We present photometric detections of dust emission at 850 and 450 µm around the pre-main sequence M1 dwarf TWA 7 using the SCUBA camera on the James Clerk Maxwell Telescope .
These data confirm the presence of a cold dust disk around TWA 7 , a member of the TW Hydrae Association .
Based on the 850 µm flux , we estimate the mass of the disk to be 18 M _ { lunar } ( 0.2 M _ { \oplus } ) assuming a mass opacity of 1.7 cm ^ { 2 } g ^ { -1 } with a temperature of 45 K. This makes the TWA 7 disk ( d = 55 pc ) an order of magnitude more massive than the disk reported around AU Microscopii ( GL 803 ) , the closest ( 9.9 pc ) debris disk detected around an M dwarf .
This is consistent with TWA 7 being slightly younger than AU Mic .
We find that the mid-IR and submillimeter data require the disk to be comprised of dust at a range of temperatures .
A model in which the dust is at a single radius from the star , with a range of temperatures according to grain size , is as effective at fitting the emission spectrum as a model in which the dust is of uniform size , but has a range of temperatures according to distance .
We discuss this disk in the context of known disks in the TW Hydrae Association and around low-mass stars ; a comparison of masses of disks in the TWA reveals no trend in mass or evolutionary state ( gas-rich vs. debris ) as a function of spectral type .