Search Publications
Enceladus: The likely dominant nitrogen source in Saturn's magnetosphere
Johnson, R. E.; Sittler, E. C.; Smith, H. T. +7 more
The spatial distribution of N + in Saturn's magnetosphere obtained from Cassini Plasma Spectrometer (CAPS) data can be used to determine the spatial distribution and relative importance of the nitrogen sources for Saturn's magnetosphere. We first summarize CAPS data from 15 orbits showing the spatial and energy distribution of the nitro…
The Young Stellar Population of NGC 4214 as Observed with the Hubble Space Telescope. II. Results
Úbeda, Leonardo; MacKenty, John W.; Maíz-Apellániz, Jesús
We present the results of a detailed UV-optical study of the nearby dwarf starburst galaxy NGC 4214 using multifilter Hubble Space Telescope WFPC2 and STIS photometry. The stellar extinction is found to be quite patchy, with some areas having values of E(4405-5495)<0.1 mag and others, associated with star-forming regions, much more heavily obsc…
Spectral shape of the UV ionizing background and He II absorption at redshifts 1.8 < z < 2.9
Reimers, D.; Levshakov, S. A.; Agafonova, I. I. +4 more
Aims:The shape of the UV ionizing background is reconstructed from optically thin metal absorption-line systems identified in spectra of
Methods: The systems are analyzed by means of the Monte Carlo…
Asymmetry and Variability in the HH 30 Circumstellar Disk
Stapelfeldt, Karl R.; Watson, Alan M.
We consider optical and near-infrared images of the edge-on disk surrounding the young stellar object HH 30 taken with the Hubble Space Telescope at 18 epochs from 1994 to 2005. These images allow us to study asymmetry and variability in the disk. The lateral brightness asymmetry in the upper nebula, first seen to strongly vary in 1998, continues …
Initial Results on Line-of-Sight Field Calibrations of SP/NFI Data Taken by SOT/Hinode
Moon, Yong-Jae; Tsuneta, Saku; Chae, Jongchul +13 more
We present initial results on the line-of-sight field calibration of the two kinds of Stokes I and V data taken by the Solar Optical Telescope on the satellite Hinode: spectral profiles of Stokes I and V parameters recorded on the Spectro-polarimeter (SP), and monochromatic images of the same parameters recorded on the Narrow-band Filter Imager (N…
Absorption of MARSIS radar signals: Solar energetic particles and the daytime ionosphere
Espley, Jared R.; Plaut, Jeffrey J.; Farrell, William M. +5 more
We present observations from the subsurface sounding mode of the MARSIS instrument onboard Mars Express that imply radar wave absorption because of increased amounts of ionization in the upper Martian atmosphere during the fall of 2005. On at least two occasions these radar disruptions lasted for several days and we find that these periods are cor…
Two newly identified, relatively old star clusters in the Small Magellanic Cloud
Piatti, Andrés E.; Sarajedini, Ata; Geisler, Doug +2 more
We present the results on the age and metallicity estimates of the Small Magellanic Cloud (SMC) clusters L110, L112 and L113 obtained from CCD Washington CT1 photometry. We confirm L113 as a relatively old and metal-poor cluster, and report for the first time that L110 and 112 are also relatively old clusters (t~ 6.5 Gyr). Their derived…
The Case for Optically Thick High-Velocity Broad-Line Region Gas in Active Galactic Nuclei
Gaskell, C. Martin; Snedden, Stephanie A.
A combined analysis of the profiles of the main broad quasar emission lines in both Hubble Space Telescope and optical spectra shows that while the profiles of the strong UV lines are quite similar, there is frequently a strong increase in the Lyα/Hα ratio in the high-velocity gas. We show that the suggestion that the high-velocity gas is opticall…
Global Coronal Mass Ejections
Zhukov, Andrei N.; Veselovsky, Igor S.
Observations of the low solar corona in the extreme ultraviolet and in soft X-rays evidence a close relationship of coronal dimmings and coronal mass ejections (CMEs). Dimmings are usually interpreted as places of plasma evacuation during a CME. We characterize a CME by the apparent angular extent of associated dimmings above the solar limb and de…
Polar wind outflow model: Saturn results
Gombosi, T. I.; Toth, G.; Ridley, A. J. +3 more
The Saturnian system's configuration and dynamics are to a large extent controlled by the planet's rapid rotation and the plasma in the magnetosphere. Therefore characterizing the relative importance of the various plasma sources is crucial to understanding Saturn's magnetosphere. Most research in this area focuses on the addition of mass from the…