Statistics
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt........11m&link_type=abstract
Thesis (PH.D.)--CALIFORNIA INSTITUTE OF TECHNOLOGY, 1995.Source: Dissertation Abstracts International, Volume: 56-07, Section: B
Statistics
1
Cygni, Outflow Shells
Scientific paper
Extensive observations were made of six FU Orionis objects (RNO 1B/1C, V1057 Cygni, Elias 1-12, V1515 Cygni and FU Orionis) and one pre-outburst candidate (V1331 Cygni) using the Owens Valley millimeter-wave array and the Caltech Submillimeter Observatory (CSO). Aperture synthesis maps of CO (1 to 0), ^ {13}CO (1 to 0), 13CO (2 to 1), C18O (1 to 0), and CS (2 to 1) molecular lines and associated dust continuum emission trace the masses, kinematics and morphology of FU Orionis disks, envelopes, and outflows. Maps from the CSO delineate outflowing gas at larger spatial scales while line strengths, when input into radiative transfer models, yield column densities and fractional chemical abundances. Unresolved 1.3 mm continuum emission from V1331 Cygni and V1057 Cygni reveal massive circumstellar disks of 0.5 and 0.09 Modot , respectively. Maps of the 2.6 and 3.1 mm continuum emission reveal that RNO 1C is surrounded by a flattened dusty envelope, 5000 AU in size, with mass >= 1.1 Modot. No evidence is seen for multiple systems with orbital periods _sp{~}>4 times 10^4 years. All sources, with the exception of RNO 1B/1C are surrounded by large molecular gas envelopes between 2000 -7500 AU in size, with masses ranging from 2 times 10^{-3} to 0.36 Modot. Aperture synthesis maps suggest the envelopes are asymmetrically distributed. Gas kinematics around V1057 Cygni and Elias 1-12 suggest, but do not demand, that this material is rotating and possibly infalling. Of the seven sources observed, all but FU Orionis show signs of outflowing molecular gas. No high velocity clumps or "bullets" are seen towards any of the sources. V1331 Cygni, V1057 Cygni, and V1515 Cygni possess arc or ring -like outflow morphologies, while emission from RNO 1B/1C and Elias 1-12 delineates filled outflow shells. All emission patterns are consistent with outflow shells being viewed at different angles. Although based on the statistics of small numbers, observations suggest shells are seen more frequently around FUors than T Tauri stars. Cross -cutting arcs within the shell structure, seen towards RNO 1B/1C and Elias 1-12, are probably ridges of gas swept -up by the most recent outbursts, confirming the repetitive nature of FUor outbursts. Estimates of the dynamical ages of the arcs suggest that the interval between outbursts is {~}5 times 10^3 and 1.3 times 10^4 years for RNO 1B/1C and Elias 1-12 respectively, consistent with previous estimates of FUor cycling times. Comparable envelopes and shell-like outflow structure are seen towards embedded sources while envelopes surrounding T Tauri stars are smaller and less massive. The strength of the molecular outflow emission is correlated with the mass of the extended envelope; the outflow has evacuated molecular gas leaving less to be swept-up by subsequent outbursts, while envelope masses are smaller since less material is available for accretion. Chemically, fractional abundances of SiO and methanol are enhanced towards RNO 1B/1C by over an order of magnitude. Methanol is enhanced relative to HCN and H_2CO towards Elias 1-12. Such large changes in fractional abundances must be caused by chemical processing. (Abstract shortened by UMI.).
No associations
LandOfFree
The Circumstellar Environments of FU Orionis Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Circumstellar Environments of FU Orionis Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Circumstellar Environments of FU Orionis Stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-837387