Transcript 幻灯片 1
Variability Study of the δ Scuti Star UY Cam and the Eclipsing Binary CD Cam 2010-04-01 Kailin Pan Beijing Normal University 1 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 2 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 3 Importance of Studying δ Scuti Star • To test the theory of stellar evolution • For asterseismology to apply 4 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 5 Our Work • To investigate the period changes of UY Cam • To check the existence of the secondary pulsation mode 6 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 7 Light Curves – 1st Period • Error: ~ 0.003 – 0.006 • 2007 Nov • Xinglong 85-cm telescope 8 Light Curves – 2nd Period • Error: ~ 0.005 – 0.01 • 2008 Feb • Xinglong 85-cm/ 50-cm telescope 9 Light Curves – 3rd Period • Error: ~ 0.004 – 0.007 • 2008 Mar • Xinglong 85-cm telescope 10 Pulsation Analysis • Period04 • data used: 2nd period of observation • Only fundamental frequency f0 : 3.744 /day • 5 harmonics detected (2f0, 3f0, 4f0, 5f0, 6f0) 11 Results of Fitting 1st Period 3rd Period 2nd Period 12 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 13 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 14 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 15 CD Cam • Eclipsing binary of W UMa type • V ~ 12.02 mag • Discovered by Broglia & Conconi (1992) - period ~ 18 hours - amplitude ~ 0.2mag 16 Lightcurves of CD Cam 17 Phase Diagram of CD Cam 18 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, 19 O – C Diagram of CD Cam 20 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 21