THE FIRST VLBI DETECTION OF AN ULTRACOOL DWARF: IMPLICATIONS FOR THE DETECTABILITY OF SUB-STELLAR COMPANIONS
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
We present milliarcsecond-resolution radio very long baseline interferometry (VLBI) observations of the ultracool dwarfs TVLM 513-46546 (M8.5) and 2MASS J00361617+1821104 (L3.5) in an attempt to detect sub-stellar companions via direct imaging or reflex motion. Both objects are known radio emitters with strong evidence for periodic emission on timescales of about 2 hr and 3 hr, respectively. Using the inner seven VLBA antennas, we detect unresolved emission from TVLM 513-46546 on a scale of 2.5 mas (approx50 stellar radii), leading to a direct limit on the radio emission brightness temperature of T{sub B} approx> 4 x 10{sup 5} K. However, with the higher spatial resolution afforded by the full VLBA we find that the source appears to be marginally resolved at a low signal-to-noise ratio, possibly indicating that TVLM 513-46546 is a binary with a projected separation of approx1 mas (approx20 stellar radii). Using the 7 hr baseline of our observation, we find no astrometric shift in the position of TVLM 513-46546, with a 3sigma limit of about 0.6 mas. This is about three times larger than expected for an equal-mass companion with a few-hour orbital period. Future monitoring of its position on a range of timescales will provide the required astrometric sensitivity to detect a planetary companion with a mass of approx10 M {sub J} in a approx>15 day (approx>0.06 AU) orbit, or with a mass of approx2 M {sub J} in an orbit of approx>0.5 yr (approx>0.3 AU).
- OSTI ID:
- 21385098
- Journal Information:
- Astrophysical Journal (Online), Vol. 706, Issue 2; Other Information: DOI: 10.1088/0004-637X/706/2/L205; ISSN 1538-4357
- Country of Publication:
- United States
- Language:
- English
Similar Records
An Astrometric Planetary Companion Candidate to the M9 Dwarf TVLM 513–46546
Periodic optical variability of radio-detected ultracool dwarfs