A Deep Spitzer Survey of Circumstellar Disks in the Young Double Cluster, h and chi Persei

TL;DR

This study uses deep infrared observations of the Double Cluster h and χ Persei to analyze circumstellar disks, revealing their evolution, frequency, and lifetimes, and comparing results across different stellar masses and ages.

Contribution

It provides detailed analysis of disk evolution and lifetimes in a 14 Myr old cluster using deep IR data, extending previous shallower surveys and combining results with other clusters.

Findings

At least 2% of stars show IR excess at 8 μm.

Disk lifetimes are estimated at 2.75 to 5.75 Myr depending on age assumptions.

Transitional disks last approximately 1 Myr.

Abstract

We analyze very deep IRAC and MIPS photometry of $\sim$ 12,500 members of the 14 Myr old Double Cluster, h and $\chi$ Persei, building upon on our earlier, shallower Spitzer studies (Currie et al. 2007a, 2008a). Numerous likely members show infrared (IR) excesses at 8 {\mu}m and 24 $\mu$m indicative of circumstellar dust. The frequency of stars with 8 $\mu$m excess is at least 2% for our entire sample, slightly lower (higher) for B/A stars (later type, lower-mass stars). Optical spectroscopy also identifies gas in about 2% of systems but with no clear trend between the presence of dust and gas. Spectral energy distribution (SED) modeling of 18 sources with detections at optical wavelengths through MIPS 24 $\mu m$ reveals a diverse set of disk evolutionary states, including a high fraction of transitional disks, although similar data for all disk-bearing members would provide better constraints. We combine our results with those for other young clusters to study the global evolution of dust/gas disks. For nominal cluster ages, the e-folding times ($\tau_{o}$) for the frequency of warm dust and gas are 2.75 Myr and 1.75 Myr respectively. Assuming a revised set of ages for some clusters (e.g. Bell et al. 2013), these timescales increase to 5.75 and 3.75 Myr, respectively, implying a significantly longer typical protoplanetary disk lifetime. The transitional disk duration, averaged over multiple evolutionary pathways, is $\sim$ 1 Myr. Finally, 24 $\mu$m excess frequencies for 4-6 M$_{\odot}$ stars appear lower than for 1-2.5 M$_{\odot}$ stars in other 10-30 Myr old clusters.