First Results from Pan-STARRS1: Faint, High Proper Motion White Dwarfs in the Medium-Deep Fields

TL;DR

This paper reports initial findings from the Pan-STARRS1 survey, identifying faint, high proper motion white dwarfs in medium-deep fields, and demonstrates the survey's potential to discover many more such objects in the future.

Contribution

First results demonstrating the effectiveness of Pan-STARRS1 in detecting faint, high proper motion white dwarfs, including new candidates and confirmation of known objects.

Findings

Identified 47 white dwarf candidates with high proper motion.

Confirmed three new white dwarfs through spectroscopy.

Estimated that many more high proper motion white dwarfs will be found with ongoing Pan-STARRS1 observations.

Abstract

The Pan-STARRS1 survey has obtained multi-epoch imaging in five bands (Pan-STARRS1 gps, rps, ips, zps, and yps) on twelve "Medium Deep Fields", each of which spans a 3.3 degree circle. For the period between Apr 2009 and Apr 2011 these fields were observed 50-200 times. Using a reduced proper motion diagram, we have extracted a list of 47 white dwarf (WD) candidates whose Pan-STARRS1 astrometry indicates a non-zero proper motion at the 6-sigma level, with a typical 1-sigma proper motion uncertainty of 10 mas/yr. We also used astrometry from SDSS (when available) and USNO-B to assess our proper motion fits. None of the WD candidates exhibits evidence of statistically significant parallaxes, with a typical 1-sigma uncertainty of 8 mas. Twelve of these candidates are known WDs, including the high proper motion (1.7"/yr) WD LHS 291. We confirm three more objects as WDs through optical spectroscopy. Based on the Pan-STARRS1 colors, ten of the stars are likely to be cool WDs with 4170 K Teff 5000 K and cooling ages <9 Gyr. We classify these objects as likely thick disk WDs based on their kinematics. Our current sample represents only a small fraction of the Pan-STARRS1 data. With continued coverage from the Medium Deep Field Survey and the 3pi survey, Pan-STARRS1 should find many more high proper motion WDs that are part of the old thick disk and halo.