相关论文: Pollution of single white dwarfs by accretion of m…
Using ultraviolet spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, we extend our previous ground-based optical determinations of the composition of the extrasolar asteroids accreted onto two white dwarfs,…
The cool white dwarf SDSS J124231.07+522626.6 exhibits photospheric absorption lines of 8 distinct heavy elements in medium resolution optical spectra, notably including oxygen. The Teff = 13000 K atmosphere is helium-dominated, but the…
Observations of heavy metal pollution in white dwarf stars indicate that metal-rich planetesimals are frequently scattered into star-grazing orbits, tidally disrupted, and accreted onto the white dwarf surface, offering direct insight into…
Many white dwarfs have accreted material from their own planetary systems. These objects can be used to infer the composition of exoplanetary material and identify evidence for key geological processes. However, the white dwarf atmospheric…
We report the relative abundances of 17 elements in the atmosphere of the white dwarf star GD 362, material that, very probably, was contained previously in a large asteroid or asteroids with composition similar to the Earth/Moon system.…
Single metal polluted white dwarfs with no dusty disks are believed to be actively accreting metals from a circumstellar disk of gas caused by the destruction of asteroids perturbed by planetary systems. We report, for the first time, the…
Although discs of dust and gas have been observed orbiting white dwarfs, the origin of this circumstellar matter is uncertain. We hypothesize that the in-situ breakup of small bodies such as asteroids spun to fission during the giant branch…
We present a bulk sample analysis of the metal polluted white dwarfs which also host infrared bright dusty debris disks, known to be direct signatures of an active exoplanetary accretion source. We explore the relative positions of these…
White dwarfs are compact objects with atmospheres containing mainly light elements, hydrogen or helium. Because of their surface high gravitational field, heavy elements diffuse downwards in a very short timescale compared to the…
This letter reports statistically significant changes in the equivalent widths of MgII and CaII lines in the dusty and polluted white dwarf WD 0106-328, based on six epochs of spectroscopy using the VLT and Keck spanning 25 yr. Furthermore,…
White dwarfs accreting planetary debris provide detailed insight into the bulk composition of rocky exo-planetesimals. However, only one Kuiper-Belt analogue has been identified in that way so far. Here, we report the accretion of an icy…
Recent infrared observations have revealed presence of compact (radii < R_Sun) debris disks around more than a dozen of metal-rich white dwarfs (WD), likely produced by tidal disruption of asteroids. Accretion of high-Z material from these…
We have performed a comprehensive ground-based observational program aimed at characterizing the circumstellar material orbiting three single white dwarf stars previously known to possess gaseous disks. Near-infrared imaging unambiguously…
WD J204713.76-125908.9 is a new addition to the small class of white dwarfs with helium-dominated photospheres that exhibit strong Balmer absorption lines and atmospheric metal pollution. The exceptional abundances of hydrogen observed in…
The magnetic white dwarfs (MWDs) are found either isolated or in interacting binaries. They divide into two groups: a high field group (0.1-1,000MegaGauss) comprising some 13% of all white dwarfs (WDs), and a low field group (B<0.1MG) whose…
We examine 14 hot white dwarfs for signs of infrared excess using the Spitzer Space Telescope. Twelve of the objects are massive white dwarfs which have been suggested to be the result of binary mergers. The remaining two objects are…
Metals observed in the atmospheres of white dwarfs suggest that many have recently accreted planetary bodies. In some cases, the compositions observed suggest the accretion of material dominantly from the core (or the mantle) of a…
The infrared excess around the white dwarf G29-38 can be explained by emission from an opaque flat ring of dust with an inner radius 0.14 of the radius of the Sun and an outer radius approximately equal to the Sun's. This ring lies within…
Studies suggest that the pollution of white dwarf (WD) atmospheres arises from the accretion of minor planets, but the exact properties of polluting material, and in particular the evidence for water in some cases are not yet understood.…
Many potential mechanisms for delivering planetary debris to within a few Roche radii of white dwarfs rely on gravitational scattering events that feature perturbers which are giant planets or terrestrial planets. However, the population of…