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تسجيل مستخدم جديدMode identification in the high-amplitude {delta} Scuti star V2367 Cyg
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We report on a multi-site photometric campaign on the high-amplitude $delta$ Scuti star V2367 Cyg in order to determine the pulsation modes. We also used high-dispersion spectroscopy to estimate the stellar parameters and projected rotational velocity. Time series multicolour photometry was obtained during a 98-d interval from five different sites. These data were used together with model atmospheres and non-adiabatic pulsation models to identify the spherical harmonic degree of the three independent frequencies of highest amplitude as well as the first two harmonics of the dominant mode. This was accomplished by matching the observed relative light amplitudes and phases in different wavebands with those computed by the models. In general, our results support the assumed mode identifications in a previous analysis of Kepler data.
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Bi-site time-series photometric and high-resolution spectroscopic observations were made for the double-mode high-amplitude $delta$ Scuti star VX Hya. The fundamental frequency $f_{0}=4.4763 rm{c days^{-1}}$, the first overtone $f_{1}=5.7897 rm{c day
s^{-1}}$ and 23 harmonics and linear combinations of $f_{0}$ and $f_{1}$ are detected by pulsation analysis. From the spectroscopic data, we get $rm{[Fe/H] = -0.2pm0.1 dex}$. The period change rate of the fundamental mode is obtained by using the Fourier-phase diagram method, which gives the value of $(1/P_{0})(dP_{0}/dt)=(1.81pm0.09) times 10^{-7} rm{yr}^{-1}$. With these results from the observations, we perform theoretical explorations with the stellar evolution code MESA, and constrain the models by fitting $f_{0}$, $f_{1}$, and $(1/P_{0})(dP_{0}/dt)$ within $3sigma$ deviations. The results show that the period change of VX Hya could be ascribed to the evolutionary effect. The stellar parameters of VX Hya could be derived as: the mass $2.385pm0.025 M_{odot}$, the luminosity $log(L/L_{odot})=1.93pm0.02$ and the age $(4.43pm0.13)times 10^8$ years. VX Hya is found to locate at the post-main-sequence stage with a helium core and a hydrogen-burning shell on the H${-}$R diagram.
In this paper, we analyze the light variations of KIC 10975348 using photometric data delivered from $Kepler$ mission. This star is exceptionally faint ($K_{p}$ = 18.6 mag), compared to most well-studied $delta$ Scuti stars. The Fourier analysis of t
he short cadence data (i.e. Q14, Q15 and Q16, spanning 220 days) reveals the variations are dominated by the strongest mode with frequency F0 = 10.231899 $rm{d^{-1}}$, which is compatible with that obtained from $RATS-Kepler$. The other two independent modes with F1 (= 13.4988 $rm{d^{-1}}$) and F2 (= 19.0002 $rm{d^{-1}}$) are newly detected and have amplitudes two orders of magnitude smaller than F0. We note that, for the first time, this star is identified to be a high-amplitude $delta$ Sct (HADS) star with amplitude of about 0.7 mag, and the lower ratio of F0/F1 = 0.758 suggests it might be a metal-rich variable star. The frequency F2 may be a third overtone mode, suggesting this target might be a new radial triple-mode HADS star. We perform $O - C$ analysis using 1018 newly determined times of maximum light and derive an ephemeris formula: $T_{max}$ = 2456170.241912(0)+0.097734(1) $times$ $E$. The $O - C$ diagram shows that the pulsation period of KIC 10975348 seems to show no obvious change, which is in contrast to that of the majority of HADS stars. The possible cause of that may be due to the current short time span of observations. To verify its possible period variations, regular observation from space with a longer time span in future is needed.
The high accuracy of space data increased the number of the periodicities determined for pulsating variable stars, but the mode identification is still a critical point in the non-asymptotic regime. We use regularities in frequency spacings for ident
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We present results of a multi-site photometric campaign on the high-amplitude $delta$,Scuti star KIC,6382916 in the {it Kepler} field. The star was observed over a 85-d interval at five different sites in North America and Europe during 2011. {it Kep
ler} photometry and ground-based multicolour light curves of KIC,6382916 are used to investigate the pulsational content and to identify the principal modes. High-dispersion spectroscopy was also obtained in order to derive the stellar parameters and projected rotational velocity. From an analysis of the {it Kepler} time series, three independent frequencies and a few hundred combination frequencies are found. The light curve is dominated by two modes with frequencies $f_{1}$= 4.9107 and $f_{2}$= 6.4314,d$^{-1}$. The third mode with $f_{3}$= 8.0350,d$^{-1}$ has a much lower amplitude. We attempt mode identification by examining the amplitude ratios and phase differences in different wavebands from multicolour photometry and comparing them to calculations for different spherical harmonic degree, $l$. We find that the theoretical models for $f_1$ and $f_2$ are in a best agreement with the observations and lead to value of l = 1 modes, but the mode identification of $f_3$ is uncertain due to its low amplitude. Non-adiabatic pulsation models show that frequencies below 6,d$^{-1}$ are stable, which means that the low frequency of $f_1$ cannot be reproduced. This is further confirmation that current models predict a narrower pulsation frequency range than actually observed.
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