NOAO >   Observing Info >   Approved Programs >   2006A-0080

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Proposal Information for 2006A-0080


PI: Abhijit Saha, NOAO, saha@noao.edu
Address: NTSS, 950 N Cherry Ave, PO Box 26732, Tucson, AZ 85726-6732, USA

Title: The Enigmatic Variable Stars in DDO 187: Are they a new kind of object?

Abstract: A variable star study in the dwarf galaxy DDO 187 has yielded a putative distance modulus of 29.24 from a very few Cepheids detected near the faint limit (r ~ 24 ) with the KP 2.1m telescope. Three very bright \langle r \rangle ~ 22 (M_r >=-7.2) red long period variables with amplitudes greater than 2 mags in r and periods longer than 800 days were also discovered. Such objects are theoretically predicted as evolved products of Hubble Sandage variables, but only if the metallicity is poor enough to suppress damping of pulsations. There are no known counterparts of such high amplitude red variables of such high intrinsic brightness in the Galaxy, M31, M33 or the Clouds. DDO 187 may be unique in providing stars that are both very young and very metal poor in the local Universe, and thus be the nearest host of this new kind of variable. Or is the inferred distance to DDO 187 wrong, as has once been alleged? A deep color- magnitude diagram will show the tip of the red giant branch, and resolve any uncertainty about the distance. Gemini is needed to reach the required faint level. The pay-off is confirmation of a new constituent of the Universe.


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 >   2006A-0080

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