Keck NIRSPEC Radial Velocity Observations of Late-M dwarfs

TL;DR

This study uses infrared spectroscopy to measure radial velocities of late-M dwarfs, achieving high precision and identifying potential companions, while providing spectral data for atmospheric analysis.

Contribution

It presents a new high-precision infrared RV measurement method for late-M dwarfs and offers spectral data to improve atmospheric models.

Findings

Achieved RV measurement precision of 45 m/s over 1-4 years.

Detected RV variations >1000 m/s in two stars, potential companions.

Placed upper mass limits of <40 M_J for potential companions.

Abstract

We present the results of an infrared spectroscopic survey of 23 late-M dwarfs with the NIRSPEC echelle spectrometer on the Keck II telescope. Using telluric lines for wavelength calibration, we are able to achieve measurement precisions of down to 45 m/s for our late-M dwarfs over a one to four year-long baseline. Our sample contains two stars with RV variations of >1000 m/s. While we require more measurements to determine whether these RV variations are due to unseen planetary or stellar companions or are the result of starspots known to plague the surface of M dwarfs, we can place upper limits of <40 MJsini on the masses of any companions around those two M dwarfs with RV variations of <160 m/s at orbital periods of 10-100 days. We have also measured the rotational velocities for all the stars in our late-M dwarf sample and offer our multi-order, high-resolution spectra over 2.0 to 2.4 micron to the atmospheric modeling community to better understand the atmospheres of late-M dwarfs.