J/ApJ/737/L7 Post-AGB star SAO 40039 equivalent widths (Rao+, 2011)
Is the post-AGB star SAO 40039 mildly hydrogen-deficient?
Rao S.S., Pandey G., Lambert D.L., Giridhar S.
<Astrophys. J., 737, L7 (2011)>
=2011ApJ...737L...7R 2011ApJ...737L...7R
ADC_Keywords: Equivalent widths ; Stars, giant ; Abundances ; Spectroscopy
Keywords: stars: abundances - stars: atmospheres - stars: evolution -
stars: fundamental parameters
Abstract:
We have conducted an LTE abundance analysis for SAO 40039, a warm
post-AGB star whose spectrum is known to show surprisingly strong HeI
lines for its effective temperature and has been suspected of being
H-deficient and He-rich. High-resolution optical spectra are analyzed
using a family of model atmospheres with different He/H ratios.
Atmospheric parameters are estimated from the ionization equilibrium
set by neutral and singly ionized species of Fe and Mg, the excitation
of FeI and FeII lines, and the wings of the Paschen lines. On the
assumption that the HeI lines are of photospheric and not
chromospheric origin, a He/H ratio of approximately unity is found by
imposing the condition that the adopted He/H ratio of the model
atmosphere must equal the ratio derived from the observed HeI triplet
lines at 5876, 4471, and 4713Å, and singlet lines at 4922 and
5015Å. Using the model with the best-fitting atmospheric parameters
for this He/H ratio, SAO 40039 is confirmed to exhibit mild dust-gas
depletion, i.e., the star has an atmosphere deficient in elements of
high condensation temperature. The star appears to be moderately
metal-deficient with [Fe/H]=-0.4dex. But the star's intrinsic
metallicity as estimated from Na, S, and Zn, elements of a low
condensation temperature, is [Fe/H]o~-0.2 ([Fe/H]o refers to the
star's intrinsic metallicity). The star is enriched in N and perhaps O
as well, changes reflecting the star's AGB past and the event that led
to He enrichment.
Description:
Spectra of SAO 40039 were obtained on the nights of 2007 November 5
and 2011 February 21 at the W. J. McDonald Observatory with the 2.7m
Harlan J. Smith Telescope and the Tull Coude Spectrograph. The spectra
taken at these epochs were found to be similar. The spectra correspond
to a resolving power of 60000 (5km/s).
An additional spectrum was obtained on 2011 January 28 using the
echelle spectrometer at Vainu Bappu Observatory (VBO) in Kavalur,
India, giving a resolution of about 28000 (10km/s).
Objects:
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RA (2000) DE Designation(s)
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05 07 50.30 +48 24 09.4 SAO 40039 = TYC 3349-1650-1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 51 185 Detailed line list for SAO 40039
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See also:
J/A+A/514/A2 : AKARI/HIP and AKARI/2MASS samples (Ita+, 2010)
J/AZh/84/714 : Optical spectral variability of BD+48 1220 (Klochkova+, 2007)
J/A+A/469/799 : Torun cat. of post-AGB and related objects (Szczerba+, 2007)
J/A+A/385/884 : BVRIJHK photometry of 27 post-AGB candidates (Fujii+, 2002)
J/A+AS/122/285 : VCS Stark broadening tables for hydrogen (Lemke, 1997)
J/A+A/275/101 : Chemical evolution of the galactic disk I. (Edvardsson+ 1993)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Species identification
7- 14 A8 0.1nm lambda Line wavelength λ in Angstroms
16- 19 A4 --- Mean [Mean ] Mean indicator (1)
21- 25 F5.2 eV ExPot ? Excitation potential
27- 32 F6.3 [-] log(gf) ? Log of the oscillator strength
34 A1 --- r_log(gf) Source of log(gf) (2)
36- 38 I3 0.1pm EW ? Equivalent width; in milli-Angstroms
40 A1 --- S [S] S: indicates EW from a synthetic spectrum
42- 46 F5.2 [-] loge Log of the number abundance derived (1)
48- 51 F4.2 [-] e_loge ? Uncertainty in loge (1)
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Note (1): "Mean" = the loge and e_loge values (logε abundances)
are the mean abundances and uncertainties for the given ion.
Note (2): Flag on log(gf) as follows:
a = NIST database (http://physics.nist.gov/PhysRefData/ASD/lines_form.html);
b = Fuhr, J. R., & Wiese, W. L., 2006, J. Phys. Chem. Ref. Data, 35, 1669;
c = Melendez, J. & Barbuy, B., 2009A&A...497..611M 2009A&A...497..611M;
d = Biemont, E., et al. 1981ApJ...248..867B 1981ApJ...248..867B
e = Curry, J. J., 2004, J. Phy. Chem. Ref. Data, 33, 725.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 10-Jan-2013