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IGR J19308+0530: Roche lobe overflow on to a compact object from a donor 1.8 times as massive

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Authors
Ratti, E.
van Grunsven, T.
Torres, M.
Jonker, P.
Miller-Jones, James
Hessels, J.
van Winkel, H.
van der Sluys, M.
Nelemans, G.
Date
2013
Type
Journal Article

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Ratti, E. and van Grunsven, T. and Torres, M. and Jonker, P. and Miller-Jones, J. and Hessels, J. and van Winkel, H. et al. 2013. IGR J19308+0530: Roche lobe overflow on to a compact object from a donor 1.8 times as massive. Monthly Notices of the Royal Astronomical Society: Letters. 431 (1): pp. L10-L14.
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Monthly Notices of the Royal Astronomical Society: Letters
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Curtin Institute of Radio Astronomy (Physics)
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters ©: 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Abstract

We present phase-resolved spectroscopy and photometry of the optical counterpart to the X-ray binary IGR J19308+0530. Ellipsoidal modulations in the light curve show that the F-type companion star in the system is Roche lobe filling. The optical spectra are dominated by absorption features from the donor star, with ~10–20 per cent disc contribution to the optical continuum. We measure an orbital period of 14.662 ± 0.001 h, a radial velocity semi-amplitude for the companion star of K2 = 91.4 ± 1.4 km s− 1 and a rotational broadening of v sin i = 108.9 ± 0.6 km s− 1. From K2 and v sin i, given that the donor star is filling its Roche lobe, we derive a mass ratio of q = M2/M1 = 1.78 ± 0.04, which is typically considered to be too large for stable Roche lobe overflow. Our observations support an inclination of ~50°. The accretor in IGR J19308+0530 is most likely a white dwarf, although a neutron star cannot entirely be excluded.