Photometric and spectroscopic variability of the Be star 48 Lib: The relation between photometric variations and rotation

Abstract

The purpose of this paper is to determine the origin of the photometric variations of 48 Lib using the data from the STEREO and to investigate their relations with the disk structure. The photometric data comprise a period of five years from 2007 to 2011. The spectroscopic data covering the same time interval are provided from the BeSS database. The Hα lines are examined by measuring their equivalent widths and line intensities. Hα variations are then compared with those displayed by the photometric data. From the photometry, high-precision results (10−5 c d−1 in frequency and 10−4 mag in amplitude) are obtained. It is detected that the star has shown 24 frequencies, mainly clustered around the peaks at 2.48896(1) and 5.08150(2) c d−1. The analysis reveals that the photometric frequencies are not due to pulsation, but caused by the rotation, and that the remaining frequencies arise from transient activities on or just above the photosphere. Also, it is shown that the spectroscopic data exhibit a significant Hα variability, and that the Hα line variation depends on the variation of frequency and amplitude, something which has been often proposed in the literature but has never before been demonstrated observationally. This proves that the disk structure and photometric variations are related.

TESS observations of Be stars: a new interpretation

“…There are several examples from CoRoT as well (Neiner et al 2009;Semaan et al 2018). The same is found in 48 Lib observed by the STEREO satellite (Ozuyar et al 2018) as do two of the three Be stars observed by Kepler (Rivinius et al 2016b). These frequency groups have been interpreted as due to a large number of g-modes driven by the κ opacity mechanism.…”

Newly Discovered Period Changes in Two mCP Stars and Updates for Previously Published Stars

“…Recently, Ozuyar et al (2018) (hereafter designated as OSS), report that they found a period increase of 660 ms yr −1 for CS Vir based on data from the Solar Terrestrial Relations Observatory (STEREO) satellite from 2007-2011 compared with previously published photometric and spectral data. We obtained FCAPT uvby data for CS Vir from 1990-2007 (Table 1, Table A2) which have not yet been published.…”