A case study of ACV variables discovered in the Zwicky Transient Facility survey

Abstract

Magnetic chemically peculiar (mCP) stars exhibit complex atmospheres that allow the investigation of the interplay of atomic diffusion, magnetic fields, and stellar rotation. A non-uniform surface distribution of chemical elements and the non-alignment of the rotational and magnetic axes result in the variability of several observables. Photometrically variable mCP stars are referred to as alpha2 Canum Venaticorum (ACV) variables. The present work presents a case study of known variables from the Zwicky Transient Facility (ZTF) survey, with the aim of investigating the survey's suitability for the detection and study of new ACV variables. Using suitable selection criteria based on the known characteristics of ACV variables, candidate ACV stars were selected from the ZTF Catalog of Periodic Variable Stars. All light curves were inspected in detail to select the most promising candidates. Where available, low-resolution spectra from the LAMOST were employed to classify the stars on the MK system and confirm their status as mCP stars. We have identified 86 new promising ACV star candidates. 15 of these stars have LAMOST spectra available, which, in all cases, confirm them as classical mCP stars, which highlights the viability of our approach. The sample stars can be sorted into four subgroups characterized by distinct light curve shapes. Anti-phase variations in different photometric passbands, in particular, is a unique characteristic of a subset of ACV stars readily usable for their identification. The availability of data in three different passbands (g, r, and i) is a major advantage of the ZTF survey. On the basis of our experience with other photometric surveys and the analysis of light curves, we conclude that the ZTF is well suited for the search for, and the analysis of, ACV variables, which, however, are not considered in the available ZTF variable star catalogues.

17 pages, 8 figures, 2 tables, accepted for Astronomy & Astrophysics

References in corpus (25)

• The Zwicky Transient Facility: System Overview, Performance, and First Results
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• Improving PARSEC models for very low mass stars
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Painting a portrait of the Galactic disc with its stellar clusters
• Updated parameters of 1743 open clusters based on Gaia DR2
• The Zwicky Transient Facility Catalog of Periodic Variable Stars
• A catalog of newly identified star clusters in GAIA DR2
• Chemically peculiar stars and their temperature calibration
• MOBSTER - II. Identification of rotationally variable A stars observed with \emph{TESS} in Sectors 1 to 4
• Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2
• Pulsation versus metallicism in Am stars as revealed by LAMOST and WASP
• TESS survey of rotational and pulsational variability of mercury-manganese stars
• Spots on Am stars
• 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
• Metallic-Line Stars Identified from Low Resolution Spectra of LAMOST DR5
• An empirical temperature calibration for the Delta a photometric system. II. The A-type and mid F-type star
• Global properties of the light curves of magnetic, chemically peculiar stars as a testbed for the existence of dipole-like symmetry in surface structures
• HD 99458: First time ever Ap-type star as a $\delta$ Scuti pulsator in a short period eclipsing binary?
• White dwarf-open cluster associations based on Gaia DR2
• HD 240121 - an ACV variable showing anti-phase variations of the B and V light curves
• The nature of the light variability of magnetic Of?p star HD 191612
• New BRITE-Constellation observations of the roAp star Alpha Circini