Transcript 幻灯片 1
Pulsation and Period Changes of the High-Amplitude Delta Scuti Star AD CMi 2010-04-05 Wenzhi WANG SUPERVISOR : Jianning FU ASTRONOMY DEPARTMENT BEIJING NORMAL UNIVERSITY Outline Introduction of AD CMi Previous study Observations and data reduction Preliminary results of our study DS: Location on HRD Inside the instability strip on or near MS Features of DS Stars Hydrogen-burning stage with 1.5-2.5 solar mass Short-period mainly low amplitudes near the detection limit of 0.5 milli-mag Mainly in the non-radial p-modes and some in g-modes What is a HADS High amplitude Delta Scuti star High amplitudes between 0.1 and 1mag Low rotational velocities no larger than 30km/s Radial pulsation Fundamental or first overtone Dwarf cepheids HADS and Period Changes Period changes when they are in or evolving across the Lower Instability Strip Other physical factors for the period changes can be excluded This permits an observational test for the stellar evolution theory HADS are observationally favored large amplitude only a few excited modes A number of HADS studied extensively AD CMi Spectral type: F2:III Magnitude : V 9.38 Amplitude : slightly above 0.3 mag ICRS (ep=2000) : 07 52 47.1834 +01 35 50.470 Proper motions mas/yr : -9.08 -2.28 Radial velocity : V (km/s) 34.5 Parallaxes mas: 8.40 Hoffmeister , 1934 Discovered the variability Abhyankar, 1959 : Found a period of 0.122972 days Identified it as an ultra-short period variable Anderson & McNamara, 1960 Made two-color observations Improved the formula for maximum light times Jiang ,1987 carried out photometry in V found maximum and minimum light changes from cycle to cycle found the period increased Rodriguez et al., 1988 Published a large set of observations Supported the increasing period Rodriguez et al.,1990; Yang et al., 1992 Kilambi & Rahman, 1993 Found that the period variation in the O-C diagram may be explained by the lighttime effect in a binary system Fu, 2000 Presented UBVR observations A normal Population-ⅠδScuti star Fu et al. 1996 Some new maxima New linear and quadratic solutions Summarized the binary models for AD CMi Pongsak et al. 2007 Discovered one low frequency of 2.27402 c/d Updated value of period of 0.122974478 days Supporting the model of the combination of the evolutionary effect and the light-time effect in a binary system Some parameters of the binary system was deduced Orbital period =27.2+-0.5 years Eccentricity = 0.8+-0.1 Hurta et al. 2007 Presented 10 new maxima during 35 years Period of 0.12297451 days Different parameters of the orbit Upper and lower limit of the companion of 0.15-1 solar mass Orbital period = 42.88+-0.83 years Eccentricity=0.71+-0.05 New data Our observation 1 meter telescope ，Yunnan Observatory 2k*2k CCD ,Johnson V filter, field 7’*7’ 2009/02/04 - 2009/02/16 12 nights (except 02/13) Data reduction Imalign package in IRAF Apphot package in IRAF M-C method with MATLAB Time of Maxima 19 maxima identified From papers: Hurta et al. 10 maxima IBVS 5774 Hubscher et al. 1 maxima IBVS 5802 Total maxima : 103 Pongsak et al. Hurta et al. Hubscher New data 73 10 1 19 Further work New period O-C Analysis Kepler ? Thanks