Young stars show evidence of accretion discs which evolve quickly and disperse with an e-folding time of similar to 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 greater than or similar to 1 minimum-mass solar nebula, and less than or similar to 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.

Old pre-main-sequence stars. Disc reformation by Bondi-Hoyle accretion / P. Scicluna, G. Rosotti, J.E. Dale, L. Testi. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 566:(2014), pp. L3.1-L3.4. [10.1051/0004-6361/201423654]

Old pre-main-sequence stars. Disc reformation by Bondi-Hoyle accretion

G. Rosotti
Secondo
;
2014

Abstract

Young stars show evidence of accretion discs which evolve quickly and disperse with an e-folding time of similar to 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 greater than or similar to 1 minimum-mass solar nebula, and less than or similar to 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.
accretion, accretion disks; protoplanetary disks; circumstellar matter; stars: formation; stars: pre-main sequence
Settore FIS/05 - Astronomia e Astrofisica
2014
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/938328
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