2018A&A...615A...4C


Query : 2018A&A...615A...4C

2018A&A...615A...4C - Astronomy and Astrophysics, volume 615A, 4-4 (2018/7-1)

Carbon line formation and spectroscopy in O-type stars.

CARNEIRO L.P., PULS J. and HOFFMANN T.L.

Abstract (from CDS):


Context. The determination of chemical abundances constitutes a fundamental requirement for obtaining a complete picture of a star. Particularly in massive stars, CNO abundances are of prime interest, due to the nuclear CNO-cycle, and various mixing processes which bring these elements to the surface. The precise determination of carbon abundances, together with N and O, is thus a key ingredient for understanding the different phases of stellar evolution.
Aims. We aim to enable a reliable carbon spectroscopy for our unified non-LTE atmosphere codeFASTWIND.
Methods. We have developed a new carbon model atom including CII/III/IV/V, and we discuss specific problems related to carbon spectroscopy in O-type stars. We describe different tests we have performed to examine the reliability of our implementation, and investigate which mechanisms influence the carbon ionization balance. By comparing with high-resolution spectra from six O-type stars, we verified to what extent observational constraints can be reproduced by our new carbon line synthesis.
Results. Carbon lines are even more sensitive to a variation of Teff, logg, and M, than hydrogen and helium lines. We are able to reproduce most of the observed lines from our stellar sample, and to estimate those specific carbon abundances which bring the lines from different ions into agreement (three stages in parallel for cool objects, two for intermediate O-types). For hot dwarfs and supergiants earlier than O7, X-rays from wind-embedded shocks can have an impact on the synthesized line strengths, particularly for CIV, potentially affecting the abundance determination. Dielectronic recombination has a significant impact on the ionization balance in the wind.
Conclusions. We demonstrate our capability to derive realistic carbon abundances by means ofFASTWIND, using our recently developed model atom. We find that complex effects can have a strong influence on the carbon ionization balance in hot stars. For a further understanding, the UV range needs to be explored as well. By means of detailed and available nitrogen and oxygen model atoms, we will be able to perform a complete CNO abundance analysis for larger samples of massive stars, and to provide constraints on corresponding evolutionary models and aspects.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: early-type - stars: fundamental parameters - stars: atmospheres - stars: abundances - line: formation

Simbad objects: 11

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Number of rows : 11
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 HD 365 * 00 08 13.6302414048 -49 43 18.594494220   10.59 10.16     F5V 15 0
2 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6280 1
3 HD 30331 * 04 46 15.6148441680 -09 50 39.628236984   10.32 9.92     Fm_dD 9 0
4 HD 35612 * 05 26 05.9973556080 +00 50 02.361914592   8.23 8.30     B8/9V 24 0
5 * ups Ori SB* 05 31 55.8601879 -07 18 05.537157 3.30 4.36 4.63 4.75 5.01 O9.7V 394 0
6 * zet Pup BY* 08 03 35.04754 -40 00 11.3321 0.89 1.98 2.25 2.36 2.58 O4I(n)fp 1125 1
7 HD 93128 SB* 10 43 54.3957741024 -59 32 57.497266716 8.82 8.97 8.77 9.40 8.71 O3.5V((fc))z 92 1
8 HD 303311 SB* 10 44 37.4602634976 -59 32 55.460525100 8.30 9.042 8.979 9.58 9.09 O6V((f))z 78 0
9 HD 169582 s*b 18 25 43.1466928224 -09 45 11.033442216 8.74 9.24 8.70     O6Iaf 85 0
10 HD 188209 s*b 19 51 59.0687638680 +47 01 38.419078944 4.61 5.55 5.63 5.54 5.64 O9.5Iab 297 0
11 Schulte 7 * 20 33 14.1095938872 +41 20 21.904113804 12.24 12.00 10.55     O3If* 137 0

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2022.05.24-10:51:28

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