Search Publications
Massive Star Clusters in Ongoing Galaxy Interactions: Clues to Cluster Formation
Keel, William C.; Borne, Kirk D.
We present HST WFPC2 observations, supplemented by ground-based Hα data, of the star-cluster populations in two pairs of interacting galaxies selected for being in very different kinds of encounters seen at different stages. Dynamical information and n-body simulations provide the details of encounter geometry, mass ratio, and timing. In NGC 5752/…
Abundance Anomalies in CP Crucis (Nova Crux 1996)
Lumsden, S. L.; Krautter, Joachim; Gehrz, R. D. +15 more
We present spectroscopic observations of the classical nova CP Crucis (Nova Crux 1996) obtained with the Infrared Space Observatory Short Wavelength Spectrometer (ISO SWS) and the Anglo-Australian Telescope using both the Infrared Imaging Spectrograph and the Royal Greenwich Observatory Spectrograph. From the expansion parallax, we find that CP Cr…
The Origin of High-Energy 3He-rich Solar Particle Events
Torsti, J.; Kocharov, L.
Observed isotope abundances in the energy range >15 MeV nucleon-1 by the ERNE instrument on board Solar and Heliospheric Observatory show a group of high-energy 3He-rich solar particle events that apparently has not been identified in earlier observations. Those events are observed to start well after the flare, when the a…
The Dusty Environment of Quasars: Far-Infrared Properties of Optical Quasars
Grazian, Andrea; La Franca, Fabio; Cristiani, Stefano +2 more
We present Infrared Space Observatory (ISO) far-IR photometry of a complete subsample of optically selected bright quasars belonging to two complete surveys selected through multicolor (U, B, V, R, I) techniques. The ISOPHOT camera on board the ISO satellite was used to target these quasars at wavelengths of 7.3, 11.5, 60, 100, and 160 µm. A…
On the Extreme-Ultraviolet/Ultraviolet Plasma Diagnostics for Nitrogen-like Ions from Spectra Obtained By SOHO/SUMER
Dwivedi, B. N.; Mohan, A.; Landi, E.
In this work we discuss the potential for plasma diagnostics of forbidden transitions from the ground levels in the nitrogen-like ions: Al VII, Si VIII, P IX, S X, Ar XII, K XIII, and Ca XIV. We also study the lines emitted by n=3 levels of Si VIII. These transitions fall in the UV spectral range and have been recently observed by the SOHO/SUMER i…
Particle drift effects on cosmic ray modulation during solar maximum
Ferreira, S. E. S.; Potgieter, M. S.; Heber, B.
A fully time-dependent cosmic ray modulation model based on the numerical solution of Parker's transport equation is used to study the amount of particle drifts needed to explain the observed 1.2 GV electron to Helium ratio at Earth and the 2.5 GV electron to proton ratio (e/p) observed by the KET instrument on the Ulysses spacecraft. The model su…
Multiwavelength Spectroscopy of the Bipolar Outflow from Cepheus E
Smith, Michael D.; Eislöffel, Jochen; Froebrich, Dirk
Cepheus E is the site of an exceptional example of a protostellar outflow with a very young dynamical age and extremely high near-infrared luminosity. We combine molecular spectroscopic data from the submillimeter to the near-infrared in order to interpret the rotational excitation of CO and the rovibrational excitation of H2. We conclu…
Magnetic helicity transport in corona and filament eruptions
Romano, P.; Contarino, L.; Zuccarello, F.
Using a 28-hour time series of line-of-sight magnetograms taken by the Michelson Doppler Imager (MDI), we determined the magnetic flux variations and the rate of magnetic helicity transport at the footpoints of a filament in active region NOAA 8375. The filament was characterized by a positive helicity change due to shearing motions in both footpo…
Positions of Uranus and Its Main Satellites
Veiga, Carlos H.; Vieira Martins, Roberto; Andrei, Alexandre H.
We present astrometric positions of Uranus and its satellites Miranda, Ariel, Umbriel, Titania, and Oberon, determined in the International Celestial Reference System, from 1758 frames observed over 105 nights between 1982 and 1998. All the positions of the satellites were reduced using secondary frames referred to the Tycho-2 Catalogue from photo…
Cosmic rays tracks on the PICsIT detector
Bird, A. J.; Segreto, A.; Bazzano, A. +3 more
Since the first in orbit activation of the PICsIT detector, frequent spikes have been noticed in its count rate. Tracks in the detector images, corresponding to the spikes, indicate that these events are generated by interaction of cosmic rays with the detector plane.
Since these events constitute a significant fraction of the instrument back…