Timescale of mass accretion in pre-main-sequence stars
Abstract
We present the initial result of a large spectroscopic survey aimed at measuring the timescale of mass accretion in young, pre-main-sequence stars in the spectral type range K0-M5. Using multi-object spectroscopy with VIMOS at the VLT we identified the fraction of accreting stars in a number of young stellar clusters and associations of the ages of between 1-30 Myr. The fraction of accreting stars decreases from ~60% at 1.5-2 Myr to ~2% at 10 Myr. No accreting stars are found after 10 Myr at a sensitivity limit of 10-11 M⊙ yr-1. We compared the fraction of stars showing ongoing accretion (f_acc) to the fraction of stars with near-to-mid infrared excess (f_IRAC). In most cases we find f_acc <f_IRAC, i.e. , mass accretion appears to cease (or drop below detectable level) earlier than the dust is dissipated in the inner disk. At 5 Myr, 95% of the stellar population has stopped accreting material at a rate of ⪆10-11 M⊙ yr-1, while ~20% of the stars show near-infrared excess emission. Assuming an exponential decay, we measure a mass accretion timescale (τ_acc) of 2.3 Myr, compared to a near-to-mid infrared excess timescale (τ_IRAC) of 3 Myr. Planet formation and/or migration, in the inner disk might be a viable mechanism to halt further accretion onto the central star on such a short timescale.
Based on observations collected at the European Southern Observatory, Paranal, Chile (Proposal ID: 078.C-0282; 081.C-0208).- Publication:
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Astronomy and Astrophysics
- Pub Date:
- February 2010
- DOI:
- 10.1051/0004-6361/200912810
- arXiv:
- arXiv:0911.3320
- Bibcode:
- 2010A&A...510A..72F
- Keywords:
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- accretion;
- accretion disks;
- stars: pre-main sequence;
- planetary systems:;
- protoplanetary disks;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication