A significant hardening and rising shape detected in the MeV/GeV νFᵥ spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February

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dc.contributor.authorTanaka, Yasuyuki T.
dc.contributor.authorGonzalez, Josefa Becerra
dc.contributor.authorItoh, Ryosuke
dc.contributor.authorFinke, Justin D.
dc.contributor.authorInoue, Yoshiyuki
dc.contributor.authorOjha, Roopesh
dc.contributor.authorCarpenter, Bryce
dc.contributor.authorLindfors, Elina
dc.contributor.authorKrauß, Felicia
dc.contributor.authorDesiante, Rachele
dc.contributor.authorShiki, Kensei
dc.contributor.authorFukazawa, Yasushi
dc.contributor.authorLongo, Francesco
dc.contributor.authorMcEnery, Julie E.
dc.contributor.authorBuson, Sara
dc.contributor.authorNilsson, Kari
dc.contributor.authorRamazani, Vandad Fallah
dc.contributor.authorReinthal, Riho
dc.contributor.authorTakalo, Leo
dc.contributor.authorPursimo, Tapio
dc.contributor.authorBoschin, Walter
dc.date.accessioned2020-03-27T12:53:40Z
dc.date.available2020-03-27T12:53:40Z
dc.date.issued2016-05-23
dc.description.abstractWe report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z = 0.368) during an exceptionally bright optical flare in 2015 February. During the time period (2015 February 13/14, or MJD 57067) when the MAGIC telescope detected VHE γ-ray emission from the source, the Fermi-LAT data indicated a significant spectral hardening at GeV energies, with a power-law photon index of 1.8 ± 0.1—compared with the 3FGL (The Fermi LAT 4-Year Point Source Catalog) value (averaged over four years of observation) of 2.34 ± 0.04. In contrast, Swift X-Ray Telescope data showed a softening of the X-ray spectrum, with a photon index of 1.72 ± 0.08 (compared with 1.38 ± 0.03 averaged during the flare from MJD 57066 to 57077), possibly indicating a modest contribution of synchrotron photons by the highest-energy electrons superposed on the inverse Compton component. Fitting of the quasi-simultaneous (<1 d) broad-band spectrum with a one-zone synchrotron plus inverse-Compton model revealed that GeV/TeV emission could be produced by inverse-Compton scattering of external photons from the dust torus. We emphasize that a flaring blazar showing high flux of ≳1.0 × 10⁻⁶ photons cm⁻²s⁻¹(E > 100 MeV) and a hard spectral index of ΓGeV < 2.0 detected by Fermi-LAT on daily timescales is a promising target for TeV follow-up by ground-based Cherenkov telescopes to discover high-redshift blazars, investigate their temporal variability and spectral features in the VHE band, and also constrain the intensity of the extragalactic background light.en_US
dc.description.sponsorshipWe appreciate the referee’s careful reading and valuable comments. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat a l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire ´ et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Etudes Spatiales in France. This research ´ was funded in part by NASA through Fermi Guest Investigator grants NNH12ZDA001N and NNH13ZDA001N-FERMI. This research has made use of NASA’s Astrophysics Data System. YTT is supported by Kakenhi 15K17652.en_US
dc.description.urihttps://academic.oup.com/pasj/article/68/4/51/2223141en_US
dc.format.extent10 pagesen_US
dc.genrejournal articles preprintsen_US
dc.identifierdoi:10.13016/m2xjke-gg15
dc.identifier.citationYasuyuki T. Tanaka, Josefa Becerra Gonzalez, Ryosuke Itoh, Justin D. Finke, Yoshiyuki Inoue, Roopesh Ojha, Bryce Carpenter, Elina Lindfors, Felicia Krauß, Rachele Desiante, Kensei Shiki, Yasushi Fukazawa, Francesco Longo, Julie E. McEnery, Sara Buson, Kari Nilsson, Vandad Fallah Ramazani, Riho Reinthal, Leo Takalo, Tapio Pursimo, Walter Boschin, A significant hardening and rising shape detected in the MeV/GeV νFν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February, Publications of the Astronomical Society of Japan, Volume 68, Issue 4, August 2016, 51, https://doi.org/10.1093/pasj/psw049en_US
dc.identifier.urihttps://doi.org/10.1093/pasj/psw049
dc.identifier.urihttp://hdl.handle.net/11603/17703
dc.identifier.urihttp://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2016PASJ...68...51T
dc.identifier.urihttps://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Search&refcode=2016PASJ...68...51T
dc.language.isoen_USen_US
dc.publisherPublications of the Astronomical Society of Japan (PASJ)en_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Physics Department Collection
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
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dc.titleA significant hardening and rising shape detected in the MeV/GeV νFᵥ spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 Februaryen_US
dc.typeTexten_US

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