A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars

TL;DR

This study conducted high-cadence photometric monitoring of young brown dwarfs and very low mass stars to detect predicted pulsations during deuterium burning, but found no such periodic signals, instead revealing diverse variability behaviors.

Contribution

The paper provides the first extensive observational search for deuterium-burning pulsations in young low-mass objects, concluding they are not observable, and catalogs variability in these objects.

Findings

No periodic pulsations detected below seven hours.

Detected diverse variability behaviors on day to week timescales.

Identified three new candidate members in Chamaeleon I.

Abstract

In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very low mass stars (VLMSs; <0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of 1-4 hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters $\sigma$ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity to periodic signals of amplitude several millimagnitudes, on timescales from 15 minutes to two weeks. Despite the exquisite data quality, we failed to detect any periodicities below seven hours. We conclude that D-burning pulsations are not able to grow to observable amplitudes in the early pre-main sequence. In spite of the non-detection, we did uncover a rich set of variability behavior- both periodic and aperiodic- on day to week timescales. We present new compilations of variable sources from our sample, as well as three new candidate cluster members in Chamaeleon I.