NOAO >   Observing Info >   Approved Programs >   2013A-0165

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Proposal Information for 2013A-0165


PI: Abhijit Saha, NOAO, saha@noao.edu
Address: 950 N. Cherry Avenue, Tucson, AZ 85749, USA

CoI: Tim Axelrod, University of Arizona
CoI: Christopher Stubbs, Harvard University
CoI: Susana Deustua, STSci
CoI: Ralph Bohlin, STSci
CoI: Edward Olszewski, University of Arizona
CoI: Jay Holberg, University of Arizona, LPL
CoI: Thomas Matheson, NOAO
CoI: Ronald Gilliland, STSci
CoI: Armin Rest, STSci

Title: Establishing a Network of DA White Dwarf SED Standards

Abstract: Systematic uncertainties in photometric calibration are the dominant source of error in current type Ia supernova dark energy studies, as well as other forefront cosmology efforts. Current and next-generation ground-based all-sky surveys require a network of calibration stars with 1) known SEDs (to properly and unambiguously take into account filter differences), and 2) that are on a common photometric zeropoint scale. Our approved Cycle 20 \emphHST program affords us the ability to establish this essential network of faint primary photometric standards, exploiting the well-understood SEDs of DA white dwarf stars, without the complications of observing through the time-variable Earth's atmosphere. A critical element is Gemini spectra, not for spectrophotometry, but to obtain the two parameters (temperature and log(g)) that determine the SED. We can use the broadband \emphHST photometry to set the overall flux scale for each source, and determine any applicable reddening. Thus calibrated, these standards can then be used as flux standards at wavelengths well beyond the range of \emphHST, and in any arbitrary, but defined passband. This precision spectroscopic and photometric heritage from Gemini and \emphHST will benefit essentially all existing and upcoming survey projects and directly address one of the current barriers to understanding the nature of dark energy.


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



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