Issue |
A&A
Volume 566, June 2014
|
|
---|---|---|
Article Number | L3 | |
Number of page(s) | 4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361/201423654 | |
Published online | 09 June 2014 |
Old pre-main-sequence stars
Disc reformation by Bondi-Hoyle accretion
1 ITAP, Universität zu Kiel, Leibnizstr. 15, 24118 Kiel, Germany
e-mail: pscicluna@astrophysik.uni-kiel.de
2 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany
3 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
4 Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany
5 Universitats-Sternwarte München, Scheinerstraße 1, 81679 München, Germany
6 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
Received: 17 February 2014
Accepted: 21 May 2014
Young stars show evidence of accretion discs which evolve quickly and disperse with an e-folding time of ~3 Myr. This is in striking contrast with recent observations that suggest evidence of numerous >30 Myr old stars with an accretion disc in large star-forming complexes. We consider whether these observations of apparently old accretors could be explained by invoking Bondi-Hoyle accretion to rebuild a new disc around these stars during passage through a clumpy molecular cloud. We combine a simple Monte Carlo model to explore the capture of mass by such systems with a viscous evolution model to infer the levels of accretion that would be observed. We find that a significant fraction of stars may capture enough material via the Bondi-Hoyle mechanism to rebuild a disc of mass ≳1 minimum-mass solar nebula, and ≲10% accrete at observable levels at any given time. A significant fraction of the observed old accretors may be explained with our proposed mechanism. Such accretion may provide a chance for a second epoch of planet formation, and have unpredictable consequences for planetary evolution.
Key words: accretion, accretion disks / protoplanetary disks / circumstellar matter / stars: formation / stars: pre-main sequence
© ESO, 2014
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