KICP Seminars & Colloquia, Summer 2007

Seminar schedule for Summer 2007
June 26, 2007
Astronomy Special Seminar
David Bennett
University of Notre Dame
Extrasolar Planets as a Blemish in Einstein's Telescope   [Abstract]
August 10, 2007
Astronomy Special Seminar
Eduard Vorobyov
University of Western Ontario
The burst mode of accretion in the early evolutionary phase of low-mass protostars   [Abstract]
September 6, 2007
Open Group seminar
Keith J B Grainge
Cavendish Astyrophysics, Cambridge University
AMI - The Arcminute Microkelvin Imager
September 14, 2007
Open Group seminar
Ramprasad Rao
Submillimeter Array (ASIAA)
Magnetic Field Observations of Star Forming Regions with the Submillimeter Array   [Abstract]
 
OPEN GROUP SEMINARS

  • September 6, 2007 | 12:00 PM | LASR Conference Room
    AMI - The Arcminute Microkelvin Imager
    Keith J B Grainge, Cavendish Astyrophysics, Cambridge University
  • September 14, 2007 | 12:00 PM | LASR Conference Room
    Magnetic Field Observations of Star Forming Regions with the Submillimeter Array
    Ramprasad Rao, Submillimeter Array (ASIAA)

    Magnetic fields are believed to play a crucial role in the star formation process. Observations of polarized dust emission from active star forming regions can be used to map the magnetic field. The Submillimeter Array (SMA) was used to obtain maps of the magnetic field in a number of Class 0 and Class I young stellar objects. I will be presenting and discussing some of these results. These observations by the SMA have been successful at providing new evidence that show that the effects of magnetic field are important in these objects.

 
ASTRONOMY SPECIAL SEMINARS

  • June 26, 2007 | 12:00 PM | AAC 123
    Extrasolar Planets as a Blemish in Einstein's Telescope
    David Bennett, University of Notre Dame

    TBA
  • August 10, 2007 | 1:00 PM | RI 180
    The burst mode of accretion in the early evolutionary phase of low-mass protostars
    Eduard Vorobyov, University of Western Ontario

    We present new numerical simulations in the thin-disk approximation which characterize the burst mode of protostellar accretion. The burst mode begins upon the formation of a centrifugally balanced disk around a newly formed protostar. It is comprised of prolonged quiescent periods of low accretion rate which are punctuated by intense bursts of accretion (typically ~ 10^{-4} Msun yr^{-1}), during which most of the protostellar mass is accumulated. The accretion bursts are associated with the formation of dense protoplanetary embryos, which are later driven onto the protostar by the gravitational torques that develop in the disk. Gravitational instability in the disk is driven by continuing infall from the cloud core envelope. We show that the disk mass always remains significantly less than the central protostar mass throughout this process. The burst phenomenon is robust enough to occur for a variety of initial values of rotation rate, frozen-in (supercritical) magnetic field, and density-temperature relations. Even in cases where the bursts are nearly entirely suppressed, a moderate increase in cloud size or rotation rate can lead to vigorous burst activity. We conclude that most (if not all) protostars undergo a burst mode of evolution during their early accretion history, as inferred empirically from observations of FU Orionis variables.