Thirty New Low-Mass Spectroscopic Binaries

TL;DR

This study identifies 30 new low-mass spectroscopic binaries among X-ray active M dwarfs, increasing known systems by 50%, and demonstrates X-ray emission as an effective method for discovering such binaries.

Contribution

The paper reports the discovery of 30 new low-mass spectroscopic binaries, significantly expanding the known sample and validating X-ray emission as a key indicator for finding M-dwarf binaries.

Findings

Discovered 30 new low-mass spectroscopic binaries, increasing known systems by 50%.

Found that strong X-ray emission is an efficient indicator for identifying M-dwarf SBs.

Provided rotation periods and orbital parameters for several systems, aiding stellar evolution studies.

Abstract

As part of our search for young M dwarfs within 25 pc, we acquired high-resolution spectra of 185 low-mass stars compiled by the NStars project that have strong X-ray emission. By cross-correlating these spectra with radial velocity standard stars, we are sensitive to finding multi-lined spectroscopic binaries. We find a low-mass spectroscopic binary fraction of 16% consisting of 27 SB2s, 2 SB3s and 1 SB4, increasing the number of known low-mass SBs by 50% and proving that strong X-ray emission is an extremely efficient way to find M-dwarf SBs. WASP photometry of 23 of these systems revealed two low-mass EBs, bringing the count of known M dwarf EBs to 15. BD -22 5866, the SB4, is fully described in Shkolnik et al. 2008 and CCDM J04404+3127 B consists of a two mid-M stars orbiting each other every 2.048 days. WASP also provided rotation periods for 12 systems, and in the cases where the synchronization time scales are short, we used P_rot to determine the true orbital parameters. For those with no P_rot, we use differential radial velocities to set upper limits on orbital periods and semi-major axes. More than half of our sample has near-equal-mass components (q > 0.8). This is expected since our sample is biased towards tight orbits where saturated X-ray emission is due to tidal spin-up rather than stellar youth. Increasing the samples of M dwarf SBs and EBs is extremely valuable in setting constraints on current theories of stellar multiplicity and evolution scenarios for low-mass multiple systems.