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" (PPNe), 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 PPNe on the basis of their large infrared excesses due to circumstellar dust. These have been the subject of follow-up studies using ground-based telescopes in Hawaii (CFHT, UKIRT, IRTF, Gemini), Arizona (KPNO), Chile (CTIO), and also space-based Hubble Space Telescope (HST), Infrared Space Observatory (ISO), and Spitzer Space Telescope. Spectacular high-resolution images of several bipolar PPNe have been obtained with HST (see below).

A long-term research program to study the light variations of PPNe has been 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:

• Science & Religious Faith

Photographs:

• Research Conferences
• Summer Research
• Observational Astronomy (ASTR 221)
• Yerkes Trips
• JOVE Program

Recent Publications:

• "Where are the Binaries? Results of a Long-term Search for Radial Velocity Binaries in Proto-Planetary Nebulae," 2017, Astrophys. J., 846, 96 (12 pp) (B.J. Hrivnak, G. Van de Steene, H. Van Winckel, J. Sperauskas, D. Bohlender, W. Lu)
• "Variability in Proto-Planetary Nebulae. IV. Light Curve Analysis of Four Oxygen-Rick, F Spectral Type Objects," 2015, Astron. J., 149, 185 (20pp) (B.J. Hrivnak, W. Lu, & K.A. Nault)
• "Variability in Proto-Planetary Nebulae. III. Light Curve Studies of Magellanic Cloudy Carbon-Rich Proto-Planetary Nebulae," 2015, Astrophys. J., 805, 78 (21 pp) (B.J. Hrivnak, W. Lu, K. Volk, R. Szczerba, I. Soszynski, & M. Hajduk)
• "Spitzer Space Telescope spectra of post-AGB stars in the Large Magellanic Clouds - polycyclic aromatic hydrocarbons at low metallicities" 2014, Mon. Not. Roy. Astron. Soc., 439, 1472-1493 (M. Matsuura, J. Bernard-Salas, T. Lloyd Evans, K.M. Volk, B.J. Hrivnak, et al.)
• "Studies of Variability in Proto-Planetary Nebulae. II. Light and Velocity Curve Analyses of IRAS 22272+5435 and 22223+4327," 2013, Astrophys. J., 766, 166 (24 pp) (B.J. Hrivnak, W. Lu, J. Sperauskas, H. Van Winckel, D. Bohlender, & L. Zacs)

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