Friday, July 19, 2013

1307.4887 (Zhongxiang Wang et al.)

Near-Infrared Imaging of White Dwarfs with Candidate Debris Disks    [PDF]

Zhongxiang Wang, Anestis Tziamtzis, Xuebing Wang
Using the Wide-field Infrared Survey Explorer (WISE) results, Debes et al. (2011) have found more than 100 white dwarfs (WDs) in the data release 7 WD catalogue from the Sloan Digital Sky Survey had excess mid-infrared (MIR) emission. These WDs were identified to have candidate debris disks, which are believed to be formed from material produced by tidal disruption of asteroids around WDs, or brown dwarf companions. Among them 86 did not have near-infrared (NIR) detections. In order to identify debris-disk systems among these sources, we have carried out NIR imaging of them and report the results from the observations of 12 of them. On the basis of positional identification and constructed flux density spectra, we find that 7 WDs have excess IR emission but mostly at WISE W1 (and W2) band and the excess emission likely indicates the existence of debris disks around the WDs. Among the remaining 5 WDs, one is identified to possibly have a brown dwarf companion, and the other 4 are resolved to have a nearby, likely unassociated brown dwarf and MIR emission from the brown dwarfs dominated that of the WISE W1/W2 counterparts. We discuss the results of our observations. Because of large uncertainties on WISE photometry of faint sources (including our targets), further accurate MIR photometry of these candidate debris-disk and brown-dwarf systems is needed for verification of their nature.
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