Protoplanetary and Transitional Disks in the Open Stellar Cluster IC 2395

TL;DR

This study investigates the evolution of protoplanetary and transitional disks in the young open cluster IC 2395, revealing how the fraction of transitional disks increases with age across multiple stellar clusters.

Contribution

It provides new deep optical and infrared observations of IC 2395, identifying disk types and analyzing transitional disk fractions across different ages, highlighting disk evolution trends.

Findings

Discovered 18 Class II, 8 transitional, and 23 debris disks in IC 2395.

Transitional disk fraction increases from ~8% at 3 Myr to ~46% at 10 Myr.

The trend of increasing transitional disks is consistent across multiple stellar clusters.

Abstract

We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (~ 6 - 10 Myr old), relatively nearby (800 pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24 microns. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii ~ 0.1 to ~ 10AU from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from ~ 1 to ~ 18 Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24 micron excesses ([8] - [24] > 1.5) increases from 8.4 +\- 1.3% at ~ 3 Myr to 46 +\- 5% at ~ 10 Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.