Accretion in Young Stellar/Substellar Objects

Astrophysics, abstract
astro-ph/0304078

From: James Muzerolle <jamesm@mips.as.arizona.edu>

Date: Thu, 3 Apr 2003 18:13:23 GMT   (127kb)

Authors:
James Muzerolle (Steward),
Lynne Hillenbrand (Caltech),
Nuria Calvet (CfA),
Cesar Briceno (CIDA),
Lee Hartmann (CfA)

Comments: 38 pages, including 8 figures and 6 tables, accepted by ApJ

We present a study of accretion in a sample of 45 young, low mass objects in
a variety of star forming regions and young associations, about half of which
are likely substellar. Based primarily on the presence of broad, asymmetric
Halpha emission, we have identified 13 objects (~30% of our sample) which are
strong candidates for ongoing accretion. At least 3 of these are substellar. We
do not detect significant continuum veiling in most of the accretors with late
spectral types (M5-M7). Accretion shock models show that lack of measurable
veiling allows us to place an upper limit to the mass accretion rates of <~
10^{-10} Msun/yr. Using magnetospheric accretion models with appropriate
(sub)stellar parameters, we can successfully explain the accretor Halpha
emission line profiles, and derive quantitative estimates of accretion rates in
the range 10^{-12} < Mdot < 10^{-9} Msun/yr. There is a clear trend of
decreasing accretion rate with stellar mass, with mean accretion rates
declining by 3-4 orders of magnitude over ~ 1 – 0.05 Msun.

References and citations for this submission:

SLAC-SPIRES HEP (refers to ,
cited by, arXiv reformatted)