Variability Study of the δ Scuti Star UY Cam and the
Eclipsing Binary CD Cam2010-04-01
Kailin PanBeijing Normal University
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Characteristics of δ Scuti Stars
• short periods: ~ 0.02 – 0.25 day• amplitudes: < 1 mag masses: ~1.5 - 2.5 Msun • spectral type: A5 - F2. • found on the intersection of the
classical instability strip and the main sequence in the Hertzsprung-Russell diagram
• excitation mechanism: κ mechanism
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LADS and HADS
• Low amplitude δ Scuti Star (LADS) - more in number - amplitudes: mmag to a few tens of a mmag - pulsation mode: non-radial p mode• High amplitude δ Scuti Star (HADS) - less in number - amplitudes: > ~0.3 mag - pulsation mode: radial mode
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Importance of Studying δ Scuti Star
• To test the theory of stellar evolution• For asterseismology to apply
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Previous Studies of UY Cam• discovered by Baker(1937) to be a variable star - period ~ 6.16 days + shape of lightcurves Cepheid variable• Willams (1964): - amplitude ~ 0.45 mag + period ~ 0.267 day c RR Lyrae star - disperion of points in the lightcurves possible cycle-to-cycle changes• Beyer(1966) - no changes in the period - varying amplitude ~ 0.17 – 0.5 mag - Instability in the lightcurves found by Williams and Beyer two or more
pulsation modes• Broglia & Conconi (1992): - no evidence of instability
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Our Work
• To investigate the period changes of UY Cam • To check the existence of the secondary
pulsation mode
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UY Cam
• α = 07h58m59s β = 72.79• V ~ 11.7 mag• Observations (Xinglong
85-cm /50-cm): I: Nov 2007II: Feb 2008III: Mar 2008• 19 days in V band
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Light Curves – 1st Period• Error: ~ 0.003 – 0.006• 2007 Nov• Xinglong 85-cm telescope
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Light Curves – 2nd Period• Error: ~ 0.005 – 0.01• 2008 Feb• Xinglong 85-cm/ 50-cm telescope
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Light Curves – 3rd Period
• Error: ~ 0.004 – 0.007• 2008 Mar• Xinglong 85-cm telescope
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Pulsation Analysis• Period04• data used: 2nd period of observation• Only fundamental frequency f0 : 3.744 /day• 5 harmonics detected (2f0, 3f0, 4f0, 5f0, 6f0)
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Results of Fitting
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1st Period
2nd Period
3rd Period
Times of Maximum Light
• 47 times of maximum light in total (13 from our work)
• Time span ~ 60 years• New ephemeris formular - HJDmax = 2432144.4377 + 0.267041135 x E - ΔT0 = 0.003 day, ΔP = 0.000000045 day
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O - C Analysis• cyclic variation binary system• quadratic plus a sine function (light
travelling time effect)
• semi-amplitude = 2557.7 s; P =0.26704121 day;
β = (-0.169 +/- 0.483) x 10^-11 day; Porb = 49.2 yr
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Mass of Companion• a1 sin i= 5.12 AU• f (m) = (a1 sin i )^3 / Porb = 0.0554• f(m) = (m2 sin i )^3/(m1 + m2)^2 m1=2Msun (Zhou & Liu 2003) (m1 = mass of UY Cam)• a1/a2 = m2/m1 • Min mass of companion : 0.75 Msun
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CD Cam
• Eclipsing binary of W UMa type
• V ~ 12.02 mag• Discovered by Broglia &
Conconi (1992) - period ~ 18 hours - amplitude ~ 0.2mag
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Lightcurves of CD Cam
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Phase Diagram of CD Cam
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Times of Minimum Light
• 14 times of maximum light in total (8 from our work)• Time span ~ 23 years• New ephemeris formular -HJDmax = 2446170.055 + 0.7641868 x E - ΔT0 = 0.002 day, ΔP = 0.0000002 day,
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O – C Diagram of CD Cam
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Conclusions UY Cam• P = 0.267041135 day• Monoperiodic (fundamental frequency: 3.744/day)• Cyclic variation in O – C diagram detection of companion - mass > 0.75 Msun - Porb = 49.2 years CD Cam• P = 0.7641868 day
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