The Unexpected Optical and Ultraviolet Variability of the Standard Star α Sex (HD 87887)

Abstract

The analysis of the available Transiting Exoplanet Survey Satellite (TESS) light curves of α Sex (HD 87887) reveals low-frequency pulsations with a period of about 9.1 hr in this spectroscopic A0 III standard star. The IUE observations in 1992 December reveal large flux variations both in the far-UV and in the mid-UV, which are accompanied by variations of the brightness in the V band recorded by the the Fine Error Sensor on board IUE. The ultraviolet variability could be due to an eclipse by an hitherto undetected companion of smaller radius, possibly 2.5 R _⊙ , but this needs confirmation by further monitoring possibly with TESS. An abundance determination yields solar abundances for most elements. Only carbon and strontium are underabundant and titanium, vanadium, and baryum mildly overabundant. Identification is provided for most of the lines absorbing more than 2% in the optical spectrum of α Sex. Stellar evolution modeling shows that α Sex is near the terminal-age main sequence, and its mass, radius, and age are estimated to be M = 2.57 ± 0.32 M _⊙ , R = 3.07 ± 0.90 R _⊙ , A = 385 ± 77 Myr, respectively.

Keywords

• A giant stars