2018A&A...616A..73W


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.14CEST02:32:44

2018A&A...616A..73W - Astronomy and Astrophysics, volume 616A, 73-73 (2018/8-1)

The hot white dwarf in the peculiar binary nucleus of the planetary nebula EGB 6.

WERNER K., RAUCH T. and KRUK J.W.

Abstract (from CDS):

EGB 6 is an extended, faint old planetary nebula (PN) with an enigmatic nucleus. The central star (PG 0950+139) is a hot DAOZ-type white dwarf (WD). An unresolved, compact emission knot was discovered to be located 0.166'' away from the WD and it was shown to be centered around a dust-enshrouded low-luminosity star. It was argued that the dust disk and evaporated gas (photoionized by the hot WD) around the companion are remnants of a disk formed by wind material captured from the WD progenitor when it was an asymptotic giant branch (AGB) star. In this paper, we assess the hot WD to determine its atmospheric and stellar parameters. We performed a model-atmosphere analysis of ultraviolet (UV) and optical spectra. We found Teff=105000±5000K, logg=7.4±0.4, and a solar helium abundance (He=0.25±0.1, mass fraction). We measured the abundances of ten more species (C, N, O, F, Si, P, S, Ar, Fe, Ni) and found essentially solar abundance values, indicating that radiation-driven wind mass-loss, with a theoretical rate of log(M/M/yr)=-11.0–0.8+1.1, prevents the gravitational separation of elements in the photosphere. The WD has a mass of M/M=0.58–0.04+0.12 and its post-AGB age (log(tevol/yr=360–0.09+1.26) is compatible with the PN kinematical age of log(tPN/yr=4.2). In addition, we examined the UV spectrum of the hot nucleus of a similar object with a compact emission region, Tol 26 (PN G298.0+34.8), and found that it is a slightly cooler DAOZ WD (Teff~=85000K), but this WD shows signatures of gravitational settling of heavy elements.

Abstract Copyright: © ESO 2018

Journal keyword(s): planetary nebulae: general - stars: abundances - stars: atmospheres - stars: AGB and post-AGB - white dwarfs

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 ACO 31 ClG 00 27 06 +22 37.6           ~ 19 0
2 ACO 35 ClG 00 27.4 -21 33           ~ 5 0
3 NGC 1360 PN 03 33 14.6471964691 -25 52 17.981057073   10.95 11.16     sdO 269 0
4 EGB 6 PN 09 52 58.9867703345 +13 44 34.624573201   15.692 15.999 16.137 16.300 DAO.5 82 0
5 PG 1034+001 WD* 10 37 03.8005751967 -00 08 19.122434186 11.589 12.863 13.228 13.383 13.587 DO 106 0
6 PN G298.0+34.8 PN 12 33 12.9828510935 -27 48 53.505736534   17       ~ 23 0
7 PN A66 35 PN 12 53 32.7840615552 -22 52 22.614854036   10.52 9.69     G8III-IV+DAO 179 1
8 HS 2115+1148 WD* 21 18 18.7294747125 +12 01 32.073147573   16.0   16.7   DAOZ.8 14 0

    Equat.    Gal    SGal    Ecl

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2020.08.14-02:32:45

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