Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21743418h&link_type=abstract
American Astronomical Society, AAS Meeting #217, #434.18; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We present initial results of an analysis of the white dwarf sequence in the globular cluster Omega Centauri aimed at testing for the presence of helium-core white dwarfs (He WDs) and identifying potential candidates. He WDs appear redward of the cooling sequence formed by carbon/oxygen white dwarfs; as recently shown in NGC 6397, they can provide a window into critical binary populations in a globular cluster (Strickler et al. 2009). We analyze a 10x10 arcminute mosaic of images we obtained with HST's Advanced Camera for Surveys in F435W (B435), F625W (R625), and F658N filters; it extends out to the half-light radius of the cluster. Using the "effective PSF" photometric technique developed for the WFC by Anderson and King (2006), we construct a B435-R625 vs. R625 color-magnitude diagram (CMD) for 1.2 million stars in the mosaic. Of the 570,000 stars that appear in at least three B435 and three R625 images, approximately 3400 lie in the region of the CMD occupied by WDs. Using the three independent measurements in each filter, we compute empirical uncertainties in the B435-R625 colors of the white dwarfs. We then compare these to the measured width of the WD sequence as a function of R to test for the presence of He WDs and identify potential candidates. We compare our results to those of Monelli et al. (2005) and Calamida et al. (2008) who first reported evidence for He WDs in Omega Centauri. This work was supported by NASA grant HST-GO-9442.
Anderson Jeffrey
Cool Adrienne M.
Hayward Suzanne G.
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