Louisiana State University Physics & Astronomy

Bradley E. Schaefer
Professor of Physics & Astronomy

Ph.D., 1983 - Massachusetts Institute of Technology

Astronomy - Astrophysics

Office: 243-A Nicholson
Telephone: 0015-Office
E-mail:

Hipparchus and The Farnese Atlas

RESEARCH INTERESTS

One primary thrust of research is to use photometry of exploding objects to get results of interest for cosmology:

For Gamma-Ray Bursts, the big advance has been the realization that the bursts are standard candles (like Type Ia Supernovae and Cepheids). With this, GRBs become tools for cosmology that can be seen out to red shifts from ~0.2 to around 20. This allows GRBs to be light sources for the first real detection of the Gunn-Peterson effect, to create a Hubble Diagram from 0.2<z<10, and to measure the star formation rate of our Universe out to z~20.

For supernovae, as part of the Supernova Cosmology Project, a Hubble Diagram was created with high accuracy out to a red shift of ~1.0. This demonstrated that the Cosmological Constant is non-zero and causes our Universe's expansion to accelerate.

For Recurrent Novae, the question is whether they are the progenitors of Type Ia supernovae, as the knowledge of the progenitor type is required for any evolution calculation such as is needed for the future precision cosmology with supernovae. To answer the progenitor question, extensive work is being pursued to get Recurrent Novae orbital periods, accretion rates, outburst dates, eruption light curves, and the average magnitudes between outbursts. A centerpiece of this work is the timing of eclipses from U Sco and CI Aql since 1897 to measure the orbital period change across the latest eruptions (in 1999 and 2000 respectively) to get the first measure of the ejected mass which allows for knowing whether the white dwarf is gaining or losing mass.

CURRENT AND SELECTED PUBLICATIONS

Schaefer, B.E., "The Hubble Diagram to Redshift >6 from 69 Gamma-Ray Bursts," Ap. J. 660, 16 (2007).
Bradley E. Schaefer and Andrew C. Collazzi, " Generalized Tests for Eight GRB Luminosity Relations," Astrophys. J. 656, L53-L56 (2007).
Schaefer, B.E., "A Test of Nova Trigger Theory," Ap. J. Letters 621, L53 (2005).
Rabinowitz, D.L., Schaefer, B.E., and Tourtellotte, S.W., "The Diverse Solar Phase Curves of Distant Icy Bodies I Photometric Observations of 18 Trans-Neptunian Objects 7 Centaurs and Nereid," Ap. J. 133, 26 (2007).
Ashcraft, T. and Schaefer B.E., "Are There Any Redshift >8 Gamma-Ray Bursts in the BATSE Catalog?," Ap. J., in press (astro-ph/0708.1331) (2007).
S. Perlmutter, G. Aldering, P. Castro, S. Deustua, S. Fabbro, G. Goldhaber, A. Goobar, D. E. Groom, I. M. Hook, A. G. Kim, M. Y. Kim, R. Knop, J. Lee, P. Nugent, N. Nunes, R. Pain, C. R. Pennypacker, C. Lidman, R. Ellis, M. Irwin, R. McMahon, P. Ruiz-Lapuente, N. Walton, B. Schaefer, B. Boyle, A. Filippenko, A. Barth, T. Matheson, A. Fruchter, N. Panagia, H. Newberg, W. Couch, "Measurements of Omega and Lambda from 42 High-Redshift Supernovae," Astrophys. J. 517, 565 (1999).
B. E. Schaefer, "Severe Limits on Variations of the Speed of Light With Frequency", Phys. Rev. Lett. 82, 4964 (1999).

Updated: Thu, 20-Sep-2007 3:27 PM