Jay Anderson et al. 2008 The Astronomical Journal 135 2114 doi:10.1088/0004-6256/135/6/2114
Jay Anderson1, Ivan R. King2, Harvey B. Richer3, Gregory G. Fahlman4, Brad M. S. Hansen5, Jarrod Hurley6, Jasonjot S. Kalirai7,8, R. Michael Rich5 and Peter B. Stetson4
Show affiliationsWe describe here the reduction methods that we developed to study the faintest red dwarfs and white dwarfs in an outer field of NGC 6397, which was observed by HST for 126 orbits in 2005. The particular challenge of this data set is that the faintest stars are not readily visible in individual exposures, so special care must be taken to combine the information in all the exposures in order to identify and measure them. Unfortunately, it is hard to find the faintest stars without also finding a large number of faint galaxies, so we developed specialized tools to distinguish between the point-like stars and the barely resolved galaxies. We found that artificial-star tests, while obviously necessary for completeness determination, can also play an important role in helping us optimize our finding and measuring algorithms. Although this paper focuses on this data set specifically, many of the techniques are new and might find application in other work, particularly when a large number of images are available for a single field.
astrometry; globular clusters: individual (NGC 6397); stars: low-mass, brown dwarfs; techniques: image processing; techniques: photometric; white dwarfs
Issue 6 (2008 June)
Received 2007 October 27, accepted for publication 2008 January 25
Published 2008 May 7
Jay Anderson et al. 2008 The Astronomical Journal 135 2114