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Visitors From The Halo: 11 Gyr Old White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al.
Visitors From The Halo: 11 Gyr Old White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al.
Ted von Hippel
We report the discovery of three nearby old halo white dwarf (WD) candidates in the Sloan Digital Sky Survey (SDSS), including two stars in a common proper motion binary system. These candidates are selected from our 2800deg2 proper motion survey on the Bok and U.S. Naval Observatory Flagstaff Station 1.3 m telescopes, and they display proper motions of 0˝.4-0˝.5 yr¯1. Follow-up MMT spectroscopy and near-infrared photometry demonstrate that all three objects are hydrogen-dominated atmosphere WDs with T eff ≈ 3700-4100 K. For average mass WDs, these temperature estimates correspond to cooling ages of 9-10 Gyr, distances of 70-80 pc, and …
Spitzer Observations Of The Oldest White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al.
Spitzer Observations Of The Oldest White Dwarfs In The Solar Neighborhood, Mukremin Kilic, Ted Von Hippel, Et Al.
Ted von Hippel
We present Spitzer 5-15 μm spectroscopy of one cool white dwarf and 3.6-8 μm photometry of 51 cool white dwarfs with T eff < 6000 K. The majority of our targets have accurate BVRIJHKphotometry and trigonometric parallax measurements available, which enables us to perform a detailed model atmosphere analysis using their optical, near- and mid-infrared photometry with state-of-the-art model atmospheres. We demonstrate that the optical and infrared spectral energy distributions of cool white dwarfs are well reproduced by our grid of models. Our best-fit models are consistent with the observations within 5% in all filters except the IRAC 8 μm band, which has the lowest signal-to-noise ratio photometry. Excluding …
A Detailed Model Atmosphere Analysis Of Cool White Dwarfs In The Sloan Digital Sky Survey, Mukremin Kilic, Ted Von Hippel, Et Al.
A Detailed Model Atmosphere Analysis Of Cool White Dwarfs In The Sloan Digital Sky Survey, Mukremin Kilic, Ted Von Hippel, Et Al.
Ted von Hippel
We present optical spectroscopy and near-infrared photometry of 126 cool white dwarfs (WDs) in the Sloan Digital Sky Survey (SDSS). Our sample includes high proper motion targets selected using the SDSS and USNO-B astrometry and a dozen previously known ultracool WD candidates. Our optical spectroscopic observations demonstrate that a clean selection of large samples of cool WDs in the SDSS (and the SkyMapper, Pan-STARRS, and the Large Synoptic Survey Telescope data sets) is possible using a reduced proper motion diagram and a tangential velocity cut-off (depending on the proper motion accuracy) of 30 km s–1. Our near-infrared observations reveal eight …
A Near-Infrared Spectroscopic Survey Of Cool White Dwarfs In The Sloan Digital Sky Survey, Murkremin Kilic, Piotr M. Kowalski, Ted Von Hippel
A Near-Infrared Spectroscopic Survey Of Cool White Dwarfs In The Sloan Digital Sky Survey, Murkremin Kilic, Piotr M. Kowalski, Ted Von Hippel
Ted von Hippel
We present near-infrared photometric observations of 15 and spectroscopic observations of 38 cool white dwarfs (WDs). This is the largest near-infrared spectroscopic survey of cool WDs to date. Combining the Sloan Digital Sky Survey photometry and our near-infrared data, we perform a detailed model atmosphere analysis. The spectral energy distributions of our objects are explained fairly well by model atmospheres with temperatures ranging from 6300 K down to 4200 K. Two WDs show significant absorption in the infrared, and are best explained with mixed H/He atmosphere models. Based on the up-to-date model atmosphere calculations by Kowalski & Saumon, we find …