Open AccessCircumstellar kinematics and the measurement of stellar mass for the protostars TMC1 and TMC1A
Author(s) -
Brown David W.,
Chandler Claire J.
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02271.x
Subject(s) - physics , protostar , astrophysics , accretion (finance) , molecular cloud , millimeter , radius , stars , astronomy , stellar mass , star formation , computer security , computer science
We present observations of two protostars in the Taurus molecular cloud, TMC1 and TMC1A, obtained using the Owens Valley Millimeter Array. 13 CO and C 18 O J= 1‐‐0 data, and observations at 2.7 mm in the continuum, reveal the presence of molecular gas in circumstellar envelopes out to a radius of 1000 au. The velocity field in these envelopes is well described by Keplerian rotation and shows no signature of infall motions. The dynamical masses of the central objects, derived from the velocity structure of the isotopic CO emission, are 0.2‐‐0.4 M ⊙ for TMC1 and 0.35‐‐0.7 M ⊙ for TMC1A, depending upon the assumed inclination, with typical uncertainties in the mass measurements at a given inclination of 10 per cent. Our determinations of the stellar masses enable us to place upper limits on the accretion rates in these sources of ˙M ∼ 4 × 10 ‐7 M ⊙ yr ‐1 , which is at least an order of magnitude lower than that needed to assemble the observed mass with a constant ˙M assuming a typical age of 10 5 yr. We conclude that the accretion rate is not constant in time.