Search Publications
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…
The Temporal Evolution of Coronal Loops Observed by GOES SXI
López Fuentes, M. C.; Klimchuk, J. A.; Mandrini, C. H.
We study the temporal evolution of coronal loops using data from the Solar X-Ray Imager (SXI) on board the Geosynchronous Operational Environmental Satellite 12 (GOES-12). This instrument provides continuous soft X-ray observations of the solar corona at a high temporal cadence permitting detailed study of the full lifetime of each of several coro…
Evidence of Stellar-driven Outflows from the Classical T Tauri Star RY Tau
Gómez de Castro, Ana I.; Verdugo, Eva
RY Tau is a rapidly rotating classical T Tauri star observed close to edge-on. The combination of new HST/STIS observations obtained in 2001 with HST/GHRS archive data from 1993 has allowed us to get, for the first time, information on the thermal structure and velocity of the wind. The repeated observations of the Si III] and C III] lines show a …
Determining the Source of Coronal Helicity through Measurements of Braiding and Spin Helicity Fluxes in Active Regions
Barnes, G.; Longcope, D. W.; Ravindra, B.
Magnetic helicity has become a valuable tool for understanding the energetics and dynamics of coronal magnetic fields. Recently, long time sequences of magnetograms have been used to measure the flux of helicity into active region coronae. We demonstrate how this helicity flux can be usefully decomposed into contributions of differing origin, call…
Discovery of an Extended Debris Disk around the F2 V Star HD 15745
Kalas, Paul; Fitzgerald, Michael P.; Graham, James R. +1 more
Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we have discovered dust-scattered light from the debris disk surrounding the F2 V star HD 15745. The circumstellar disk is detected between 2.0" and 7.5" radius, corresponding to 128-480 AU radius. The circumstellar disk morphology is asymmetric about the star, resembling a f…