2003 Robert Cormack Bequest Meeting

The University of Aberdeen

Mon 31 March 2003 (full day)

  • RSE Events Diary .
  • Aberdeen Meeting web page . This annual one-day meeting is intended to enable astronomers and those interested in astronomy in Scotland to present, and to see, a broad selection of what is currently going on in Scottish astronomy. The meeting focuses primarily on research but also encompasses teaching and public understanding initiatives. For further information and to register for this event please contact Professor Graham Hall, FRSE, Professor of Mathematics, Department of Mathematical Sciences, The University of Aberdeen, Meston Building, Aberdeen AB24 3UE Telephone: 01224 272748 Fax: 01224 272607. Lunch will be provided.
  • St.Andrews Astrophysics attendees:
  • J.Barnes --- Starspots on a Contact Binary (talk)
  • M.Dominik --- PLANET microlensing probes of stellar atmospheres (poster)
  • V.Holzwarth --- Transport of angular momentum in magnetic stellar winds (poster)
  • K.Horne --- The Search for Extra-Solar Planets (talk)
  • S.Jeffers --- The Densely Spotted Photosphere of Active Type Stars (poster)
    S.Jeffers --- Theoretical Cratering on Ida,Gaspra,Eros and Mathilde (poster)
  • T.Lloyd Evans --- "Carbon Stars with Enhanced $^{13}$C" (poster)
  • T.McIvor --- Polar fields for AB Dor (poster)
  • R.Stapleton --- not presenting
  • M.Truss --- The quiescence of dwarf novae (talk or poster)
  • C.Walker --- The Structure of Circumstellar Disks around Brown Dwarfs (talk or poster)
  • C.Leigh --- TBD (Reflected light from Hot Jupiters) (poster?)
  • F.Vincent --- not presenting
    not planning to attend: I.Bonnell, P.Clark, S.Kane, K.Rice, R.Wijnands.
    no information: everybody else.
    Abstracts of proposed contributions:
    John Barnes --- Starspots on a Contact Binary (talk)
    Martin Dominik --- PLANET microlensing probes of stellar atmospheres (poster)
    Volkmar Holzwarth --- Transport of angular momentum in magnetic stellar winds (poster)
    The transport of angular momentum by a stellar wind along open magnetic field lines is investigated in the case of rapidly rotating stars to examine whether different field topologies are capable to weaken the dependence of the angular momentum loss rate on the rotation rate in the way needed to model the rapid spindown of stars in young open clusters. To this end, both simple analytical field geometries as well as complex structures based on Zeeman-Doppler images of surface magnetic fields are used in the framework of a stationary model to investigate the principal effects.
    Keith Horne --- The Search for Extra-Solar Planets (talk)
    Sandra Jeffers --- The Densely Spotted Photosphere of Active Type Stars (poster)
    Sandra Jeffers --- Theoretical Cratering on Ida,Gaspra,Eros and Mathilde (poster)
    Chris Leigh --- TBD (Reflected light from Hot Jupiters) (poster?)
    T.Lloyd Evans --- Carbon Stars with Enhanced $^{13}$C (poster)
    Carbon stars usually have $^{12}$C/$^{13}$C of about 30, but some have values of 10 or less. These fall into four discrete groups, of which two may be understood as extrinsic carbon stars which have received processed matter from an initially more massive companion and as Hot-Bottom Burning AGB stars, respectively. The origin of the other two groups, the strong-banded J stars and the related J-silicate stars with O-rich circumstellar shells or disks, remain a puzzle.
    Thomas McIvor --- Polar fields for AB Dor (poster)
    While polar spots are observed on rapidly-rotating cool stars, the nature of the magnetic field in these spots - whether in uniform or mixed polarity - and the consequences for the global topology of the corona are as yet unknown. While Zeeman-Doppler imaging can provide surface magnetic field maps over much of the observed stellar surface, the Zeeman signature is supressed in the dark polar regions. We have determined the effect on the global coronal structure of various models for the polar field of the young, rapid rotator AB Dor. Using Zeeman-Doppler maps of the surface field, we assume the field to be potential and have extrapolated the coronal field. We have also determined the effect on locations of stable gravitational-centrifugal potential minima within the field configurations of each model using a method presented by (Jardine et al.2002). The X-ray emission and rotational modulation for each model has been calculated using a Monte Carlo technique. The results form the field topology, possible prominence sites and X-ray emission compliment each other in the comparisons with observations to give us a clearer picture of what is or is not at pole of AB Dor.
    Mike Truss --- The Quiescence of Dwarf Novae (talk or poster)
    The constant luminosity observed between the outbursts of dwarf novae has been puzzling accretion disc instability theorists for several years. The total energy dissipation rate is expected to increase with increasing surface density and temperature, yet it remains roughly constant. I show that secular changes in the energy dissipation rate brought about by increasing surface density and temperature can be regulated by the response of a critically stable, hot inner region of the accretion disc. The hypothesis is supported by two-dimensional time-dependent numerical models of accretion discs in dwarf novae.
    Christina Walker --- The Structure of Circumstellar Disks around Brown Dwarfs (talk or poster)
    We present synthetic spectra for circumstellar disks that are heated by radiation from a central brown dwarf. In order to reproduce observed near-IR excess emission from candidate brown dwarfs in the Chameleon, IC348, rho Ophiucus, Taurus and Trapezium clusters, we require circumstellar disks with large scaleheights. Our models suggest disk scaleheights for brown dwarfs in excess of three timesare those derived for T-Tauri disks. The larger scaleheights in brown dwarf disks are naturally explained by hydrostatic structure models of a passively heated disk around a very low mass star. If the near-IR excess emission observed from brown dwarfs is indeed due to circumstellar disks, then the large scaleheights we find will have a significant impact on the optical and near-IR detectability of such systems. Our radiation transfer calculations show that such highly flared disks around brown dwarfs will result in a large fraction of obscured sources due to extinction of direct starlight by the disk over a wide range of sightlines. We show that the obscured fraction for brown dwarfs may be as high as 70% depending on disk mass and size. This compares with less than 20% for a typical classical T-Tauri star.
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    Keith Horne (kdh1@st-andrews.ac.uk)