P. Lopez De Coca

Detection of 75+ pulsation frequencies in the delta Scuti star FG Virginis

Extensive photometric multisite campaigns of the 6 Scuti variable FG Vir are presented. For the years 2003 and 2004, 926 h of photometry at the millimag precision level were obtained. The combinations with earlier campaigns lead to excellent frequency resolution and high signal/noise. A multifrequency analysis yields 79 frequencies. This represents a new record for this type of star. The modes discovered earlier were confirmed. quencies. This represents a new Pulsation occurs over a wide frequency band from 5.7 to 44.3 c/d with amplitudes of 0.2 mmag or larger Within this wide band the frequencies are not distributed at random, but tend to cluster in groups. A similar feature is seen in the power spectrum of the residuals after 79 frequencies are prewhitened. This indicates that many additional modes are excited. The interpretation is supported by a histogram of the photometric amplitudes, which shows an increase of modes with small amplitudes. The old question of the missing modes may be answered now: the large number of detected frequencies as well as the large number of additional frequencies suggested by the power spectrum of the residuals confirms the theoretical prediction of a large number of excited modes. FG Vir shows a number of frequency combinations of the dominant mode at 12.7162 c/d (m = 0) with other modes of relatively high photometric amplitude. The amplitudes of the frequency sums are higher than those of the difference;. A second mode (20.2878 c/d) also shows combinations. This mode of azimuthal order m = -1 is coupled with two other modes of m = + 1.

Detection of 75+ pulsation frequencies in the Delta Scuti star FG Vir

Extensive photometric multisite campaigns of the 6 Scuti variable FG Vir are presented. For the years 2003 and 2004, 926 h of photometry at the millimag precision level were obtained. The combinations with earlier campaigns lead to excellent frequency resolution and high signal/noise. A multifrequency analysis yields 79 frequencies. This represents a new record for this type of star. The modes discovered earlier were confirmed. quencies. This represents a new Pulsation occurs over a wide frequency band from 5.7 to 44.3 c/d with amplitudes of 0.2 mmag or larger Within this wide band the frequencies are not distributed at random, but tend to cluster in groups. A similar feature is seen in the power spectrum of the residuals after 79 frequencies are prewhitened. This indicates that many additional modes are excited. The interpretation is supported by a histogram of the photometric amplitudes, which shows an increase of modes with small amplitudes. The old question of the missing modes may be answered now: the large number of detected frequencies as well as the large number of additional frequencies suggested by the power spectrum of the residuals confirms the theoretical prediction of a large number of excited modes. FG Vir shows a number of frequency combinations of the dominant mode at 12.7162 c/d (m = 0) with other modes of relatively high photometric amplitude. The amplitudes of the frequency sums are higher than those of the difference;. A second mode (20.2878 c/d) also shows combinations. This mode of azimuthal order m = -1 is coupled with two other modes of m = + 1.

The delta Scuti star FG Vir. V. The 2002 photometric multisite campaign

A high-accuracy multisite campaign was carried out from 2002 January to May with a photometric coverage of 398 h at five observatories. The concentration on a few selected sites gives better consistency and accuracy than collecting smaller amounts from a larger number of sites. 23 frequencies were detected with a high statistical significance. 6 of these are new. The 17 frequencies found in common with the 1992-1995 data are the modes with highest amplitudes. This indicates that the pulsation spectrum of FG Vir is relatively stable over the ten-year period. Two frequencies have variable amplitudes and phases from year to year as well as during 2002. These were both found to be double modes with close frequencies. For the mode at 12.15 c/d this leads to an apparent modulation with a time scale of ∼ 129 d. The close frequencies at 12.15 c/d are composed of a radial and a nonradial mode, suggesting a similarity with the Blazhko Effect seen in RR Lyrae stars.

Asteroseismology with the WIRE satellite - I. Combining ground- and space-based photometry of the δ Scuti star ϵ Cephei

Aims. We have analysed ground-based multi-colour Stromgren photometry and single-filter photometry from the star tracker on the WIRE satellite of the 6 Scuti star ∈ Cephei. Methods. The ground-based data set consists of 16 nights of data collected over 164 days, while the satellite data are nearly continuous coverage of the star during 14 days. The spectral window and noise level of the satellite data are superior to the ground-based data and this data set is used to locate the frequencies. However, we can use the ground-based data to improve the accuracy of the frequencies due to the much longer time baseline. Results. We detect 26 oscillation frequencies in the WIRE data set, but only some of these can be seen clearly in the ground-based data. We have used the multi-colour ground-based photometry to determine amplitude and phase differences in the Stromgren b - y colour and the y filter in an attempt to identify the radial degree of the oscillation frequencies. We conclude that the accuracies of the amplitudes and phases are not sufficient to constrain theoretical models of e Cep. We find no evidence for rotational splitting or the large separation among the frequencies detected in the WIRE data set. Conclusions. To be able to identify oscillation frequencies in 6 Scuti stars with the method we have applied, it is crucial to obtain more complete coverage from multi-site campaigns with a long time baseline and in multiple filters. This is important when planning photometric and spectroscopic ground-based support for future satellite missions like COROT and KEPLER.

Multimode Pulsations of the λ Bootis Star 29 Cygni: The 1995 and 1996 Multisite Campaigns

In this paper we present the results of multisite photometric and spectroscopic campaigns, carried out during the years 1995 and 1996, to study the pulsations of a typical λ Bootis star, 29 Cyg. During the 1995 campaign we found well-defined multiperiodicity in 29 Cyg, which was studied in detail during a multilongitude campaign covering a 65 day time interval in 1996. The frequency analysis of the 1996 campaigns data easily revealed 11 excited low l degree modes with frequencies of oscillation ranging from 20.3 to 37.4 cycles day-1 and mean photometric amplitudes ranging from 10.65 to 0.96 mmag in the V filter. After removing the well-identified frequencies, the discrete Fourier transform of the residuals showed excess power in the 20-40 cycle day-1 domain, which indicates the probable existence of unresolved rich p-mode spectra with photometric V amplitudes below 0.5 mmag. We found a regular spacing of 2.41 cycles day-1 within the modes of 29 Cyg, which was interpreted as the spacing of consecutive even and odd l-values. The asteroseismic luminosity log L/L⊙ = 1.12, calculated from the frequency spacing, is in good agreement with the Hipparcos luminosity log L/L⊙ = 1.16 and with luminosities from photometric and spectroscopic calibrations. Using our multicolor photometry we tentatively identified the dominant f1 = 37.425 cycle day-1 mode as an l = 2, n = 5 mode, and made radial overtone identification for all frequencies. These ranged from n = 2 to 5. Analysis of the photometric data shows the long-term (years) and probable short-term (days) variability of amplitudes for all of these modes in 29 Cyg. Using our multicolor WBVR filter photometry, we found the wavelength dependence of the pulsation amplitudes for the five highest amplitude modes. Based on the Hα line radial velocity observations of 29 Cyg, we detected multiperiodic radial velocity variations with frequencies of 38.36 and 29.99 cycles day-1 and semiamplitudes of 1.0 and 0.8 km s-1, respectively. These frequencies coincide within the errors with the photometric frequencies of the two highest amplitude modes, 37.425 and 29.775 cycles day-1. For the highest amplitude l = 2, n = 5 mode (37.425 cycles day-1), the radial velocity-to-light amplitude ratio and velocity-to-light phase shift are equal to 2K(Hα)/ΔV = 94 km mag-1 s-1 and Φf1 = - V = +0.08 ± 0.01, respectively, and are in good agreement with values for δ Scuti stars. The rich multiperiodic spectrum makes 29 Cyg a promising target for future multisite campaigns.

Empirical P-L-C relation for ? scuti stars

Empirical period-luminosity-colour (P-L-C) relations are obtained for the four lowest modes corresponding to radial pulsations. Agreement with predicted values indicates that, in general, both Strömgren photometric calibration and pulsation theory work well for these stars.

The SX Phe stars

A systematic photometry study of SX Phe stars together with high amplitude δ Sct stars have been carried out. Theuvbyß indices are obtained and the physical parameters are determined. The results obtained by using the pulsation and evolution theories independently are compared. A good agreement is found.

Strömgren photometry of the δ Scuti star 67 UMa

We present preliminary results derived from the data obtained during five observing campaigns in 2001, 2003, 2004, 2006 and 2007, of the δ Set-type variable star 67 UMa, at Sierra Nevada Observatory, Spain. The analysis of the data was performed by means of the Fourier Transform method, and results are shown. The intrinsic b-y, m1, c1 values are derived and the physical parameters are determined.