DETECTION OF RADIO EMISSION FROM THE HYPERACTIVE L DWARF 2MASS J13153094-2649513AB

作者：Burgasser Adam J^*; Melis Carl; Zauderer B Ashley; Berger Edo

来源：Astrophysical Journal Letters, 2013, 762(1): L3.

DOI：10.1088/2041-8205/762/1/L3

• brown dwarfs
• stars: chromospheres
• stars: individual (2MASS J13153094-2649513)
• stars: low mass
• stars: magnetic field

We report the detection of radio emission from the unusually active L5e + T7 binary 2MASS J13153094-2649513AB made with the Australian Telescope Compact Array. Observations at 5.5 GHz reveal an unresolved source with a continuum flux of 370 +/- 50 mu Jy, corresponding to a radio luminosity of L-rad = nu L-nu = (9 +/- 3) x 10(23) erg s(-1) and log(10) L-rad/L-bol = -5.44 +/- 0.22. No detection is made at 9.0 GHz to a 5 sigma limit of 290 mu Jy, consistent with a power-law spectrum S-nu proportional to nu(-alpha) with alpha greater than or similar to 0.5. The emission is quiescent, with no evidence of variability or bursts over three hours of observation, and no measurable polarization (V/I < 34%). 2MASS J1315-2649AB is one of the most radio-luminous ultracool dwarfs detected in quiescent emission to date, comparable in strength to other cool sources detected in outburst. Its detection indicates no decline in radio flux through the mid-L dwarfs. It is unique among L dwarfs in having strong and persistent Ha and radio emission, indicating the coexistence of a cool, neutral photosphere (low electron density) and a highly active chromosphere (high electron density and active heating). These traits, coupled with the system's mature age and substellar secondary, make 2MASS J1315-2649AB an important test for proposed radio emission mechanisms in ultracool dwarfs.

• 出版日期2013-1-1