Dr. Bruce J. Hrivnak

Research activity:

Observational astronomy: studying the properties of evolved stars and binary stars, primarily at visible and infrared wavelengths.

Prof. Hrivnak has been actively engaged in the identification and study of "proto-planetary nebulae" (PPN), objects in transition between the asymptotic giant branch (AGB) and planetary nebula (PN) phases in the evolution of stars. This is a short-lived phase (few thousand years) near the end of the life of most stars. During this phase, the star, which had been losing mass during the previous AGB phase, becomes enshrouded in an expanding shell of gas and dust.

In collaboration with Dr. Sun Kwok (Hong Kong University), he has used data from the Infrared Astronomical Satellite (IRAS) to identify candidate PPNs on the basis of their large infrared excesses due to circumstellar dust. These have been the subject of follow-up studies using telescopes in Hawaii (CFHT,UKIRT,IRTF,Gemini), Arizona (KPNO), Chile (CTIO), and more recently the Hubble Space Telescope (HST) and Infrared Space Observatory (ISO). Spectacular high-resolution images of several bipolar PPN have been obtained with HST (see below).

A program to study the light variations of PPN is being carried out at the Valparaiso Univ. Observatory, with undergraduates actively participating in this research.

Prof. Hrivnak has also been involved in the study of binary star systems. By combining spectroscopic and photometric observations, he has determined the fundamental properties (mass, size, luminosity, temperature) of a number of these interacting binary stars.

2001 Rubel Lecture in Christianity and Higher Learning (Valparaiso University):
"Glorious are the Works of the Lord: Studying the Heavens" (B. J. Hrivnak).

Other Interests:

• Family
• Christianity
• Running

Recent Publications:

• "From Red Giants to Planetary Nebulae: Studies of the Transitional Objects (Invited Review)," 2001, in ASP Conf. Ser. 226: 12th European Conference on White Dwarfs, eds. J.L. Provencal, H.L. Shipman, J. MacDonald, & S. Goodchild (San Francisco; ASP), 3-12 (B.J. Hrivnak).
• "High-Resolution Imaging of Proto-Planetary Nebulae: The Effects of Orientation," 2001, Astron. J., 122, 1525-1537 (K.Y.L. Su, B.J. Hrivnak, & S. Kwok).
• "The Discovery of Circumstellar Arcs Around Two Bipolar Proto-Planetary Nebulae," 2001, Astron. J., 121, 2775-2780 (B.J. Hrivnak, S. Kwok, & K.Y.L. Su).
• "An Ultraviolet Study of the Short-Period Binary OO Aquilae," 2001, Astron. J., 121, 1084-1090 (B.J. Hrivnak, E.F. Guinan, L.E. DeWarf, & I. Ribas).
• "Discovery of a Disk-Collimated Bipolar Outflow in the Proto-Planetary Nebula IRAS 17106-3046," 2000, Astrophys. J., 544, L149-L152 (S. Kwok, B.J. Hrivnak, & K.Y.L. Su).
• "2-45 Micron Infrared Spectroscopy of Carbon-Rich Proto-Planetary Nebulae," 2000, Astrophys. J., 535, 275-292 (B.J. Hrivnak, K. Volk, & S. Kwok).

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