Photospheric and chromospheric activity of the short period X-ray and Algol eclipsing binary UX CrB

Abstract

We present six $\mbox{V}R_{c}I_{c}$ light curves of UX CrB from observations carried out from 2011–2015. We also obtained three optical spectra using the 2.16-m optical telescope and LAMOST survey at the national astronomical observatories. We classified its spectral type as $\mbox{G2}\pm\mbox{2V}$ . We noticed that there are strong absorptions in the Hα, Hβ, Ca ii H&K and infrared triplet lines in the observed spectra. By subtracting away the photospheric contribution, we also noticed that there are small excess emissions in these chromospheric active lines, which indicate there are weak chromospheric activities. We tried and obtained four photometric solutions with different spot positions from our full and high time-resolution light curves in 2012, using the updated Wilson-Devinney code. The model with two spots on the primary produced the best result for explaining the observed light curves from 2012. Moreover, we explained all other light curves based on our photometric solution using our 2012 light curves. There are two active longitudes at about 68∘ and 255∘. We noticed that the starspots have both long-time (years) and short-time (about two months) variation by analyzing the light curves and its starspot parameters. There is also an obvious oscillation of light curve maximum between 0.25 and 0.75 phases by analyzing the values of $\mbox{Max.~I} - \mbox{Max.~II}$ . We conclude UX CrB are the evolved main-sequence stars with strong photometric and chromospheric activities.