The nature of the X-ray transient MAXI J0556-332
arXiv:1111.6946 · doi:10.1111/j.1365-2966.2011.20274.x
Abstract
Phase-resolved spectroscopy of the newly discovered X-ray transient MAXI J0556-332 has revealed the presence of narrow emission lines in the Bowen region that most likely arise on the surface of the mass donor star in this low mass X-ray binary. A period search of the radial velocities of these lines provides two candidate orbital periods (16.43+/-0.12 and 9.754+/-0.048 hrs), which differ from any potential X-ray periods reported. Assuming that MAXI J0556-332 is a relatively high inclination system that harbors a precessing accretion disk in order to explain its X-ray properties, it is only possible to obtain a consistent set of system parameters for the longer period. These assumptions imply a mass ratio of q~0.45, a radial velocity semi-amplitude of the secondary of K_2~190 km/s and a compact object mass of the order of the canonical neutron star mass, making a black hole nature for MAXI J0556-332 unlikely. We also report the presence of strong N III emission lines in the spectrum, thereby inferring a high N/O abundance. Finally we note that the strength of all emission lines shows a continuing decay over the ~1 month of our observations.
8 pages, 6 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society
References in corpus (4)
- Variations in the dip properties of the low-mass X-ray binary XB 1254-69 observed with XMM-Newton and INTEGRAL
- An anti-correlation between X-ray luminosity and H-alpha equivalent width in X-ray binaries
- A detection of the donor star of Aquila X-1 during its 2004 outburst?
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- Thermal evolution and quiescent emission of transiently accreting neutron stars
- Black Holes in Short Period X-ray Binaries and the Transition to Radiatively Inefficient Accretion
- Constraints on Bygone Nucleosynthesis of Accreting Neutron Stars
- Spectral Evolution of a New X-ray Transient MAXI J0556-332 Observed by MAXI, Swift, and RXTE
- The relation between outburst rate and orbital period in low-mass X-ray binary transients