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The evolution and masses of the neutron star and donor star in the high mass X-ray binary OAO 1657-415

Mason, A. B.; Clark, J. S.; Norton, A. J.; Crowther, P. A.; Tauris, T. M.; Langer, N.; Negueruela, I. and Roche, P. (2012). The evolution and masses of the neutron star and donor star in the high mass X-ray binary OAO 1657-415. Monthly Notices of the Royal Astronomical Society, 422(1) pp. 199–206.

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We report near-infrared radial velocity measurements of the recently identified donor star in the high mass X-ray binary system OAO 1657-415 obtained in the H band using ISAAC on the VLT.

Cross-correlation methods were employed to construct a radial velocity curve with a semi-amplitude of 22.1 ± 3.5 km s-1. Combined with other measured parameters of this system this provides a dynamically determined neutron star mass of 1.42 ± 0.26 M and a mass of 14.3 ± 0.8 M for the Ofpe/WN9 highly evolved donor star.

OAO 1657-415 is an eclipsing High Mass X-ray binary pulsar with the largest eccentricity and orbital period of any within its class. Of the ten known eclipsing X-ray binary pulsars OAO 1657-415 becomes the ninth with a dynamically determined neutron star mass solution and only the second in an eccentric system. Furthermore, the donor star in OAO 1657-415 is much more highly evolved than the majority of the supergiant donors in other High Mass X-ray binaries (HMXBs), joining a small but growing list of HMXBs donors with extensive hydrogen depleted atmospheres.

Considering the evolutionary development of OAO 1657-415, we have estimated the binding energy of the envelope of the mass donor and find that there is insufficient energy for the removal of the donor's envelope via spiral-in, ruling out a Common Envelope evolutionary scenario. With its non-zero eccentricity and relatively large orbital period the identification of a definitive evolutionary pathway for OAO1657-415 remains problematic, we conclude by proposing two scenarios which may account for OAO1657-415 current orbital configuration.

Item Type: Journal Article
Copyright Holders: 2012 The Authors
ISSN: 1365-2966
Keywords: eclipsing binaries; binaries; OAO 1657−415; Wolf–Rayet; X-ray binaries
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 32338
Depositing User: Andrew Norton
Date Deposited: 03 Feb 2012 09:29
Last Modified: 23 Feb 2016 21:16
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