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Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480
Joshi, S; Girish, V; Sagar, R; Kurtz, DW; Martinez, P; Kumar, B; Seetha, S; Ashoka, BN; Zhou, A
2003-09-11
发表期刊MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷号344期号:2页码:431-438
摘要The chemically peculiar (CP) stars HD 98851 and HD 102480 have been discovered to be unusual pulsators during the 'Naini Tal-Cape Survey' programme to search for pulsational variability in CP stars. Time series photometric and spectroscopic observations of these newly discovered stars are reported here. Fourier analyses of the time series photometry reveal that HD 98851 is pulsating mainly with frequencies 0.208 and 0.103 mHz, and HD 102480 is pulsating with frequencies 0.107, 0.156 and 0.198 mHz. The frequency identifications are all subject to 1 d(-1) cycle count ambiguities. We have matched the observed low-resolution spectra of HD 98851 and HD 102480 in the range 3500-7400 Angstrom with theoretical synthetic spectra using Kurucz models with solar metallicity and a micro-turbulent velocity of 2 km s(-1). These yield T-eff=7000+/-250 K, log g=3.5+/-0.5 for HD 98851 and T-eff=6750+/-250 K, log g=3.0+/-0.5 for HD 102480. We determined the equivalent H-line spectral class of these stars to be F1 IV and F3 III/IV, respectively. A comparison of the location of HD 98851 and HD 102480 in the HR diagram with theoretical stellar evolutionary tracks indicates that both stars are about 1-Gyr-old, 2-M-circle dot stars that lie towards the red edge of the delta Sct instability strip. From comparison between the observed and calculated physical parameters, we conclude that HD 98851 and HD 102480 are cool, evolved Am pulsators. The light curves of these pulsating stars have alternating high and low amplitudes, nearly harmonic (or subharmonic) period ratios, high pulsational overtones and Am spectral types. This is unusual for both Am and delta Sct pulsators, making these stars interesting objects for further observational and theoretical studies.
关键词Stars : Chemically Peculiar Stars : Individual : Hd 98851 Stars : Individual : Hd 10248 Delta Scuti
收录类别SCI
语种英语
WOS记录号WOS:000185190900012
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被引频次:17[WOS]   [WOS记录]     [WOS相关记录]
文献类型期刊论文
条目标识符http://ir.bao.ac.cn/handle/114a11/8471
专题光学天文研究部
作者单位1.Uttar Pradesh State Observ, Naini Tal 263129, India
2.ISRO Satellite Ctr, Bangalore 560034, Karnataka, India
3.Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England
4.S African Astron Observ, ZA-7935 Cape Town, South Africa
5.Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
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Joshi, S,Girish, V,Sagar, R,et al. Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480[J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,2003,344(2):431-438.
APA Joshi, S.,Girish, V.,Sagar, R.,Kurtz, DW.,Martinez, P.,...&Zhou, A.(2003).Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,344(2),431-438.
MLA Joshi, S,et al."Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480".MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 344.2(2003):431-438.
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