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

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

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

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

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

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

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

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

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

Light Curves – 3rd Period Error: ~ 0.004 – 0.007 2008 Mar Xinglong 85-cm telescope

Pulsation Analysis 5 harmonics detected (2f0, 3f0, 4f0, 5f0, 6f0) Period04 data used: 2nd period of observation Only fundamental frequency f0 : 3.744 /day 5 harmonics detected (2f0, 3f0, 4f0, 5f0, 6f0)

Results of Fitting 3rd Period 1st Period 2nd 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

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

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

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

Lightcurves of CD Cam

Phase Diagram of CD Cam

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,

O – C Diagram of 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