44 New & Known M Dwarf Multiples In The SDSS-III/APOGEE M Dwarf Ancillary Science Sample

TL;DR

This study identifies and characterizes 44 M dwarf spectroscopic binaries using APOGEE data, providing new insights into their properties and orbital parameters, and comparing mass ratio distributions with previous surveys.

Contribution

It introduces a method to detect SB2s in APOGEE spectra and reports the first orbital fits for some M dwarf binaries, expanding knowledge of their mass ratios and orbital characteristics.

Findings

44 candidate SB2s identified, including 11 known systems.

Radial velocities extracted for 36 systems, enabling mass ratio calculations.

Mass ratio distribution peaks near unity, consistent with prior studies.

Abstract

Binary stars make up a significant portion of all stellar systems. Consequently, an understanding of the bulk properties of binary stars is necessary for a full picture of star formation. Binary surveys indicate that both multiplicity fraction and typical orbital separation increase as functions of primary mass. Correlations with higher order architectural parameters such as mass ratio are less well constrained. We seek to identify and characterize double-lined spectroscopic binaries (SB2s) among the 1350 M dwarf ancillary science targets with APOGEE spectra in the SDSS-III Data Release 13. We measure the degree of asymmetry in the APOGEE pipeline cross-correlation functions (CCFs), and use those metrics to identify a sample of 44 high-likelihood candidate SB2s. At least 11 of these SB2s are known, having been previously identified by Deshapnde et al, and/or El Badry et al. We are able to extract radial velocities (RVs) for the components of 36 of these systems from their CCFs. With these RVs, we measure mass ratios for 29 SB2s and 5 SB3s. We use Bayesian techniques to fit maximum likelihood (but still preliminary) orbits for 4 SB2s with 8 or more distinct APOGEE observations. The observed (but incomplete) mass ratio distribution of this sample rises quickly towards unity. Two-sided Kolmogorov-Smirnov tests and probabilities of 18.3% and 18.7%, demonstrating that the mass ratio distribution of our sample is consistent with those measured by Pourbaix et al. and Fernandez et al., respectively.