Multiepoch Radial Velocity Observations of L Dwarfs

TL;DR

This paper introduces a near-infrared radial velocity measurement technique for L dwarfs using telluric features as references, achieving 300 m/s precision and enabling detection of close-in companions.

Contribution

The authors develop a novel near-infrared radial velocity method for cool stars and brown dwarfs using telluric absorption as a wavelength reference, demonstrating its effectiveness.

Findings

Achieved 300 m/s radial velocity precision with high-resolution spectra.

No companions detected in the current sample of nine L dwarfs.

Future improvements could reach 100 m/s precision with better data quality.

Abstract

We report on the development of a technique for precise radial-velocity measurements of cool stars and brown dwarfs in the near infrared. Our technique is analogous to the Iodine (I2) absorption cell method that has proven so successful in the optical regime. We rely on telluric CH4 absorption features to serve as a wavelength reference, relative to which we measure Doppler shifts of the CO and H2O features in the spectra of our targets. We apply this technique to high-resolution (R~50,000) spectra near 2.3 micron of nine L dwarfs taken with the Phoenix instrument on Gemini-South and demonstrate a typical precision of 300 m/s. We conduct simulations to estimate our expected precision and show our performance is currently limited by the signal-to-noise of our data. We present estimates of the rotational velocities and systemic velocities of our targets. With our current data, we are sensitive to companions with M sin i > 2MJ in orbits with periods less than three days. We identify no companions in our current data set. Future observations with improved signal-to-noise should result in radial-velocity precision of 100 m/s for L dwarfs.