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Observations of the SX Phoenicis Star XX Cygni

Observations of the SX Phoenicis Star XX Cygni. X.H. Yang Beijing Normal University 2010.4.1. Contents. Introduction of the SX Phe stars New observations Data reduction Light curves Analysis Conclusions. Introduction. δ Scuti Stars: 1.The SX Phoneicis stars

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Observations of the SX Phoenicis Star XX Cygni

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  1. Observations of the SX Phoenicis Star XX Cygni X.H. Yang Beijing Normal University 2010.4.1

  2. Contents • Introduction of the SX Phe stars • New observations • Data reduction • Light curves • Analysis • Conclusions

  3. Introduction δ Scuti Stars: 1.The SX Phoneicis stars 2.High-amplitude δ Scuti Stars (HADS) Period changes: Period increasing and period decreasing were detected in different δ Scuti Stars • The SX Phoenicis stars: • Found in the field stars • Found in the blue straggler populations of globular clusters • short-period • Single- or multiple-mode pulsations

  4. Importance of studying SX Phe stars 1.Studying stellar evolution 2. Potential targets for Asterseismology

  5. XX Cygni: 20h03m15.6 58°57'17.0" Spectral type: A5-F5, V=11.m7, P≈0.d1349, △V=0.m84 Mass:1 Msun [Fe/H]=-0.49 dex Teff: 7530 K Radial Velocity=-108 km/s

  6. Discovered by Ceraski (1904) • Constant period, marked by occasional discontinuous period changes (Szeidl & Mahdy 1981) • Single-mode pulsation (Hintz & Joner1997) • Both amplitude and period changes (Zhou et al. 2001) • If the small secondary peak(maximum) is real,it is transient (Blake 2002)

  7. The secondary peak or maximum From BLAKE Period Changes in SX Phoenicis Stars. II. XX Cygni

  8. New observations • Telescope used in observations 1. The 85-cm telescope located at the Xinglong Station of NAOC Focal ratio: 3.27 ; Focal length: 2780mm CCD camera: CCD,PI1024 BFT Filters: Standard Johnson-Cousin-Bessel UBVRI Field of view: 16’.5×16’.5 2.The 60-cm telescope located in Kunming (Yunnan Astronomical Observatory)

  9. Journal of new observations in V band for XX Cyg

  10. Totally, 24 nights of data in V band

  11. Data Reduction Data reduction was performed using the APPHOT program in IRAF: 1.Bias and Dark correction, Flat fielding 2.Multiple aperture photometry 3.Determination of the best aperture

  12. Example of the best aperture selected: FWHM: 4 pixel

  13. Field of view: 16’.5*16’.5 Xinglong

  14. Light Curves 2007 07.15-08.30 Xinglong 85cm Error: 0.004-0.02

  15. 2008.08.31 Xinglong Error: 0.003

  16. 2009 07.09 -10.17 Xinglong Error: 0.003-0.02 Kunming 60cm Kunming

  17. Analysis Observed new times of maximum: 37

  18. Fourier analysis: Software: Period04 Data set: 2007.08 8 nights of observations

  19. Frequency solutions of XX Cyg

  20. Fitting curves

  21. Conclusions No secondary peaks were found in our data. • Next work: • O-C analysis • Period change analysis

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