期刊
ASTROPHYSICAL JOURNAL
卷 554, 期 2, 页码 L197-L200出版社
UNIV CHICAGO PRESS
DOI: 10.1086/321706
关键词
open clusters and associations : individual (Orion Nebula Cluster); stars : pre-main-sequence; stars : rotation
We have determined new rotation periods for 404 stars in the Orion Nebula cluster (ONC) using the Wide Field Imager attached to the MPG/ESO 2.2 m telescope on La Silla, Chile. Mass estimates are available for 335 of these, and most have M<0.3 M-.. We confirm the existence of a bimodal period distribution for the higher mass stars in our sample and show that the median rotation rate decreases with increasing mass for stars in the range 0.1 M-. < M < 0.4 M-.. While the spread in angular momentum J at any given mass is more than a factor of 10, the majority of lower mass stars in the ONC rotate at rates approaching 30% of their critical breakup velocity, as opposed to 5%-10% for solar-like stars. This is a consequence of both a small increase in observed specific angular momentum (j=J/M) and a larger decrease in the critical value of j with decreasing mass. Perhaps the most striking fact, however, is that j varies by so little-less than a factor of 2-over the interval 0.1-1.0 M-.. The distribution of rotation rates with mass in the ONC (with an age of 1 Myr) is similar in nature, to what is found in the Pleiades (with an age of similar to 100 Myr). These observations provide a significant new guide and test for models of stellar angular momentum evolution during the protostellar and pre-main-sequence phases.
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