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2009 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 707, no 1, 55-60 p.Article in journal (Refereed) Published
Abstract [en]

We report the Fermi Large Area Telescope (LAT) discovery of high-energy (MeV/GeV) gamma-ray emission positionally consistent with the center of the radio galaxy M87, at a source significance of over 10 sigma in 10 months of all-sky survey data. Following the detections of Cen A and Per A, this makes M87 the third radio galaxy seen with the LAT. The faint point-like gamma-ray source has a >100 MeV flux of 2.45 (+/-0.63) x 10(-8) photons cm(-2) s(-1) (photon index = 2.26 +/- 0.13) with no significant variability detected within the LAT observation. This flux is comparable with the previous EGRET upper limit (<2.18 x 10-8 photons cm(-2) s(-1), 2 sigma), thus there is no evidence for a significant MeV/GeV flare on decade timescales. Contemporaneous Chandra and Very Long Baseline Array data indicate low activity in the unresolved X-ray and radio core relative to previous observations, suggesting M87 is in a quiescent overall level over the first year of Fermi-LAT observations. The LAT gamma-ray spectrum is modeled as synchrotron self-Compton (SSC) emission from the electron population producing the radio-to-X-ray emission in the core. The resultant SSC spectrum extrapolates smoothly from the LAT band to the historical-minimum TeV emission. Alternative models for the core and possible contributions from the kiloparsec-scale jet in M87 are considered, and cannot be excluded.

Place, publisher, year, edition, pages
2009. Vol. 707, no 1, 55-60 p.
Keyword [en]
galaxies: active, galaxies: individual (M87), galaxies: jets, gamma, rays: observations, radiation mechanisms: non-thermal, active galactic nuclei, synchrotron-proton blazar, supermassive, black-hole, tev emission, unified schemes, lac objects, source list, egret data, jet, variability
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-18991DOI: 10.1088/0004-637x/707/1/55ISI: 000272162900004ScopusID: 2-s2.0-72849139693OAI: diva2:337038

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2016-04-21Bibliographically approved

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Axelsson, MagnusRyde, FelixConrad, JanYlinen, Tomi
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