1. 2010-04-01 Kailin Pan Beijing Normal University
Variability Study of the δ Scuti Star UY Cam and the Eclipsing Binary CD Cam
Kailin Pan
Beijing Normal University

2. Characteristics of δ Scuti Stars
short periods: ~ 0.02 – 0.25 day
amplitudes: < 1 mag
masses: ~ 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

3. 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

4. Importance of Studying δ Scuti Star
To test the theory of stellar evolution
For asterseismology to apply

5. 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 ~ 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

6. Our Work To investigate the period changes of UY Cam
To check the existence of the secondary pulsation mode

7. 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

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

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

10. Light Curves – 3rd Period
Error:
~ – 0.007
2008 Mar
Xinglong
85-cm telescope

11. Pulsation Analysis 5 harmonics detected (2f0, 3f0, 4f0, 5f0, 6f0)
Period04
data used:
2nd period of
observation
Only fundamental
frequency f0 : /day
5 harmonics detected
(2f0, 3f0, 4f0, 5f0, 6f0)

12. Results of Fitting
3rd Period
1st Period
2nd Period

13. Times of Maximum Light
47 times of maximum light in total (13 from our work)
Time span ~ 60 years
New ephemeris formular
- HJDmax = x E
- ΔT0 = day, ΔP = day

14. O - C Analysis cyclic variation  binary system
quadratic plus a sine function (light travelling time effect)
semi-amplitude = s; P = day;
β = ( / ) x 10^-11 day;
Porb = 49.2 yr

15. Mass of Companion a1 sin i= 5.12 AU
f (m) = (a1 sin i )^3 / Porb =
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

16. CD Cam Eclipsing binary of W UMa type V ~ 12.02 mag
Discovered by Broglia & Conconi (1992)
- period ~ 18 hours
- amplitude ~ 0.2mag

17. Lightcurves of CD Cam

18. Phase Diagram of CD Cam

19. Times of Minimum Light
14 times of maximum light in total (8 from our work)
Time span ~ 23 years
New ephemeris formular
-HJDmax = x E
- ΔT0 = day, ΔP = day,

20. O – C Diagram of CD Cam

21. 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 = day