A Study of the Variability of Yellow Supergiant Stars John Crooke - - PowerPoint PPT Presentation

4/23/2016 Physics, Astronomy, and Materials Science | |

A Study of the Variability

• f Yellow Supergiant

Stars

John Crooke Advisor: Dr. Robert Patterson Physics, Astronomy, and Materials Science

4/23/2016 1 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

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Observations & Reductions

• 10 days from Oct. – Dec.

2015

• 7 Program Stars
• SIMBAD1: Spectral Class

F0K0, Luminosity Class ≤ II

• HD 200803 was the control

pair

• IRAF2
• Bias, Dark, Flat
• Differential Aperture

Photometry

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Analysis

HD WSI

• Avg. ΔV

σ (Avg. ΔV) 240073 1371 1.18 0.110 216105 632 1.48 0.150 200803 13.7 0.38 0.015 193205 8.1 2.07 0.009 200805 1.8 1.99 0.004 191010 1.7 2.00 0.006 212312 1.4 0.89 0.004 235518 0.9 1.93 0.005

• Welch Stetson Index3
• Avg. ΔV with respect

to comparison star

• pdm used to find

periods

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Light Curves

• HD 212312: Non-Variable YSG
• HD 200803: Control Pair
• HD 193205: Suspected Variable
• HD 240073: Known Cepheid
• HD 216105: Known Cepheid

4/23/2016 5 Physics, Astronomy, and Materials Science | | 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 7300 7310 7320 7330 7340 7350 7360 7370

Delta V HJD -2,450,000

HD 212312 (Non-Variable)

4/23/2016 6 Physics, Astronomy, and Materials Science | | 0.13 0.23 0.33 0.43 0.53 0.63 7300 7310 7320 7330 7340 7350 7360 7370

Delta V HJD - 2,450,000

HD 200803 (Control)

• WSI = 13.7
• σ Avg. ΔV = 0.015

4/23/2016 7 Physics, Astronomy, and Materials Science | | 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 2.3 7300 7310 7320 7330 7340 7350 7360 7370

Delta V HJD -2,450,000

HD 193205 (Suspected Variable)

• WSI = 8.1
• σ Avg. ΔV = 0.009

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0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 7310 7320 7330 7340 7350 7360 7370

Delta V HJD -2,450,000

HD 240073 (=V Lac)

• WSI = 1371
• σ Avg. ΔV = 0.11
• Known Cepheid
• HIPPARCOS4 = 4.98 days
• pdm = 5.5 days

4/23/2016 9 Physics, Astronomy, and Materials Science | | 1.2 1.3 1.4 1.5 1.6 1.7 1.8 7310 7320 7330 7340 7350 7360 7370

Delta V HJD -2,450,000

HD 216105 (=X Lac)

• WSI = 632
• σ Avg. ΔV = 0.15
• Known Cepheid
• HIPPARCOS4 = 5.44 days
• pdm = N/A

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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

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• YSG are evolved stars
• Evolutionary tracks
• scillate horizontally
• Non-variable YSG

must lie outside the instability strip

Mihos, C.

http://burro.case.edu/Academics/Astr222/G alaxy/Distances/variables.html

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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.