UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)
UvA-DARE (Digital Academic Repository)
Observations and analysis of early-type stars at infrared wavelengths
Zaal, P.A.
Publication date
2000
Link to publication
Citation for published version (APA):
Zaal, P. A. (2000). Observations and analysis of early-type stars at infrared wavelengths.
General rights
It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s)
and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open
content license (like Creative Commons).
Disclaimer/Complaints regulations
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please
let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material
inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter
to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You
will be contacted as soon as possible.
11 Introduction 1
1.11 Infrared spectroscopy 3 1.1.11 The ISO-mission 4 1.1.22 The infrared spectral region of hot stars .' 5
1.22 Overview of the different sub-classes of OB stars 6
1.2.11 The "normal" OBB stars 8 1.2.22 The OB supergiants 10 1.2.33 The Be stars 11 1.33 Modeling of OB stars 13 1.3.11 Photospheric models 13 1.3.22 Wind models 15 1.3.33 Disc models 15 Referencess 16
22 The HI infrared line spectrum for Be stars with low-density discs. 19
2.11 Introduction 19 2.22 The HI line calculations 21
2.2.11 The line optical depth 21 2.2.22 The curve of growth 22 2.2.33 The simple approximation 26 2.2.44 An example; A full HI IR spectrum for r Sco, a BO star
sur-roundedd by a low-density disc 29 2.33 A study of B stars surrounded by a low-density disc 31
2.3.11 The Ha and IR line profile calculations with the disc model. . . . 32 2.3.22 The approximate HI IR line fluxes in the low-density limit 33
2.3.33 The density range for low-density discs 35
2.44 Discussion 36 Referencess 37
V11
Contents
33 Emission features in Bro and Br- spectra of normal O and B stars. 39
3.11 Introduction 39 3.22 The observations 43 3.33 Description of the observed spectra 44
3.3.11 The late-O and early-B stars with vsim'< 180 k m s- 1 45
3.3.22 The rapidly rotating B stars 49
3.3.33 The ;3 Cephei stars 53
3.3.44 Others 54 3.44 Conclusions 56 3.55 Acknowledgments 58
Referencess 58
44 On the nature of the H I infrared emission lines of r Scorpii 61
4.11 Introduction 62 4.22 The observations 63
4.2.14.2.1 The INT data 64 4.2.22 The UKIRT data 65 4.2.33 The ISO data 66 4.33 The model calculations 69
4.3.11 Atomic physics 69 4.3.24.3.2 The influence of turbulent velocity 70
4.44 The formation of emission lines due to non-LTE effects 71 4.4.11 The principle of non-LTE line emission 71 4.4.24.4.2 The T(r) and bn(r) effect within TLUSTY 73
4.55 Alternative effects that may produce IR emission lines 75 4.5.11 Emission from a circumstellar disc around r Sco 76
4.5.24.5.2 The stellar wind of r Sco 76
4.66 Results 78 4.6.11 The Equivalent Width dependence on Teff and log g 79
4.6.24.6.2 The dependence ofthe line profile on Teff and log g 81 4.6.33 Comparison of observed and predicted profiles 83
4.77 Discussion & Conclusions 86
Referencess 88
55 Infrared Spectral classification of OB stars with ISO-SWS. 91
5.11 Introduction 92 5.22 The observations 94
5.2.11 Description of observed spectra 100 5.33 The H I infrared lines as a diagnostic for Teff 102
5.44 The validity ofthe H&He model ,108 5.4.11 Equivalent width predictions from LTE models 108
5.4.22 The effect of including line blanketing 110
5.4.33 The effect of turbulence 110 5.4.44 The effectsofa stellar wind I l l
5.55 discussion 112 5.66 Summary 114
Referencess 115
66 Wind effects on the infrared hydrogen lines of O-type stars 117
6.11 Introduction . . . - 11 ^
6.22 The grid of models 119 6.2.11 Photospheric models 119
6.2.22 Wind models 119 6.33 The validity domains of TLUSTY and ISA-WIND 122
6.3.11 The weak wind limit 123 6.3.22 The strong wind limit 126 6.3.33 Errors in equivalent width due to the Sobolev Approximation . . . 127
6.44 The hydrogen infrared lines as a diagnostic of mass loss 128
6.4.11 "Curve of growth" method 130
6.55 Summary 132 Referencess 132 77 Nederlandse Samenvatting I3 5
7.11 Introductie I3 5 7.22 Infrarood waarnemingen van massieve sterren 138
7.33 Het modelleren van ster spectra 139
7.44 Resultaten I4 0
Publicationss 1 4 3
