Search Publications
Plasma sheet formation during long period of northward IMF
Phan, Tai D.; Øieroset, Marit; Raeder, Joachim +2 more
We have studied the entry paths of solar wind plasma into the magnetosphere during an extended period of northward IMF using an OpenGGCM MHD simulation of the cold dense plasma sheet (CDPS) event observed on October 23, 2003 by the Cluster spacecraft. We find that high-latitude reconnection occurs tailward of both cusps between the IMF and geomagn…
Discovery of a Primitive Damped Lyα Absorber near an X-Ray-bright Galaxy Group in the Virgo Cluster
Bowen, David V.; Tripp, Todd M.; Jenkins, Edward B. +3 more
We present a new ultraviolet echelle spectrum of PG 1216+069, obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, that reveals damped Lyα absorption, as well as O I, C II, Si II, and Fe II absorption lines, at zabs=0.00632 near the NGC 4261 galaxy group in the periphery of the Virgo Cluster. The a…
The Optical and Ultraviolet Spectral Energy Distributions of Short-Period Black Hole X-Ray Transients in Outburst
Hynes, R. I.
We compile optical and UV spectra of a sample of ``typical'' short-period black hole X-ray transients in outburst. We also survey determinations of interstellar extinction and distance to deredden spectra and compare absolute fluxes. Hence, we perform a comparative study of the broadband spectral energy distributions (SEDs). We find that, given su…
The Stellar Populations in the Central Parsecs of Galactic Bulges
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +5 more
We present Hubble Space Telescope blue spectra at intermediate spectral resolution for the nuclei of 23 nearby disk galaxies. These objects were selected to have nebular emission in their nuclei and span a range of emission-line classifications, as well as Hubble types. In this paper we focus on the stellar population as revealed by the continuum …
How typical are atypical current sheets?
Balogh, A.; Zhang, T. L.; Klecker, B. +7 more
Using multi-satellite Cluster magnetic field data, we statistically examined how often an atypical, i.e., non-Harris type, current sheet is formed. We found that a cross-tail current sheet with an off-equatorial current density maximum, indicating bifurcation, is frequently formed in thin current sheets with a half thickness of ~1500 km. The occur…
The White Dwarf Cooling Sequence in NGC 6791
Anderson, Jay; Salaris, Maurizio; Bedin, Luigi R. +4 more
In the old, populous, and metal-rich open cluster NGC 6791, we have used deep Hubble Space Telescope Advanced Camera for Surveys images to track the white dwarf cooling sequence down to mF606W~=28.5. The white dwarf luminosity function shows a well-defined peak at mF606W~=27.4 and a bending to the blue in the color-magnitude …
The XMM Large-Scale Structure survey: an initial sample of galaxy groups and clusters to a redshift z < 0.6*
Altieri, B.; Valtchanov, I.; Pierre, M. +14 more
We present X-ray and optical spectroscopic observations of 12 galaxy groups and clusters identified within the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey. Groups and clusters are selected as extended X-ray sources from a 3.5 deg2XMM image mosaic above a flux limit 8 × 10-15 erg s-1 cm-2 …
GRB 020410: A Gamma-Ray Burst Afterglow Discovered by Its Supernova Light
Garnavich, Peter; Tanvir, Nial; Hjorth, Jens +19 more
We present the discovery and monitoring of the optical transient (OT) associated with GRB 020410. The fading OT was found by Hubble Space Telescope (HST) observations taken 28 and 65 days after burst at a position consistent with the X-ray afterglow, making this the first time that the optical afterglow of a gamma-ray burst (GRB) has been discover…
Titan's ionosphere: Model comparisons with Cassini Ta data
Coates, A. J.; Luhmann, J. G.; Wahlund, J. -E. +13 more
On October 26, 2004, during its first encounter with Titan (Ta), the Cassini Orbiter moved from the dayside to the nightside with a closest approach altitude of 1174 km. In situ measurements of the main part of Titan's ionosphere were made by the Langmuir probe on the Cassini Radio and Plasma Wave Experiment (RPWS), while the Ion and Neutral Mass …
Cluster observations of traveling compression regions in the near-tail
Balogh, A.; Glassmeier, K. -H.; Owen, C. J. +6 more
Examination of Cluster measurements has revealed the presence of traveling compression regions (TCRs) in the lobes of the Earth's magnetotail at X ∼ -11-19 RE. These TCRs strongly resemble those observed in the more distant tail, but their mean duration is only ∼35 s as compared with ∼160 s for the TCRs in the distant tail. Furthermore,…