Research

My research interests include compact neutron star binary systems such as transitional millisecond pulsar systems (tMSPs), high & low mass X-ray binaries (XRBs), and accreting millisecond pulsars (AMXPs). I also have done work related to stellar evolution, formation, and variability, as well as long baseline optical interferometry.

2015 - Present: Performing follow-up observations to unassociated Fermi-LAT sources

I have been pursuing follow-up observations of unassociated Fermi-LAT gamma-ray sources in an effort to identify new Milky Way compact binaries. I have been a part of numerous studies detailing multiwavelength observations of gamma-ray emitting millisecond pulsar binaries. Objects like these show unusual orbital and variability characteristics and some of these systems could constitute a distinct class of compact binaries.

Why?: The source of the gamma-ray emission in many millisecond pulsar binaries is still unknown and the peculiar variability in some of these systems warrants further study.

Collaborators: Jay Strader, C. C. Cheung, Laura Chomiuk, David Sand, Laura Shishkovsky, Paul Ray, Tyrel Johnson, Asher Wasserman, Soren Larsen, Jean Brodie, Evangelia Tremou

Above: Ellipsoidal modulations in B (blue), V (green) and R (red) bands due to tidal distortion of the secondary in a millisecond pulsar binary. Two maxima and two minima are observed over each orbital period. Photometry can be modeled to constrain the inclination of the system, and, in conjunction with spectroscopic data, component masses can be derived.

2013 - 2016: Developing a Catalog of Calibrator Stars for Next-Generation Optical Interferometers

I have compiled a catalog of uniformly derived angular diameters for ~1600 bright stars visible from newly commissioned optical interferometers in the Northern hemisphere. This catalog has been carefully vetted for binary and multiple stellar systems. I derived the angular diameters for each of the stars by fitting spectral templates to the observed spectral energy distributions (SEDs) from literature fluxes. I compared these derived angular diameters against those measured by optical interferometry for 75 of the stars, as well as to 176 diameter estimates from previous calibrator catalogs, finding in general excellent agreement.

This work has been published in The Astronomical Journal (Swihart et al. 2017, AJ, 153, 16). The catalog I present permits selection of the best calibrator stars for current and future visible-light interferometric observations.

Why?: Benchmark stars with known angular diameters are key to calibrating interferometric observations. With the advent of optical interferometry, there is a need for suitably bright, well vetted calibrator stars over a large portion of the sky.

Collaborators: Victor Garcia, Keivan Stassun, Matthew Muterspaugh, Gerard van Belle

Above: Comparison of estimated angular diameters I derived from SED fits and those measured interferometrically from the literature. Each cross is the angular diameter for a calibrator star estimated by my fitting procedure and its corresponding directly measured limb darkened disk angular diameter from the literature.

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