* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Stars/galaxy News -> White Dwarf Debris Disks
Post Info TOPIC: White Dwarf Debris Disks
Blobrana


L

Posts: 131433
Date:
RE: White Dwarf Debris Disks
Permalink  
 

Title: Finding rocky asteroids around white dwarfs by their periodic thermal emission
Author: Henry Lin, Abraham Loeb

Since old white dwarfs are exceptionally dim, the contrast between the thermal emission of an orbiting object and a white dwarf is dramatically enhanced compared to a main sequence host. Furthermore, rocky objects much smaller than the moon have no atmospheres and are tidally locked to the white dwarf if they orbit near the Roche zone. We show that this leads to temperature contrasts between their day and night side of order unity that should lead to temporal variations in infrared flux over an orbital period of ~ 0.2 to ~ 2 days. Ground based telescopes could detect objects with a mass as small as 1% of the lunar mass ML around Sirius B with a few hours of exposure. The James Webb Space Telescope (JWST) may be able to detect objects as small as 10-3ML around most nearby white dwarfs. The tightest constraints will typically be placed on 12,000 K white dwarfs, whose Roche zone coincides with the dust sublimation zone. Constraining the abundance of minor planets around white dwarfs as a function of their surface temperatures (and therefore age) provides a novel probe for the physics of planetary formation.

Read more (271kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: A Spitzer Space Telescope Study of the Debris Disks around four SDSS White Dwarfs
Authors: Carolyn Brinkworth, Boris Gaensicke, Jon Girven, Don Hoard, Tom Marsh, Stephen Parsons, Detlev Koester

We present Spitzer Space Telescope data of four isolated white dwarfs that were previously known to harbour circumstellar gaseous disks. IRAC 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-micron 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 microns 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 SEDs to within 3 sigma 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.

Read more (222kb, PDF)



__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Stars/galaxy News -> White Dwarf Debris Disks


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard