LAMOST J064137.77+045743.8: A New Binary of an A7-type Pulsating Subgiant and an M-type Red Dwarf

Abstract

With the progressive release of data from numerous sky surveys, humanity has entered the era of astronomical big data. Multi-wavelength, multi-method research is playing an increasingly crucial role. Binaries account for a substantial fraction of all stellar systems and research into binaries is of fundamental importance. LAMOST J064137.77+045743.8 has not yet been recorded in the SIMBAD astronomical database. We conducted a comprehensive analysis of LAMOST J064137.77+045743.8 using multi-band spectroscopic, astrometric, and photometric data. The low-resolution spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) suggest that LAMOST J064137.77+045743.8 is a binary consisting of an A7-type subgiant star ($T_{\rm eff}$ $\sim$ 7500\,K and log\,$g$ $\sim$ 3.9) and a cool red dwarf star. Astrometric data from Globe Astrometric Interferometers for Astrophysics support the binary speculation with a Renormalized Unit Weight Error metric value of 1.9. Additional flux observations in the infrared bands further corroborate the presence of a red dwarf companion. The i-band flare detected by the Zwicky Transient Facility (ZTF) photometric observations bolsters the interpretation of an M-type red dwarf companion. The radial velocity variations in the H$\alpha$ lines from LAMOST medium-resolution spectra and the light curves from ZTF both support the classification of the A7 subgiant as a pulsating star. The binary either has a long orbital period, a non-eclipsing binary orbit, or extremely shallow eclipses. Future asteroseismology studies will further probe the internal physics of the A7 subgiants. Research on binaries is incredibly fascinating.