paper

Physical Properties of 29 sdB+dM Eclipsing Binaries in Zwicky Transient Facility

arXiv:2201.03721 · doi:10.1088/1674-4527/ac49e5

Abstract

The development of large-scale time-domain surveys provides an opportunity to study the physical properties as well as the evolutionary scenario of B-type subdwarfs (sdB) and M-type dwarfs (dM). Here, we obtained 33 sdB+dM eclipsing binaries based on the Zwicky Transient Facility (ZTF) light curves and $G aia$ early data release 3 (EDR3) parallaxes. By using the PHOEBE code for light curve analysis, we obtain probability distributions for parameters of 29 sdB+dM. $R_{1}$ , $R_{2}$ , and $i$ are well determined, and the average uncertainty of mass ratio $q$ is 0.08. Our parameters are in good agreement with previous works if a typical mass of sdB is assumed. Based on parameters of 29 sdB+dM, we find that both the mass ratio $q$ and the companion's radius $R_{2}$ decrease with the shortening of the orbital period. For the three sdB+dMs with orbital periods less than 0.075 days, their companions are all brown dwarfs. The masses and radii of the companions satisfy the mass--radius relation for low-mass stars and brown dwarfs. Companions with radii between $0.12 R_{⊙}$ and $0.15 R_{⊙}$ seem to be missing in the observations. As more short-period sdB+dM eclipsing binaries are discovered and classified in the future with ZTF and $G aia$ , we will have more information to constrain the evolutionary ending of sdB+dM.

16 pages, 10 figures, 5 tables, 2 appendices (14 pages, 27 figures), accepted for publication in Research in Astronomy and Astrophysics