The Optical Counterpart of the X-ray Transient
RX J0117.6-7330: Spectroscopy and Photometry

Roberto Soria, PASA, 16 (2), in press.
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Conclusions

We have presented spectroscopic and photometric observations of the optical counterpart of the X-ray transient RX J0117.6-7330 in the Small Magellanic Cloud, currently in an inactive state, as inferred from the All Sky Monitor 2-12 keV lightcurve. The data allow us to identify the primary star as a B0.5IIIe star, of mass

$M_* = (18 \pm 2) M_{\odot}$, radius

$R_* = (10 \pm 3) R_{\odot}$, effective temperature

$T_{\mbox{{\footnotesize eff}}} = (2.75 \pm 0.20)\times 10^4$ K and bolometric magnitude

$M_{\mbox{{\footnotesize bol}}} = (-7.4 \pm 0.2)$ mag. We have derived an inclination angle of the binary system

$i = (21 \pm 3)\deg$ and an average projected radial velocity

$\gamma = (184 \pm 4)$ km ${\rm s}^{-1}$; we have also measured the equivalent widths of the main optical lines. Further observations at different orbital phases are necessary to determine the binary period and the mass function of the compact object. Comparison between this set of data and observations taken during an X-ray active state (phase of enhanced mass loss from the Be star) may be useful to determine the orbital parameters of the binary systems and to improve the current models of mass transfer in HMXBs.

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