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تسجيل مستخدم جديدRotational velocities of low-mass stars in the Pleiades and Hyades
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We have obtained high-resolution spectra of 89 M dwarf members of the Pleiades and Hyades and have derived radial velocities, H-alpha equivalent widths, and spectroscopic rotational velocities for these stars. Typical masses of the newly-observed Pleiades and Hyades stars are ~ 0.4 M_{sun} and ~ 0.2 M_{sun}, respectively. We combine our new observations with previously published data to explore the rotational evolution of young stars with M < 0.4 M_sun. The average rotation rate in the Hyades (age 600 Myr) is about 0.4 that of the Pleiades (110 Myr), and the mean equivalent widths of H-alpha are also lower. As found in previous studies, the correlation between rotation and chromospheric activity is identical in both clusters, implying that the lower activity in the Hyades is a result of the lower rotation rates. We show that a simple scaling of the Pleiades rotational distribution for M leq 0.4 M_{sun}, corrected for the effects of structural evolution, matches that of the Hyades if the average angular momentum loss from the Pleiades to the Hyades age is factor of approx 6. This suggests that the distribution of initial angular momenta and disk-locking lifetimes for the lowest mass stars was similar in both clusters. We argue that this result provides further evidence for a saturation of the angular momentum loss rate at high rotational velocities.
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Stellar rotation is a crucial parameter driving stellar magnetism, activity and mixing of chemical elements. Furthermore, the evolution of stellar rotation is coupled to the evolution of circumstellar disks. Disk-braking mechanisms are believed to be
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The projected stellar rotational velocity ($v sin i$) is critical for our understanding of processes related to the evolution of angular momentum in pre-main sequence stars. We present $v sin i$ measurements of high-resolution infrared and optical sp
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