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Constraints on the lifetimes of disks resulting from tidally destroyed rocky planetary bodies
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Girven, Jonathan, Brinkworth, C. S., Farihi, J., Gaensicke, B. T., Hoard, D. W., Marsh, T. R. and Koester, Detlev (2012) Constraints on the lifetimes of disks resulting from tidally destroyed rocky planetary bodies. The Astrophysical Journal, Vol.749 (No.2). p. 154. doi:10.1088/0004-637X/749/2/154 ISSN 0004-637X.
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Official URL: http://dx.doi.org/10.1088/0004-637X/749/2/154
Abstract
Spitzer IRAC observations of 15 metal-polluted white dwarfs reveal infrared excesses in the spectral energy distributions of HE 0110–5630, GD 61, and HE 1349–2305. All three of these stars have helium-dominated atmospheres, and their infrared emissions are consistent with warm dust produced by the tidal destruction of (minor) planetary bodies. This study brings the number of metal-polluted, helium and hydrogen atmosphere white dwarfs surveyed with IRAC to 53 and 38, respectively. It also nearly doubles the number of metal-polluted helium-rich white dwarfs found to have closely orbiting dust by Spitzer. From the increased statistics for both atmospheric types with circumstellar dust, we derive a typical disk lifetime of log [t disk(yr)] = 5.6 ± 1.1 (ranging from 3 × 104 to 5 × 106 yr). This assumes a relatively constant rate of accretion over the timescale where dust persists, which is uncertain. We find that the fraction of highly metal-polluted helium-rich white dwarfs that have an infrared excess detected by Spitzer is only 23%, compared to 48% for metal-polluted hydrogen-rich white dwarfs, and we conclude from this difference that the typical lifetime of dusty disks is somewhat shorter than the diffusion timescales of helium-rich white dwarf. We also find evidence for higher time-averaged accretion rates onto helium-rich stars compared to the instantaneous accretion rates onto hydrogen-rich stars; this is an indication that our picture of evolved star-planetary system interactions is incomplete. We discuss some speculative scenarios that can explain the observations.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QB Astronomy | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Library of Congress Subject Headings (LCSH): | White dwarf stars, Cosmic dust | ||||
Journal or Publication Title: | The Astrophysical Journal | ||||
Publisher: | Institute of Physics Publishing, Inc. | ||||
ISSN: | 0004-637X | ||||
Official Date: | 2012 | ||||
Dates: |
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Volume: | Vol.749 | ||||
Number: | No.2 | ||||
Page Range: | p. 154 | ||||
DOI: | 10.1088/0004-637X/749/2/154 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Funder: | United States. National Aeronautics and Space Administration (NASA), National Science Foundation (U.S.) (NSF) | ||||
Grant number: | 1407 (NASA), 960785 (NASA) |
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