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K. Zwintz

Publications and source records attributed to K. Zwintz.

57 records · Page 4Linked to original sources

A multisite photometric campaign on the Pre-Main-Sequence delta Scuti pulsator IP Per

We present the results of a photometric multisite campaign on the $δ$ Scuti Pre-Main-Sequence star IP Per. Nine telescopes have been involved in the observations, with a total of about 190 hours of observations over 38 nights. Present data confirms the multiperiodic nature of this star and leads to the identification of at least nine pulsational frequencies. Comparison with the predictions of linear non-adiabatic radial pulsation models allowed us to identify only five of the nine observed frequencies, and to constrain the position of IP Per in the HR diagram. The latter is in good agreement with the empirical determination of the stellar parameters obtained by Miroshnichenko et al. (2001). An initial interpretation of the observed frequencies using the Aarhus non-radial pulsation code suggests that three frequencies could be associated with non-radial ($l$=2) modes. Finally, we present new evolutionary and pulsation models at lower metallicity (Z=0.008) to take into account the possibility that IP Per is metal deficient, as indicated by Miroshnichenko et al. (2001).

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Search for pulsating PMS stars in NGC 6383

A search for pulsating pre-main sequence (PMS) stars was performed in the young open cluster NGC 6383 using CCD time series photometry in Johnson B & V filters. With an age of only ~1.7 million years all cluster members later than spectral type A0 have not reached the ZAMS yet, hence being ideal candidates for investigating PMS pulsation among A and F type stars. In total 286 stars have been analyzed using classical Fourier techniques. From about a dozen of stars within the boundaries of the classical instability strip, two stars were found to pulsate: NGC 6383 #170, with five frequencies simultaneously, and NGC 6383 #198, with a single frequency. In addition, NGC 6383 #152 is a suspected PMS variable star, but our data remain inconclusive. Linear, non-adiabatic models assuming PMS evolutionary phase and purely radial pulsation were calculated for the two new PMS pulsators. NGC 6383 #170 appears to pulsate radially in third and fifth overtones, while the other three frequencies seem to be of non-radial nature. NGC 6383 #198 pulsates monoperiodically, most probably in the third radial overtone. Magnitudes and B-V colours were available in the literature for only one third of all stars and we used them for calibrating the remaining.

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New Variable Stars in Open Clusters I: Methods and Results for 20 Open Clusters

We present high precision CCD photometry of 1791 objects in 20 open clusters with an age from 10 Myr to 1 Gyr. These observations were performed within the Delta a photometric system which is primarily used to detect chemically peculiar stars of the upper main sequence. Time bases range between 30 minutes and up to 60 days with data from several nights. We describe the way of time series analysis reaching a detection limit of down to 0.006 mag. In total, we have detected 35 variable objects from which four are not members of their corresponding clusters. The variables cover the entire Hertzsprung-Russell-diagram, hence they are interesting targets for follow-up observations.

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