相关论文: Testing Theoretical Evolutionary Models with AB Do…

We have derived a new age estimate for the nearby young star AB Dor and have investigated the resulting implications for testing theoretical evolutionary models with the data reported by Close and coworkers for the low-mass companion AB Dor…

We expand upon the results of Close et al. 2005 regarding the young, low-mass object AB Dor C and its role as a calibration point for theoretical tracks. We present an improved spectral reduction and a new orbital solution with two…

Studies of fundamental parameters of very low-mass objects are indispensable to provide tests of stellar evolution models that are used to derive theoretical masses of brown dwarfs and planets. However, only objects with dynamically…

We present new photometric and spectroscopic measurements for the unique, young, low-mass evolutionary track calibrator AB Dor C. While the new Ks photometry is similar to that previously published in Close et al. (2005) the spectral type…

AB Dor C, a low-mass companion to the young star AB Dor A has recently been imaged. Direct detection and astrometric observations have been used to solve the AB Dor C orbit and obtain a dynamical mass estimate. Near-infrared magnitudes and…

Observations of low-mass companions for which the dynamical masses are well constrained help to improve the calibration of evolutionary models. Such observations thereby provide more confidence in the estimation of the mass of a companion…

We have obtained images of the Trapezium Cluster (140" x 140"; 0.3 pc x 0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R=800)…

We test state-of-the-art model atmospheres for young very low-mass stars and brown dwarfs in the infrared, by comparing the predicted synthetic photometry over 1.2-24 {\mu}m to the observed photometry of M-type spectral templates in…

Chauvin et al. 2005 imaged a co-moving companion at ~260 AU from the young star AB Pic A. Evolutionary models predictions based on J H K photometry of AB Pic b suggested a mass of ~13 - 14 MJup, placing the object at the deuterium-burning…

Low-mass stars exhibit substantial pre-main sequence evolution during the first ~100 Myrs of their lives. Thus, young M-type stars are prime targets for isochronal dating, especially in young moving groups (YMGs), which contain large…

We present resolved NACO photometry of the close binary AB Dor B in H- and Ks-band. AB Dor B is itself known to be a wide binary companion to AB Dor A, which in turn has a very low-mass close companion named AB Dor C. These four known…

I present infrared spectroscopy of 37 brown dwarf candidates in the Upper Sco association, 35 of which are classified as young and cool, making them likely members. This sample includes many of the faintest spectroscopically confirmed…

Substellar members of young ($\lesssim$150 Myr) moving groups are valuable benchmarks to empirically define brown dwarf evolution with age and to study the low-mass end of the initial mass function. We have combined Pan-STARRS1 (PS1) proper…

I present new results from a continuing program to identify and characterize the low-mass stellar and substellar populations in the young cluster IC 348 (1-10~Myr). Optical spectroscopy has revealed young objects with spectral types as late…

We demonstrate the feasibility of detecting directly low mass stars in unresolved super-star clusters with ages < 10 Myr using near-infrared spectroscopy at modest resolution (R ~ 1000). Such measurements could constrain the ratio of high…

I review efforts to determine the form and any lower limit to the initial mass function in the Galactic disk, using observations of low-mass stars and brown dwarfs in the field, young clusters and star forming regions. I focus on the…

We present results from a near-infrared spectroscopic study of candidate brown dwarfs and low mass stars in the young cluster NGC 2024. Using FLAMINGOS on the KPNO 2.1m and 4m telescopes, we have obtained spectra of ~70 new members of the…

The determination of the lower-end of the initial mass function (IMF) provides strong constraints on star formation theories. We report here on a search for isolated planetary-mass objects in the 3 Myr-old star-forming region IC 348. Deep,…

We present the results of a program to acquire photometry for eighty-six late-M, L, and T dwarfs using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We examine the behavior of these cool dwarfs in various color-color and…

Mass measurements and absorption line studies indicate that the stellar initial mass function (IMF) is bottom-heavy in the central regions of many early-type galaxies, with an excess of low mass stars compared to the IMF of the Milky Way.…