Debris Disks of Members of the Blanco 1 Open Cluster

TL;DR

This study used Spitzer MIPS 24 um photometry to detect debris disks around members of the Blanco 1 cluster, revealing a 32% excess detection rate and a link between binarity and debris disk presence.

Contribution

It provides the first debris disk frequency measurement for Blanco 1 and examines the relation between binarity and debris disks in young clusters.

Findings

32% of bright stars show mid-IR excesses indicating debris disks.

Photometric binaries have fewer debris disks than single stars.

Similar trends observed in NGC 2547 and Pleiades clusters.

Abstract

We have used the Spitzer Space Telescope to obtain Multiband Imaging Photometer for Spitzer (MIPS) 24 um photometry for 37 members of the ~100 Myr old open cluster Blanco 1. For the brightest 25 of these stars (where we have 3sigma uncertainties less than 15%), we find significant mid-IR excesses for eight stars, corresponding to a debris disk detection frequency of about 32%. The stars with excesses include two A stars, four F dwarfs and two G dwarfs. The most significant linkage between 24 um excess and any other stellar property for our Blanco 1 sample of stars is with binarity. Blanco 1 members that are photometric binaries show few or no detected 24 um excesses whereas a quarter of the apparently single Blanco 1 members do have excesses. We have examined the MIPS data for two other clusters of similar age to Blanco 1 -- NGC 2547 and the Pleiades. The AFGK photometric binary star members of both of these clusters also show a much lower frequency of 24 um excesses compared to stars that lie near the single-star main sequence. We provide a new determination of the relation between V-Ks color and Ks-[24] color for main sequence photospheres based on Hyades members observed with MIPS. As a result of our analysis of the Hyades data, we identify three low mass Hyades members as candidates for having debris disks near the MIPS detection limit.