Hubble Space Telescope Observations of White Dwarfs in the Globular Cluster M4
Abstract
With the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope, we have discovered in M4 (NGC 6121, C 1620-264) the first extensive sequence of cooling white dwarfs seen in a globular cluster. Adopting a distance modulus of (m-M)_V = 12.65 and a reddening of E(B-V) = 0.37, we show that the sequence, which extends over 9 < M_U < 13, is comprised of white dwarfs of mass \sim 0.5 M_{\odot}. The total mass loss from the present turnoff to the white dwarf sequence is 0.31 M_{\odot} and the intrinsic dispersion in the mean mass appears to be < 0.05 M_{\odot}. Both the location of the white dwarf cooling sequence in the cluster color-magnitude diagram and the cumulative luminosity function attest to the basic correctness and completeness of the physics in theoretical models for the upper three magnitudes of the observed white dwarf cooling sequence. To test the theory in globular clusters at cooling ages beyond \sim 3 \times 10^8 years will require deeper and more complete data.
Keywords
Cite
@article{arxiv.astro-ph/9507109,
title = {Hubble Space Telescope Observations of White Dwarfs in the Globular Cluster M4},
author = {Harvey B. Richer and Gregory G. Fahlman and Rodrigo A. Ibata and Peter B. Stetson and Roger A. Bell and Michael Bolte and Howard E. Bond and William E. Harris and James E. Hesser and Georgi Mandushev and Carlton Pryor and Don A. VandenBerg},
journal= {arXiv preprint arXiv:astro-ph/9507109},
year = {2009}
}
Comments
To appear in the Astrophysical Journal Letters, 451, September 20, 1995. The text is also available as a postscript file from http://www.astro.ubc.ca/people/richer/m4wd/m4wd.ps with postscript files of the figures available in http://www.astro.ubc.ca/people/richer/m4wd/fig1.ps http://www.astro.ubc.ca/people/richer/m4wd/fig2.ps http://www.astro.ubc.ca/people/richer/m4wd/fig3.ps