Résumé
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) ×10-7 photon cm-2 s-1, with a cutoff at 2.1 ± 0.3(stat) 1.1(syst) GeV and photon index Γ = 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.
| langue originale | Anglais |
|---|---|
| Pages (de - à) | L56-L61 |
| journal | Astrophysical Journal |
| Volume | 706 |
| Numéro de publication | 1 PART 2 |
| Les DOIs | |
| état | Publié - 1 janv. 2009 |
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