp=85053505295&partnerID=8YFLogxK
dc.identifier.other PURE FILEURL: https://research.aalto.fi/files/28401515/ELEC_Lahteenmaki_et_al_Detection_of_the_blazar_aa32624_18.pdf
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/34310
dc.description.abstract Aims. The very high energy (VHE ≥ 100 GeV) -ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z = 0.368 or z ≥ 0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. Methods. We investigated the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and have put it in context with possible emission scenarios. We collected photometric data in radio, optical, X-ray, and γ-ray. We studied both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Results. Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy γ-ray(HE, 100MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100. Conclusions. The high emission state during the flare allows us to compile the simultaneous broadband SED and to characterize it in the scope of blazar jet emission models. The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars (FSRQs), that is, inverse Compton scattering on an external soft photon field from the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to FSRQs and low-frequency peaked BL Lac objects (LBL). en
dc.format.mimetype application/pdf
dc.language.iso en en
dc.relation.ispartofseries Astronomy and Astrophysics en
dc.relation.ispartofseries Volume 617 en
dc.rights openAccess en
dc.title Detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state en
dc.type A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä fi
dc.description.version Peer reviewed en
dc.contributor.department Department of Electronics and Nanoengineering en
dc.subject.keyword BL Lacertae objects: individual: S4 0954+65
dc.subject.keyword Galaxies: active
dc.subject.keyword Gamma rays: galaxies
dc.identifier.urn URN:NBN:fi:aalto-201810165387
dc.identifier.doi 10.1051/0004-6361/201832624
dc.type.version publishedVersion

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