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We demonstrate a new Bayesian technique to invert color-magnitude diagrams of main sequence and white dwarf stars to reveal the underlying cluster properties of age, distance, metallicity, and line-of-sight absorption, as well as individual stellar masses. The advantages our technique has over traditional analyses of color-magnitude diagrams are(More)
We investigate the application of neural networks to the automation of MK spectral classification. The data set for this project consists of a set of over 5000 optical (3800–5200Å) spectra obtained from objective prism plates from the Michigan Spectral Survey. These spectra, along with their two-dimensional MK classifications listed in the Michigan Henry(More)
We explore the application of artificial neural networks (ANNs) for the estimation of atmospheric parameters (T eff , log g, and [Fe/H]) for Galactic F-and G-type stars. The ANNs are fed with medium-resolution (∆λ ∼ 1 − 2 ˚ A) non flux-calibrated spectroscopic observations. From a sample of 279 stars with previous high-resolution determinations of(More)
We have extended our Bayesian modeling of stellar clusters—which uses main-sequence stellar evolution models, a mapping between initial masses and white dwarf (WD) masses, WD cooling models, and WD atmospheres—to include binary stars, field stars, and two additional main-sequence stellar evolution models. As a critical test of our Bayesian modeling(More)
Our mid-infrared survey of 124 white dwarfs with the Spitzer Space Telescope and the IRAC imager has revealed an infrared excess associated with the white dwarf WD 2115−560 naturally explained by circumstellar dust. This object is the fourth white dwarf observed to have circumstellar dust. All four are DAZ white dwarfs, i.e., they have both photospheric(More)
A sample of white dwarfs is selected from SDSS DR3 imaging data using their reduced proper motions, based on improved proper motions from SDSS plus USNO-B combined data. Numerous SDSS and followup spectra (Kilic et al. 2005) are used to quantify completeness and contamination of the sample; kine-matic models are used to understand and correct for(More)
Using HST and the WFPC2 we have acquired very deep V-and I-band photometry of stars in NGC 2420 and NGC 2477 to study cluster luminosity functions at approximately solar metallicity. We have determined these cluster luminosity functions down to M I = 10.5 (0.2 M ⊙) and find that the luminosity function of NGC 2420 turns over at M I ≈ 9.0, and possibly stops(More)
The discovery of probable X-ray, optical, and radio counterparts to Gamma Ray Bursts (GRBs) may allow signiicant advances in GRB research. More data are sorely needed, however. We have a target of opportunity program this semester at the 0.9 meter telescope to search for optical counterparts to GRBs. Images from the search will be made publicly available at(More)
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