Browsing by Author "Vogt, N"

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    An extensive Δa-photometric survey of southern B and A type bright stars
    (1998) Vogt, N; Kerschbaum, F; Maitzen, HM; Faundez-Abans, M
    Photoelectric photometry of 803 southern BS objects in the aa-system as detection tool for magnetic chemically peculiar (=CP2) stars has been carried out and compared to published spectral types. The statistical yield of such objects detected by both techniques is practically the same. We show that there are several factors which contaminate the search for these stars, but this contamination is only of the order of 10% in both techniques. We find a smooth transition from normal to peculiar stars.
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    Long-term photometry of Be stars -: III.: Evidence for periodic outbursts of λ Eri and photometric activity in HR 2142
    (1998) Mennickent, RE; Sterken, C; Vogt, N
    Stromgren differential uvby photometry of lambda Eri and HR 2142 is analyzed. The data were taken during the time interval 1983-1994 in the framework of the Long-Term Photometry of Variables project at La Silla. lambda Eri exhibited four photometric events (probably associated with line emission episodes) that last several months and which were characterized by a common pattern of change in all passbands (similar to +/-10(-3) mag/day) along with an apparent decrease of the amplitude of the short-term variability and an increase of the stellar temperature. A. search for periodicities reveals that these events fit a 486 d recurrence time. On the other hand, HR 2142 showed a relatively "quiet" long-term photometric behaviour, the orbital period being detected only marginally in the photometric data set. In contrast, a 344 d period optimally fits the data. We discuss the possibility of an internal "clock" regulating the outburst activity of lambda Eri and show that the photometric variability of HR 2142 can hardly be explained by its interacting binary nature. We also discuss an empirical relationship found between partial derivative c(1)/partial derivative u and v sini in a sample of 11 Be stars.
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    Simultaneous multiwavelength observations of dwarf novae .1. SU Ursae Majoris: Minihumps at a minioutburst?
    (1996) Echevarria, J; Tovmassian, G; Shara, M; Tapia, M; Bohigas, J; Jones, DHP; Gilmozzi, R; Costero, R; Lopez, JA; Roth, M; Alvarez, M; Rodriguez, LF; DeLara, E; Stover, RJ; MartinezRoger, C; Garzon, F; Asatrian, N; Vogt, N; Szkody, P; Zsoldos, E; Mattei, J; Bateson, FM
    SU Ursae Majoris-the prototype of a subgroup of dwarf novae that display superhumps in superoutbursts has been observed during an international campaign dedicated to the observation of the first day of outburst of dwarf novae during 1986 February. After the start of a brightening was reported, the star was monitored by IUE, ground-based photometry and spectrophotometry, IR-photometry, and radio observations by VLA. However, it did not undergo a normal outburst or a superoutburst.