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

P. Scicluna, G. Rosotti, L. Testi, James Dale

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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.
Original languageEnglish
Article numberL3
Number of pages4
JournalAstronomy & Astrophysics
Publication statusPublished - 9 Jun 2014


  • accretion, accretion disks, protoplanetary disks, circumstellar matter, stars: formation, stars: pre-main sequence


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