Multi-Survey and Statistical Methods for Cool White Dwarf Discovery

Abstract

Selecting astrometric and photometric data from the Sloan Digital Sky Survey (SDSS), the Lépine & Shara Proper Motion North Catalog (LSPM‐North), the Two Micron All Sky Survey (2MASS), and the USNO‐B catalog, we explore a succession of methods to isolate white dwarf (WD) candidates for followup spectroscopy. Our preliminary methods include: reduced proper motion diagram cuts, color cuts, and atmospheric model adherence. After initial spectroscopic observations with the CTIO 4m Blanco telescope, we realized high subdwarf (SD) contamination solely in the cool WD temperature regime (Teff<7000 K). To mitigate SD contamination within this cool Teff regime, we apply linear discriminant analysis (LDA) before continuing with spectroscopic observations at APO. We present spectroscopy of 17 new WDs obtained from CTIO and APO. Additionally, we confirm 28 WDs with spectra available in the SDSS spectral database, for a total of 45 new WD discoveries. We determine physical parameters and distance estimates based on atmospheric models for WDs. Three new WDs are estimated to be within 25 pc and another two are confirmed ZZ Ceti pulsators.