A Study of the Variability of Yellow Supergiant Stars John Crooke Advisor: Dr. Robert Patterson Physics, Astronomy, and Materials Science | | 0 4/23/2016 Physics, Astronomy, and Materials Science
Background • Yellow Supergiants • Population I • F and G Spectral Class • Instability Strip • Variable Stars By Rursus - Own work, CC BY-SA 3.0 , https://commons.wikimedia.org/w/index.php?curid=3142076 | | 1 4/23/2016 Physics, Astronomy, and Materials Science
Observations & Reductions • 10 days from Oct. – Dec. 2015 • 7 Program Stars • SIMBAD 1 : Spectral Class F0 K0, Luminosity Class ≤ II • HD 200803 was the control pair • IRAF 2 • Bias, Dark, Flat • Differential Aperture Photometry | | 2 4/23/2016 Physics, Astronomy, and Materials Science
Analysis HD WSI Avg. ΔV σ (Avg. ΔV) 240073 1371 1.18 0.110 • Welch Stetson Index 3 216105 632 1.48 0.150 • Avg. Δ V with respect 200803 13.7 0.38 0.015 to comparison star 193205 8.1 2.07 0.009 • pdm used to find 200805 1.8 1.99 0.004 periods 191010 1.7 2.00 0.006 212312 1.4 0.89 0.004 235518 0.9 1.93 0.005 | | 3 4/23/2016 Physics, Astronomy, and Materials Science
Light Curves • HD 212312: Non-Variable YSG • HD 200803: Control Pair • HD 193205: Suspected Variable • HD 240073: Known Cepheid • HD 216105: Known Cepheid | | 4 4/23/2016 Physics, Astronomy, and Materials Science
HD 212312 (Non - Variable) 1.15 1.1 1.05 1 0.95 Delta V 0.9 0.85 0.8 0.75 0.7 0.65 7300 7310 7320 7330 7340 7350 7360 7370 HJD -2,450,000 | | 5 4/23/2016 Physics, Astronomy, and Materials Science
HD 200803 (Control) 0.63 0.53 0.43 Delta V 0.33 • WSI = 13.7 0.23 • σ Avg . ΔV = 0.015 0.13 7300 7310 7320 7330 7340 7350 7360 7370 HJD - 2,450,000 | | 6 4/23/2016 Physics, Astronomy, and Materials Science
HD 193205 (Suspected Variable) 2.3 2.25 2.2 2.15 2.1 Delta V 2.05 2 1.95 • WSI = 8.1 1.9 • σ Avg . ΔV = 0.009 1.85 1.8 7300 7310 7320 7330 7340 7350 7360 7370 HJD -2,450,000 | | 7 4/23/2016 Physics, Astronomy, and Materials Science
HD 240073 (=V Lac) 1.35 1.3 1.25 1.2 1.15 Delta V 1.1 1.05 • WSI = 1371 1 • σ Avg . ΔV = 0.11 0.95 • Known Cepheid HIPPARCOS 4 = 4.98 days • 0.9 • pdm = 5.5 days 0.85 7310 7320 7330 7340 7350 7360 7370 HJD -2,450,000 | | 8 4/23/2016 Physics, Astronomy, and Materials Science
HD 216105 (=X Lac) 1.8 • WSI = 632 • σ Avg . ΔV = 0.15 1.7 • Known Cepheid HIPPARCOS 4 = 5.44 days • 1.6 • pdm = N/A Delta V 1.5 1.4 1.3 1.2 7310 7320 7330 7340 7350 7360 7370 HJD -2,450,000 | | 9 4/23/2016 Physics, Astronomy, and Materials Science
Conclusions • Four of the Seven stars were found non-variable at 1% precision level • Two Classical Cepheids, HD 240073 (=V Lac) and HD 216105 (=X Lac), were recovered • HD 193205 – possible low-level variability with an amplitude of .01 magnitude • HD 200803 (Control) – Exhibits some variability, not seen in past | | 10 4/23/2016 Physics, Astronomy, and Materials Science
• YSG are evolved stars • Evolutionary tracks oscillate horizontally • Non-variable YSG must lie outside the instability strip Mihos, C . http://burro.case.edu/Academics/Astr222/G alaxy/Distances/variables.html | | 11 4/23/2016 Physics, Astronomy, and Materials Science
References / Acknowledgements 1. Wenger, M., et al. 2000, The SIMBAD astronomical database (Strasbourg, France: CDS) 2. IRAF is distributed by the National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc. under contract to the National Science Foundation 3. Welch, Stetson, 1993, The Welch-Stetson Variability Index 4. Perryman, M., et al. 1997, The HIPPARCOS Catalogue (European Space Agency) _______________________________________________________ Thank you to Dr. Patterson for his assistance and guidance in this project and to the NASA-Missouri Space Grant Consortium for giving me the opportunity to pursue this project. | | 12 4/23/2016 Physics, Astronomy, and Materials Science
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