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 Not
all stars shine with a constant light, some stars can double in brightness
in a few seconds, and increase in brightness by a factor of a hundred
within a few hours. These stars are accreting binary systems, where a
compact object such as a white dwarf, neutron star, or black hole is in
a close orbit with an ordinary star. The two stars are almost touching,
and the orbital periods are very small ´ as little as 11 minutes. The
gravitational field of the compact object pulls gas off the surface of
the ordinary star, and this gas spirals around the compact object to form
an accretion disk, and then slams onto its surface. Rather than flowing
in an even stream, the gas comes off the surface of the donor star in
irregular chunks. As each chunk hits the disk of gas spiraling in to the
compact object, the collision heats the gas and causes a burst of X-rays
and light. Blobs of gas from the inner edge of the accretion disk similarly
slam on to the surface of the compact object and cause a flash of X-rays
and light.
In a collaboration with Dr. Keith Horne that began 30 years ago when
we were freshmen in college, I have been designing and building detectors
and data systems to study rapidly varying light from stars. Some of the
systems I built were:
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a millisecond photometer
for use on small telescopes
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a millisecond photometer
for use on the 60" and 100" telescopes at Mount Wilson,
the 60" at Palomar, and the 100" at Las Campanas
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a data link between Steve
Shectman's Shectograph on the 100" at Mt. Wilson and the 60"
at Mt. Wilson, allowing us to do exact simultaneous spectroscopy and
photometry with the two telescopes.
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a high speed datasystem
for Steve Shectman's 2D-Fruitti spectrometer. This allowed us to do
continuous millisecond spectroscopy of the black hole binary A0260-00
with the 200" at Palomar, and similar work with the 100"
at Las Campanas.
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a datasystem for the
LRIS spectrograph at the 10 meter Keck telescope on Mauna Kea, allowing
us to take 14 spectra per second continuously, with coordinated observations
using the Rossi XTE X-ray satellite.
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I am currently designing
a datasystem for the spectrograph on the 15 meter HET telescope in
West Texas.
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With these datasystems, we are finding a wealth of unexpected phenomena.
For instance, in AE Aquarii, we have found that the rapidly rotating magnetic
field from the spinning white dwarf acts a propeller, spraying gas out
of the system.
Keith Horne and me with the datasystems at Keck
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Bev Oke, Keith, and me in the control room
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Hawaii in July; scraping ice off the windshield. Bev is in the car.
Recent Papers
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Doppler signatures of Ha flares in AE
Aquarii. Welsh, W.F., Horne, K., and Gomer, R.H. (1998) Monthly
Notices of the Royal Astronomical Society 298, 285-302.
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The discovery and broad-band follow-up of the transient afterglow
of GRB 980703. Bloom, J.S., Frail, D.A., Kulkarni, S.R., Djorgovski,
S.G., Halpern, J.P., Marzke, R.O., Patton, D.R., Oke, J.B., Horne,
K.D., Gomer, R., Goodrich, R., Campbell, R., Moriarty-Schieven,
F.H., Redman, R.O., Feldman, P.A., Costa, E., Masetti, N. (1998)
Astrophysical Journal. 508, L21-L24.
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Emission
line oscillations in the dwarf nova V2051 Ophuichi. Steeghs,
D., O›Brien, K., Horne, K., Gomer, R., and Oke, B. (2001) Monthly
Notices of the Royal Astronomical Society 323, 484-496.
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Keck
II spectroscopy of mHz quasi-periodic oscillations in Hercules X-1.
O'Brien, K., Horne, K., Boroson, B., Still, M., Gomer, R., Oke,
J.B., Boyd, P., and Vrtilek, S.D. (2001) Monthly Notices
of the Royal Astronomical Society 326, 1067-1075.
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Fireballs and oscillations
in AE Aqr. Skidmore, W., Pearson, K.J., O'Brien, K., Horne, K.,
and Gomer, R. The Physics of Cataclysmic Variables and Related
Objects: ASP Conference Series 261, 169-170 (2002)
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High
speed Keck spectroscopy of flares and oscillations in AE Aquarii.
Skidmore, W. , O'Brien, K., Horne, K., Gomer, R.H., Oke, J.B., and
Pearson, K.J. Monthly Notices of the Royal Astronomical Society
338, 1057-1066 (2003).
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High-speed Keck
II and RXTE spectroscopy of Cygnus X-2: (I) Three X-ray components
revealed by spectral variability.O'Brien, K., Horne, Gomer, R.H,,
Oke, J.B., and van der Klis, M. Monthly Notices of the Royal
Astronomical Society 350, 587-595 (2003).
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High speed Keck spectroscopy
of flickering in AE Her. Skidmore, W., Gomer, R.H, Horne, K., O'Brien,
K., and Oke, J.B. ASP Conference Series, Capetown Meeting on
Magnetic Cataclysmic Variables. In press.
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