NOAO >   Observing Info >   Approved Programs >   2007B-0228

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Proposal Information for 2007B-0228


PI: Tim Axelrod, University of Arizona and LSST Corp, taxelrod@gmail.com
Address: Steward Observatory, 933 N Cherry, Tucson, AZ 85721, USA

CoI: Edward Olszewski, Steward Observatory
CoI: Abi Saha, NOAO
CoI: Chuck Claver, NOAO

Title: A Test of the Use of Hot DA White Dwarfs to Calibrate AB-Magnitude Photometry

Abstract: Proposed all-sky surveys wish to have photometry on an energy-based system (AB magnitudes, for instance). Two important projects requiring such photometry are luminosity distances of supernovae and high quality photometric redshifts. In order to achieve sub-1% energy-based photometry, hot DA White Dwarfs (WDs) with spectroscopically determined T_eff and log(g) and model-atmosphere spectral-energy distributions (SEDs) are needed as standards. What is not known is exactly how to use these WDs as standards most correctly. We do not know how quickly in angular distance and time the atmospheric conditions of a program star observation and standard observation, even with extinction applied, become different enough to turn sub-1% photometry into the more normal 1.5-2% standard star solutions typically derived for a night. This knowledge is critical in understanding how many faint standards need to be set up, and in planning a strategy for calibrating a large survey such as LSST.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2007B-0228

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