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THE PROGENITORS of TYPE IIP SUPERNOVAE Emma R. Beasor

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THE PROGENITORS of TYPE IIP SUPERNOVAE Emma R. Beasor THE PROGENITORS OF TYPE IIP SUPERNOVAE Emma R. Beasor A thesis submitted in partial fulfilment of the requirements of Liverpool John Moores University for the degree of Doctor of Philosophy. April 2019 Declaration The work presented in this thesis was carried out at the Astrophysics Research Insti- tute, Liverpool John Moores University. Unless otherwise stated, it is the original work of the author. While registered as a candidate for the degree of Doctor of Philosophy, for which sub- mission is now made, the author has not been registered as a candidate for any other award. This thesis has not been submitted in whole, or in part, for any other degree. Emma R. Beasor Astrophysics Research Institute Liverpool John Moores University IC2, Liverpool Science Park 146 Brownlow Hill Liverpool L3 5RF UK ii Abstract Mass-loss prior to core collapse is arguably the most important factor affecting the evolution of a massive star across the Hertzsprung-Russel (HR) diagram, making it the key to understanding what mass-range of stars produce supernova (SN), and how these explosions will appear. It is thought that most of the mass-loss occurs during the red supergiant (RSG) phase, when strong winds dictate the onward evolutionary path of the star and potentially remove the entire H-rich envelope. Uncertainty in the driving mechanism for RSG winds means the mass-loss rate (M_ ) cannot be determined from first principles, and instead, stellar evolution models rely on empirical recipes to inform their calculations. At present, the most commonly used M_ -prescription comes from a literature study, whereby many measurements of mass- loss were compiled. The sample sizes are small (<10 stars), highly heterogeneous in terms of mass and metallicity, and have very uncertain distances from observations and analysis techniques that at best provide order-of-magnitude estimates compared to what is possible today. The relation itself contains large internal scatter, which could be the difference between a star losing its entire H-envelope, or none of it at all. More modern efforts to update the RSG mass-loss rate prescription rely on samples which suffer from statistical biases, for example by selecting objects based on mid-IR brightness or circumstellar maser emission, and hence are inevitably biased towards higher mass-loss rate objects. It is the aim of this thesis to overhaul our understanding of RSG mass-loss. By se- lecting RSGs in clusters, where the initial mass and metallicity are known, I will be able to observe how mass-loss changes as the star approaches SN and compare this to iii what is currently implemented in stellar evolutionary models. Ultimately, I will mea- sure M_ values and luminosities for RSGs in 5 different clusters of varying ages, thus targeting RSGs of different initial masses. I will then combine these mass-loss rate- luminosity relations to derive a new initial mass-dependent mass-loss rate, which can be implemented into stellar evolutionary models. iv Publications In the course of completing the work presented in this thesis, the following papers have been submitted for publication in a refereed journal: 1. The evolution of red supergiants to supernova in NGC 2100 Beasor, E. R. & Davies, B. , 2016, MNRAS, 463, 1269 2. Red Supergiants as Cosmic Abundance Probes: Massive Star Clusters in M83 and the Mass-Metallicity Relation of Nearby Galaxies Davies, B., Kudritzki, R. P., Lardo, C., Bergemann, M., Beasor, E. R., Plez, B., Evans, C., Bastian, N., Patrick, L., 2017, ApJ, 847, 112 3. The evolution of red supergiant mass loss rates Beasor, E. R. & Davies, B. , 2018, MNRAS, 475, 55 4. The initial masses of the red supergiant progenitors to Type II supernovae Davies, B. & Beasor, E. R., 2018, MNRAS, 474, 2116 5. The luminosities of cool supergiants in the Magellanic Clouds, and the Humphreys- Davidson limit revisited Davies, B., Crowther, P. J., Beasor, E. R., 2018, MNRAS, 478, 3138 6. A critical re-evalution of Thorne-Z_ ytkow Object candidate HV 2112 Beasor, E. R., Davies, B., Cabrera-Ziri, I., Hurst, G., 2018, MNRAS, 479, 3101 v 7. Age discrepancies in young clusters; evidence for mergers? Beasor, E. R., Davies, B., Smith, N., Bastian, N., 2019, MNRAS 8. The distances to star-clusters hosting Red Supergiants; χ Per, NGC 7419 and Weesterlund 1 Davies, B. & Beasor, E. R., 2019, MNRAS vi Acknowledgements I want to begin by thanking my supervisor, Ben Davies, for providing such an inter- esting project in the first place and for unwavering support since then. I’ve had a fair few wobbles throughout the PhD and you always knew the right moments to push me and the right moments to say “lets get a coffee”. I feel lucky to have come out of this process with not only a great scientific collaborator, but a great friend. Not forgetting of course many other members of staff at the ARI, in particular Nate Bastian, Phil James and Steve Longmore, who were always willing to read drafts, write references and run mock interviews. A huge thanks also has to go to all my friends in the department, especially Ted, Lawrence and Ashley. Thanks for all the laughs fellas. Next, I thank my parents for always believing in me and supporting me, and for pro- viding good roasts whenever I’ve needed them. Finally, Caela. Thanks for all the silliness and for being the person who makes me laugh the most in the world. I truly couldn’t have done this without you. vii Contents Declaration ii Abstract iii Publications v Acknowledgements vii Contents viii List of Tables . xiii List of Figures . xv 1 Introduction 1 1.1 Massive star evolution . .2 1.1.1 Core Evolution . .3 1.1.2 Effect of mass-loss on evolution . .5 1.2 Observations I: The Humphreys-Davidson Limit . .6 1.3 Observations II: Type IIP Progenitors . .8 1.3.1 The Red Supergiant Problem . .9 viii 1.3.2 A possible resolution to the red supergiant problem? . 13 1.4 Observations III: The blue-to-red supergiant ratio . 15 1.5 Red Supergiant Mass-Loss . 16 1.5.1 The winds of RSGs . 17 1.5.2 Mass-loss rate measurements . 17 1.5.3 Implementation of mass-loss in evolution models . 22 1.6 This thesis . 23 2 The Evolution of Red Supergiants to Supernova I: NGC 2100 25 2.1 Introduction . 25 2.2 Dust shell models . 26 2.2.1 Model parameters . 27 2.2.2 Fitting methodology . 31 2.3 Application to NGC2100 . 32 2.3.1 Modeling results . 35 2.3.2 Cluster age and initial masses . 42 2.3.3 Extinction . 45 2.3.4 Sensitivity to grain size distribution . 47 2.4 Discussion . 48 2.4.1 Evidence for enhanced extinction to stars #1 and #2 . 48 2.4.2 Effects of using a shallower density distribution . 51 2.4.3 Consequences for stellar evolution . 53 2.5 Conclusion . 57 ix 3 The Evolution of Red Supergiants to Supernova II: Galactic clusters 59 3.1 Introduction . 59 3.2 Application to Galactic clusters . 60 3.2.1 Sample selection . 60 3.2.2 Initial masses . 61 3.3 Dust shell models . 63 3.3.1 Model Setup . 63 3.3.2 Fitting methodology . 64 3.4 Modelling results . 65 3.5 Discussion . 67 3.5.1 The M_ - Luminosity Relation . 67 3.5.2 The luminosity distribution of RSGs . 70 3.6 Conclusions . 75 4 Age discrepancies in young clusters; evidence for mergers? 77 4.1 Introduction . 77 4.2 Observations . 79 4.2.1 Sample . 79 4.2.2 Photometry . 80 4.2.3 Distances . 80 4.3 Age estimations . 82 4.3.1 Estimating the foreground extinction . 82 4.3.2 Brightest turn-off star method . 83 x 4.3.3 Luminosity function . 84 4.3.4 Lowest luminosity red supergiant . 85 4.4 Results . 87 4.4.1 NGC 7419 . 92 4.4.2 χ Persei . 93 4.4.3 NGC 2100 . 93 4.4.4 NGC 2004 . 94 4.5 Discussion . 94 4.5.1 Possible causes for age discrepancies . 95 4.5.2 How should we determine ages for young clusters? . 98 4.6 Conclusions . 99 5 The evolution of red supergiants to supernova III: A new mass-loss rate prescription for RSGs 102 5.1 Introduction . 102 5.2 Observations . 103 5.2.1 Sample selection . 103 5.2.2 Observations and data reduction . 105 5.2.3 Determining cluster ages . 106 5.3 Spectral energy distribution modeling . 106 5.4 Results . 108 5.4.1 Luminosities . 109 5.5 Discussion . 111 xi 5.5.1 The M_ -luminosity relation for red supergiants . 111 5.5.2 Comparison to other M_ -prescriptions . 114 5.5.3 Total mass lost during the RSG phase . 117 5.5.4 Implications . 120 5.6 Conclusions . 124 6 Conclusions and future work 126 6.1 Future work . 127 Bibliography 131 xii List of Tables 2.1 Star designations and positions. Stars are numbered based on their [5.6]-band magnitude. 33 2.2 Observational data. All fluxes are in units of mJy. 34 2.3 Results for stars in NGC 2100. Stars are numbered with #1 having the highest [5.6]-band magnitude and #19 having the lowest. Luminosities quoted are in units of log(Lbol/L ). AV is the extinction intrinsic to the dust shell. 44 3.1 Observational data for RSGs in χ Per & NGC 7419. All fluxes are in units of Jy. All photometry for WISE 1 and 2 are upper limits. 62 3.2 Fitting results for the RSGs in χ Per and NGC 7419.
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