Douglas Hoffman Research Assistant Entered: 2004 Office: 107 Astronomy Phone: (575)646-4834 Fax: (575)646-1602   E-mail: dhoffman (append "@nmsu.edu")
M.S. New Mexico State University, 2007 B.S. Georgia Institute of Technology, 2004

Research

I am currently working with Tom Harrison and collaborators at the Los Alamos National Laboratory (LANL) to extract cataclysmic variable and eclipsing binary light curves from the Robotic Optical Transient Search Experiment (ROTSE) database. This database was originally developed to look for the optical counterparts of gamma-ray bursts. It is an excellent resource for monitoring relatively bright variable stars, as it imaged the entire sky each night for over a year. I have used Fourier analysis to find and classify all variable stars in the database that are brighter that 13.5 magnitudes and vary by at least 0.1 magnitudes. I plan to search for low mass eclipsing binaries in this database to help constrain atmosphere models of these low mass stars, since the few that have been found do not match the current models.

Short period pulsating stars (Delta Scuti and RR Lyr type) are rather common, though the details of their pulsation, mass, and radius are largely unknown. By finding and analyzing eclipsing pulsators, the masses and radii of these objects can be derived and will help constrain models. It is also largely unknown whether a companion star can alter the pulsational properties of these objects. My PhD thesis will answer these questions, and consists of two main parts.

The first is discovering and identifying eclipsing pulsators for study. There are currently only 26 known short period eclipsing pulsators. Eleven of these were discovered by the All Sky Automated Survey (ASAS) in the southern hemisphere. The rest were discovered by searching known eclipsing systems in both hemispheres. I plan on using a very similar database, the Robotic Optical Transient Search Experiment (ROTSE-I) to search the northern hemisphere. Other databases will be used as well to aid in the search. An automated identification and classification of variable objects scheme will be employed to perform the search. This scheme will be a major part of the project and can be used on a variety of current and upcoming large astronomical databases.

The second part is scouring the eclipsing systems discovered for a pulsating component and then analyzing them. By subtracting off the oscillations due to the eclipse and performing Fourier analysis, pulsating components can be identified. Follow-up observations can then be used to aid in the determination of stellar parameters. I estimate that around 15 new eclipsing pulsators will be found in the ROTSE-I database alone.

Papers

Hoffman, Douglas, T.E. Harrison, B. McNamara, J. Holtz, W.T. Vestrand, T. Barker. The Case for Third Bodies as the Cause of Period Changes in Selected Algol Systems. AJ, 132, 2260.

Meetings

I presented a poster on the light curves of newly discovered variable stars from ROTSE-I observations at the January 2007 AAS meeting.

I presented a poster on the extraction of data from the ROTSE database at the August, 2005 "A Life with Stars" conference in Amsterdam, The Netherlands, and at the January 2006 AAS meeting