| The Vulcan photometer: a dedicated photometer for extrasolar planet searches (2001) | |||||||||||||||
Abstract | |||||||||||||||
| THE VULCAN PHOTOMETER DEDICATED PHOTOMETER FOR EXTRASOLAR PLANET SEARCHES William Borucki Douglas Caldwell David Koch Larry Webster NASA Ames Research Center Moffett Field Jon Jenkins SETI Institute Mountain View Zoran Ninkov Rochester Institute Technology Rochester Robert Showen Raytheon Systems Company Moffett Field Abstract small CCD photometer dedicated the detection extrasolar planets has been developed and put into operation Hamilton California simultaneously monitors stars brighter than magnitude its square degree field view Observations are conducted all night every clear night the year single field monitored cadence eight images per hour for period about three months When the data are folded for the purpose discovering low amplitude transits transit amplitudes are readily detected This precision sufficient find jovian size planets orbiting solar like stars which have signal amplitudes from depending the inflation the planet atmosphere and the size the star investigation possible noise sources indicates that neither star field crowding scintillation noise nor photon shot noise are the major noise sources for stars brighter than visual magnitude Over one hundred variable stars have been found each star field About fifty these stars are eclipsing binary stars several with transit amplitudes only few percent Three stars that showed only primary transits were examined with high precision spectroscopy Two were found nearly identical stars binary pairs orbiting double the p. A small CCD photometer dedicated to the detection of extrasolar planets has been developed and put into operation at Mount Hamilton, California. It simultaneously monitors 6000 stars brighter than 13th magnitude in its 49 deg2 field of view. Observations are conducted all night every clear night of the year. A single field is monitored at a cadence of eight images per hour for a period of about 3 months. When the data are folded for the purpose of discovering low-amplitude transits, transit amplitudes of 1% are readily detected. This precision is sufficient to find Jovian-size planets orbiting solar-like stars, which have signal amplitudes from 1% to 2% depending on the inflation of the planet’s atmosphere and the size of the star. An investigation of possible noise sources indicates that neither star field crowding, scintillation noise, nor photon shot noise are the major noise sources for stars brighter than visual magnitude 11.6. Over one hundred variable stars have been found in each star field. About 50 of these stars are eclipsing binary stars, several with transit amplitudes of only a few percent. Three stars that showed only primary transits were examined with high-precision spectroscopy. Two were found to be nearly identical stars in binary pairs orbiting at double the photometric period. Spectroscopic observations showed the third star to be a high mass ratio single-lined binary. On 1999 November 22 the transit of a planet orbiting HD 209458 was observed and the predicted amplitude and immersion times were confirmed. These observations show that the photometer and the data reduction and analysis algorithms have the necessary precision to find companions with the expected area ratio for Jovian-size planets orbiting solar-like stars.. The authors would like to thank the observers who spent many sleepless nights obtaining the data; especially Tim Castellano, Tony Dobrovolskis, Wendy Hansen, Carol Harper, Lynn Harper, Ralph Libby, Alan Meyer, Patrick Maloney, William Trublood. The superb work of the machine shop headed by Dave Scimeca was critical to the success of the project. Scripts to control and automate the operation of the camera were written by Bob Slawson of the Rochester Institute of Technology. John Caldwell, on sabbatical from York University, investigated the influence of star crowding on photometric precision. Robert Yee directed system operation and maintenance. Kim Kubota (Orbital Science Corp.) and Walt Miller (Man Tech Corp) directed the observers. The cooperation and help of the Lick Observatory staff, especially Remington Stone, and their permission to use the Crocker Dome made the project possible. Special thanks are due to Geoff Marcy, Paul Butler, Jack Lissauer, Eduardo Martin, David Ardilla, and Dave Latham who made spectroscopic observations of candidate stars. Advice from Tim Brown (HAO, UCAR), Ted Dunham (Lowell Obs.), and Laurence Doyle (SETI Institute) contributed the success of the project. The patience, support, and funding received from Origins and Advanced Project Offices at NASA Headquarters and the Astrobiology Office at NASA Ames is gratefully acknowledged. | |||||||||||||||
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