Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Physical Sciences and Mathematics
A Monte Carlo Method For Evaluating Empirical Gyrochronology Models And Its Application To Wide Binary Benchmarks, Tomomi Otani, Ted Von Hippel, Derek Buzasi, Terry Oswalt, Alexander Stone-Martinez, Patrice Majewski
A Monte Carlo Method For Evaluating Empirical Gyrochronology Models And Its Application To Wide Binary Benchmarks, Tomomi Otani, Ted Von Hippel, Derek Buzasi, Terry Oswalt, Alexander Stone-Martinez, Patrice Majewski
Publications
No abstract provided.
Nearly 30,000 Late-Type Main-Sequence Stars With Stellar Age From Lamost Dr5, Jiajun Zhang, Terry D. Oswalt, Jingkun Zhao, Xilong Liang, Xianhao Ye, Gang Zhao
Nearly 30,000 Late-Type Main-Sequence Stars With Stellar Age From Lamost Dr5, Jiajun Zhang, Terry D. Oswalt, Jingkun Zhao, Xilong Liang, Xianhao Ye, Gang Zhao
Publications
We construct a sample of nearly 30,000 main-sequence stars with 4500K < Teff < 5000K and stellar ages estimated by the chromospheric activity−age relation. This sample is used to determine the age distribution in the R − Z plane of the Galaxy, where R is the projected Galactocentric distance in the disk midplane and Z is the height above the disk midplane. As |Z| increases, the percentage of old stars becomes larger. It is known that scale-height of Galactic disk increases as R increases, which is called flare. A mild flare from R ∼ 8.0 to 9.0 kpc in stellar age distribution is found. We also find that the velocity dispersion increases with age as confirmed by previous studies. Finally we present spiral-shaped structures in Z − υZ phase space in three stellar age bins. The spiral is clearly seen in the age bin of [0, 1] Gyr, which suggests that a vertical perturbation to the disk probably took place within the last ∼ 1.0 Gyr.
An Independent Calibration Of Stellar Ages: Hst Observations Of White Dwarfs At V=25, Ted Von Hippel, Gerard Gilmore, D.H.P. Jones
An Independent Calibration Of Stellar Ages: Hst Observations Of White Dwarfs At V=25, Ted Von Hippel, Gerard Gilmore, D.H.P. Jones
Publications
The white dwarf luminosity function of a stellar cluster will have a sharp trunca- tion at a luminosity which is determined by the time since formation of the first white dwarfs in that cluster. Calculation of the dependence of this limiting luminosity on age requires relatively well-understood physics and is independent of stellar evolutionary models. Thus, measurement of the termination of the white dwarf luminosity func- tion provides an independent method to determine the age of a cluster, and thereby to calibrate stellar evolutionary ages. We have obtained HST WFPC2 data in two open clusters, identified the white dwarf sequence, …