A Blue Brown Dwarf

Not all brown dwarfs are brown

We report observations of an unusually blue brown dwarf, a nearby object that may be among the coldest and oldest brown dwarfs known.  The source, ULAS J141623.94+134836.3, was originally discovered in the UKIDSS survey independently by R. Scholz and B. Burningham et al., and early results indicated its surface could be as cool as 500 K. It could even be the first Y dwarf.   Our near-infrared spectrum, obtained with the IRTF SpeX spectrograph, instead shows it to be somewhat warmer (650 K), as well as old, massive and depleted in “metals” (any element other than hydrogen and helium).  ULAS J1416+1348 is also a companion to the unusually blue L dwarf SDSS J141624.08+134826.7 discovered earlier this year by several groups.  This nearby brown dwarf pair has generated a lot of interest among astronomers, with five publications in six months.

This result was published in in the Astronomical Journal; it was also an IRTF science highlight.

June 2010

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