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Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
Are Ti44-Producing Supernovae Exceptional?, L.-S. The, Donald D. Clayton, R Diehl, Dieter H. Hartmann, A F. Iyudin, M D. Leising, B S. Meyer, Y Motizuki, V Schönfelder
Are Ti44-Producing Supernovae Exceptional?, L.-S. The, Donald D. Clayton, R Diehl, Dieter H. Hartmann, A F. Iyudin, M D. Leising, B S. Meyer, Y Motizuki, V Schönfelder
Publications
According to standard models supernovae produce radioactive 44Ti, which should be visible in gamma-rays following decay to 44Ca for a few centuries. 44Ti production is believed to be the source of cosmic 44Ca, whose abundance is well established. Yet, gamma-ray telescopes have not seen the expected young remnants of core collapse events. The 44Ti mean life of 89 y and the Galactic supernova rate of 3/100 y imply several detectable 44Ti gamma-ray sources, but only one is clearly seen, the 340-year-old Cas A SNR. Furthermore, supernovae which produce much 44Ti are expected …
Spatially Resolved Mid-Infrared Spectroscopy Of Ngc 1068: The Nature And Distribution Of The Nuclear Material, R. E. Mason, T. R. Geballe, C. Packham, N. A. Levenson, Moshe Elitzur, R. S. Fisher, E. Perlman
Spatially Resolved Mid-Infrared Spectroscopy Of Ngc 1068: The Nature And Distribution Of The Nuclear Material, R. E. Mason, T. R. Geballe, C. Packham, N. A. Levenson, Moshe Elitzur, R. S. Fisher, E. Perlman
Physics and Astronomy Faculty Publications
We present spatially resolved, near-diffraction-limited 10 μm spectra of the nucleus of the Seyfert 2 galaxy NGC 1068, obtained with Michelle, the mid-IR imager and spectrometer on the 8.1 m Gemini North Telescope. The spectra cover the nucleus and the central 6.0” × 0.4” of the ionization cones at a spatial resolution of approximately 0.4” (≈30 pc). The spectra extracted in 0.4” steps along the slit reveal striking variations in continuum slope, silicate feature profile and depth, and fine-structure line fluxes on subarcsecond scales, illustrating in unprecedented detail the complexity of the circumnuclear regions of NGC 1068 at mid-IR …
Near-Infrared And The Inner Regions Of Protoplanetary Disks, Dejan Vinković, Željko Ivezić, Tomislav Jurkić, Moshe Elitzur
Near-Infrared And The Inner Regions Of Protoplanetary Disks, Dejan Vinković, Željko Ivezić, Tomislav Jurkić, Moshe Elitzur
Physics and Astronomy Faculty Publications
We examine the “puffed-up inner disk” model proposed by Dullemond, Dominik, & Natta for explaining the near-IR excess radiation from Herbig Ae/Be stars. Detailed model computations show that the observed near-IR excess requires more hot dust than is contained in the puffed-up disk rim. The rim can produce the observed near-IR excess only if its dust has perfectly gray opacity, but such dust is in conflict with the observed 10 μm spectral feature. We find that a compact (~10 AU), tenuous (τV ≲ 0.4), dusty halo around the disk inner regions contains enough dust to readily explain …
An Explicit Scheme For Multifluid Magnetohydrodynamics, Stephen O'Sullivan, Turlough Downes
An Explicit Scheme For Multifluid Magnetohydrodynamics, Stephen O'Sullivan, Turlough Downes
Articles
When modelling astrophysical fluid flows, it is often appropriate to discard the canonical magnetohydrodynamic approximation, thereby freeing the magnetic field to diffuse with respect to the bulk velocity field. As a consequence, however, the induction equation can become problematic to solve via standard explicit techniques. In particular, the Hall diffusion term admits fast-moving whistler waves which can impose a vanishing time-step limit.Within an explicit differencing framework, a multifluid scheme for weakly ionized plasmas is presented which relies upon a new approach to integrating the induction equation efficiently. The first component of this approach is a relatively unknown method of accelerating …