Optical spectroscopy of the quiescent counterpart to EXO 0748-676 - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




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Abstract: We present phase resolved optical spectroscopy and X-ray timing of theneutron star X-ray binary EXO 0748-676 after the source returned to quiescencein the fall of 2008. The X-ray light curve displays eclipses consistent inorbital period, orbital phase and duration with the predictions andmeasurements before the return to quiescence. Halpha and He I emission linesare present in the optical spectra and show the signature of the orbit of thebinary companion, placing a lower limit on the radial velocity semi-amplitudeof K2>405 km-s. Both the flux in the continuum and the emission lines showorbital modulations, indicating that we observe the hemisphere of the binarycompanion that is being irradiated by the neutron star. Effects due to thisirradiation preclude a direct measurement of the radial velocity semi-amplitudeof the binary companion; in fact no stellar absorption lines are seen in thespectrum. Nevertheless, our observations place a stringent lower limit on theneutron star mass of M1>1.27 Msun. For the canonical neutron star mass ofM1=1.4 Msun, the mass ratio is constrained to 0.075


Autor: C.G. Bassa SRON, Imapp, P.G. Jonker SRON, Cfa, D. Steeghs Warwick, Cfa, M.A.P. Torres CfA

Fuente: https://arxiv.org/



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