Low-mass eclipsing binaries in the WFCAM Transit Survey: the persistence of the M-dwarf radius inflation problem

Author(s)

Cruz, Patricia ^[1] ; Diaz, Marcos ^[1] ; Birkby, Jayne ^[2] ; Barrado, David ^[3] ; Sipocz, Brigitta ^{[4, 5]} ; Hodgkin, Simon ^[5]

Affiliation

^[1] Univ Sao Paulo IAG USP, Inst Astron Geofis & Ciencias Atmosfer, Dept Astron, Rua Matao 1226, BR-05508900 Sao Paulo - Brazil

^[2] Univ Amsterdam, Anton Pannekoek Inst Astron, Sci Pk 904, NL-1098 XH Amsterdam - Netherlands

^[3] Ctr Astrobiol INTA CSIC, Dept Astrofis, ESAC Campus, POB 78, E-28691 Villanueva De La Canada - Spain

^[4] Univ Hertfordshire, Ctr Astrophys Res, Coll Lane, Hatfield AL10 9AB, Herts - England

^[5] Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA - England

• Document type: Journal article
• Source: Monthly Notices of the Royal Astronomical Society; v. 476, n. 4, p. 5253-5267, JUN 2018.
• Web of Science Citations: 9

Abstract

We present the characterization of five new short-period low-mass eclipsing binaries (LMEBs) from the WFCAM Transit Survey. The analysis was performed by using the photometric WFCAM J-mag data and additional low-and intermediate-resolution spectroscopic data to obtain both orbital and physical properties of the studied sample. The light curves and the measured radial velocity curves were modelled simultaneously with the JKTEBOP code, with Markov chain Monte Carlo simulations for the error estimates. The best-model fit have revealed that the investigated detached binaries are in very close orbits, with orbital separations of 2.9 <= a <= 6.7 R-circle dot and short periods of 0.59 <= P-orb <= 1.72 d, approximately. We have derived stellar masses between 0.24 and 0.72 M-circle dot and radii ranging from 0.42 to 0.67 R-circle dot. The great majority of the LMEBs in our sample has an estimated radius far from the predicted values according to evolutionary models. The components with derived masses of M < 0.6 M-circle dot present a radius inflation of similar to 9 per cent or more. This general behaviour follows the trend of inflation for partially radiative stars proposed previously. These systems add to the increasing sample of low-mass stellar radii that are not well-reproduced by stellar models. They further highlight the need to understand the magnetic activity and physical state of small stars. Missions like TESS will provide many such systems to perform high-precision radius measurements to tightly constrain low-mass stellar evolution models. (AU)

• FAPESP's process: 15/18496-8 - M-dwarf eclipsing binaries in the WFCAM Transit Survey: a study of the mass-radius relationship and of the radius anomaly of low-mass stars
• Grantee: Patricia Cardoso Cruz
• Support Opportunities: Scholarships in Brazil - Post-Doctoral