Yazar "Budding, E" seçeneğine göre listele

Listeleniyor 1 - 8 / 8
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    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.
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    Astrometric solution of the multiple system XY Leo
    (Springer, 2005) Bakis, V; Erdem, A; Budding, E; Demircan, O; Bakis, H
    An astrometric solution, together with time of minimum analysis, has been made for the multiple system XY Leonis (HIP 49136) to identify the properties of the remote companion to the eclipsing pair (AB). From this solution, we derive the inclination of the wide orbit (AB-cd) as 94.4 degrees +/- 0.2 degrees, angle of nodes as 247.3 degrees +/- 0.2 degrees, and the mass of the wide component (the dwarf binary cd) as 0.98 +/- 0.2 M-.. This study confirms that the light travel time effect can explain the sinusoidal O - C variation of the eclipsing system.
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    Catalogue of Algol type binary stars
    (Edp Sciences S A, 2004) Budding, E; Erdem, A; Çiçek, C; Bulut, I; Soydugan, F; Soydugan, E; Bakis, V
    A catalogue of (411) Algol-type (semi-detached) binary stars is presented in the form of five separate tables of information. The catalogue has developed from an earlier version by including more recent information and an improved layout. A sixth table lists (1872) candidate Algols, about which fewer details are known at present. Some issues relating to the classification and interpretation of Algol-like binaries are also discussed.
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    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.
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    One fellow's view of the Royal Road
    (Springer, 2005) Budding, E
    The paper attempts to discern the place and direction of the Royal Road of astronomical usage, with the particular perspective that the late Prof. Zdenek Kopal may have had of it. In seeking further insights into the Kopalian royal road map, we take note of his own guide stars. Referring then more closely to the royal road of eclipses, the information content of photometric light curves is discussed, noting in particular, their Fourier representation and the relationship of that to generally believed causes of the light variation.
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    Photometric study of the binary system V397 cephei
    (Oxford Univ Press, 2005) Bulut, I; Demircan, O; Budding, E; Erdem, A; Çiçek, C; Esenoglu, H; Soydugan, F
    The first ground-based UBV observations (2001, Inf. Bull. Variable Stars, 5129) of V397 Cep were analyzed by using the Wilson-Devinney method, and the results were compared with others in the literature. A consistent geometry with a photometric mass-ratio close to unity and an eccentric orbit of e similar or equal to 0.13 was found. The longitude of the periastron (omega) was found significantly different for two different light curves, which is strongly suggestive of an apsidal motion with a period of about 300 yr. This makes V397 Cep an important candidate for studies of apsidal motion.
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    The close binary system EG cephei
    (Wiley-V C H Verlag Gmbh, 2005) Erdem, A; Budding, E; Demircan, O; Degirmenci, OL; Gülmen, Ö; Sezer, C
    New light curves and available times of minima of a beta Lyr system EG Cep were analysed to deduce more information on the nature of the system. The main U-shaped (O - C) variation was interpreted in terms of the mass transfer and mass loss in the system. The same variation was also considered as a part of a sinusoidal variation and thus interpreted in terms of a light-time effect due to an unseen component in the system. New B and V light curves were analyzed with different fitting procedures, and there is general agreement that both stars must be very close to each other and to stability limits. A model that fits all the data well has a near main sequence primary and a secondary star that is overflowing matter towards it. This secondary is also reasonably close to main sequence conditions. The configuration thus appears to be a (relatively uncommon) ' Case A ' type evolving Algol and raises interesting questions about such interactive evolution and potentially useful tests of theory.
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    UBV photometry of the massive eclipsing binary TT Aur
    (C S I R O Publishing, 2001) Özdemir, S; Ak, H; Tanriver, M; Gülseçen, H; Gülseçen, S; Saygaç, AT; Budding, E
    UBV observations of the massive binary system TT Aur were carried out mainly at the Turkish National Observatory (TUG). These observations, together with IUE spectra and times of eclipse minima collected from the literature, were used to study the system parameters. Simultaneous solution of the light curves by the Wilson-Devinney code allows a semi-detached configuration with a slightly larger Roche-lobe filling secondary. This picture is supported by other evidence. The shoulders of the primary minimum suggest some excess absorption, in keeping with circumstellar material in the form of a disk-like structure around the primary component. The deeper primary minimum in the U filter may indicate a hotter region on the secondary-facing hemisphere of the primary. The period variation of the system can also be related to the possible existence of a third component in a circular orbit around the system. An alternative. detached representation is also considered using optimal curve-fitting techniques. We appeal for further observations to help resolve some outstanding issues in this interesting massive binary.