# Mass and Temperature of the TWA 7 Debris Disk

## TL;DR

This study detects and characterizes a cold debris disk around the M1 dwarf TWA 7, revealing its mass, temperature distribution, and comparison with other disks in the TW Hydrae Association, contributing to understanding disk evolution around low-mass stars.

## Contribution

First detection of a cold debris disk around TWA 7 with detailed modeling of dust temperature distribution and mass, expanding knowledge of disks around M dwarfs.

## Key findings

- Disk mass estimated at 0.2 Earth masses.
- Dust at a range of temperatures is required to fit the spectrum.
- No correlation between disk mass and stellar spectral type in TWA.

## Abstract

We present photometric detections of dust emission at 850 and 450 micron 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 micron flux, we estimate the mass of the disk to be 18 lunar masses (0.2 Earth masses) assuming a mass opacity of 1.7 cm^2/g 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.