Spectroscopic analyses of subluminous B stars: observational constraints for the theory of stellar evolution, pulsation, and diffusion Den Naturwissenschaftlichen Fakult¨aten der Friedrich-Alexander-Universit¨at Erlangen-N¨urnberg zur Erlangung des Doktorgrades vorgelegt von Heinz Edelmann aus N¨urnberg Als Dissertation genehmigt von den Naturwissenschaftlichen Fakult¨aten der Universit¨at Erlangen-N¨urnberg Tag der m¨undlichen Pr¨ufung: 03.07.2003 Stellvertretender Vositzender der Promotionskommission: Prof. Dr. H. Kisch Erstberichterstatter: Prof. Dr. U. Heber Zweitberichterstatter: Prof. Dr. K. Werner Contents Zusammenfassung 1 Abstract 5 1 Introduction 9 2 Program stars 13 2.1 Spectral classification system . ........ 13 2.2 BrightsdBstars .................................. 15 2.2.1 Selection of the program stars . ..... 15 2.2.2 Observations and data reduction . ..... 15 2.2.3 Classification of the program stars . ...... 17 2.3 sdBstarsfromtheHamburgQuasarSurvey . ....... 19 2.3.1 HamburgQuasarSurvey. 19 2.3.2 Preselection of the program stars . ...... 20 2.3.3 Observations and data reduction . ..... 20 2.3.4 Selection and classification of the program stars . ........... 21 2.3.5 Completeness.................................. 22 2.4 sdBstarsfromtheHamburgESOSurvey . ..... 22 2.4.1 HamburgESOSurvey ............................. 22 2.4.2 Selection of sdB candidates . 23 2.4.3 Observations and data reduction . ..... 26 2.4.4 Classification of the program stars . ...... 28 2.4.5 Completeness.................................. 29 3 Atmospheric parameters 31 3.1 Spectralanalysis ................................ 31 3.1.1 Model atmospheres and synthetic spectra . ....... 31 3.1.2 Fitprocedure.................................. 32 3.2 Results......................................... 35 3.2.1 Brightstars................................... 37 3.2.2 StarsfromHamburgQuasarSurvey . 38 3.2.3 StarsfromHamburgESOSurvey. 38 3.2.4 Comparisonwithpreviousresults. ...... 38 3.3 Constraints on the evolution of sdB stars . ......... 41 3.3.1 Evolutionarystatus .. .. .. .. .. .. .. .. 41 3.3.2 Evolutionaryscenarios . 44 i ii CONTENTS 3.4 Constraints on stellar pulsations . ......... 45 4 Chemical composition 48 4.1 Spectralanalysis ................................ 49 4.1.1 Metalabundances ............................... 49 4.1.2 Microturbulences. .. .. .. .. .. .. .. .. 50 4.1.3 Ionisationequilibria . 50 4.1.4 Projected rotational velocities . ........ 50 4.2 Resultsforindividualobjects . ........ 53 4.2.1 ’Normal’sdBstars .............................. 57 4.2.2 PeculiarsdBstars .............................. 83 4.2.3 Summaryoftheresults . .. .. .. .. .. .. .. 88 4.3 Trendswithatmosphericparameters? . ........ 90 4.3.1 Heliumabundances.............................. 90 4.3.2 Metalabundances ............................... 94 4.4 Heliumlineshifts................................ 99 5 Radial velocity variations 101 5.1 Radial velocity measurements . ....... 101 5.2 Radial velocity curves, and the nature of the invisible companions . 105 5.2.1 PG0001+275.................................. 105 5.2.2 PG1519+640.................................. 107 5.2.3 HD188112 ................................... 107 5.2.4 PB5333..................................... 109 5.2.5 PG0133+114.................................. 109 5.2.6 UVO1735+22 ................................. 111 5.2.7 HD171858 ................................... 113 5.2.8 PB7352..................................... 113 5.2.9 Feige108 .................................... 114 5.3 Summary of the radial velocity curve analyses . ........... 115 6 HE 0437−5439 — a main sequence B star leaving the galaxy 117 6.1 Observationsanddataanalysis . ....... 117 6.2 Atmospheric parameters and projected rotational velocity ............. 117 6.3 Mass, evolutionary time, radial velocity, and distance ................ 119 6.4 Metalabundances ................................. 119 6.5 Discussion...................................... 119 7 Conclusions and outlook 120 A Program stars – observing logs 122 A.1 HamburgQuasarSurvey. .. .. .. .. .. .. .. .. 122 A.2 HamburgESOSurvey ................................ 125 A.3 BrightsdBstars .................................. 128 A.3.1 Low-Resolution observations . 128 A.3.2 High-Resolution observations . 128 CONTENTS iii B Analyses results 130 B.1 HamburgQuasarSurvey. .. .. .. .. .. .. .. .. 130 B.2 HamburgESOSurvey ................................ 133 B.3 BrightsdBstars .................................. 136 C Equivalent widths measurements 137 D Radial velocity measurements 147 E List of abbreviations 155 References 159 Acknowledgements 167 Lebenslauf 169 List of Figures 1.1 Illustration of post-EHB evolution . ......... 10 2.1 Spectral classification scheme . ........ 14 2.2 BinaryHQSsdBstars ............................... 18 2.3 HQSbrightnessdistribution . ....... 22 2.4 Sample of HES finding charts and objective prism spectra . ............ 24 2.5 SampleofHESmisclassifications . ....... 25 2.6 Classification of HES objective prism spectra using model flux distributions . 27 2.7 HESbrightnessdistribution . ....... 29 3.1 SamplefitsforthreeprogramsdBstars . ....... 32 3.2 Comparison of results determined from spectra with many Balmer lines to those fromthreeBalmerlines ............................... 33 3.3 Comparison of results determined from LTE and NLTE model atmospheres . 36 3.4 ProgramstarsintheHRD. .. .. .. .. .. .. .. .. 39 3.5 Plot of numbers of stars versus luminosity . .......... 43 3.6 Distribution of log(gθ4)forHQSandHESsamples . 45 3.7 SdBinstabilitystrip ............................. ..... 47 4.1 Discrepancy of abundances determined from different multiplets of S ii ...... 50 4.2 Sensitivity of the microturbulence . .......... 51 4.3 Microturbulence for CD−35◦ 15910.......................... 51 4.4 Determination of v sin(i) from Mg ii doublet..................... 52 4.5 Metal lines within ’normal’ sdB stars . ......... 54 4.6 Metal lines of peculiar sdB stars . ....... 55 4.7 Metal abundances for HD 205805 . ..... 56 4.8 Metal abundances for PG 0001+275 . ..... 58 4.9 MetalabundancesforHD4539 . 60 4.10 MetalabundancesforPHL932 . ..... 62 4.11 Metal abundances for PG 0133+114 . ...... 64 4.12 Metal abundances for PG 0342+026 . ...... 66 4.13 Metal abundances for Feige 65 . ...... 68 4.14 Metal abundances for UVO 1735+22 . ...... 70 4.15 Metal abundances for BD+48◦ 2721 ......................... 72 4.16 Metal abundances for HD 171858 . ...... 74 4.17 MetalabundancesforLB1516 . ..... 76 4.18 MetalabundancesforPB7352 . ..... 78 iv LIST OF FIGURES v 4.19 Metal abundances for CD−35◦ 15910......................... 80 4.20 Metal abundances for UVO 0512−08......................... 82 4.21 Metal abundances for PG 0909+276 . ...... 84 4.22 Metal abundances for UVO 1758+36 . ...... 86 4.23 Similarity of metal abundance patterns for ’normal’ sdBstars........... 89 4.24 Plot of the helium abundance versus effective temperature............. 91 4.25 Plot of the helium abundance versus gravity . ........... 92 4.26 Plot of the helium abundance versus luminosity . ............ 93 4.27 LTE abundances for C ii, C iii, N ii, and O ii versus Teff , log(g), and L/Le . 95 4.28 LTE abundances for Mg ii, Al iii,Si iii, and S ii versus Teff , log(g), and L/Le . 96 4.29 LTE abundances for S iii, Ar ii, and Fe iii versus Teff , log(g), and L/Le ...... 97 4.30 Heliumlineshifts............................... 100 5.1 RV measurements for three non-variables . ......... 103 5.2 RV measurements for two variables, and three absolute high RV stars . 104 5.3 RVcurveforPG0001+275 ............................ 106 5.4 RVcurveforPG1519+640 ............................ 106 5.5 RVcurveforHD188112.............................. 108 5.6 RVcurveforPB5333 ................................ 108 5.7 RVcurveforPG0133+114 ............................ 110 5.8 RVcurveforUVO1735+22 .. .. .. .. .. .. .. .. 110 5.9 RVcurveforHD171858.............................. 112 5.10 RVcurveforPB7352 ............................... 112 5.11 RVcurveforFeige108.. .. .. .. .. .. .. .. .. 114 5.12 Histogramoforbitalperiods. ........ 116 6.1 LTE line fit for HE 0437−5439 for the coadded UVES spectra . 118 List of Tables 2.1 Echelle high-resolution observations . ........... 16 2.2 Spectral classification of bright program stars compared to literature . 17 2.3 HQSfollow-upobservationruns. ....... 19 2.4 BinaryHQSsdBstars ............................... 20 2.5 Spectral classification of HQS program stars compared to literature . 21 2.6 Statistics for visual inspection of sdB candidates from theHES .......... 26 2.7 HESfollow-upobservationruns . ....... 26 2.8 BinaryHESsdBstars ............................... 28 2.9 Spectral classification of HES program stars compared to literature . 30 3.1 Comparison of results determined from different HES runs ............. 34 3.2 Comparison of determined parameters to those from literature .......... 40 4.1 Metal abundances for HD 205805 . ..... 56 4.2 Metal abundances for PG 0001+275 . ..... 58 4.3 MetalabundancesforHD4539 . 60 4.4 MetalabundancesforPHL932 . 62 4.5 Metal abundances for PG 0133+114 . ..... 64 4.6 Metal abundances for PG 0342+026 . ..... 66 4.7 MetalabundancesforFeige65 . ..... 68 4.8 Metal abundances for UVO 1735+22 . ..... 70 4.9 Metal abundances for BD+48◦ 2721 ......................... 72 4.10 Metal abundances for HD 171858 . ...... 74 4.11 MetalabundancesforLB1516 . ..... 76 4.12 MetalabundancesforPB7352 . ..... 78 4.13 Metal abundances for CD−35◦ 15910......................... 80 4.14 Metal abundances