Time Variable Accretion in White Dwarfs with Debris Disks

Details Time Variable Accretion in White Dwarfs with Debris Disks Time Variable Accretion in White Dwarfs with Debris Disks

May 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007sptz.prop40369v&link_type=abstract

Spitzer Proposal ID #40369

Other

Scientific paper

We propose to search for evolution in the flux from debris disks around white dwarf stars and to correlate that variability with ground-based measurements of changes in the accretion rates of metals onto the white dwarf photospheres. The contamination of WD photospheres with metals is an enduring puzzle because the extreme gravitational field of WDs should cause the denser metal atoms to sink on timescales as short as days. From recent ground-based and especially Spitzer observations, we now know of a handfull of WDs with debris disks, and we even know the size distribution and composition of the disk dust grains. The fact that the atmosphere of every WD with a debris disk is polluted by these metals means that the disks are almost certainly the source of the material. The disks themselves are thought to be created by tidally disrupted asteroids, comets, or other planetary bodies. Yet, at present, neither the accretion from the debris disk nor the formation of the disk is understood. Recently we have found compelling evidence for episodic accretion in the most studied WD of this class, G29-38. The photospheric Ca abundance varies by up to 70% and shows variations over periods as short as 15 days. We request 4 hours of Spitzer IRAC and IRS observations to monitor five debris disk WDs. These observations will compare the timescales and amplitudes of variations in the surface metal abundances (measured with simultaneous observations at Palomar, the Hobby Eberly Telescope, and Gemini) in these stars with the timing and degree of variability in mid-IR dust emission from the disks. Our measurements will be sensitive to the creation and accretion of micron and sub-micron grains, the time lag between dust creation in the disks and its accretion onto the stellar photospheres, indicating the dust source location(s), as well as temperature variations in the disks.

Affiliated with

Also associated with

No associations

Rating

Time Variable Accretion in White Dwarfs with Debris Disks does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Time Variable Accretion in White Dwarfs with Debris Disks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Time Variable Accretion in White Dwarfs with Debris Disks will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1749146