Modeling TeV γ-rays from LS 5039: an active OB star at the extreme

Perhaps the most extreme examples of "Active OB stars" are the subset of high-mass X-ray binaries - consisting of an OB star plus compact companion - that have recently been observed by Fermi and ground-based Cerenkov telescopes like HESS to be sources of very high energy (VHE; up to 30 Te...

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Autores principales: Owocki, Stan P., Okazaki, Atsuo T., Romero, Gustavo Esteban
Formato: Articulo Preprint
Lenguaje:Inglés
Publicado: 2010
Materias:
Ciencias Exactas
Active OB stars
Radiación
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/84061
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-84061
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Exactas
Active OB stars
Radiación
spellingShingle Ciencias Exactas
Active OB stars
Radiación
Owocki, Stan P.
Okazaki, Atsuo T.
Romero, Gustavo Esteban
Modeling TeV γ-rays from LS 5039: an active OB star at the extreme
topic_facet Ciencias Exactas
Active OB stars
Radiación
description Perhaps the most extreme examples of "Active OB stars" are the subset of high-mass X-ray binaries - consisting of an OB star plus compact companion - that have recently been observed by Fermi and ground-based Cerenkov telescopes like HESS to be sources of very high energy (VHE; up to 30 TeV!) γ-rays. This paper focuses on the prominent γ-ray source, LS5039, which consists of a massive O6.5V star in a 3.9-day-period, mildly elliptical (e ≈ 0.24) orbit with its companion, assumed here to be a black-hole or unmagnetized neutron star. Using 3-D SPH simulations of the Bondi-Hoyle accretion of the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows very closely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model, wherein intrinsic emission of γ-rays is assumed to track this accretion rate, reproduces quite well Fermi observations of the phase variation of γ-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by the HESS Cerenkov telescope, it is important to account also for photon-photon interactions between the γ-rays and the stellar optical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included, we find that this simple BHL accretion model also quite thus making it a strong alternative to the pulsar-wind-shock models commonly invoked to explain such VHE γ-ray emission in massive-star binaries.
format Articulo
Preprint
author Owocki, Stan P.
Okazaki, Atsuo T.
Romero, Gustavo Esteban
author_facet Owocki, Stan P.
Okazaki, Atsuo T.
Romero, Gustavo Esteban
author_sort Owocki, Stan P.
title Modeling TeV γ-rays from LS 5039: an active OB star at the extreme
title_short Modeling TeV γ-rays from LS 5039: an active OB star at the extreme
title_full Modeling TeV γ-rays from LS 5039: an active OB star at the extreme
title_fullStr Modeling TeV γ-rays from LS 5039: an active OB star at the extreme
title_full_unstemmed Modeling TeV γ-rays from LS 5039: an active OB star at the extreme
title_sort modeling tev γ-rays from ls 5039: an active ob star at the extreme
publishDate 2010
url http://sedici.unlp.edu.ar/handle/10915/84061
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AT romerogustavoesteban modelingtevgraysfromls5039anactiveobstarattheextreme
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