Photometric variability of the LAMOST sample of magnetic chemically peculiar stars as seen by TESS^★

¹ LESIA, Paris Observatory, PSL University, CNRS, Sorbonne University, Université Paris-Cité, 5 place Jules Janssen, 92195 Meudon, France
e-mail: jonathan.bartz@obspm.fr
² Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, SP, Brazil
³ Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019, USA
⁴ Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V. (BAV), Berlin, Germany
⁵ American Association of Variable Star Observers (AAVSO), Cambridge, USA
⁶ Faculty of Science, Masaryk University, Department of Theoretical Physics and Astrophysics, Kotlářská 2, 611 37 Brno, Czech Republic
⁷ Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716, USA

Received: 14 April 2023
Accepted: 28 May 2023

Abstract

Context. High-quality light curves from space-based missions have opened up a new window on the rotational and pulsational properties of magnetic chemically peculiar (mCP) stars and have fuelled asteroseismic studies. They allow the internal effects of surface magnetic fields to be probed and numerous astrophysical parameters to be derived with great precision.

Aims. We present an investigation of the photometric variability of a sample of 1002 mCP stars discovered in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) archival spectra with the aims of measuring their rotational periods and identifying interesting objects for follow-up studies.

Methods. Transiting Exoplanet Survey Satellite (TESS) data were available for 782 mCP stars and were analysed using a Fourier two-term frequency fit to determine the stars’ rotational periods. The rotational signal was then subtracted from the light curve to identify additional non-rotational variability signals. A careful pixel-level blending analysis was performed to check whether the variability originates in the target star or a nearby blended neighbour. We investigated correlations between the observed rotational periods, fractional age on the main sequence, mass, and several other observables.

Results. We present rotational periods and period estimates for 720 mCP stars. In addition, we have identified four eclipsing binary systems that likely host an mCP star, as well as 25 stars with additional signals consistent with pulsation (12 stars with frequencies above 10 day⁻¹ and 13 stars with frequencies below 10 day⁻¹). We find that more evolved stars have longer rotation periods, which is in agreement with the assumption of the conservation of angular momentum during the main-sequence evolution.

Conclusions. With our work, we increase the sample size of mCP stars with known rotation periods and identify prime candidates for detailed follow-up studies. This enables two paths towards future investigations: population studies of even larger samples of mCP stars and the detailed characterisation of high-value targets.