Detection of Transits of Extrasolar Giant Planets with Inexpensive Telescopes and CCDs

 

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Timothy P. Castellano

NASA Ames Research Center, Astrophysics Branch, MS 245-6, Moffett Field, CA 94035

 

Gregory Laughlin

Richard Stone Terry

UCO/Lick Observatory, University of California, Santa Cruz, CA 95064

 

Michael Kaufman

Seth Hubbert

GionMatthias Schelbert

San Jose State University, Department of Physics, One Washington Square, San Jose, CA, 95192

 

Dorian Bohler

Randy Rhodes

National Association for Equal Opportunity in Higher Education, NASA Ames Research Academy, MS 19-48, Moffett Field, CA 94035

 

Received August 26, 2004; revised November 10, 2004; accepted November 10, 2004

 

Abstract  A typical short-period giant planet occulting a parent star can produce a ~1% dimming of the star’s light for an interval of several hours. The combination of photometric and Doppler radial velocity (RV) measurements of a transiting extrasolar planet can yield unambiguous measurements of the planet’s mass, radius, density, and exact orbital parameters. In this article, we describe a low-cost observational and data-reduction pipeline which can be used to obtain 3 milli-magnitude photometry with a small-aperture telescope and a consumer-grade CCD detector. This precision is sufficient to reliably detect the transit of a giant planet. We discuss noise sources, and evaluate strategies for achieving a low overall noise floor. We describe the performance of our pipeline in a successful observation of an HD 209458 “b” transit, and in a photometric survey of GJ 876 during an epoch in which we predicted that GJ 876 “c” (P ~30d) could potentially be observed to transit. We also briefly describe the status of the ongoing www.transitsearch.org project, which coordinates a photometric search for planetary transits among known planet-bearing stars.

 

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