NOAO > Observing Info > Approved Programs > 2012A-0214
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NOAO > Observing Info > Approved Programs > 2012A-0214 |
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PI: S.O. Kepler, Universidade Federal do Rio Grande do Sul, kepler@if.ufrgs.br
Address: Instituto de Fisica, 91501-970 Porto Alegre RS, Brazil
CoI: Alejandro Corsico, Universidad Nacional de La Plata
CoI: Leandro Althaus, Universidad Nacional de La Plata
CoI: Barbara Castanheira, University of Texas at Austin
CoI: Don Winget, University of Texas
CoI: Detlev Koester, University Kiel
CoI: Mike Montgomery, University of Texas at Austin
CoI: Atsuko Nitta, Gemini Observatory
Title: The Most Massive Pulsating White Dwarf Stars
Abstract:
We propose to obtain S/N>70 GMOS spectra to accurately determine masses and
effective temperatures of the most massive known pulsating white dwarfs. Our
targets, with masses above 0.9Msun, were selected from comparison between the
low S/N SDSS spectra to new theoretical spectral and evolutionary models.
Massive white dwarfs are probably SNIa progenitors through accretion or
merger. They are rare, being the final product of massive stars (less common)
and have smaller radius (less luminous). Kepler et al. 2007 estimate only
1-2% white dwarfs have masses above 1 Msun. Massive pulsating white dwarfs
are tools for studying physics at extreme conditions, especially the
crystallization phenomenon. At temperatures within the instability strip,
they should already have a substantial part of their interior crystallized.
These stars are also an important tool to measure the C(alpha,gamma)O
reaction rate (Metcalfe 2005), which is crucial for chemical evolution models
and life forming elements. However, there is no consensus from the models,
due to uncertainties in the C(alpha,gamma) reaction rate, overshooting and
mass loss at which stellar mass stars have an oxygen/neon core (Garcia-Berro
et al. 1997), instead of carbon/oxygen. The core chemical composition will be
investigated through asteroseismology (Castanheira & Kepler 2009, Romero et
al. 2011).
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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NOAO > Observing Info > Approved Programs > 2012A-0214 |
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