Bibcode
Makidon, R. B.; Strom, S. E.; Tingley, B.; Adams, M. T.; Hillenbrand, L.; Hartmann, L.; Calvet, N.; Jones, B. F.
Referencia bibliográfica
American Astronomical Society, 191st AAS Meeting, #05.06; Bulletin of the American Astronomical Society, Vol. 29, p.1214
Fecha de publicación:
12
1997
Número de citas
0
Número de citas referidas
0
Descripción
We present the initial results of a study aimed at: (1) determining the
lifetime of the disk accretion phase among low mass pre-main sequence
stars; (2) establishing the time dependence of disk mass accretion
rates; and (3) further exploring the role played by accretion disks in
regulating stellar rotation. Our laboratory for this study is NGC 2264,
a young cluster which contains more than 300 proper motion members with
ages ranging from 0.1 to 10 Myr and masses ranging from 0.1 to 10 Msun.
We diagnose the presence of circumstellar accretion disks from observed
ultraviolet excesses, estimate accretion rates from the magnitude of
those excesses, and determine stellar rotation periods for more than 200
stars from the analysis of spot-modulated I-band light curves. We find
for PMS stars with masses M <= 0.4 Msun: (1) that accretion disk
lifetimes can exceed 10 Myr; (2) that accretion rates decay with time
(dM/dt ~ M(-n) ; 0.9 < n < 2); and (3) that disks appear to play a
critical role in regulating stellar rotation periods. In particular, PMS
stars stars surrounded by accretion disks on average rotate more slowly
than their counterparts which show no evidence of such disks: the median
rotation period for stars surrounded by disks is 7.91 days, while for
stars which lack disks the median period is 3.97 days. However, our
results suggest the range of periods (0.5 < P < 30 days) among
stars surrounded by disks is considerably larger than reported in
previous studies. The authors would like to thank Dr. Brian Patten for
his many contributions to this project. This work was supported by a
grant awarded under the NASA Origins of Solar Systems Program.