V1097 Her - A W-Type Overcontact Eclipsing Binary
R. Nelson, Robb Roussell · Information Bulletin on Variable Stars · 2020
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±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 ± 0.01 and 1.11 ± 0.02 M⊙ and luminosities of 0.77 ± 0.01 and 1.75 ± 0.03 L⊙ respectively.The distance estimate of r = 237 ± 11 pc is consistent with the Gaia value of r = 250.3± 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 dP/dt = (1.85 ± 0.11) × 10 -7 d/yr.