BRITE photometry and STELLA spectroscopy of bright stars in Auriga: Rotation, pulsation, orbits, and eclipses

Abstract

Continuous photometry with up to three BRITE satellites was obtained for 12 targets and subjected to a period search. Contemporaneous high-resolution optical spectroscopy with STELLA was used to obtain radial velocities through cross correlation with template spectra as well as to determine astrophysical parameters through a comparison with model spectra. The Capella red light curve was found to be constant over 176 days with a root mean square of 1 mmag, but the blue light curve showed a period of 10.1$\pm$0.6 d, which we interpret to be the rotation period of the G0 component. The BRITE light curve of the F0 supergiant $\epsilon$Aur suggests 152 d as its main pulsation period, while the STELLA radial velocities reveal a clear 68 d period. An ingress of an eclipse of the $\zeta$Aur binary system was covered with BRITE and a precise timing for its eclipse onset derived. $\eta$Aur is identified as a slowly pulsating B (SPB) star with a main period of 1.29 d and is among the brightest SPB stars discovered so far. The rotation period of the magnetic Ap star $\theta$Aur is detected from photometry and spectroscopy with a period of 3.6189 d and 3.6177 d, respectively, likely the same within the errors. Photometric rotation periods are also confirmed for the magnetic Ap star $\tau$Aur of 2.463 d and for the solar-type star ${\kappa }^1$Cet of 9.065 d, and also for the B7 HgMn giant $\beta$Tau of 2.74 d. Revised orbital solutions are derived for the eclipsing SB2 binary $\beta$Aur, for the 27 year eclipsing SB1 $\epsilon$Aur, and for the RS CVn binary HR 1099. The two stars $\nu$ Aur and $\iota$Aur are found to be long-term, low-amplitude RV and brightness variables, but provisional orbital elements based on a period of 20 yr and an eccentricity of 0.7 could only be extracted for $\nu$Aur. The variations of $\iota$Aur are due to oscillations with a period of $\approx$4 yr.

References in corpus (12)

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• Time-lapse Very Long Baseline Interferometry Imaging of the Close Active Binary HR 1099
• XRISM view of a stellar flare: High-resolution Fe K spectra of HR 1099, an RS CVn-type star
• Further Investigation on Chromospheric Activity Patterns of the RS Canum Venaticorum Star V711 Tauri
• Halo Photometry and Asteroseismology for 98 of the Brightest Stars Observed by TESS
• On the binary orbit of Henry Draper one (HD 1)