V1097 Her - A W-Type Overcontact Eclipsing Binary

Nelson, Robert H. and Russell, Robb (2019) V1097 Her - A W-Type Overcontact Eclipsing Binary. Information Bulletin on Variable Stars, 63 (6270). ISSN 1587-2440

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Abstract

V1097 Her, an overcontact (W-type) eclipsing binary, has a short period, a relatively low degree of contact (or fill-out parameter), and an increasing period. It has now been classified: for the more luminous star a spectral type of F8.5V$\pm$1 has been determined. B,V,Ic light curves and, for the first time, radial velocity curves for the overcontact binary V1097 Her have been obtained; these have been subjected to a Wilson-Devinney analysis, yielding fundamental parameters; in particular masses of $0.41 \pm 0.01$ and $1.11 \pm 0.02$ M$_\odot$ and luminosities of $0.77 \pm 0.01$ and $1.75 \pm 0.03$ L$_\odot$ respectively. The distance estimate of $r = 237 \pm 11$ pc is consistent with the Gaia value of $r = 250.3 \pm 1.4$ pc (Bailer-Jones et al., 2018; Gaia Collaboration, 2018). A period analysis, again believed to be the first ever, has been undertaken, revealing a constant rate of period increase of ${\rm d}P/{\rm d}t = (1.85 \pm 0.11)\times10^{-7}$ d/yr.

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