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Massive Stars: an Infrared Exploration Across the HR Diagram

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Massive Stars: an Infrared Exploration Across the HR Diagram Massive Stars: An Infrared Exploration Across the HR Diagram A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Michael Scott Gordon IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy Advisors: Terry J. Jones, Roberta M. Humphreys, Robert D. Gehrz July, 2018 © Michael Scott Gordon 2018 ALL RIGHTS RESERVED Acknowledgements There are many who have earned my gratitude for their contribution to my time in graduate school. I offer here my sincerest thanks and dedicate this work in part to each of you: to Mom, Dad, and Mom-mom for creating a world where I could pursue any dream, and through whose eyes I am always the best possible version of myself. to Robyn, for being my closest confidante, for never needing me to explain myself, and for never letting me go. to Micaela, for being my strongest pillar from the very beginning of this journey. to Skyler and Breanne, for letting me crash into your lives and your many years of tough love. to Karlen, for always being my comrade-in-arms on every adventure. to Dylan for being a constant source of humor and perspective. to my college friends, Randy, Mike S, Mike H, Josh, and Sean for keeping me honest. to MIfA grads past and present, for sharing the long road of frustration. to Dr. Gehrz, for teaching me that science is tenacity. to Dr. Humphreys, for teaching me that science is passion. to Dr. Jones, for teaching me that science is fun. i Contents Acknowledgementsi List of Tables iv List of Figuresv 1 Introduction1 1.1 YSGs and Post-RSG Evolution.........................1 1.2 Galactic RSGs..................................3 1.3 VY CMa & the Southwest Clump.......................4 1.4 Obscured RSGs in M33.............................5 2 Luminous and Variable Stars in M31 and M33. The Yellow and Red Supergiants and Post-Red Supergiant Evolution7 2.1 Introduction....................................8 2.2 Sample Selection and Observations.......................9 2.2.1 Target List................................9 2.2.2 Observations............................... 11 2.3 The Intermediate-Type or Yellow Supergiants................. 13 2.3.1 Spectral Characteristics......................... 13 2.3.2 Multi-Wavelength Photometry..................... 16 2.3.3 Extinction Correction and the Spectral Energy Distributions.... 19 2.3.4 Two New Hypergiants in M31...................... 22 2.4 Red Supergiants................................. 25 2.5 Discussion..................................... 33 2.5.1 Circumstellar Dust and Mass Loss................... 33 2.5.2 HR Diagrams............................... 35 2.6 Conclusion.................................... 36 ii 3 Searching for Cool Dust: Infrared Imaging of OH/IR Supergiants and Normal RSGs 40 3.1 Introduction.................................... 40 3.2 Observations and Data Reduction....................... 42 3.2.1 SOFIA/FORCAST: Far-IR Imaging (11 37 µm).......... 42 − 3.2.2 Adaptive Optics Mid-IR Imaging (8 10 µm)............. 44 − 3.2.3 IRAS, AKARI, WISE, and ISO-SWS (2 100 µm).......... 45 − 3.2.4 Herschel/PACS (70, 160 µm)...................... 45 3.3 Results & Discussion............................... 49 3.3.1 DUSTY modeling.............................. 49 3.3.2 VX Sgr.................................. 52 3.3.3 S Per................................... 56 3.3.4 RS Per and T Per............................ 59 3.3.5 NML Cyg................................. 63 3.4 Conclusions.................................... 66 4 Thermal Emission in the Southwest Clump of VY CMa 70 4.1 Introduction.................................... 70 4.2 Observations & Data Reduction......................... 72 4.3 Results & Discussion............................... 76 4.3.1 DUSTY modeling.............................. 76 4.3.2 Scattered vs. Thermal Emission..................... 79 4.3.3 Mass Estimates.............................. 80 4.4 Conclusions.................................... 81 5 Obscured Red Supergiants in M33 83 5.1 Introduction.................................... 83 5.2 Target Selection.................................. 84 5.3 Observations & Data Reduction......................... 86 5.4 Modeling & Analysis............................... 88 5.5 Object X & M33-8................................ 92 5.6 Conclusions.................................... 98 6 Conclusions & Future Work 99 References 104 iii List of Tables 2.1 Luminous Stars: Journal of Observations................... 11 2.2 Luminous Stars: Spectroscopically-Confirmed YSGs............. 16 2.3 Luminous Stars: Photometry of YSGs and YSG candidates......... 18 2.4 Luminous Stars: Extinction and Luminosities of YSGs and YSG Candidates 21 2.5 Luminous Stars: YSGs with Mass-Loss Indicators............... 24 2.6 Luminous Stars: Photometry of Candidate RSGs............... 28 2.7 Luminous Stars: Extinction and Luminosities of Candidate RSGs...... 30 2.8 Luminous Stars: RSG Candidates with Evidence for CS Dust........ 33 3.1 Searching for Cool Dust: Summary of Observations.............. 43 3.2 Searching for Cool Dust: New Mid-Infrared Photometry........... 48 3.3 Searching for Cool Dust: DUSTY Model Parameters and Mass-Loss Rates.. 52 4.1 VY CMa and the SW Clump: Photometry of the SW Clump........ 75 4.2 VY CMa and the SW Clump: DUSTY Model Parameters........... 78 iv List of Figures 1.1 Evolutionary Tracks in the HRD........................2 1.2 HST Composite of VY CMa...........................5 2.1 M33 with Spectral Targets............................ 12 2.2 YSG spectra with Hα emission......................... 14 2.3 Sample A- and F-type supergiant spectra from M31 and M33........ 15 2.4 SEDs of two F-type supergiants in M31.................... 22 2.5 SEDs of two warm supergiants in M33..................... 23 2.6 Spectra of new LBV candidates......................... 26 2.7 SEDs of new LBV candidates.......................... 27 2.8 SEDs of two red supergiants in M31...................... 31 2.9 SEDs of two red supergiants in M33...................... 32 2.10 Luminosity vs. mass lost for RSGs in M31 and M33............. 35 2.11 HR Diagram of M31............................... 37 2.12 HR Diagram of M33............................... 38 3.1 SOFIA/FORCAST imaging of S Per...................... 47 3.2 DUSTY model with \enhanced" mass loss.................... 51 3.3 Optical and IR SED of VX Sgr......................... 54 3.4 Radial profiles of VX Sgr............................ 55 3.5 Optical and IR SED of S Per.......................... 57 3.6 Radial profiles of S Per with FORCAST.................... 58 3.7 Radial profiles of S Per with MIRAC...................... 59 3.8 Optical and IR SED of RS Per......................... 60 3.9 Radial profiles of RS Per............................. 61 3.10 Optical and IR SED of T Per.......................... 62 3.11 Radial profiles of T Per with FORCAST.................... 63 3.12 Radial profiles of T Per with MIRAC...................... 63 3.13 Optical and IR SED of NML Cyg........................ 64 v 3.14 Radial profiles of NML Cyg with FORCAST................. 65 3.15 Radial profiles of NML Cyg with MIRAC................... 66 3.16 Luminosity vs. mass-loss rates.......................... 68 4.1 ALMA Contours of VY CMa.......................... 72 4.2 Near-IR imaging of VY CMa.......................... 73 4.3 Near-IR imaging of the SW Clump....................... 73 4.4 Photometry of VY CMa and the SW Clump.................. 77 5.1 CMD of Spitzer/IRAC sources......................... 85 5.2 M33 with IRTF Targets............................. 86 5.3 SEDs of Obscured RSG Candidates....................... 87 5.4 SEDs and IRTF Spectra of RSG Candidates.................. 89 5.5 IRTF Spectrum of J013403.84+303752.9.................... 90 5.6 IR Spectrum of WX Ser............................. 91 5.7 CMD of IRTF Sample.............................. 92 5.8 R-band and Hα Images of Object X...................... 93 5.9 SED and IR Spectrum of Object X....................... 94 5.10 MODS Spectrum of Object X.......................... 94 5.11 Ca II Absorption in Object X.......................... 95 5.12 V-band and Hα Images of M33-8........................ 96 5.13 SED and IR Spectrum of M33-8........................ 97 6.1 NGC 7419 at 2 µm................................ 100 6.2 LMIRCam Radial Profile of B139........................ 101 6.3 RSGC1 in FORCAST FOV........................... 102 vi Chapter 1 Introduction The main goal of this dissertation is to understand how stellar winds, dusty ejecta, and overall mass-loss histories affect the end-stage evolution of supergiant stars. To what extent mass loss and periods of enhanced stellar outflow can influence the terminal state of the most massive stars remains an outstanding question in the fields of stellar physics, chemical enrichment of the Galaxy, and supernova research. Here, we focus on characterizing the circumstellar (CS) ejecta around supergiants through a combination of observing techniques. Over the last several years, using the Large Binoc- ular Telescope (LBT), MMT, NASA's Infrared Telescope Facility (IRTF), the Very Large Telescope (VLT), and the Stratospheric Observatory for Infrared Astronomy (SOFIA), we have performed high-resolution imaging, spectroscopy, and polarimetry|methods that pro- vide us with keen insight on mass-loss histories and the 3D morphology of the material ejected by the Local Group's most fascinating stars. 1.1 YSGs and Post-RSG Evolution Mass loss in massive stars has a profound effect on their late-stage evolution and eventual fate.
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