Magnetic chemically peculiar stars investigated by the Solar Mass Ejection Imager

Abstract

Since the discovery of the spectral peculiarities of their prototype alpha2 Canum Venaticorum in 1897, the so-called ACV variables, which are comprised of several groups of chemically peculiar stars of the upper main sequence, have been the target of numerous photometric and spectroscopic studies. Especially for the brighter ACV variables, continuous observations over about a century are available, which are important to study long-term effects such as period changes or magnetic cycles in these objects. The present work presents an analysis of 165 Ap/CP2 and He-weak/CP4 stars using light curves obtained by the Solar Mass Ejection Imager (SMEI) between the years 2003 and 2011. These data fill an important gap in observations for bright ACV variables between the Hipparcos and TESS satellite missions. Using specifically tailored data treatment and period search approaches, we find variability in the accuracy limit of the employed data in 84 objects. The derived periods are in excellent agreement with the literature; for one star, the here presented solution represents the first published period. We discuss the apparently constant stars and the corresponding level of non-variability. From an investigation of our target star sample in the Hertzsprung-Russell diagram, we deduce ages between 100 Myr and 1 Gyr for the majority of our sample stars. Our results support that the variable CP2/4 stars are in a more advanced evolutionary state and that He and Si peculiarities, preferentially found in the hotter, and thus more massive, CP stars, produce larger spots or spots of higher contrast.

Accepted for publication in MNRAS, 13 pages, 11 figures, 3 tables

References in corpus (15)

• The Transiting Exoplanet Survey Satellite
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Searching for links between magnetic fields and stellar evolution III. Measurement of magnetic fields in open cluster Ap stars with ESPaDOnS
• Chemically peculiar stars and their temperature calibration
• New Photometrically Variable Magnetic Chemically Peculiar Stars in the ASAS-3 Archive
• New and improved rotational periods of magnetic CP stars from ASAS-3, KELT and MASCARA data
• Revisiting the pulsational characteristics of the exoplanet host star $\beta$ Pictoris
• An empirical temperature calibration for the Delta a photometric system. II. The A-type and mid F-type star
• Seismic modelling of early B-type pulsators observed by BRITE: I. $\theta$ Ophiuchi
• Global properties of the light curves of magnetic, chemically peculiar stars as a testbed for the existence of dipole-like symmetry in surface structures
• Statistical analysis of roAp, He-weak and He-rich stars
• Be and Bn stars: Balmer discontinuity and stellar-class relationship
• New BRITE-Constellation observations of the roAp star Alpha Circini
• An Investigation of Four Chemically Peculiar Stars with Photometric Periods below 12 Hours
• A revisit to the enigmatic variable star 21 Comae

Cited by in corpus (6)

• Analysis of photometric and spectroscopic variability of red supergiant Betelgeuse
• Surface structure of 45 Hercules: An otherwise unremarkable Ap star with a surprisingly weak magnetic field
• Magnetic field topology, chemical spot distributions and photometric variability of the Ap star phi Draconis
• The Great Dimming of Betelgeuse: the photosphere as revealed by tomography over the past 15 years
• A new sample of super-slowly rotating Ap (ssrAp) stars from the Zwicky Transient Facility survey
• Chemically peculiar stars on the pre-main sequence