Fundamental parameters of the massive eclipsing binary HM1 8

Abstract

We present a comprehensive study of the massive binary system HM1~8, based on multi-epoch high resolution spectroscopy, $V$-band photometry and archival X-ray data. Spectra from the OWN Survey, a high resolution optical monitoring of Southern O and WN stars, are used to analyse the spectral morphology and perform quantitative spectroscopic analysis of both stellar components. The primary and secondary components are classified as O4.5~IV(f) and O9.7~V, respectively. From a radial-velocity (RV) study we derived a set of orbital parameters for the system. We found an eccentric orbit ($e=0.14\pm 0.01$) with a period of $P=5.87820\pm 0.00008$~days. Through the simultaneous analysis of the RVs and the $V$-band light curve we derived an orbital inclination of $70.0^{\circ }\pm 2.0$ and stellar masses of $M_a=33.6^{+1.4}_{-1.2}~\text{M}_{\sun}$ for the primary, and $M_b=17.7^{+0.5}_{-0.7}~\text{M}_{\sun}$ for the secondary. The components show projected rotational velocities $v_1\sin i=105\pm 14{\text{km s}}^{-1}$ and $v_2\sin i=82\pm 15{\text{km s}}^{-1}$, respectively. A tidal evolution analysis is also performed and found to be in agreement with the orbital characteristics. Finally, the available X-ray observations show no evidence of a colliding winds region, therefore the X-ray emission is attributed to stellar winds.

15 pages, 15 figures, to be published in MNRAS

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