A Spitzer Space Telescope Study of the Debris Disks Around Four SDSS White Dwarfs

Creators: Brinkworth, C. S.; Gänsicke, B. T.; Girven, J. M.; Hoard, D. W.; Marsh, T. R.; Parsons, S. G.; Koester, D.

Abstract

We present Spitzer Space Telescope data of four isolated white dwarfs that were previously known to harbor circumstellar gaseous disks. Infrared Array Camera photometry shows a significant infrared excess in all of the systems, SDSS0738+1835, SDSS0845+2257, SDSS1043+0855, and SDSS1617+1620, indicative of a dusty extension to those disks. The 4.5 μm excesses seen in SDSS0738, SDSS0845, and SDSS1617 are 7.5, 5.7, and 4.5 times the white dwarf contribution, respectively. In contrast, in SDSS1043, the measured flux density at 4.5 μm is only 1.7 times the white dwarf contribution. We compare the measured IR excesses in the systems to models of geometrically thin, optically thick disks, and find that we are able to match the measured spectral energy distributions to within 3σ of the uncertainties, although disks with unfeasibly hot inner dust temperatures generally provide a better fit than those below the dust sublimation temperature. Possible explanations for the dearth of dust around SDSS1043+0855 are briefly discussed. Including our previous study of SDSS1228+1040, all five white dwarfs with gaseous debris disks have significant amounts of dust around them. It is evident that gas and dust can coexist around these relatively warm, relatively young white dwarfs.

Additional Information

© 2012 American Astronomical Society. Received 2011 May 13; accepted 2012 February 28; published 2012 April 17. The authors thank the referee for detailed and useful comments that helped to improve this paper. The DA white dwarf models used in the analysis were calculated with the modified Stark broadening profiles of Tremblay & Bergeron (2009), kindly made available by the authors. Co-authors Gaensicke and Marsh were supported by an STFC rolling grant. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, Caltech, under NASA contracts 1407 and 960785. This work makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and IPAC/Caltech, funded by NASA and the NSF. The SOFI results in this paper are based on observations collected at the European Southern Observatory (La Silla) under program ID 085.D-0541. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U. S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web site is http://www.sdss.org/. The SDSS is managed by a very long list of institutions, who can all be found at the following Web site: http://www.sdss.org/collaboration/credits.html. This research has made use of NASA's Astrophysics Data System. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

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