A Photometric Search for Extrasolar Planets Around White Dwarfs
by Michael J. Wilson

Abstract:

This thesis is an observational survey, using the Iowa Robotic Observatory,
with the goal of detecting an extrasolar planet around a white dwarf. With the large
number of planets that have been discovered around solar-type stars, a natural
assumption is that some of these planets may remain in orbit around the remnant white
dwarf. A brief look at the conditions under which a Jovian planet orbiting near a
white dwarf may form is taken in order to see that the drag force experienced by the
orbiting planet causes it to spiral in. The Roche radius is considered for how close
a potential planet can approach along with the probability of an eclipse if the planet
is close to the star. An initial number of the local sample (within 20 parsecs) of
white dwarfs is chosen, with 84 targets remaining out of 105 initial targets after known
binary systems are removed. Of these 84 white dwarfs, 75 were observed and 128 light
curves generated over 578 good hours of observation out of 698 hours total during survey
period of October 2002 until July 2003. No eclipse events were detected, which led to
the conclusion that planets surviving very close to the Roche limit (within a few
hundredths of an AU) are not common. In addition, a study of the variability of
these white dwarfs was undertaken. It was found that a few possibilities arose,
including the possibility of a variable that was not a white dwarf, but was one of
the calibration stars used.

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Sample White Dwarf Images

RA 04:23 Dec 12:00 click to enlarge	RA 04:26 Dec 58:48 click to enlarge

Images and Charts:

WD0000-345 WD0009+501 WD0011-134 WD0038-226 WD0046+051 WD0115+159 WD0123-262 WD0135-052 WD0148+641 WD0208+396 WD0230-144 WD0235+064 WD0245+541 WD0322-019 WD0326-273 WD0341+182 WD0357+081 WD0435-088 WD0532+414 WD0548-001 WD0552-041 WD0553+053 WD0644+025 WD0644+375 WD0657+320 WD0727+482 WD0728+642 WD0738-172 WD0743-336 WD0747+073.1 WD0747+073.2 WD0824+288 WD0839-327 WD0912+536 WD0939+071 WD1019+637 WD1033+714 WD1036-204 WD1055-072 WD1121+216 WD1126+185 WD1134+300 WD1257+037 WD1309+853 WD1327-083 WD1334+039 WD1344+106 WD1345+238 WD1444-174 WD1514+033 WD1609+135 WD1620-391 WD1626+368 WD1633+433 WD1633+572 WD1647+591 WD1705+030 WD1743-132 WD1748+708 WD1756+827 WD1820+609 WD1829+547 WD1900+705 WD1917+386 WD1917-077 WD1919+145 WD1935+276 WD1953-011 WD2002-110 WD2007-219 WD2007-303 WD2032+248 WD2047+372 WD2048+263 WD2054-050 WD2055+221 WD2117+539 WD2140+207 WD2246+223 WD2251-070 WD2326+049 WD2351-335