The unexpected optical and ultraviolet variability of the standard star $\alpha$ Sex (HD 87887)

Abstract

The analysis of the available TESS light curves of $\alpha$ Sex (HD 87887) reveals low-frequency pulsations with a period of about 9.1 hours in this spectroscopic A0 III standard star. The IUE observations in December 1992 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 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${}_{\odot }$ 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 barium mildly overabundant. Identification is provided for most of the lines absorbing more than 2% in the optical spectrum of $\alpha$ Sex. Stellar evolution modeling shows that $\alpha$ Sex is near the terminal-age main sequence, and its mass, radius and age are estimated to be $M=2.57\pm 0.32$ M${}_{\odot }$, $R=3.07\pm 0.90$ R${}_{\odot }$, $A=385\pm 77$ Myr, respectively.

arXiv commentAccepted for publication in AJ on 14 Jun 2023; 9 pages and 11-page appendix

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