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Research
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Summer 1997: For my first project, I tried to find orbital modulations in the
X-ray emission from the
low-mass X-ray binary 4U 1820-30. Couldn't find them. About a year later, my
advisor managed to find them in data taken at the same time as the data I
analyzed. It turned out that the data that contained the modulation was not
publicly available when I did my analysis.
Spring 1998: Tried to write a new code to model the spectrum of the accretion
disks around black hole binaries. It turned out that I didn't have enough
constraints on the outer portion of the disk to make the exercise worthwhile.
Summer 1998: I wrote a code to do "acceleration searches" for periodic signals
from a couple dozen bright low-mass X-ray binaries. The code performed a
series of quadratic correction to the arrival times of the photons, to
try to correct for the unknown orbital period. I was hoping to find signals
at the spin frequencies of the neutron stars. I didn't find any. Some of the
upper limits were close to 0.1%, but that wasn't much better than what
Brian Vaughan did with Ginga in the 90's.
Sometime in 1998: Since I had gained so much experience in not finding the
orbital period in 4U 1820-30, I also tried to find the orbital modulations in
the newly-discovered accreting millisecond pulsar SAX J1808.4-3658. That
didn't work either.
Fall 1999: I wrote code to track the phases of quasi-periodic oscillations
in the X-ray emission of LMXBs, with the intention of eventually creating
average profiles of the oscillations. There were two ways to measure the
phase: either with the minimum or maximum of the QPO pulses. It turned out
that the two ways of measuring phases produced significantly different pulse
profiles, because the pulses differed significantly from cycle to cycle.
I gave up on that project.
Also in 1999: Not exactly a failure, but I wrote a bunch of code for timing
analyses that I never used: an auto-correlator, cross-correlator, and a
polynomial-based power spectral analyzer that was supposed to be good
for measuring power with very steep frequency dependence. I don't really
remember why I did all that.
Sometime in 2000: I failed to find the (then unknown) orbital period
of GRS 1915+105 in long-term radio monitoring data. Anyway, I don't
think anyone else has seen its 13-day orbital period in radio either.
Also in 2000: I succeeded in getting my first proposal accepted, for the X-ray
satellite ASTRO-E. I wanted to look at my pet X-ray binary, GRS 1915+105.
ASTRO-E failed to decouple from the final stage of its rocket, and ended up
burning up in the atmosphere.
Throughout 2001: I tried to reduce a Chandra grating spectrum of GRS 1915+105.
The output of the software didn't make sense, so I gave up and found something
easier to work on.
2004-2005: After a nice lucky streak, I found something else to fail at.
We obtained some pioneering observations to search for
circumbinary disks around low-mass X-ray binaries (LMXB) in the mid-infrared
using Spitzer. The idea was motivated by the fact that the first planets
were found around an isolated millisecond pulsar, which probably descended
from an LMXB, so we hoped to find the proto-planetary disk. We didn't
find any evidence for disks.
Summer 2005: A few of us obtained observations of the nucleus
of M81 with the laser guide-star system on Lick. We hoped to look for
variability in the amount of infrared light from accretion onto the central
super-massive black hole. It would have been a key measurement as part
of a coordinated campaign using radio, submm, and X-ray observatories.
Instead, we found that it was impossible to tell changes in flux from the
nucleus apart from changes in the efficiency with which the adaptive
optics system was able to correct for the blurring caused by the
atmosphere. In retrospect, we could have anticipated that.
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