Showing papers by "Jay Farihi published in 2007"
TL;DR: In this article, the Spitzer Space Telescope photometry of 11 externally polluted white dwarfs is reported, including GD 40, GD 133, and PG 1015+161, showing that the metals in the atmosphere of GD 40 are the result of accretion of a tidally disrupted asteroid with a chondritic composition.
Abstract: We report Spitzer Space Telescope photometry of 11 externally polluted white dwarfs. Of the nine stars for which we have IRAC photometry, we find that GD 40, GD 133, and PG 1015+161 each has an infrared excess that can be understood as arising from a flat, opaque, dusty disk. GD 56 also has an infrared excess characteristic of circumstellar dust, but a flat-disk model cannot reproduce the data unless there are grains as warm as 1700 K and perhaps not even then. Our data support the previous suggestion that the metals in the atmosphere of GD 40 are the result of accretion of a tidally disrupted asteroid with a chondritic composition.
187 citations
TL;DR: In this article, the Spitzer Space Telescope photometry between 3.6 and 24?m and spectroscopy between 5 and 15?m of GD 362, a white dwarf with an effective temperature near 10,000 K that displays a remarkably high concentration of metals in its photosphere and a thermal infrared excess.
Abstract: We report Spitzer Space Telescope photometry between 3.6 and 24 ?m and spectroscopy between 5 and 15 ?m of GD 362, a white dwarf with an effective temperature near 10,000 K that displays a remarkably high concentration of metals in its photosphere and a thermal infrared excess. We approximately reproduce both the infrared continuum and the very strong 10 ?m silicate emission feature with a model of an orbiting dusty disk that is flat out to 50 stellar radii and warped between 50 and 70 stellar radii. The relatively small amount of cold material implied by the weak 24 ?m flux argues that the disk lies within the Roche radius of the star, and we may be witnessing a system where an asteroidal-size body has been tidally destroyed. If so, determination of the photospheric metal abundances may measure the bulk composition of an extrasolar minor planet.
131 citations
TL;DR: In this article, the Spitzer Space Telescope photometry of eleven externally-polluted white dwarfs was reported, including GD 40, GD 133 and PG 1015+161.
Abstract: We report Spitzer Space Telescope photometry of eleven externally-polluted white dwarfs. Of the nine stars for which we have IRAC photometry, we find that GD 40, GD 133 and PG 1015+161 each has an infrared excess that can be understood as arising from a flat, opaque, dusty disk. GD 56 also has an infrared excess characteristic of circumstellar dust, but a flat-disk model cannot reproduce the data unless there are grains as warm as 1700 K and perhaps not even then. Our data support the previous suggestion that the metals in the atmosphere of GD 40 are the result of accretion of a tidally-disrupted asteroid with a chondritic composition.
4 citations