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Open Research Online Oro.Open.Ac.Uk Open Research Online The Open University’s repository of research publications and other research outputs Galactic Chemical Evolution Signatures in Stellar Atmospheres and Their Possible Planetary Connection Thesis How to cite: Nickson, Elena (2016). Galactic Chemical Evolution Signatures in Stellar Atmospheres and Their Possible Planetary Connection. PhD thesis The Open University. For guidance on citations see FAQs. c 2016 The Author https://creativecommons.org/licenses/by-nc-nd/4.0/ Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.0000ef7c Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk C -M Q_ L_ o & I - =D A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF P h i l o s o p h y E l e n a N ic k s o n G a la c tic c h e m ic a l e v o l u t io n SIGNATURES IN STELLAR ATMOSPHERES AND THEIR POSSIBLE PLANETARY CONNECTION T h e O pe n Un iv e r s it y D e p a r t m e n t o f P h y s i c a l S c i e n c e s July 8, 2016 ProQuest Number: 13834776 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 13834776 Published by ProQuest LLC(2019). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 Abstract In recent years there have been many studies to determine whether there is a chem­ ical signature in stellar atmospheres that can be linked to the presence of planets. Most of these studies have involved bulk analysis of stars to identify whether planet-hosting stars have a higher metallicity than non planet-hosting stars. These studies led to the work of Melendez et al. [49], which identified a signature in the solar photosphere which was likely caused by the presence of planets. To further explore this theory, I obtained high-quality spectra from the ESPaDOnS spectropolarimeter at the CFHT for 10 stars with similar stellar parameters (effective temperature, surface gravity, microturbulence velocity and metallicity). I performed a differential abundance analysis on the planet-hosting star 61 Vir against 9 comparison stars. This analysis indicated that there is no planetary signature present in 61 Vir but instead, that there is a signature observed when performing the same analysis on an individual star basis, which is observable with age. I determined the relative ages of the stars and then perform a differential abundance analysis of 9 stars using a younger tenth star as reference. From this I found likely evidence of galactic chemical evolution in the stellar atmospheres. Acknowledgements Firstly, I would like to thank my supervisors: Dr Carole Haswell, Dr Luca Fossati and Dr Ulrich Kolb. Without them this project wouldn’t have existed and I wouldn’t have had the incredible opportunities I have experienced throughout my PhD. I will be for­ ever indebted to them for the time and dedication they put in to help me succeed. I am particularly thankful to Dr Luca Fossati who spent many long hours helping me to understand the topic at the start, and continued to help me whenever needed. Secondly, I would like to thank my Mum and my Dad. They both went above and beyond the call of duty to help me in any way that I needed throughout the 1738 days of my PhD. Their support helped me through the painful times as well as the brilliant times. Finally, I would like to thank my three loves: E.T., Dr Ellie Arroway, and my husband. E.T. and Dr Ellie Arroway always inspired me to keep going and find the answers whilst my husband put up with everything, including marrying me, whilst I undertook and completed this thesis. To him especially, I will be eternally grateful. Contents 1 Introduction 1 1.1 The Solar System ........................................................................................ 2 1.2 Spectral L in e s ............................................................................................... 4 1.2.1 B roadening ..................................................................................... 5 1.2.2 Equivalent W id th ............................................................................ 7 1.2.3 Abundances..................................................................................... 8 1.3 Exoplanet signatures .................................................................................. 10 1.4 Melendez 2009 ............................................................................................ 11 1.4.1 Impact of Melendez 2009 ............................................................ 14 2 Observations and Data Reduction 15 2.1 ESPaDOnS .................................................................................................. 15 2.2 Target selection ............................................................................................ 17 2.3 Solar d a t a ................................. 19 2.4 Normalisation ............................................................................................... 19 3 Differential abundance analysis 24 3.1 Model atmospheres ..................................................................................... 24 3.2 Spectral synthesis ......................................................................................... 26 3.3 Line selection and measurement ............................................................... 29 3.3.1 Hyperfine structure lin e s .............................................................. 35 3.3.2 Melendez line list........................................................................... 37 3.4 Molecular lines ............................................................................................ 38 3.5 Parameter determ ination ............................................................................ 39 3.5.1 Absolute p aram eters ...................................................................... 39 iii Contents iv 3.5.2 Differential parameters .................................................................. 46 3.5.3 Remarks on the method .............................................................. 48 3.6 Abundance determination ........................................................................... 49 3.6.1 U ncertainties.................................................................................. 51 4 Attempting the detection of a planetary signature in the chemical compo­ sition of 61 Virginis 54 4.1 Signatures ..................................................................................................... 54 4.1.1 Comparison to the average of the s a m p le ................................... 55 4.1.2 Individual analysis . ........................................................... 58 4.2 Comparisons with Melendez line lis t ........................................................ 69 4.3 Remarks on the analysis ........................................................................... 75 5 Determining the ages of the stellar sample 76 5.1 l o g g ............................................................................................................... 77 5.2 HR diagram .................................................................................................. 77 5.3 L ith iu m .................................................................................................... 80 5.4 Wilson-Bappu .......................... 82 5.5 Measurement of chromospheric activity .................................................. 86 5.6 Determination of age order ........................................................................ 88 6 The abundance relationship with stellar age 91 6.1 Trend with age ............................................................................................ 92 6.1.1 Age correlation ............................................................................... 98 6.2 Age relationship .............................................................................. 101 6.2.1 I r o n .................................................................................................. 103 6.2.2 Carbon, Nitrogen, Sodium, Alum inium ...................................... 104 6.2.3 Type II supernovae alpha elements .............................................. 106 6.2.4 Iron peak elements ................................................................. 108 6.2.5 Explosive nucleosynthesis of massive stars elem ents .............. 109 6.2.6 R-process elements ........................................................................ 110 6.2.7 S-process elements ......................................................................... I l l 6.2.8 R and S process elements .............................................................. 113 Contents v 6.2.9 Trend in stars with similar parameters ......................................... 114 6.3 Discussion .................................................................................................... 115 6.3.1 Light e le m e n ts...............................................................................
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