Wednesday, July 15, 2015

The Differences in Protoplanetary Disk Evolution Around Single and Binary Stars

Protoplanetary Disk Evolution: Singles vs. Binaries


Daemgen et al


Based on a large number of observations carried out in the last decade it appears that the fraction of stars with protoplanetary disks declines steadily between ~1 Myr and ~10 Myr. We do, however, know that the multiplicity fraction of star-forming regions can be as high as greater than 50% and that multiples have reduced disk lifetimes on average. As a consequence, the observed roughly exponential disk decay can neither be fully attributed to single nor binary stars and its functional form may need revision. Observational evidence for the latter has been provided by Kraus et al. (2012), who statistically correct previous disk frequency measurements for the presence of binaries and find agreement with models that feature a constantly high disk fraction up to ~3 Myr, followed by a rapid (≲2 Myr) decline. We present results from our high-angular resolution observational program to study the fraction of protoplanetary disks of single and binary stars separately. We find that disk evolution timescales of stars bound in close binaries (less than 100 AU) are significantly reduced compared to wider binaries. The frequencies of accretors among single stars and wide binaries appear indistinguishable, and are found lower than predicted from planet forming disk models governed by viscous evolution and photoevaporation.

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