Discovery of Gas Accretion Onto Stars in 13 Myr old h and chi Persei

TL;DR

This study discovers ongoing gas accretion in ~13 million-year-old stars in h and chi Persei, indicating that circumstellar gas can persist longer than previously thought, especially around stars later than G5 spectral type.

Contribution

It provides the first evidence of gas accretion in intermediate/low-mass stars at ~13 Myr, challenging existing models of disk dissipation timescales.

Findings

Accretion disks are present in ~13 Myr-old stars.

Accretion is more common in stars later than G0.

Gas can last longer than 10-15 Myr in some systems.

Abstract

We report the discovery of accretion disks associated with ~ 13 Myr-old intermediate/low-mass stars in h and chi Persei. Optical spectroscopy of ~ 5000 stars in these clusters and a surrounding halo population reveal 32 A-K stars with H(alpha) emission. Matching these stars with 2MASS and optical photometry yields 25 stars with the highest probability of cluster membership and EW(H(alpha)) > 5 angstroms. Sixteen of these sources have EW(H(alpha)) > 10 angstroms. The population of accreting sources is strongly spectral type dependent: H(alpha) emission characteristic of accretion, especially strong accretion (EW(H(alpha)) > 10 angstroms), is much more prevalent around stars later than G0. Strong H(alpha) emission from accretion is typically associated with redder Ks-[8] colors. The existence of accreting pre-main sequence stars in h and chi Persei implies that circumstellar gas in some systems, especially those with primaries later than G5 spectral type, can last longer than 10-15 Myr.