Gamma-ray follow-up studies on η Carinae

Reitberger, K.; Reimer, O.; Reimer, A.; Werner, M.; Egberts, K.; Takahashi, H.

doi:10.1051/0004-6361/201219249

Gamma-ray follow-up studies on η Carinae

Journal Article · Wed Aug 01 00:00:00 EDT 2012 · Astronomy and Astrophysics

DOI:https://doi.org/10.1051/0004-6361/201219249· OSTI ID:1356685

Reitberger, K. ^[1]; Reimer, O. ^[2]; Reimer, A. ^[2]; Werner, M. ^[1]; Egberts, K. ^[1]; Takahashi, H. ^[3]

Leopold Franzens Univ. Innsbruck (Austria). Inst. of Astrophysics and Particle Physics and Inst. for Theoretical Physics
Leopold Franzens Univ. Innsbruck (Austria). Inst. of Astrophysics and Particle Physics and Inst. for Theoretical Physics; Stanford Univ. and SLAC National Accelerator Lab., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology
Hiroshima Univ. (Japan). Hiroshima Astrophysical Science Center

Observations of high-energy γ-rays recently revealed a persistent source in spatial coincidence with the binary system η Carinae. Since modulation of the observed γ-ray flux on orbital time scales has not been reported so far, an unambiguous identification was hitherto not possible. In particular, the observations made by the Fermi Large Area Telescope (LAT) posed additional questions regarding the actual emission scenario. Analyses show two energetically distinct components in the γ-ray spectrum, which are best described by an exponentially cutoff power-law function (CPL) at energies below 10 GeV and a power-law (PL) component dominant at higher energies. The increased exposure in conjunction with the improved instrumental response functions of the LAT now allow us to perform a more detailed investigation of location, spectral shape, and flux time history of the observed γ-ray emission. Furthermore, we detect a weak but regular flux decrease over time. This can be understood and interpreted in a colliding-wind binary scenario for orbital modulation of the γ-ray emission. We find that the spectral shape of the γ-ray signal agrees with a single emitting particle population in combination with significant absorption by γ-γ pair production. We are able to report on the first unambiguous detection of GeV γ-ray emission from a colliding-wind massive star binary. By studying the correlation of the flux decrease with the orbital separation of the binary components allows us to predict the behaviour up to the next periastron passage in 2014.

View Accepted Manuscript (DOE)

Research Organization:: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: Fermi LAT Collaboration

Grant/Contract Number:: AC02-76SF00515

OSTI ID:: 1356685

Journal Information:: Astronomy and Astrophysics, Journal Name: Astronomy and Astrophysics Vol. 544; ISSN 0004-6361

Publisher:: EDP SciencesCopyright Statement

Country of Publication:: United States

Language:: English

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