Browsing by Author "Tappert, C"

Now showing 1 - 8 of 8
  • No Thumbnail Available
    Item
    Cataclysmic variables from the Calan-Tololo Survey - I. Photometric periods
    (2004) Tappert, C; Augusteijn, T; Maza, J
    In a search for cataclysmic variables in the Calan-Tololo Survey, we have detected 21 systems, 16 of them previously unknown. In this paper we present detailed time-series photometry for those six confirmed cataclysmic variables that show periodic variability in their light curves. Four of them turned out to be eclipsing systems, while the remaining two show a modulation consisting of two humps. All derived periods are below or, in one case, just at the lower edge of the period gap.
  • No Thumbnail Available
    Item
    Doppler tomography of the dwarf novae VY Aquari and WX Ceti
    (2006) Mennickent, RE; Unda-Sanzana, E; Tappert, C
    Aims. We present the optical spectroscopy of the dwarf novae VY Aqr and WX Cet in quiescence.
  • No Thumbnail Available
    Item
    Photographic surface photometry of the Southern Milky Way - VIII. High-resolution U, V and R surface photometries of the Southern Milky Way
    (1998) Hoffmann, B; Tappert, C; Schlosser, W; Schmidt-Kaler, T; Kimeswenger, S; Seidensticker, K; Schmidtobreick, L; Hovest, W
    We present photometries of the Southern Milky Way (l = 200 degrees... 0 degrees... 60 degrees, \b\ less than or equal to 40 degrees) in the U, V and R-passbands. The resolution is 0.25" x 0.25". Together with the B-photometry (Kimeswenger et al. 1993 = Paper VII), this paper gives final results of the Bochum Super-Wide-Angle-Camera photographs obtained in 1971 at La Silla, calibrated by means of accompanying photoelectric observations. The techniques employed and procedures used for the reductions are the same as described in Paper VIII and the references quoted therein. Therefore, this paper is restricted to those points, where either modifications proved to be necessary or additional information will help to judge the accuracy obtained. For this purpose, the chapters are arranged in the same manner as in Paper VII.
  • No Thumbnail Available
    Item
    Photopolarimetric observations of the new eclipsing polar CTCV J1928-5001
    (2005) Potter, SB; Augusteijn, T; Tappert, C
    We report photopolarimetric observations of a new eclipsing polar (AM Herculis system) discovered in the Calan-Tololo survey. The photometry and polarimetry are modulated on a period of similar to 101 min. Circular polarization variations are seen from similar to-8 to +12 per cent and from similar to 0 to 5 per cent in the red and blue parts of the optical spectrum, respectively. Two linearly polarized pulses are detected at orbital phases coinciding with the reversals in the circular polarization. This is consistent with a magnetic field strength of similar to 20 MG for the white dwarf primary, where accretion takes place at two regions. Both the accretion regions are self-occulted by the white dwarf during parts of the orbit. We estimate some of the system's parameters from its eclipses, which we further refine by modelling the polarimetric observations.
  • No Thumbnail Available
    Item
    Spectroscopic analysis of tremendous-outburst-nova candidates
    (2005) Schmidtobreick, L; Tappert, C; Bianchini, A; Mennickent, RE
    In the course of a long-term project investigating classical novae with large outburst amplitudes, we have performed optical spectroscopy of several old-nova candidates. We here present the spectra of the candidates V630 Sgr, XXTau, CQVel, V842 Cen, and V529 Ori, that hitherto lacked such classification. While the first four show spectra typical of cataclysmic variables and can thus be identified as such, V529 Ori is probably misclassified. Of special interest are the two systems XXTau and V842 Cen, which show signs of being low mass transfer systems. As such they can be used to judge the evolution scenarios for novae. In particular, given the rather young age of their outbursts, it appears more likely that these systems are not on their way into hibernation (i.e., cutting off mass transfer for a longer period of time), but are simply settling down towards their original configuration of comparatively low, but steady, mass transfer, such as for dwarf novae.
  • No Thumbnail Available
    Item
    Spectroscopic classification of cataclysmic variable candidates
    (2005) Schmidtobreick, L; Galli, L; Whiting, A; Tappert, C; Carver, AJ
    We present low-resolution optical spectroscopy for six cataclysmic variable candidates and the old nova V888 Cen. We confirm the classification as cataclysmic variable for LB 9963 and FQ Mon, while the other four candidates turn out to be different types of stars. We discuss the individual spectra and pay special attention to the mass transfer rate and disk temperature and density of the three cataclysmic variables.
  • No Thumbnail Available
    Item
    The cataclysmic variable WW Ceti: physical parameters and periodic phenomena
    (1997) Tappert, C; Wargau, WF; Hanuschik, RW; Vogt, N
    We present spectroscopic and photometric data of the cataclysmic variable WW Get. By comparison of our radial velocity data with earlier published ones we are able to restrict possible orbital periods to the two choices 0.175 806 90(25)(d) and 0.175 289 02(35)(d). We derive as inclination of the system i = 48(11)degrees, which is supported by the fact that the photometric lightcurve shows periodic phenomena folded on the orbital period. These features are identified as a main and an intermediate hump which vary strongly with the brightness level of the system. Our derived periods place them at very unusual phases which are not conform with the normal explanation that the humps are caused by a hot spot which is seen from both front and back. However, our spectroscopy in quiescence indicates that these phasings are real and do not result from an error in the calculation of the ephemerides.
  • No Thumbnail Available
    Item
    UBV photometry of galactic foreground and LMC member stars .2. Galactic foreground stars (supplement)
    (1997) Grothues, HG; Oestreicher, MO; Gochermann, J; Tappert, C; Zaum, A; Brugger, HR; SchmidtKaler, T
    In addition to the list of UBV photometries of 955 galactic foreground stars in the direction to the Large Magellanic Cloud published by Gochermann et al. (1993a), a supplement of 545 stars is presented, which have been measured with the same photometric accuracy. Moreover, less reliable photometries of 379 further foreground stars are listed in a separate table. The homogeneous data base of more than 1500 high accuracy photometries represented by these stars has been used to construct a reddening distribution map of the galactic foreground towards the LMC by Oestreicher et al. (1995).