HALE BRADT, Professor of
Physics, Emeritus
Research Interests
RXTE, an earth-orbiting X-ray astronomy observatory, studies X-ray
emission from black-holes and neutron stars with high statistics
so the plasmas in their vicinities can be studied with time resolutions
comparable to the dynamical time constants of matter in the deep
potential wells. The mission, among other important results, has
revealed the presence of accreting X-ray pulsars (neutron stars)
with spin periods of a few milliseconds. It has also demonstrated
a link between accretion and jet formation in (black-hole) "microquasars."
Microquasars are black-hole accretors in the Milky-Way Galaxy which
exhibit pronounced radio jets, as do their more massive and distant
counterparts, the well known extragalactic quasars.
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Biographical Sketch
Professor Bradt joined the Department of Physics as an Instructor
in 1961, was promoted to Assistant Professor in 1963, to Associate
Professor in 1968, to Professor in 1972, and became Professor Emeritus
in 2001. A music major, he earned his A.B. from Princeton University
in 1952 and his Ph.D. in Physics from MIT in 1961. Bradt founded
MIT's sounding rocket program in X-ray astronomy in 1967, was a
co-Investigator on the MIT SAS-3 mission (launched in 1975), was
a co-Principal Investigator on the High-Energy Astronomy Observatory,
HEAO-1 (1977). He was Principal Investigator of the All-Sky-Monitor
(ASM) instrument on the Rossi X-ray Timing Explorer (RXTE, 1995),
which is still operating in 2004. Bradt's work has long been directed
toward the determination of X-ray source positions and the follow-up
studies of the objects identified. With students and associates,
he has carried out studies with RXTE of the unusual neutron-star
binary Cir X-1, of gamma-ray bursts, and of the behavior of transient
X-ray sources.
Bradt served terms as the Secretary/Treasurer and Chairman of the
High Energy Astrophysics Division (HEAD) of the American Astronomical
Society (AAS) in the 1970s. He was awarded the Buechner Teaching
Prize of the MIT Physics Department in 1990 and was the 1999 co-recipient
of the Rossi Prize of the HEAD/AAS.
Since retirement, Bradt has focused on textbook writing; Astronomy
Methods was published by Cambridge University Press in 2004.
His forthcoming textbook, Astrophysics Processes, is due
in 2005.
[top] Selected Publications
Astronomy Methods, Hale Bradt, textbook, Cambridge
University Press (2004).
Highlights of RXTE studies of compact objects after ~5 years.
H. Bradt, R. E. Rothschild, J. H. Swank. In: The Ninth Marcel Grossmann
Meeting. Eds. V. G. Gurzadyan, R. T. Jantzen, R. Ruffini. Singapore:
World Scientific Publishing, 2002, Part A, p. 694 - 7, astro-ph/0106508.
Transient X--Ray Sources Observed with the Rxte All-Sky Monitor
after 3.5 Years, H. Bradt, A.M. Levine, R. A. Remillard,
D. A. Smith, in Proceedings of the Vulcano May 1999 Workshop on
Multifrequency Behaviour of High Energy Cosmic Sources: III, F.
Giovannelli and Lola Sabau-Graziati (eds.), Mem SAIt, Vol 71, (2000);
astro-ph/0001460 (in press).
X 1908+075: An X-ray Binary with a 4.4 day Period,
L. Wen, R. A. Remillard, H. V. Bradt, ApJ, in press; astro-ph/9907424
(2000).
Localizations of Thirteen Gamma-ray Bursts by the All-Sky
Monitor on RXTE, D. A. Smith, A. M. Levine, H. V. Bradt,
R. Remillard, J. G. Jernigan, K. C. Hurley, L. Wen, M. Briggs, T.
Cline, E. Mazets, S. Golenetskii, D. Frederics, ApJ 526, 683 (1999).
X-ray Orbital Modulation of Cygnus X-1, L. Wen,
Wei Cui, A.M. Levine, H. V. Bradt, ApJ 525, 968 (1999) "Gamma-ray
Burst Positions from the ASM on RXTE", H. V. Bradt & D. A. Smith,
Proceedings of "Gamma-Ray Bursts in the Afterglow Era", Rome, 3-6
Nov, 1998; astro-ph/9905271.
Scattering and Iron Fluorescence Revealed During Absorption
Dips in Circinus X-1, R. E. Shirey, A.M. Levine & H. V.
Bradt, ApJ 524, 1048 (1999). "RXTE All-Sky Monitor Localization
of SGR 1627-41", D. A. Smith, H. V. Bradt, A.M. Levine, ApJL 519,
L147 (1999).
Highlights from RXTE after 2.5 Years: Neutron-star Spins
at KiloHertz Frequencies, Microquasars and More, H. V. Bradt
in Frontier Objects in Astrophysics and Particle Physics, Proceedings
of the Vulcano Workshop, Vulcano, Italy, May 1998, eds. F. Giovannelli
& G. Mannoccihi, Societa' Italiana di Fisica, Editrice Compositori,
Bologna, Italy; astro-ph/9901174.
X-ray Timing Explorer Mission. H. V. Bradt, R.E.
Rothschild, J. H. Swank, Astronomy and Astrophysics Supplement Series,
vol. 97, p. 355-360 (1993).
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