Cool Customers in the Stellar Graveyard IV: Spitzer Search for Mid-IR excesses Around Five DAs - AstrophysicsReport as inadecuate




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Abstract: Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, requireexternal accretion of material to explain the presence of weak metal lineabsorption in their photospheres. The source of this material is currentlyunknown, but could come from the interstellar medium, unseen companions, orrelic planetesimals from asteroid belt or Kuiper belt analogues. Accuratemid-infrared photometry of these white dwarfs provide additional information tosolve the mystery of this accretion and to look for evidence of planetarysystems that have survived post main sequence evolution. We present {\emSpitzer} IRAC photometry accurate to $\sim$3% for four DAZs and one DA withcircumstellar absorption lines in the UV. We search for excesses due to unseencompanions or circumstellar dust disks. We use {\em Hubble Space Telescope}NICMOS imaging of these white dwarfs to gauge the level of backgroundcontamination to our targets as well as rule out common proper motioncompanions to WD 1620-391. All of our targets show no excesses due tocompanions $>$20 M$ {J}$, ruling out all but very low mass companions to thesewhite dwarfs at all separations. No excesses due to circumstellar disks areobserved, and we place limits on what types of disks may still be present.



Author: J.H. Debes, S. Sigurdsson, B. Hansen

Source: https://arxiv.org/



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