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Page 1: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 2: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 3: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 4: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

Importance of Studying δ Scuti Star

• To test the theory of stellar evolution• For asterseismology to apply

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Page 5: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 6: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

Our Work

• To investigate the period changes of UY Cam • To check the existence of the secondary

pulsation mode

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Page 7: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 8: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

Light Curves – 1st Period• Error: ~ 0.003 – 0.006• 2007 Nov• Xinglong 85-cm telescope

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Page 9: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

Light Curves – 2nd Period• Error: ~ 0.005 – 0.01• 2008 Feb• Xinglong 85-cm/ 50-cm telescope

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Page 10: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 12: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

Results of Fitting

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1st Period

2nd Period

3rd Period

Page 13: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 14: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 15: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 16: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 17: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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Page 21: Variability Study of the  δ Scuti Star UY Cam and the Eclipsing Binary CD Cam

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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