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.

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

References in corpus (9)

• The Transiting Exoplanet Survey Satellite
• {\em Gaia}-derived luminosities of {\em Kepler} A/F stars and the pulsator fraction across the δ Scuti instability strip
• Internal mixing of rotating stars inferred from dipole gravity modes
• Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry
• The first view of $\delta$ Scuti and $\gamma$ Doradus stars with the TESS mission
• The role of turbulent pressure as a coherent pulsational driving mechanism: the case of the delta Scuti star HD 187547
• The CubeSpec space mission. I. Asteroseismology of massive stars from time series optical spectroscopy: science requirements and target list prioritisation
• SPInS, a pipeline for massive stellar parameter inference: A public Python tool to age-date, weigh, size up stars, and more
• Pulsating B stars in the Scorpius-Centaurus Association with TESS