Debris discs in the 27 Myr old open cluster IC 4665

作者：Smith R^*; Jeffries R D; Oliveira J M

来源：Monthly Notices of the Royal Astronomical Society, 2011, 411(4): 2186-2198.

DOI：10.1111/j.1365-2966.2010.17835.x

• circumstellar matter
• open clusters and associations: individual: IC 4665
• infrared: stars

We present Spitzer IRAC and MIPS 24-mu m imaging of members of the 27 +/- 5 Myr old open cluster IC 4665. Models for the assembly of terrestrial planets through planetesimal collisions and mergers predict episodic dust debris discs at this epoch. We determine that 42+18(-13) per cent of the solar-type (F5-K5) cluster members have excess emission at 24 mu m indicative of these debris discs, the highest frequency of the clusters studied with Spitzer to date. The majority of these discs have intermediate levels of excess (F-24/F-phot < 2), and no source is found to have extreme levels of excess indicative of a recent transient event as opposed to steady-state collisional evolution. We find no evidence of a link between multiplicity and 24-mu m excess in this cluster sample. Only the early-type star TYC424-473-1 (T-eff similar to 8420 K) has significant near-infrared excess from 4.5 mu m as measured with IRAC. Two solar-type targets have low-significance 8-mu m excess but no significant 24-mu m excess. All other targets show no evidence for near-infrared excess which could indicate the presence of an optically thick primordial disc, demonstrating that the observed 24-mu m excess arises from a debris disc.

• 出版日期2011-3