Search for Cold Debris Disks around M-dwarfs. II

TL;DR

This study investigates the presence of cold debris disks around M-dwarfs using millimeter observations, finding a lower disk fraction compared to more massive stars, with potential implications for planetary system evolution.

Contribution

First comprehensive millimeter survey of M-dwarfs for cold debris disks, revealing a lower occurrence rate and potential dependence on stellar mass and age.

Findings

Only one significant debris disk detection among 30 M-dwarfs.

Cold disk fraction is approximately 5.3% for young M-dwarfs.

Lower disk occurrence compared to A- and FGK-type stars.

Abstract

Although 70 % of the stars in the Galaxy are M-dwarfs, thermal emission searches for cold debris disks have been conducted mostly for A-type and solar-type stars. We report on new lambda=1.2 mm continuum observations of thirty M-dwarfs, using the MAMBO-2 bolometer array camera at the IRAM 30m telescope. For a statistical analysis, we combine these data with our prior SCUBA and MAMBO-2 observations of 20 other M-dwarfs. Our total sample divides in M-dwarfs in moving groups, with relatively young ages, and in nearby M-dwarfs with unknown ages. Only one cold debris disk (GJ842.2) was detected significantly. We compare the implied disk abundance constraints with those found in two comparable submillimeter surveys of 10 to 190 Myr old A- and FGK-type stars. For the 19 youngest (ages less than 200 Myr) M-dwarfs in our sample, we derive a cold disk fraction of 5.3^{+10.5}_{-5.0} %, compared to 15 +/-11.5 % for FGK-stars and 22^{+33}_{-20} % for A-stars. Hence, for this age group, there is an apparent trend of fewer cold disks for later stellar types, i.e., lower star masses. Although its statistical significance is marginal, this trend is strengthened by the deeper sensitivity of observations in the M-dwarf sample. We derive a cold disk fraction of < 10 % for the older (likely a few Gyr) M-dwarfs in our sample. Finally, although inconclusively related to a debris disk, we present the complex millimeter structure found around the position of the M1.5 dwarf GJ526 in our sample.