Search for a Debris Disk Around GJ 876 Paul Shankland (USNO, JCU) David Blank (JCU) Dave Boboltz (USNO) Joe Lazio (NRL) Graeme White (JCU)

GJ 876 The Planetary System Next Door GJ 876 M4V d= 4.7 pc GJ 876b M=1.89 M Jup, P=60 days GJ 876c M=0.57 M Jup, P=30 days GJ 876d M= 7.5 M Earth, P=1.9 days One of only 3 of about 130 M dwarfs searched that has planets and only one with giant planets One of only 3 of about 130 M dwarfs searched that has planets and only one with giant planets

Debris Disks Dust has short lifetime (few Myrs), so detection means presence of larger bodies (10’s of km in size) Dust has short lifetime (few Myrs), so detection means presence of larger bodies (10’s of km in size) Dust is produced from collisions of such bodies Dust is produced from collisions of such bodies Dust traces distribution of parent bodies Dust traces distribution of parent bodies Sometimes can infer presence of planets Sometimes can infer presence of planets (e.g. epsilon Eridani) (e.g. epsilon Eridani)

ATCA and VLA Observations Date Freq. Config. Time S rms Date Freq. Config. Time S rms GHz hrs mJy/Beam GHz hrs mJy/Beam ATCA 9/05 94 H VLA 11/05 43 D

No Detection M < M Earth (3σ limit) within about 5 AU (one beam). Comparisons (Greaves et al. 2004) Comparisons (Greaves et al. 2004) ε Eridani M ~ M Earth ε Eridani M ~ M Earth τ Ceti M ~ M Earth τ Ceti M ~ M Earth