Research

Artist's conception of the planet Kepler-16b, which orbits a K- and M-dwarf binary star. [Credit: NASA/JPL-Caltech/R. Hurt]

Stellar Companions of Planet Host Stars Observed with Kepler/K2 and TESS:

Binary stars are common throughout the galaxy, with roughly half of all nearby Sun-like stars having at least one companion. Exoplanet transit surveys, such as Kepler/K2, have discovered thousands of planets orbiting other stars and shown that planetary systems are remarkably common. While many exoplanet searches target only single stars or very wide binaries, Kepler was relatively unbiased to stellar multiplicity, resulting in the discovery of planets orbiting one or both stars in a number of binary systems. However, as the impact of stellar multiplicity on planet occurrence is not well understood and many binaries remain unresolved in such surveys, planet properties and population statistics are, in general, determined as if all stars are single. Not accounting for the effects of stellar multiplicity statistically biases planets toward smaller radii and gives rise to systematic errors in planet occurrence rates and completeness corrections. Detecting unresolved stellar companions can mitigate some of these biases and help us understand the fraction of exoplanets found in binaries. I use high angular resolution speckle imaging to detect stellar companions within ~1 arc second of Kepler\K2 and TESS planet candidate host stars in order to validate planets, determine the binary fraction of exoplanet host stars, and study the binary properties of such systems.

Fundamental Parameters of Eclipsing Binaries in the Kepler Field of View:

Eclipsing binaries are valuable sources of fundamental stellar parameters, including stellar masses and radii, that constrain stellar evolutionary models and serve as valuable tests of stellar evolution. The exquisite light curves generated by space-based missions such as Kepler enable the study of eclipsing binaries to unprecedented detail and provide insight into additional astrophysical processes. Using a sample of eclipsing binaries that were studied as part of a Kepler Guest Observer Program searching for tertiary companions to close binaries via eclipse timing, I derive fundamental parameters for each system in order to constrain the masses of any tertiary companions and fully characterize the binaries. I obtain moderate resolution optical spectra from the Kitt Peak 4-m and Lowell Observatory 1.8-m telescopes for the intermediate mass (1 - 4 M_sun) systems in order to produce double-lined radial velocity curves and spectroscopic orbital solutions. I then reconstruct spectra of the individual binary components using Doppler Tomography and fit them with synthetic spectra to determine effective temperatures, surface gravities, and rotational velocities. Using these data and constraints I then model the radial velocities and Kepler photometry to determine physical parameters for each system, providing fundamental determinations of stellar masses and radii while placing constraints on any low mass companions.

Artist's impression of an eclipsing binary. [Credit: ESO/L. Calçada]

A Hubble Space Telescope image of Pismis 24, a star cluster at the core of the NGC 6357 nebula. The star cluster includes some of the most massive stars known in the galaxy. [Credit: NASA, ESA and Jesús Maíz Apellániz]

The Structure of Mass Loss from Massive Stars:

I also worked on a survey of mass outflows in luminous, evolved, massive stars using Gemini North and NIFS (Near-Infrared Integral Field Spectrometer). The goal was to determine the frequency of He I 10830 among the different groups of objects, document emission line profiles to determine where the emission forms, and search for evidence of resolved emission on the scale of arc seconds.

Additionally, I have been involved in various projects involving spectroscopic observations and analyses of single and double-lined O and B star systems, and obtaining near IR spectrophotometry of luminous blue variables and Be stars.

Previous Work

The Wilson-Bappu Effect 50 Years Later:

During my time at the University of Denver, I used the Paranal Observatory library of high-resolution spectra from the ESO Very Large Telescope and UVES (Ultraviolet and Visual Echelle Spectrograph) to measure line widths and wing emission for Ca II H and K lines in late type stars. By plotting the measured FWHM and absolute magnitude, we re-evaluated the Wilson-Bappu-Stencel line-width-to-luminosity correlation for the K core emission and H-K core wing emission lines.

Basic Parameters of Open Cluster NGC 2420:

As an REU (research experiences for undergraduates) student at Indiana University, I determined refined parameters of the canonical metal-poor open cluster NGC 2420 from photometric observations at the WIYN 0.9m Telescope. The photometry was performed with DAOPHOT, allowing for spatially-dependent PSFs and aperture corrections. Using color-color and color-magnitude diagrams we determined the cluster's reddening metallicity, distance, and age.

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