Nuclear, Particle, Astroparticle and Cosmology (NUPAC) Seminars
Measuring Gravitational Redshifts of Central Stars of Planetary Nebulae
Presented by Daniel Zirzow, UNM
Planetary Nebulae (PNe), the chemically enriched ejecta of the atmospheres evolved stars, mark a short-lived stage in the rapid evolution of the condensed stellar cores of stars into quiescent white dwarfs. Distances to PNe with sufficiently bright central stars (CSPN) can be estimated using spectroscopically determined surface gravities and temperatures in conjunction with detailed evolutionary tracks calculated with modern stellar evolution codes. The existence of multiple distinct late stage (post-AGB) evolutionary scenarios complicates the use of post-AGB tracks in the gravity-temperature plane for estimating stellar masses because points in this plane are suspected to be multi-valued with respect to stellar mass. Gravitational redshifts are discussed as a potentially useful tool for measuring masses of central stars. High-resolution echelle spectra of several bright PN central stars have been obtained with the newly-commissioned High Resolution Spectrometer (HRS) installed at the 12-meter South African Large Telescope (SALT) with the goal of directly measuring central star masses using gravitational redshifts. We discuss the physical parameters of the measured nebulae and the CSPN spectra, including the technique for referencing the gravitational redshift of the central stars. We also report progress on the development of a unique data reduction pipeline specific to SALT HRS and will comment on some challenges in the reduction of echelle spectra.
2:00 pm, Tuesday, November 3, 2015
PAIS-2540, PAIS
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