Search Publications
Dependence of Heliospheric Lyα Absorption on the Interstellar Magnetic Field
Wood, Brian E.; Linsky, Jeffrey L.; Izmodenov, Vladislav V. +1 more
We use newly developed three-dimensional kinetic MHD models of the heliosphere to predict heliospheric H I Lyα absorption for various lines of sight. These predictions are compared with actual Lyα spectra from the Hubble Space Telescope, many of which have yielded previous detections of heliospheric absorption. We find that the absorption predicte…
Multiobject Spectroscopy of Young Star Clusters in NGC 4676
Kewley, Lisa J.; Chambers, Kenneth C.; Barnes, Joshua E. +1 more
Galaxy interactions are known to trigger starbursts. The young star clusters formed in mergers may be young globular clusters. The ages of these young star clusters yield the timing of interaction-triggered star formation and provide an important way to reconstruct the history of merging galaxies. Here we present the first results from our investi…
Are Moreton Waves Coronal Phenomena?
Balasubramaniam, K. S.; Pevtsov, A. A.; Neidig, D. F.
We report on permeability characteristics of the upper solar atmosphere due to the progression of a Moreton wave. An exceptional Moreton wave is tracked to cover most of the Sun, following an unusually large solar X-ray flare observed on 2003 October 29. Using Hα intensity and Doppler measurements, the Moreton wave is tracked for as long as 12 min…
INTEGRAL Spectral Variability Study of the Atoll 4U 1820-30: First Detection of Hard X-Ray Emission
Ubertini, P.; Bazzano, A.; Tarana, A. +1 more
We study the 4-200 keV spectral and temporal behavior of the low-mass X-ray binary 4U 1820-30 with INTEGRAL during 2003-2005. This source as been observed in both the soft (banana) and hard (island) spectral states. A high-energy tail, above 50 keV, in the hard state has been observed for the first time. This places the source in the category of X…
Magnetic Field Properties of Flux Cancellation Sites
Kubo, M.; Shimizu, T.
It has been frequently observed in longitudinal magnetograms that magnetic elements disappear when a magnetic polarity element approaches and collides with another polarity element. We examine 12 collision events observed with the Advanced Stokes Polarimeter. We find formation of new magnetic connection between the colliding opposite polarity elem…
Evolution of Field Spiral Galaxies up to Redshifts z = 1
Böhm, Asmus; Ziegler, Bodo L.
We have gained intermediate-resolution spectroscopy with the FORS instruments of the Very Large Telescope (VLT) and high-resolution imaging with the Advanced Camera for Surveys aboard HST for a sample of 220 distant field spiral galaxies within the FORS Deep Field and William Herschel Deep Field. Spatially resolved rotation curves were extracted a…
Comparative Study of the Initial Spikes of Soft Gamma-Ray Repeater Giant Flares in 1998 and 2004 Observed with Geotail: Do Magnetospheric Instabilities Trigger Large-Scale Fracturing of a Magnetar's Crust?
Kawai, N.; Tanaka, Y. T.; Yoshikawa, I. +5 more
We present the unsaturated peak profile of the giant flare from SGR 1900+14 on 1998 August 27. This was obtained by the particle counters of the Low Energy Particles instrument on board the Geotail spacecraft. The observed peak profile revealed four characteristic features: an initial steep rise, an intermediate rise to the peak, an exponential de…
The AGN Nature of 11 out of 12 Swift/RXTE Unidentified Sources through Optical and X-Ray Spectroscopy
Palazzi, E.; Minniti, D.; Masetti, N. +9 more
The Swift Burst Alert Telescope (BAT) is performing a high Galactic latitude survey in the 14-195 keV band at a flux limit of ~10-11 ergs cm-2 s-1, leading to the discovery of new high-energy sources, most of which have not yet been properly classified. A similar work has also been performed with the RXTE slew surv…
Demonstrating the Negligible Contribution of Optical HST ACS Galaxies to Source-subtracted Cosmic Infrared Background Fluctuations in Deep Spitzer IRAC Images
Kashlinsky, A.; Arendt, R. G.; Moseley, S. H. +1 more
We study the possible contribution of optical galaxies detected with the Hubble ACS instrument to the near-IR cosmic infrared (CIB) fluctuations in deep Spitzer images. The Spitzer data used in this analysis are obtained in the course of the GOODS project, from which we select four independent 10'×10' regions observed at both…
Chromospheric Evaporation in a Remote Solar Flare-like Transient Observed at High Time Resolution with SOHO's CDS and RHESSI
Brosius, Jeffrey W.; Holman, Gordon D.
We present EUV light curves and Doppler velocity measurements for a small, remote flarelike transient observed at high time resolution (9.8 s) with SOHO's CDS during a GOES M1.6 solar flare. The EUV observations include a brief precursor and an impulsive peak followed by a more gradual rise and decline of emission. Hard X-ray light curves obtained…