Search Publications
Observing the Unobservable? Modeling Coronal Cavity Densities
de Toma, G.; Gibson, S. E.; Fan, Y. +1 more
Prominence cavities in coronal helmet streamers are readily detectable in white-light coronagraph images, yet their interpretation may be complicated by projection effects. In order to determine a cavity's density structure, it is essential to quantify the contribution of noncavity features along the line of sight. We model the coronal cavity as a…
Absorption features in the spectra of X-ray bursting neutron stars
Rauch, T.; Werner, K.; Suleimanov, V.
Context: The discovery of photospheric absorption lines in XMM-Newton spectra of the X-ray bursting neutron star in
Seismic Halos around Active Regions: A Magnetohydrodynamic Theory
Hanasoge, Shravan M.
Comprehending the manner in which magnetic fields affect propagating waves is a first step toward constructing accurate helioseismic models of active region subsurface structure and dynamics. Here we present a numerical method for computing the linear interaction of waves with magnetic fields embedded in a solar-like stratified background. The ide…
Chandra spectroscopy of the hot star βCrucis and the discovery of a pre-main-sequence companion
Miller, Nathan A.; Cohen, David H.; Jensen, Eric L. N. +2 more
In order to test the O star wind-shock scenario for X-ray production in less luminous stars with weaker winds, we made a pointed 74-ks observation of the nearby early B giant, βCrucis (βCru B0.5III), with the Chandra High Energy Transmission Grating Spectrometer. We find that the X-ray spectrum is quite soft, with a dominant thermal component near…
Surface Brightness Profiles of Composite Images of Compact Galaxies at z ≃ 4-6 in the Hubble Ultra Deep Field
Hathi, N. P.; Keel, W. C.; Jansen, R. A. +4 more
The Hubble Ultra Deep Field (HUDF) contains a significant number of B-, V-, and i'-band dropout objects, many of which were recently confirmed to be young star-forming galaxies at z ≃ 4-6. These galaxies are too faint individually to accurately measure their radial surface-brightness profiles. Their average light profiles are potentially of great …
Sputtering of ice grains and icy satellites in Saturn's inner magnetosphere
Johnson, R. E.; Sittler, E. C.; Smith, H. T. +3 more
Icy grains and satellites orbiting in Saturn's magnetosphere are immersed in a plasma that sputters their surfaces. This limits the lifetime of the E-ring grains and ejects neutrals that orbit Saturn until they are ionized and populate its magnetosphere. Here we re-evaluate the sputtering rate of ice in Saturn's inner magnetosphere using the recen…
Solar wind excitation of Pc5 fluctuations in the magnetosphere and on the ground
Kessel, R. L.
The primary purpose of this paper is to show the importance of solar wind excitation as a source of magnetospheric and ground Pc5 fluctuations. In particular, we show that pressure fluctuations, a nearly ubiquitous feature of the solar wind, drive magnetospheric compressional Pc5, whose amplitude and power increase in direct proportion to the ampl…
Deep Chandra Monitoring Observations of NGC 3379: Catalog of Source Properties
Zezas, A.; Gallagher, J.; King, A. R. +11 more
We present the properties of the discrete X-ray sources detected in our monitoring program of the 'typical' elliptical galaxy, NGC 3379, observed with Chandra ACIS-S in five separate pointings, resulting in a co-added exposure of 324 ks. From this deep observation, 132 sources have been detected within the region overlapped by all observations, 98…
High Spatial Velocity Features in the Orion Nebula,
O'Dell, C. R.; Henney, W. J.
We have used widely spaced in time Hubble Space Telescope images to determine tangential velocities of features associated with outflows from young stars. These observations were supplemented by ground-based telescope spectroscopy, and from the resultant radial velocities, space velocities were determined for many outflows. Numerous new moving fea…
The fundamental parameters of the roAp star α Circini
Tuthill, P. G.; Davis, J.; Kurtz, D. W. +12 more
We have used the Sydney University Stellar Interferometer to measure the angular diameter of α Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, α Cir being the brightest member of its class. We used the new and more accurate Hipparcos parallax to determine the radius to be 1.967 ± 0.066 R⊙. W…