OPTICAL SPECTROSCOPY OF THE HIGH-MASS γ-RAY BINARY 1FGL J1018.6−5856: A PROBABLE NEUTRON STAR PRIMARY

Journal Article · Tue Nov 10 00:00:00 EST 2015 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/813/2/L26· OSTI ID:22518708

Strader, Jay; Chomiuk, Laura; Peacock, Mark ^[1]; Cheung, C. C. ^[2]; Salinas, Ricardo ^[3]

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1. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
2. Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)
3. Gemini Observatory, Casilla 603, La Serena (Chile)

We present medium-resolution optical spectroscopy with the SOAR telescope of the O star secondary of the high-mass γ-ray binary 1FGL J1018.6–5856 to help determine whether the primary is a neutron star or black hole. We find that the secondary has a low radial velocity semi-amplitude of 11–12 km s{sup −1}, with consistent values obtained for H and He absorption lines. This low value strongly favors a neutron star primary: while a black hole cannot be excluded if the system is close to face on, such inclinations are disallowed by the observed rotation of the secondary. We also find the high-energy (X-ray and γ-ray) flux maxima occur when the star is behind the compact object along our line of sight, inconsistent with a simple model of anisotropic inverse Compton scattering for the γ-ray photons.

• OSTI ID: 22518708
• Journal Information: Astrophysical Journal Letters, Vol. 813, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION SPECTROSCOPY
AMPLITUDES
ANISOTROPY
BLACK HOLES
COMPTON EFFECT
COSMIC PHOTONS
COSMIC RAY FLUX
EMISSION SPECTROSCOPY
GAMMA RADIATION
INCLINATION
MASS
NEUTRON STARS
PULSARS
RADIAL VELOCITY
ROTATION
TELESCOPES
X RADIATION