J/A+A/470/317 UV spectra of the central star of Sh 2-216 (Rauch+, 2007)
High-resolution FUSE and HST ultraviolet spectroscopy of the white dwarf central
star of Sh 2-216.
Rauch T., Ziegler M., Werner K., Kruk J.W., Oliveira C.M., Vande Putte D.,
Migniani R.P., Kerber F.
<Astron. Astrophys. 470, 317 (2007)>
=2007A&A...470..317R 2007A&A...470..317R
ADC_Keywords: Planetary nebulae ; Spectra, ultraviolet
Keywords: ISM: planetary nebulae: individual: Sh 2-216 - stars: abundances -
stars: atmospheres - stars: evolution -
stars: individual: LS V +46 21 - stars: AGB and post-AGB
Abstract:
We perform a comprehensive spectral analysis of LS V +46 21 in order
to compare its photospheric properties to theoretical predictions from
stellar evolution theory as well as from diffusion calculations.
LS V +46 21 is the DAO-type central star of the planetary nebula
Sh 2-216. High-resolution, high-S/N ultraviolet observations obtained
with FUSE and STIS aboard the HST as well as the optical spectrum have
been analyzed in order to determine the photospheric parameters and
the spectroscopic distance. We performed a detailed spectral analysis
of the ultraviolet and optical spectrum by means of state-of-the-art
NLTE model-atmosphere techniques.
From the NIV-NV, OIV-OVI, SiIV-SiV, and FeV-FeVII ionization
equilibria, we determined an effective temperature of 95±2kK with
high precision. The surface gravity is logg=6.9±0.2. An unexplained
discrepancy appears between the spectroscopic distance
d=224+46-58pc and the parallax distance d=129+6-5pc of
LS V +46 21. For the first time, we have identified Mg IV and Ar VI
absorption lines in the spectrum of a hydrogen-rich central star and
determined the Mg and Ar abundances as well as the individual
abundances of iron-group elements (Cr, Mn, Fe, Co, and Ni). With the
realistic treatment of metal opacities up to the iron group in the
model-atmosphere calculations, the so-called Balmer-line problem
(found in models that neglect metal-line blanketing) vanishes.
Spectral analysis by means of NLTE model atmospheres has presently
arrived at a high level of sophistication, which is now hampered
largely by the lack of reliable atomic data and accurate
line-broadening tables. Strong efforts should be made to improve upon
this situation.
Objects:
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RA (2000) DE Designation(s)
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04 43 21.3 +46 42 06 Sh 2-216 = LBN 158.73+00.83
04 43 20.9 +46 42 05 LS V +46 21 = WD 0441+467
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 44 2607 Positions of identified lines in the FUSE (Fig. A1)
and STIS (Fig. A2) spectra of LS V +46 21,
the white dwarf central star of Sh 2-216
tablea2.dat 22 20610 Spectrum of LS V +46 21 observed with FUSE (Fig. A1)
tablea3.dat 22 38510 Spectrum of LS V +46 21 observed with
HST/STIS (Fig. A2)
tablea4.dat 27 99908 Synthetic spectrum of LS V +46 21 (Fig. A1)
tablea5.dat 27 101871 Synthetic spectrum of LS V +46 21 (Fig. A2)
figurea1.png 512 1444 *Synthetic spectrum of our final model of LS V +46 21
compared with the FUSE observation
figurea2.png 512 1043 *Synthetic spectrum of our final model of LS V +46 21
compared with the STIS observation
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Note on figurea1.png and figurea2.png: Identified lines are marked (see
tablea[12].dat for their wavelengths). The lines at the bottom of the panels
denote positions of H2 lines (for figurea1.png).
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Line Line identification (ion)
17- 20 A4 --- n_Line Photospheric (ph) or interstellar (is) origin
21- 32 F12.3 0.1nm lambdaObs Observed spectrum is shifted to the stellar
rest wavelength, the given wavelength is the
NIST wavelength
33- 44 F12.3 0.1nm lambdaLab ? Rest wavelength of interstellar lines
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Byte-by-byte Description of file: tablea2.dat tablea3.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda Wavelength
10- 22 E13.7 10mW/m2/nm F(lambda) Observed flux
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Byte-by-byte Description of file (* are comments): tablea4.dat tablea5.dat
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Bytes Format Units Label Explanations
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1- 13 E13.8 0.1nm lambda Wavelength
16- 27 E12.7 10mW/m2/nm F(lambda) Astrophysical flux
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Acknowledgements:
Thomas Rauch, rauch(at)astro.uni-tuebingen.de
(End) Patricia Vannier [CDS] 07-May-2007