Discovery of a “wide” M dwarf-L dwarf binary

Vanderbilt University graduate student Saurav Dhital and collaborators report the discovery an unusually wide low-mass star plus brown dwarf binary. The dim pair of dwarfs, separated by over 100 AU, presents a new challenge to theories describing the formation of very low mass stars and brown dwarfs.

Clouds on a Young Planet: First Science Results with FIRE

A UKIDSS false color image of the Ross 458 system, composed of a pair of M dwarfs (bright star in upper left corner) and the planetary-mass brown dwarf Ross 458C (circled in lower right corner).

To study the atmospheres of young planets outside our Solar System, we need not look  far.  The first brown dwarf science with the newly-commissioned FIRE spectrograph has revealed the presence of rock clouds in the atmosphere of a planetary-mass companion to the nearby Ross 458 system.  The presence of these clouds, and the planetary nature of the source, defy prior expectations.

The source in question is Ross 458C, a brown dwarf candidate identified in the UKIDSS survey in early 2010 by two independent studies led by Drs. Rolf-Dieter Scholz and Betrand Goldman.  This source, also known as ULAS J130041.72+122114.7, is located 1.7′ (0.028 degrees) southeast of the Ross 458 system, a pair of magnetically active M dwarfs only 11.2 pc (36.5 light-years) from the Sun. The colors and faintness of Ross 458C, and that fact that it co-moves with the Ross 458 system, led both studies to conclude that it was potentially a very cool and very low-mass brown dwarf companion.  However, neither study had the necessary spectral data to probe its atmosphere.

Discovery of a Wacko Star

Jets, disks and accretion in nearby low mass star

U. Hawaii Graduate student Dagny Looper reports the discovery of a young, low-mass nearby star that is both unusually active and highly variable. The star, TWA 30, is a member of the TW Hydrae Association, roughly two dozen ~8 million year-old stars located about 50 pc away. TWA 30 is the newest member of this group, and one of the most intriguing. Its optical spectrum shows classical and forbidden emission lines, indicating that it is both accreting material and emitting high-speed jets of gas. The star’s near-infrared color also varies dramatically on week-long timescales, evidence that it periodically hides behind a nearly edge-on circumstellar disk. This makes TWA 30 one of the nearest T Tauri stars to the Sun.

The paper was published in the Astrophysical Journal.

May 2010