Astronomy

Supergiant-Star/Black-Hole Binary System (SS 433)  [Dr. Todd Hillwig]

SS 433 (also known as V1343 Aql) is a fascinating interacting binary system. It is currently believed to consist of an A-type supergiant star approximately 27 times the diameter of the Sun and a black hole. The star and black hole orbit one another in just over thirteen days. At this close proximity, the black hole in the system is pulling material from the supergiant star. This material circles the black hole forming a large disk of gas. Some of the material gets ejected perpendicular to the disk as very narrow "jets", travelling at 0.26c, or 26% the speed of light! I am working with collaborators around the country to understand the complicated nature of this system.

 Black Hole Binary

[Simulated image from Sky & Telescope Magazine]
 Planetary Nebula Central Stars [Dr. Todd Hillwig]

Planetary Nebula Central Stars are remnants of sunlike stars which have shed their outer envelopes. These envelopes are blown away from the star and appear to us as planetary nebulae. Many planetary nebulae have very complex shapes and we aren't sure what creates the varied and fascinating structures we observe. One possibility is that there is a companion to the central star and that the orbit of these two stars creates the physical conditions which shape the outflowing gas. My research has been focused on determining how many, and specifically which, planetary nebulae have binary central stars. Primarily this is being done using the SARA telescope at Kitt Peak National Observatory.

Planetary Nebula 

[Hubble Space Telescope Image]

Observational Studies of Evolved Stars [Dr. Bruce Hrivnak]

My main research is the observational study of the evolution of stars like the Sun. Such stars have evolved beyond the red giant stage and have ejected their outer gaseous layer. I have been working to identify such objects, determine the properties of the stars – spectral type, chemical composition, variability, and determining the properties of their surrounding gas and dust – composition, kinematics, structure of the nebula. This research has made use of large ground-based telescopes in Hawaii, Arizona, and Chile and space-based telescopes such as the Hubble Space Telescope, Spitzer Space Telescope, and Infrared Space Observatory. I am presently involved in a long-term study of the variability of these objects, which is being carried out at the VU Observatory with active collaboration by VU undergraduate students. The goal is to determine the pulsational properties of the objects and to search for evidence of binary companions. This research is being carried out with support from the National Science Foundation and NASA.

 IRAS-17150-3224
Observational Studies of Interacting Binary Stars [Dr. Bruce Hrivnak]

I am also studying eclipsing binary star systems to determine the fundamental properties of the individual stars, such as mass, size, and temperature. This involves the observations of their light curves using the VU Observatory and the observations of their velocity curves at other observatories. This study has resulted in several recent publications with VU undergraduate students as co-authors.

 Binary light curve