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Probing the stellar wind geometry in Vela X-1 with infrared interferometry

Published online by Cambridge University Press:  21 February 2013

Élodie Choquet*
Affiliation:
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, PSL, Meudon, France
Pierre Kervella
Affiliation:
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, PSL, Meudon, France
Jean-Baptiste Le Bouquin
Affiliation:
UJF-Grenoble 1/CNRS-INSU, IPAG, UMR 5274, Grenoble, France
Antoine Mérand
Affiliation:
European Southern Observatory, Santiago, Chile
Xavier Haubois
Affiliation:
Instituto de Astronomia, Geofìsica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil
Jean-Philippe Berger
Affiliation:
European Southern Observatory, Santiago, Chile
Guy Perrin
Affiliation:
LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, PSL, Meudon, France
Pierre-Olivier Petrucci
Affiliation:
UJF-Grenoble 1/CNRS-INSU, IPAG, UMR 5274, Grenoble, France
Bernard Lazareff
Affiliation:
UJF-Grenoble 1/CNRS-INSU, IPAG, UMR 5274, Grenoble, France
Rafael Millan-Gabet
Affiliation:
California Institute of Technology, NASA Exoplanet Science Institute, Pasadena, USA
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Abstract

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High-mass X-ray Binaries (HMXBs) are keys to study stellar remnants that are otherwise extremely faint and difficult to observe when isolated. Vela X-1 is a well-known eclipsing HMXB composed of a very massive neutron star orbiting a B0.5I supergiant with a period of 9 days. The supergiant wind is the main feeding material for the accreting neutron star, and its properties are of prime interest to understand the physics at stakes in the accretion process.

In order to characterize the geometry and physical properties of the dense wind at a scale of a few stellar radii, we obtained infrared interferometric observations of Vela X-1 in 2010 using the VLTI/AMBER instrument in the K band (2.2 μm), and in 2012 using the VLTI/PIONIER instrument in the H band (1.6 μm).

Although the apparent disk of the supergiant and the orbital separation of the two objects are beyond the present resolution limit of the VLTI, the K-band observations partially resolve the wind envelope on the two longest baselines. We were able to measure the radius of 265±82 R for the circumstellar wind at a temperature of 1300 K, assuming a distance of 1.9 kpc. The H-band observations do not resolve the system, and we were able to set an upper limit of 112 R for the envelope radius at a temperature of 1800 K.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2013

References

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