J/A+A/655/A106 GO And, 84 UMa, kappa Psc ESPaDOnS spectra (Romanovskaya+, 2021)
Fundamental parameters of Ap-stars GO And, 84 UMa and kappa Psc.
Romanovskaya A.M., Shulyak D.V., Ryabchikova T.A., Sitnova T.M.
<Astron. Astrophys. 655, A106 (2021)>
=2021A&A...655A.106R 2021A&A...655A.106R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Ap ; Spectra, optical ; Spectra, infrared
Keywords: stars: abundances - stars: chemically peculiar -
stars: fundamental parameters
Abstract:
The aim of this work is to determine fundamental parameters of three
Ap stars, GO And (HD 4778), κ Psc (HD 220825), and 84 UMa (HD
120198), using spectroscopic techniques. By analysing these stars, we
complete the sample of Ap stars for which fundamental parameters have
additionally been derived by means of interferometry. This enables a
cross-comparison of results derived by direct and indirect methods.
Our study is based on the analysis of high-resolution spectra with a
high signal-to-noise ratio that were obtained with ESPaDOnS
spectrograph. We used an iterative method of fundamental parameter
determinations that includes self-consistent modelling of the stellar
atmosphere, taking individual abundances of chemical elements into
account and subsequently fitting a theoretical spectral energy
distribution to the observed distribution. The quality of the
spectroscopic determinations was evaluated through a comparison with
the interferometric results.
For all investigated stars we determined fundamental parameters and
derived chemical abundances that turn to be typical for Ap stars and
are characterised mainly by gradual increase of heavy elements
atmospheric abundance from an order of magnitude for iron peak
elements up to very significant excesses of 3-4dex of the rare-earth
elements relative to the solar values. The only exception is Ba which
abundance is close to the solar one. There is also a significant He
deficiency in the atmospheres of HD 120198 and HD 220825, whereas He
abundance in HD 4778 is close to the solar one.
We do not find significant Fe and Cr stratification. Using these
abundances we constructed self-consistent atmospheric models for each
star. The effect of the surface chemical inhomogeneity on the derived
fundamental parameters did not exceed ±100K in effective temperature
which lies within a range of errors in similar self-consistent
analyses of Ap stars. Finally, we compared spectroscopically derived
effective temperatures, radii, and luminosity for 13 out of 14 Ap
stars in benchmarking sample with the interferometric results. While
radii and luminosity agree within the quoted errors of both
determinations, spectroscopic effective temperatures are higher than
the interferometric ones for stars with Teff>9000K. The observed
hydrogen line profiles favour the spectroscopically derived
temperatures.
Description:
Normalised spectra of HD 4778, HD 120198, and HD 220825 are presented.
Spectroscopic observations were extracted from the ESPaDOnS
spectrograph archive (Canada-France-Hawaii Telescope,
http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/cfht/) and cover the
spectral range of 3700-10500Å. The resolving power of the instrument
is R=68000.
Objects:
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RA (2000) DE Designation(s)
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00 50 18.27 +45 00 08.1 HD 4778 = GO And
13 46 35.66 +54 25 57.6 HD 120198 = 84 UMa
23 26 55.96 +01 15 20.2 HD 220825 = kap Psc
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
hd4778.dat 24 227363 Spectrum of HD 4778
hd120198.dat 24 220080 Spectrum of HD 120198
hd220825.dat 24 220063 Spectrum of HD 220825
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Byte-by-byte Description of file: hd120198.dat hd220825.dat hd4778.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 0.1nm lambda Wavelength
10- 24 E15.7 ---- Int Normalized intensity
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Acknowledgements:
Anna Romanovskaya, annarom(at)inasan.ru
(End) Anna Romanovskaya [INASAN, Russia], Patricia Vannier [CDS] 26-Oct-2021