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arXiv · 0901.4119

Dynamical constraints on the neutron star mass in EXO 0748-676

T. Muñoz-Darias·J. Casares·K. O'Brien·D. Steeghs·I. G. Martinez-Pais·R. Cornelisse·P. A. Charles
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Abstract

We present VLT intermediate resolution spectroscopy of UY Vol, the optical counterpart of the LMXB X-ray burster EXO 0748-676. By using Doppler tomography we detect narrow components within the broad He II 4542 A, 4686 A and 5412 A emission lines. The phase, velocity and narrowness of these lines are consistent with their arising from the irradiated hemisphere of the donor star, as has been observed in a number of LMXBs. Under this assumption we provide the first dynamical constraints on the stellar masses in this system. In particular, we measure K_2>K_em = 300 +/- 10 km/s. Using this value we derive 1 M_sun < M_1 < 2.4 M_sun and 0.11 < q < 0.28. We find M_1 > 1.5 M_sun for the case of a main sequence companion star. Our results are consistent with the presence of a massive neutron star as has been suggested by Ozel (2006), although we cannot discard the canonical value of ~1.4 M_sun.

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T. Muñoz-Darias, J. Casares, K. O'Brien, D. Steeghs, I. G. Martinez-Pais, R. Cornelisse, P. A. Charles. 2009-01-26. Dynamical constraints on the neutron star mass in EXO 0748-676. https://doi.org/10.1111/j.1745-3933.2009.00630.x

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