2006A&A...460..831K


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.29CET11:53:54

2006A&A...460..831K - Astronomy and Astrophysics, volume 460, 831-842 (2006/12-4)

Chemical stratification in the atmosphere of Ap star HD 133792. Regularized solution of the vertical inversion problem.

KOCHUKHOV O., TSYMBAL V., RYABCHIKOVA T., MAKAGANYK V. and BAGNULO S.

Abstract (from CDS):

High spectral resolution studies of cool Ap stars reveal conspicuous anomalies of the shape and strength of many absorption lines. This is a signature of large atmospheric chemical gradients (chemical stratification) produced by the selective radiative levitation and gravitational settling of chemical species. Previous observational studies of the chemical stratification in Ap stars were limited to fitting simple parametrized chemical profiles. Here we present a new approach to mapping the vertical chemical structures in stellar atmospheres. We have developed a regularized chemical inversion procedure that uses all information available in high-resolution stellar spectra. The new technique for the first time allowed us to recover chemical profiles without making a priori assumptions about the shape of chemical distributions. We have derived average abundances and applied the vertical inversion procedure to the high-resolution VLT UVES spectra of the weakly magnetic, cool Ap star HD133792. Our spectroscopic analysis yielded improved estimates of the atmospheric parameters of HD133792. We show that this star has negligible vesin i and the mean magnetic field modulus <B≥1.1±0.1kG. We have derived average abundances for 43 ions and obtained vertical distributions of Ca, Si, Mg, Fe, Cr, and Sr. All these elements except Mg show high overabundance in the deep layers and solar or sub-solar composition in the upper atmosphere of HD133792. In contrast, the Mg abundance increases with height. We find that transition from the metal-enhanced to metal-depleted zones typically occurs in a rather narrow range of depths in the atmosphere of HD133792. Based on the derived photospheric abundances, we conclude that HD133792 belongs to the rare group of evolved cool Ap stars, which possesses very large Fe-peak enhancement, but lacks a prominent overabundance of the rare-earth elements.

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Journal keyword(s): stars: abundances - stars: atmospheres - stars: chemically peculiar - stars: individual: HD 133792

Simbad objects: 6

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Number of rows : 6

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 V* HN And a2* 01 24 18.6762637253 +43 08 31.629302597   6.704 6.676     A4VpSrSi 131 0
2 HD 66318 * 07 59 27.4746869367 -60 47 47.109578700   9.69 9.56   9.555 A0pEuCrSr 84 0
3 HD 133792 * 15 09 25.5214568039 -63 38 34.552502511   6.298 6.247     ApSrCrEu 68 0
4 * 73 Dra a2* 20 31 30.3893892230 +74 57 16.597317688   5.271 5.185     A9:VpCrSrEu 246 1
5 HD 204411 a2* 21 26 51.6210422364 +48 50 06.598904376 5.54 5.38 5.31     A4VpSiCrHg 172 0
6 V* MX Cep a2* 22 52 41.9148863625 +58 48 23.283881252   7.98 7.88     A2p 84 0

    Equat.    Gal    SGal    Ecl

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2020.02.29-11:53:54

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