Spectroscopy of Putative Brown Dwarfs in Taurus

TL;DR

This study used infrared spectroscopy to verify the substellar nature of candidate brown dwarfs in Taurus, finding they are actually background stars or galaxies, not young brown dwarfs or protostellar binaries.

Contribution

The paper provides spectroscopic evidence that previously identified brown dwarf candidates in Taurus are misclassified background objects.

Findings

Spectroscopy showed these objects lack features of cool brown dwarfs.

Optical colors suggest they are background stars or galaxies.

The candidate binary is likely a galaxy, not a Taurus member.

Abstract

Quanz and coworkers have reported the discovery of the coolest known member of the Taurus star-forming complex (L2+/-0.5) and Barrado and coworkers have identified a possible protostellar binary brown dwarf in the same region. We have performed infrared spectroscopy on the former and the brighter component of the latter to verify their substellar nature. The resulting spectra do not exhibit the strong steam absorption bands that are expected for cool objects, demonstrating that they are not young brown dwarfs. The optical magnitudes and colors for these sources are also indicative of background stars rather than members of Taurus. Although the fainter component of the candidate protostellar binary lacks spectroscopy, we conclude that it is a galaxy rather than a substellar member of Taurus based on its colors and the constraints on its proper motion.