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Fermi/lat observations of LS 5039
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2009 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 706, no 1, L56-L61 p.Article in journal (Refereed) Published
Abstract [en]

The first results from observations of the high-mass X-ray binary LS 5039 using the Fermi Gamma-ray Space Telescope data between 2008 August and 2009 June are presented. Our results indicate variability that is consistent with the binary period, with the emission being modulated with a period of 3.903 +/- 0.005 days; the first detection of this modulation at GeV energies. The light curve is characterized by a broad peak around superior conjunction in agreement with inverse Compton scattering models. The spectrum is represented by a power law with an exponential cutoff, yielding an overall flux ( 100 MeV-300 GeV) of 4.9 +/- 0.5(stat) +/- 1.8(syst) x 10(-7) photon cm(-2) s(-1), with a cutoff at 2.1 +/- 0.3(stat) +/- 1.1(syst) GeV and photon index G = 1.9 +/- 0.1(stat) +/- 0.3(syst). The spectrum is observed to vary with orbital phase, specifically between inferior and superior conjunction. We suggest that the presence of a cutoff in the spectrum may be indicative of magnetospheric emission similar to the emission seen in many pulsars by Fermi.

Place, publisher, year, edition, pages
2009. Vol. 706, no 1, L56-L61 p.
Keyword [en]
binaries: close, gamma rays: observations, stars: variables: other, X-rays: binaries, X-rays: individual (LS 5039)
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-31952DOI: 10.1088/0004-637X/706/1/L56ISI: 000271533200012ScopusID: 2-s2.0-77949528567OAI: diva2:407493
Knut and Alice Wallenberg FoundationSwedish Research Council

QC 20110330

Available from: 2011-03-30 Created: 2011-03-30 Last updated: 2016-04-21Bibliographically approved

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Axelsson, M.Ryde, FelixYlinen, Tomi
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