Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/~debes/data/mike.pdf Дата изменения: Tue Sep 6 22:31:58 2011 Дата индексирования: Tue Oct 2 04:28:39 2012 Кодировка: Поисковые слова: http www.astronomy.ru forum index.php topic 4644.0.html

Results From a MIKE Spectroscopic Monitoring Campaign of DAZs
John H. Debes (ORAU/NASA GSFC), Mukremin
1

1

2 Kilic

(CFA)

NASA Postdoctoral Program Fellow 2Spitzer Fellow

Abstract
The MIKE optical spectrograph on the Magellan Telescopes is a powerful instrument for detecting and monitoring the faint metal lines present in nearby metal enriched white dwarfs. With a spectral resolution of 30,000 and spectra with S/N>20 that cover from 3500е to 9500е, we can both monitor the Ca H and K lines as well as search for other metal lines of Mg and Fe. We present monitoring of 30 southern DAZs for variability in their Ca H and K lines, presenting some of our strongest candidates for variability . In addition to these white dwarfs, we have searched other white dwarfs for evidence of metal line absorption. We have also discovered two new DAZs within 20 pc, and a double degenerate that will merge within 1 Gyr.
Name WD 0032-175 HS 0047+1903 HE 0106-3253 WD 0141-675
NEW!

Teff 9235 16600 15700 6577 11420 6798 14400 19300 12200 9700 12800 8800 11200 7826 9400 9400 6945 20400 17400 7029 9200 20890 10300 9700 13200 17300 10100 18600 20300 12100

log D (yr) 2.72 -1.48 -1.82 3.5 -1.04 3.39 -1.56 -1.59 -1.73 2.29 -1.63 2.59 -0.34 3.13 2.48 2.02 3.68 -1.73 -1.46 2.89 2.58 -1.7 1.23 2.29 -1.47 -1.62 1.84 -1.60 -1.7 -1.70

N

obs

Disk?

1 1 3 2 2 2 4 2 4 6 3 3 2 2 2 2 2 3 2 3 3 2 5 6 4 6 4 2 3 6 X X X X X X X X X X

Variable Accretion for DAZs
Variable Candidates Stable Accretion

WD 0235+064 WD 0243-026 WD 0408-041 WD 1015+161 WD 1116+026 WD 1124-293 WD 1150-153 WD 1202-232 WD 1204-136 WD 1223-659
NEW!

HE 1225+0038 HE 1315-1105 WD 1344+106 WD 1457-086 WD 1614+160 WD 1821-131 WD 1826-045 GALEX1931 WD 2105-820 WD 2115-560 HS 2132+0941 WD 2149+021 HE 2221-1630 HS 2229+2335 HE 2230-1230 WD 2326+049

Effective temperatures are from Koester & Wilken (2006), except for WD 0141-675, WD 1223-659, (Kilic et al., 2008) and GALEX1931 (Vennes et al., 2009). The calculations for D are from Koester & Wilken (2006) or interpolated from Table 4 in Koester (2009).

Variable Selection Criteria: >36 for constant EW, at least 2 MIKE epochs

New DAZs within 20 pc

A Double Degenerate that will Merge in <1 Gyr
K1=-123±1 km/s K2=180±1 km/s P=2.85 hr V1=64±1 km/s V2=50±1 km/s M1=0.59±0.03 M M2=0.41±0.02 M
Masses were determined following the procedure of Napiwotzki et al., (2002)

EW=82 mе D=9 pc

EW=210 mе D=16 pc

Tmerge=680 Myr