The WFCAM transit survey and cool white dwarfs

Abstract

Abstract. We present results from our search for cool white dwarfs in the WTS (WFCAM Transit Survey). Repeat observations starting in 2007 allowed to produce deep stacked images in J and measure proper motions. We combine this with deep optical imaging to select cool white dwarf candidates (T eff < 5000 K). About 27 cool white dwarf candidates with proper motions above 0.10 arcsec/yr were identified in one of the fields representing 1/8th of the survey area. Follow-up spectroscopy with the 10.2 m GTC telescope at La Palma confirmed the white dwarf status for all observed candidates. On-going work is being carried out to increase the sample of cool white dwarfs that will allow a more comprehensive study of the thick disk/halo white dwarf population.

The James Webb Space Telescope North Ecliptic Pole Time-domain Field. I. Field Selection of a JWST Community Field for Time-domain Studies

“…Whereas LSST's limit for variability studies over a large portion of the sky in the near-UV-near-IR reaches to m AB ∼ < 24 mag (10 σ) per 2×15 s visit on time-scales of ∼15 min-1 hour (Tyson 2002;Ivezić 2014;LSST Science Collaboration et al 2017), JWST / NIRCam (e.g., Horner & Rieke 2004;Greene et al 2012) could potentially reach m AB ∼ 26.8-28.3 mag (10 σ) per epoch in the near-mid-IR on similar time-scales in a suit-ably dark survey field 1 . This would enable a wide range of new and exciting time-domain science in an unexplored magnitude regime, including high redshift transient searches and monitoring (e.g., Type Ia SNe to z ∼ 5 and Core Collapse SNe to z ∼ 1.5 (Graur et al 2014;Rodney et al 2014Rodney et al , 2015bStrolger et al 2015;Mesinger et al 2006) and Pair Instability SNe in the Epoch of Reionization (Pan, Kasen, & Loeb 2012;Gal-Yam 2012;Nicholl et al 2013;Whalen et al 2013Whalen et al , 2014; variability studies from (weak) Active Galactic Nuclei (AGN; e.g., MacLeod et al 2011) to brown dwarf atmospheres (Artigau et al 2009;Buenzli et al 2014;Radigan et al 2014;Rajan et al 2015); as well as perhaps proper motions of extreme scattered Kuiper Belt, inner Oort Cloud Objects and comets on their way in toward the inner Solar System, and of nearby Galactic brown dwarfs and low-mass stars (Ryan et al 2011;Ryan & Reid 2016), and ultracool white dwarfs (Harris et al 2006;Catalán et al 2013).…”