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Dynamical Evolution of White Dwarfs in Triples in the Era of Gaia
Cheyanne Shariat, Smadar Naoz, Bradley M. S. Hansen +3
The mission has detected many white dwarfs (WDs) in binary and triple configurations, and while observations suggest that triple stellar systems are common in our Galaxy, no…
When Do Stars Go BOOM?
Harvey B. Richer, Roger E. Cohen, Matteo Correnti +10
The maximum mass of a star that can produce a white dwarf (WD) is an important astrophysical quantity. One of the best approaches to establishing this limit is to search for WDs in…
Minimal conditions for survival of technological civilizations in the face of stellar evolution
Brad Hansen, Ben Zuckerman
The ease of interstellar rocket travel is an issue with implications for the long term fate of our own and other civilizations and for the much-debated number of technological civi…
The Effect of Stellar Evolution on Migrating Warm Jupiters
Shane Frewen, Brad Hansen
Warm jupiters are an unexpected population of extrasolar planets that are too near to their host to have formed in situ, but distant enough to retain a significant eccentricity in…
Constraining Neutrino Cooling using the Hot White Dwarf Luminosity Function in the Globular Cluster 47 Tucanae
Bradley Hansen, Harvey Richer, Jason Kalirai +3
We present Hubble Space Telescope observations of the upper part (T_eff> 10 000 K) of the white dwarf cooling sequence in the globular cluster 47 Tucanae and measure a luminosity f…
The Spectral Evolution of Convective Mixing White Dwarfs, the non-DA Gap, and White Dwarf Cosmochronology
Eugene Y. Chen, Brad M. S. Hansen
The spectral distribution of field white dwarfs shows a feature called the "non-DA gap". As defined by Bergeron et al., this is a temperature range (5100K--6100K) where relatively…
A Deep, Wide-Field, and Panchromatic View of 47 Tuc and the SMC with HST: Observations and Data Analysis Methods
Jason S. Kalirai, Harvey B. Richer, Jay Anderson +10
In HST Cycle 17, we imaged the well known globular star cluster 47 Tucanae for 121 orbits using ACS and both the UVIS and IR channels of WFC3 (GO-11677, PI - H. Richer). This uniqu…
Migration then assembly: Formation of Neptune mass planets inside 1 AU
Brad M. S. Hansen, Norm Murray
We demonstrate that the observed distribution of `Hot Neptune'/`Super-Earth' systems is well reproduced by a model in which planet assembly occurs in situ, with no significant migr…
Old White Dwarf Stars with Some Hydrogen -- Cooling Curves
Eugene Y. Chen, Brad M. S. Hansen
We present theoretical analysis on old white dwarf stars with \emph{some} hydrogen, that possess a mass of surface hydrogen from $1\times10^{-11}M_{\sun}$ to $1\times10^{-7}M_{\sun…
Calibration of Equilibrium Tide Theory for Extrasolar Planet Systems
Brad Hansen
We provide an 'effective theory' of tidal dissipation in extrasolar planet systems by empirically calibrating a model for the equilibrium tide. The model is valid to high order in…
The Masses of Population II White Dwarfs
Jason S. Kalirai, D. Saul Davis, Harvey B. Richer +4
Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still bu…