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Full-Text Articles in Stars, Interstellar Medium and the Galaxy

The Power Of Principled Bayesian Methods In The Study Of Stellar Evolution, Ted Von Hippel, David Van Dyk, David Stenning, Elliot Robinson, Elizabeth Jeffery, Nathan Stein, William Jefferys, Erin M. O'Malley Aug 2019

The Power Of Principled Bayesian Methods In The Study Of Stellar Evolution, Ted Von Hippel, David Van Dyk, David Stenning, Elliot Robinson, Elizabeth Jeffery, Nathan Stein, William Jefferys, Erin M. O'Malley

Ted von Hippel

It takes years of effort employing the best telescopes and in- struments to obtain high-quality stellar photometry, astrometry, and spectroscopy. Stellar evolution models contain the experience of life- times of theoretical calculations and testing. Yet most astronomers fit these valuable models to these precious datasets by eye. We show that a principled Bayesian approach to fitting models to stellar data yields substantially more information over a range of stellar astrophysics. We highlight advances in determining the ages of star clusters, mass ratios of binary stars, limitations in the accuracy of stellar models, post-main-sequence mass loss, and the ages of individual …


A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk Aug 2019

A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk

Ted von Hippel

We apply a self-consistent and robust Bayesian statistical approach to determine the ages, distances, and zero-age main sequence (ZAMS) masses of 28 field DA white dwarfs (WDs) with ages of approximately 4-8 Gyr. Our technique requires only quality optical and near-infrared photometry to derive ages with <15% uncertainties, generally with little sensitivity to our choice of modern initial-final mass relation. We find that age, distance, and ZAMS mass are correlated in a manner that is too complex to be captured by traditional error propagation techniques. We further find that the posterior distributions of age are often asymmetric, indicating that the standard approach to deriving WD ages can yield misleading results.


Bayesian Analysis For Stellar Evolution With Nine Parameters (Base-9): User's Manual, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, Rachel Wagner-Kaiser, Steven Degennaro, Nathan Stein, David Stenning, William H. Jefferys, David Van Dyk Aug 2019

Bayesian Analysis For Stellar Evolution With Nine Parameters (Base-9): User's Manual, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, Rachel Wagner-Kaiser, Steven Degennaro, Nathan Stein, David Stenning, William H. Jefferys, David Van Dyk

Ted von Hippel

BASE-9 is a Bayesian software suite that recovers star cluster and stellar parameters from photometry. BASE-9 is useful for analyzing single-age, single-metallicity star clusters, binaries, or single stars, and for simulating such systems. BASE-9 uses Markov chain Monte Carlo and brute-force numerical integration techniques to estimate the posterior probability distributions for the age, metallicity, helium abundance, distance modulus, and line-of-sight absorption for a cluster, and the mass, binary mass ratio, and cluster membership probability for every stellar object. BASE-9 is provided as open source code on a version-controlled web server. The executables are also available as Amazon Elastic Compute Cloud …