New UltraCool and Halo White Dwarf Candidates in SDSS Stripe 82

TL;DR

This study utilizes SDSS Stripe 82 data to identify new ultra-cool and halo white dwarf candidates, expanding the known population and demonstrating the survey's effectiveness in detecting these faint objects.

Contribution

It presents a new catalog of light-motion curves and identifies previously unknown ultra-cool and halo white dwarf candidates using proper motion and photometric data.

Findings

Discovered 8-21 new ultracool white dwarfs.

Identified at least 10 new halo white dwarfs.

Created the deepest light-motion curve catalog for Stripe 82.

Abstract

A 2.5 x 100 degree region along the celestial equator (Stripe 82) has been imaged repeatedly from 1998 to 2005 by the Sloan Digital Sky Survey. A new catalogue of ~4 million light-motion curves, together with over 200 derived statistical quantities, for objects in Stripe 82 brighter than r~21.5 has been constructed by combining these data by Bramich et al. (2007). This catalogue is at present the deepest catalogue of its kind. Extracting the ~130000 objects with highest signal-to-noise ratio proper motions, we build a reduced proper motion diagram to illustrate the scientific promise of the catalogue. In this diagram disk and halo subdwarfs are well-separated from the cool white dwarf sequence. Our sample of 1049 cool white dwarf candidates includes at least 8 and possibly 21 new ultracool H-rich white dwarfs (T_eff < 4000K) and one new ultracool He-rich white dwarf candidate identified from their SDSS optical and UKIDSS infrared photometry. At least 10 new halo white dwarfs are also identified from their kinematics.