Open AccessBe‐star rotation: how close to critical?
Author(s) -
Townsend R. H. D.,
Owocki S. P.,
Howarth I. D.
Publication year - 2004
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 - 10.1111/j.1365-2966.2004.07627.x
Subject(s) - physics , rotation (mathematics) , astrophysics , stars , line (geometry) , astronomy , star (game theory) , observational study , be star , angular velocity , classical mechanics , geometry , medicine , mathematics , pathology
We argue that, in general, observational studies of Be‐star rotation have paid insufficient attention to the effects of equatorial gravity darkening. We present new line‐profile calculations that emphasize the insensitivity of line width to rotation for fast rotators. Coupled with a critical review of observational procedures, these calculations suggest that the observational parameter v sin i may systematically underestimate the true projected equatorial rotation velocity, v e sin i , by some tens of per cent for rapid rotators. A crucial implication of this work is that Be stars may be rotating much closer to their critical velocities than is generally supposed, bringing a range of new processes into contention for the elusive physical mechanism responsible for the circumstellar disc thought to be central to the Be phenomenon.