Search Publications
A soft solid surface on Titan as revealed by the Huygens Surface Science Package
Banaszkiewicz, Marek; Zarnecki, John C.; Lorenz, Ralph D. +23 more
The surface of Saturn's largest satellite-Titan-is largely obscured by an optically thick atmospheric haze, and so its nature has been the subject of considerable speculation and discussion. The Huygens probe entered Titan's atmosphere on 14 January 2005 and descended to the surface using a parachute system. Here we report measurements made just a…
Density-potential pairs for spherical stellar systems with Sérsic light profiles and (optional) power-law cores
Graham, Alister W.; Terzić, Balša
Popular models for describing the luminosity-density profiles of dynamically hot stellar systems (e.g. Jaffe, Hernquist, Dehnen) were constructed with the desire to match the deprojected form of an R1/4 light profile. Real galaxies, however, are now known to have a range of different light-profile shapes that scale with mass. Consequent…
A model of the Alfvén speed in the solar corona
Mann, G.; Warmuth, A.
We present an analytic model of the Alfvén speed vA in the solar corona. The coronal magnetic field is modeled by a radial component representing the global field and by a dipole representing an active region. The free parameters of the model are constrained by actual observations of solar magnetic fields and coronal electron densities.…
X-Ray/Ultraviolet Campaign on the Mrk 279 AGN Outflow: Constraining Inhomogeneous Absorber Models
Kriss, Gerard A.; Kaastra, Jelle; Korista, Kirk T. +3 more
We investigate the applicability of inhomogeneous absorber models in the formation of active galactic nucleus outflow absorption troughs. The models we explore are limited to monotonic gradients of absorbing column densities in front of a finite emission source. Our main finding is that simple power-law and Gaussian distributions are hard-pressed …
Near-infrared (0.8-4.0 µm) spectroscopy of Mimas, Enceladus, Tethys, and Rhea
Brown, R. H.; Emery, J. P.; Burr, D. M. +2 more
Spectral measurements from the ground in the time leading up to the Cassini mission at Saturn provide important context for the interpretation of the forthcoming spacecraft data. Whereas ground-based observations cannot begin to approach the spatial scales Cassini will achieve, they do possess the benefits of better spectral resolution, a broader …
Far-Ultraviolet Spectroscopy of Magnetic Cataclysmic Variables
Szkody, Paula; Sion, Edward M.; Gänsicke, Boris T. +4 more
We have obtained Hubble Space Telescope (HST) STIS data for a total of 11 polars as part of a program aimed at compiling a homogeneous database of high-quality far-ultraviolet (FUV) spectra for a large number of cataclysmic variables (CVs). Of the 11 polars, eight were found in a state of low accretion activity (V347 Pav, VV Pup, V834 Cen, BL Hyi,…
Turbulence-driven Solar Wind Heating and Energization of Pickup Protons in the Outer Heliosphere
Isenberg, Philip A.
We improve and extend the ``dominant turbulence'' model of Isenberg et al., which describes the turbulent heating of the distant solar wind by the dissipation of wave energy generated by the isotropization of interstellar pickup protons. We first modify some of the detailed expressions in Isenberg et al. to fully incorporate the effects of wave di…
X-rays from accretion shocks in T Tauri stars: The case of BP Tau
Schmitt, J. H. M. M.; Ness, J. -U.; Robrade, J. +2 more
We present an XMM-Newton observation of the classical T Tauri star BP Tau. In the XMM-Newton RGS spectrum the O vii triplet is clearly detected with a very weak forbidden line indicating high plasma densities and/or a high UV flux environment. At the same time concurrent UV data point to a small hot spot filling factor suggesting an accretion funn…
Ly-α and ultraviolet emission from high-redshift gamma-ray burst hosts: to what extent do gamma-ray bursts trace star formation?
Östlin, G.; Jóhannesson, G.; Watson, D. +9 more
We report the result of a search for Lyα emission from the host galaxies of the gamma-ray bursts (GRBs) 030226 (z= 1.986), 021004 (z= 2.335) and 020124 (z= 3.198). We find that the host galaxy of GRB 021004 is an extended (around 8 kpc) strong Lyα emitter with a rest-frame equivalent width (EW) of 68+12-11Å, and a star format…
Local Correlation Tracking and the Magnetic Induction Equation
Schuck, P. W.
Recently, local correlation tracking has been applied to magnetograms to estimate photospheric velocities. This Letter demonstrates that local correlation tracking is inconsistent with the magnetic induction equation, which governs the temporal evolution of the photospheric magnetograms. A modified formulation, consistent with the magnetic inducti…