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Shashi M. Kanbur September 2010 Slide 2 Results In 5 years, > 21 papers in the two leading peer reviewed journals in Astrophysics (Astrophysical Journal, Monthly Notices of the Royal Astronomical Society). No course release. 5 papers with undergraduate co-authors. Worked with about 30 undergraduates on research projects. About 30 presentations at regional, national and International conferences. 2006 Chretein award of the American Astronomical Society. Slide 3 Collaborators Chow Choong Ngeow, NCU, Taiwan. Lucas Macri, Texas A&M. Douglas Leonard, SDSU. Ata Saradjeni, University of Florida. Martin Hendry, University of Glasgow, UK. Niall Tanvir, University of Leicester, UK. Robert Szabo, Konkoly Observatory, Hungary. Chris Koen, University of Witwatersand, S. Africa. Antonio Kanaan, UFSC, Brazil. Anil Pradhan, Ohio State Marcello Marconi, Naples Observatory, Italy Amplavanar Nanthakumar (Oswego) Steven Reyner (Oswego) Robert Buchler (University of Florida) Hilding Nielson (University of Bonn) Elio Antonello (Merate Observatory - Italy) Slide 4 Students Gregory Feiden (Dartmouth) Jill Neeley (Ithaca College) Dylan Wallace (University of Alaska) Matthew Turner (Rice) Daniel Crain (Clarkson) Isaac Richter (UofR) Sean Scott (SUNY Binghampton) Tim de Haas (UofR) Jim Young (RPI) Alex James (SUNY Geneseo) Frank Ripple (University of Massachusetts Eamonn Moyer (SUNY Genseo) Robin Dienhoffer (University of Virginia) Brandon Gilfus Earl Bellinger Peter Thompson (University of Rochester) Joshua Primrose Joshua Brown (UofR) Adam Biesenbach (Wall Street) Dennis Quill Sid Meyers Martin Berke Stephanie Magin Anna Bontorno Jessica Halsey Joe Bennett Samantha Hoffman (Texas A&M) Danielle Citro Michael Evans Lillie Ghobrial Slide 5 Slide 6 Variable Stars Intrinsic variation, well defined period of oscillation. Regularly repeating brightness variations light curve. Physics of this is reasonably well understood. Cepheids: pop I, young, high metallicity, in galactic disk, crucial importance for the extra-galactic distance scale. RR Lyraes: pop II< old, low metallicity, in globular clusters in galactic halo, important as secondary distance indicator and for age determinations. Slide 7 PL relation m: apparent magnitude M: absolute magnitude m-M = distance modulus m-M = 5log(d) -5 M = a + blogP Extra-Galactic Distance Scale V=H 0 x d Know H 0 to 1% accuracy imples knowledge of the equation of state for dark energy. PL relation related to PC relation. Slide 8 Multiphase Cepheid PC/PL Relations in the LMC/SMC using OGLE III data Cepheid Period-Luminosity (PL) relation is one of the most fundamental relations in Astrophysics. M = a + b log P At mean light. Its not linear! Two distinct relations. Formulate a relation between log P and magnitude at different phases of pulsation. New window onto stellar pulsation. Permits a detailed comparison with models. Slide 9 Multiphase Movies: http://www.oswego.edu/~kanbur/IRES2009/Vphase.mov A great deal of things to understand here. Not scratched the surface yet. Color is the difference between two magnitudes. Period-Color relations as a function of phase http://www.oswego.edu/~kanbur/IRES2009/Cphase.mov Definitive evidence of sharp nonlinearity. New tool to constrain theoretical models of stellar pulsation. Comparison with models http://www.oswego.edu/~kanbur/IRES2008/keele.ppt Slide 10 Random Walk Methods E i = V i - a - b.logP i Order according to period: P 1