The triple system HIP96515: a low-mass eclipsing binary with a DB white dwarf companion

Abstract

HIP96515A is a double-lined spectroscopic binary with a visual companion (HIP96515B) at 8.6 arcsec. It is included in the SACY catalog as a potential young star and classified as an eclipsing binary in the ASAS Catalog. We have analyzed spectroscopic and photometric observations of the triple system. The high-resolution optical spectrum of HIP96515A has been used to derive a mass ratio, M_2/M_1, close to 0.9, with the SB2 components showing spectral types of M1 and M2. The ASAS and Hipparcos light-curves of HIP96515A show periodic variations with P=2.3456 days, confirming that HIP96515A is an eclipsing binary with preliminary parameters of i=89, M_Aa=0.59+-0.03 Msun and M_Ab=0.54+-0.03 Msun, for the primary and secondary, respectively, at an estimated distance of 42+-3 pc. This is a new eclipsing binary with component masses below 0.6 Msun. Multi-epoch observations of HIP 96515 A&B show that the system is a common proper motion pair. The optical spectrum of HIP 96515B is consistent with a pure helium atmosphere (DB) white dwarf. We estimate a total age (main-sequence lifetime plus cooling age) of 400 Myr for the white dwarf. If HIP 96515 A&B are coeval, and assuming a common age of 400 Myr, the comparison of the masses of the eclipsing binary members with evolutionary tracks shows that they are underestimated by ~15% and ~10%, for the primary and secondary, respectively.

Accepted for publication in A&A, 9 pages, 9 figures

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