Yazar "Slee, OB" seçeneğine göre listele

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    Öğe
    A radio and optical study of the active young F star HR 1817 (=HD 35850)
    (C S I R O Publishing, 2002) Budding, E; Carter, BD; Mengel, MW; Slee, OB; Donati, JF
    This paper presents the results of a multiwavelength observational study of the active young F-type star HR 1817. The star was monitored at 4.80 and 8.64 GHz over 2 x 12 h allocations with the Australia Telescope Compact Array on 8 and 9 December, 2000. The Anglo-Australian Telescope was used for simultaneous optical spectropolarimetry during a 2 h period on 9 December. The low levels of observed radio emission have characteristics that are similar to those seen in other active stars, and a gyrosynchrotron mechanism is proposed to explain them; this is supported by the relatively low fractions of circular polarisation measured in HR 1817. Comparison of the emissions from 4.80 and 8.64 GHz shows a very strong cross-correlation peak, indicative of a common origin, although the shift of this peak indicates that 8.64 GHz variations tend to precede those at 4.80 GHz by, typically, similar to20 min. The optical spectropolarimetry reveals polarisation signals characteristic of surface magnetic fields, with profile changes indicating a complex dynamo-type magnetic topology is present on the star. This result makes HR 1817 the star with the earliest spectral type on which dynamo magnetic fields have been detected directly up to now.
  • [ X ]
    Öğe
    Multi-facility study of the Algol-type binary ? Librae
    (Springer, 2005) Budding, E; Bakis, V; Erdem, A; Demircan, O; Iliev, L; Iliev, I; Slee, OB
    Various branches of observational information, and related physical problems concerning the bright, relatively close, Algol binary 8 Lib are discussed. Times of minimum light confirm the classical Algol status, which, combined with the optical and IR photometry of Lazaro et al. (2002), provide the basis for a good understanding of the system's basic parameters. New spectroscopy from the Coude spectrograph of the Rozhen Observatory (Bulgaria) allows further information on the model and the mass transfer process. Very high resolution radio observations would also have much to reveal about astrophysics of the semi-detached configuration, not only directly, by informing about the outermost envelopes of the components, but indirectly through high accuracy positional information. We show how this may be related to careful period and astrometric studies. delta Lib thus provides a rich source of information on the astrophysics of the Algol configuration.