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Milliarcsecond radio structure of weak-lined T Tauri starsVLBI and VLA observations of six radio-bright weak-lined T Taur (WTT) stars are reported, as well as direct measurements of the sizes of the emitting regions. VLBI measurements established that essentially all the radio emission from these premain-sequence stars originates in regions 15 stellar radii or less in size. Corresponding brightness temperatures ranged from 10 exp 7.5 to not less than 10 exp 9 K, ruling out a thermal process such as free-free bremsstrahlung radiation from a circumstellar wind. The radio luminosity and structure of several stars changed significantly between measurements separated by 1 day. HD 283447 showed intraday radio variability on time scales as short as 1 hr. Corresponding VLBI measurements show a new unresolved component appearing after an increase in flux density, possibly indicating that the driving agent for larger radio flares originates close to the star. The high conformation rate of nonthermal radio emission from this initial sample of radio-bright WTT stars show that these solar-type premain-sequence stars alter their immediate environments via magnetic processes to an extent comparable to that shown by RS CVn or Algol close binaries.
Document ID
19920030879
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Phillips, R. B.
(Northeast Radio Observatory Corp. Westford, MA, United States)
Lonsdale, C. J.
(Haystack Observatory Westford, MA, United States)
Feigelson, E. D.
(Pennsylvania State University University Park, United States)
Date Acquired
August 15, 2013
Publication Date
November 20, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 382
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
92A13503
Distribution Limits
Public
Copyright
Other

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