I study the formation and evolution of binary stars.

Wide Double White Dwarfs

Based on our population synthesis predictions, my advisor Marcel Agueros and I expected that wide double white dwarfs should be detectable in large scale Galactic surveys. We searched for common proper motion companions to spectroscopically confirmed white dwarfs in SDSS DR7. We redetected a previously known wide double white dwarfs and identified 11 new systems.

Andrews, Agüeros, Belczynski, Dhital, Kleinman, & West, ApJ, 2012

Common Proper-motion Wide White Dwarf Binaries Selected from the Sloan Digital Sky Survey

The Initial-Final Mass Relation

We continued our search for wide double white dwarfs in SDSS, using the entire DR9 photometric catalog. Our search yielded an additional 65 new systems. Including the previously known sample, there are now 142 confirmed and candidate wide double white dwarfs, which is provided as a csv file below. We engaged in a spectroscopic follow-up campaign, observing some 57 white dwarfs. Our systems place 18 new constraints on the initial-final mass relation based on a method successfully used by Finley & Koester (1997). This relies heavily on stellar evolution models that we ran using the open source code, MESA.

Andrews, Agüeros, Gianninas, Kilic, Dhital, & Anderson (submitted)

Wide Double White Dwarf Catalog

Polar Neutron Star Natal Kicks

Observations of the space velocity of pulsars moving throughout the Galaxy gave some indication that they may be preferentially moving along their spin axis. The source of this motion would have to be the neutron star's natal kick. While the physical source of this mechanism was never explained, we theorized that this may show an effect in the orbits and spin periods of double neutron stars. We tested this using a population synthesis code, StarTrack, created by Chris Belczynski and collaborators. Our results indicated an observable effect only when the neutron star's natal kick was small, and therefore could not explain the observed double neutron star eccentricity and spin period distribution.

Willems, Andrews, Kalogera & Belczynski, AIPC, 2008

Polar kicks and the spin period-eccentricity relation in double neutron stars

Double Neutron Star Formation

We further engaged in a more complete study of the population of double neutron stars, paying particular attention to the evolutionary channels of formation. In particular, the formation of J0737-3039, B1913+16, and B1534 is well constrained. We used this as a prior for our statistical model to determine the likelihood of any given model at producing the observed distribution in orbital period - eccentricity space. We find that the entire population of double neutron stars, including their evolutionary constraints can be explained using standard prescriptions and parameters

Andrews, Farr, Kalogera, & Willems (submitted)