SuperWASP project can detect Earth-radius transit planets

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SuperWASP project can detect Earth-radius transit planets

Post by Borislav on 14th August 2010, 2:42 pm

http://arxiv.org/abs/1008.1089

We have performed extensive simulations to explore the possibility of detecting eclipses and transits of close, sub-stellar and planetary companions to white dwarfs in WASP light-curves. Our simulations cover companions $\sim0.3\Re<{\rm R}_{pl}<12\Re$ and orbital periods $2{\rm h}<P<15{\rm d}$, equivalent to orbital radii $0.003{\rm AU} < a < 0.1{\rm AU}$. For Gaussian random noise WASP is sensitive to transits by companions as small as the Moon orbiting a $\textrm{V}\simeq$12 white dwarf. For fainter white dwarfs WASP is sensitive to increasingly larger radius bodies. However, in the presence of correlated noise structure in the light-curves the sensitivity drops, although Earth-sized companions remain detectable in principle even in low S/N data. Mars-sized, and even Mercury-sized bodies yield reasonable detection rates in high-quality light-curves with little residual noise. We searched for eclipses and transit signals in long-term light-curves of a sample of 194 white dwarfs resulting from a cross-correlation of the McCook $\&$ Sion catalogue and the WASP archive. No evidence for eclipsing or transiting sub-stellar and planetary companions was found. We used this non-detection and results from our simulations to place tentative upper limits to the frequency of such objects in close orbits at white dwarfs. While only weak limits can be placed on the likely frequency of Earth-sized or smaller companions, brown dwarfs and gas giants (radius $\approx \Rjup$) with periods $<0.1-0.2$~days must certainly be rare ($<10\%$). More stringent constraints likely requires significantly larger white dwarf samples, higher observing cadence and continuous coverage. The short duration of eclipses and transits of white dwarfs compared to the cadence of WASP observations appears to be one of the main factors limiting the detection rate in a survey optimised for planetary transits of main sequence stars.


Last edited by Borislav on 14th August 2010, 4:50 pm; edited 1 time in total

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Re: SuperWASP project can detect Earth-radius transit planets

Post by Lazarus on 14th August 2010, 4:39 pm

Question is whether you'd expect to find Earth-sized planets at that kind of orbital distance around a white dwarf star, given the evolutionary history of the system.

(On the other hand, finding something you don't expect to find makes things interesting for the theorists...)
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Re: SuperWASP project can detect Earth-radius transit planets

Post by Borislav on 14th August 2010, 4:58 pm

Apologies for the typo. I had a hard week. : (

Similar project
http://www.noao.edu/meetings/eventful-universe/Thursday0318/morning/CRTS_TucsonMar10.pdf

Eclipsing White Dwarfs: Planets?
Color-selected sample of WD candidates from CRTS + SDSS
Light curves from CRTS: looking for eclipses
Companion radii as low as a few Earth radii
Some could be ~ Earth-size planets; or late-M/brown dwarfs;
IR spectroscopy will tell

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