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Variability Study of the
δ Scuti Star UY Cam and the
Eclipsing Binary CD Cam
2010-04-01
Kailin Pan
Beijing 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 2007
II: Feb 2008
III: 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
1st Period
3rd Period
2nd Period
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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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