533 research outputs found
The WISE InfraRed Excesses around Degenerates (WIRED) Survey
The Wide-field Infrared Survey Explorer (WISE) is a NASA medium class Explorer
mission that performed an all sky survey in four infrared bands. We present an overview of the WISE
InfraRed Excesses around Degenerates (WIRED) Survey, which has the goals of characterizing
white dwarf stars in the WISE bands, confirming objects known to have infrared excess from past
observations, and revealing new examples of white dwarfs with infrared excess that can be attributed
to unresolved companions or debris disks. We obtained preliminary WISE detections (S/N > 2) in
at least one band of 405 white dwarfs from the 9316 unique possible targets in the Sloan Digital
Sky Survey Data Release 4 Catalog of Spectroscopically Identified White Dwarfs (not all potential
targets were available in the sky coverage used here). A companion paper in this volume discusses
specific results from our target detections
Color Gradients Detected in the HD 15115 Circumstellar Disk
We report HST/NICMOS coronagraphic images of the HD 15115 circumstellar disk
at 1.1\micron. We find a similar morphology to that seen in the visible and at
H band--an edge-on disk that is asymmetric in surface brightness. Several
aspects of the 1.1\micron data are different, highlighting the need for
multi-wavelength images of each circumstellar disk. We find a flattening to the
western surface brightness profile at 1.1\micron interior to 2\arcsec (90 AU)
and a warp in the western half of the disk. We measure the surface brightness
profiles of the two disk lobes and create a measure of the dust scattering
efficiency between 0.55-1.65\micron at 1\arcsec, 2\arcsec, and 3\arcsec. At
2\arcsec the western lobe has a neutral spectrum up to 1.1\micron and a strong
absorption or blue spectrum 1.1\micron, while a blue trend is seen in the
eastern lobe. At 1\arcsec the disk has a red F110W-H color in both lobes.Comment: 4 pages, 4 figures, emulateapj; accepted to ApJ
Cool Customers in the Stellar Graveyard IV: Spitzer Search for Mid-IR excesses Around Five DAs
Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, require
external accretion of material to explain the presence of weak metal line
absorption in their photospheres. The source of this material is currently
unknown, but could come from the interstellar medium, unseen companions, or
relic planetesimals from asteroid belt or Kuiper belt analogues. Accurate
mid-infrared photometry of these white dwarfs provide additional information to
solve the mystery of this accretion and to look for evidence of planetary
systems that have survived post main sequence evolution. We present {\em
Spitzer} IRAC photometry accurate to 3% for four DAZs and one DA with
circumstellar absorption lines in the UV. We search for excesses due to unseen
companions or circumstellar dust disks. We use {\em Hubble Space Telescope}
NICMOS imaging of these white dwarfs to gauge the level of background
contamination to our targets as well as rule out common proper motion
companions to WD 1620-391. All of our targets show no excesses due to
companions 20 M, ruling out all but very low mass companions to these
white dwarfs at all separations. No excesses due to circumstellar disks are
observed, and we place limits on what types of disks may still be present.Comment: 18 pages, 8 figures, Accepted to A
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