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  KELT - The Kilodegree Extremely Little Telescope

The KELT project developed out of research I began in 2002, working with Andrew Gould at Ohio State. That work turned into the paper "Using All-Sky Surveys to Find Planetary Transits", which described the optimal telescope configuration for an all-sky transit survey. In short, we found that a small-aperture, wide-field telescope would be the best instrument to detect planetary transits of bright stars. Based on the calculations from the paper, we decided to build such an instrument. That became the KELT-North telescope, which is based at Winer Observatory in Southwestern Arizona. The telescope is described in the paper "The Kilodegree Extremely Little Telescope (KELT): A Small Robotic Telescope for Large-Area Synoptic Surveys", and the results from the KELT-North commissioning survey, "A Photometric Survey for Variables and Transits in the Field of Praesepe with KELT".

After taking a position at Vanderbilt University, I began building the KELT-South Telescope - a twin of KELT-North. KELT-South is located at Sutherland, South Africa, and is entering regular scientific mode. For those interested, the deployment and testing of KELT-South is outlined in exhaustive detail on the KELT-South Wiki.

The first KELT discoveries are out!

KELT-1b is a 27 MJ, 1.1 RJ transiting brown dwarf in a 1.2 day orbit around a V=10.7, F5 star. It is the shortest period and brightest transiting brown dwarf discovered, and is only the second definitively inflated brown dwarf known. "KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star".

KELT-2Ab is a 1.5 MJ, 1.3 RJ mildly inflated hot Jupiter in a 4.1 day orbit around a slightly evolved V=8.77, F7 star. It is the ninth brightest transiting planet, and the third-brightest one discovered by a ground-based survey. The evolutionary state of the star means that this exoplanet has one of the best measured ages of any known exoplanet. The host star also has a common proper motion M-dwarf binary companion (KELT-2B) that may be the cause of KELT-2Ab's orbital location. "KELT-2Ab: A Hot Jupiter Transiting the Bright (V=8.77) Primary Star of a Binary System".

Both of these discoveries are extremely exciting, and are exactly what KELT was built to do. These two discoveries come from the KELT-North telescope, which has been operating longer than KELT-South and so if further along with its search. We also have several more interesting targets from both telescopes that we are working to confirm and hopefully publish over the next year.

Here is a photo of the KELT-South building at Sutherland. The telescope is fully automated - no human interaction is involved in regular operations. Each night, the control computer opens the control computer checks the weather, opens the roll-off roof, and starts the telescope scanning a series of fields across the sky. The telescope is described in the paper "The KELT-South Telescope".

  Predicting the Yields of Transit Surveys
Before designing and constructing a survey for planetary transits, it is important to understand the factors that will increase or decrease the number of transits one expects to find. Simple calculations that consider the total numbers of stars observed, the frequency of planets, and the transit probability dramatically overestimate the number of expected transits by ignoring significant issues. A full, consistent model for a survey must account for many complicated effects, and is typically performed either as forward modeling, using assumed distributions of the stellar and planetary properties to statistically predict the ensemble properties of the target stars and the detection efficiency of the survey as a whole, or reverse modeling, in which one uses the known properties of an observed sample of stars to determine the survey yield. For an introduction to these topics, see the conference proceeding, "Statistics and Simulations of Transit Surveys for Extrasolar Planets" by Scott Gaudi. A full example in great detail can be found in "Predicting the Yields of Photometric Surveys for Transiting Extrasolar Planets", which is probably the best reference paper for this topic.

While performing an all-sky survey is one strategy for a transit search, another option is to focus on a single population of stars that share some fundamental property, to learn something about how planet frequency varies within a somewhat homogeneous population. That is the strategy behind transit surveys of star clusters. The basic statistics of such surveys are fundamentally different than all-sky surveys, and in "Searching for Transiting Planets in Stellar Systems" Scott Gaudi and I outline the formalism needed to conduct such modeling. In "Toward the Detection of Transiting Hot Earths and Hot Neptunes in Open Clusters" we apply the methods from the first paper to a number of specific star clusters, with special attention to the potential for the discovery of low-mass planets. The analysis in that paper was updated in "On the potential of transit surveys in star clusters: Impact of correlated noise and radial velocity follow-up" by Suzanne Aigrain and Frederic Pont to include consideration of red noise and follow-up issues.


Last modified: Wed Jun 13 17:28:52 CDT 2012