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

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.

arXiv comment12 pages, 3 figures, accepted for publication in The Astrophysical Journal Letters, updated references

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