Stellar rotation: a clue to the origin of high-mass stars?
WOLFF S.C., STROM S.E., DROR D., LANZ L. and VENN K.
Abstract (from CDS):
We present the results of a study aimed at assessing whether low- and high-mass stars form similarly. Our approach is (1) to examine the observed projected rotational velocities among a large sample of newly formed stars spanning a range in mass between 0.2 and 50 M☉ and (2) to search for evidence of a discontinuity in rotational properties that might indicate a difference in the stellar formation process at some characteristic mass. Our database includes recently published values of vsini for young intermediate- and low-mass stars in Orion, as well as new observations of O stars located in young clusters and OB associations. We find that the median of the quantity vobs/vc (observed rotational speed divided by equatorial breakup velocity) is typically about 0.15 and shows no evidence of a discontinuity over the full range of stellar masses, while the quantity Jsini/M (derived angular momentum per unit mass) exhibits a slow, monotonic rise (J/M∼M0.3) with increasing mass with no evidence of a discontinuity. We suggest that these observations are most simply interpreted as indicative of a single stellar formation and angular momentum regulation mechanism, one that results in rotation rates well below breakup and angular momenta per unit mass that differ systematically by no more than a factor of 3-4 over a mass range spanning a factor of 250.
open clusters and associations: individual (NGC 6611) - Galaxy: Open Clusters and Associations: Individual: Name: Orion - Stars: Rotation
VizieR on-line data:
<Available at CDS (J/AJ/132/749): table1.dat>
Table 1 : coordinates for the star in Cyg OB 2 (stars [MT91] in Simbad) are for 1950, not 2000.