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Cassini UVIS observations of Europa's oxygen atmosphere and torus
Hendrix, A. R.; Shemansky, Donald E.; Hansen, Candice J.
Observations of the Europa environment using the Cassini UltraViolet Imaging Spectrograph (UVIS) show the presence of an extended atomic oxygen atmosphere in addition to the bound molecular oxygen atmosphere first detected by Hubble Space Telescope in 1994 [D.T. Hall, D.F. Strobel, P.D. Feldman, M.A. McGrath, H.A. Weaver, 1995, Detection of an oxy…
A Solar Minimum Irradiance Spectrum for Wavelengths below 1200 Å
Warren, Harry P.
NRLEUV represents an independent approach to modeling the Sun's EUV irradiance and its variability. Our model utilizes differential emission measure distributions derived from spatially and spectrally resolved solar observations, full-disk solar images, and a database of atomic physics parameters to calculate the solar EUV irradiance. In this pape…
Ejection of nitrogen from Titan's atmosphere by magnetospheric ions and pick-up ions
Luhmann, J. G.; Johnson, R. E.; Leblanc, F. +3 more
A 3-D Monte Carlo model is used to describe the ejection of N and N 2 from Titan due to the interaction of Saturn's magnetospheric N + ions and molecular pick-up ions with its N 2 atmosphere. Based on estimates of the ion flux into Titan's corona, atmospheric sputtering is an important source of both atomic and mol…
Proton and helium release times in SEP events observed with SOHO/ERNE
Laitinen, T.; Valtonen, E.; Huttunen-Heikinmaa, K.
We determine the proton and helium nuclei release times at the Sun for 25 SEP events within the time period May 8, 1996-June 20, 2001, and compare them to each other. The event onset times at 1 AU are determined with a Poisson-CUSUM method, and the solar release times are obtained by the velocity dispersion analysis. Velocity dispersions were deri…
XMM-Newton and Gemini Observations of Eight RASSCALS Galaxy Groups
Geller, Margaret J.; Mahdavi, Andisheh; Finoguenov, Alexis +2 more
We study the distribution of gas pressure and entropy in eight groups of galaxies belonging to the ROSAT All-Sky Survey/Center for Astrophysics Loose Systems (RASSCALS). We use archival and proprietary XMM-Newton observations, supplementing the X-ray data with redshifts derived from the literature; we also list 127 new redshifts measured with the …
The Stellar Content of Nearby Star-forming Galaxies. III. Unravelling the Nature of the Diffuse Ultraviolet Light
de Mello, Duilia; Aloisi, Alessandra; Meurer, Gerhardt R. +4 more
We investigate the nature of the diffuse intracluster ultraviolet light seen in 12 local starburst galaxies, using long-slit ultraviolet spectroscopy obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST). We take this faint intracluster light to be the field in each galaxy and compare its spectroscop…
The Structural Properties of Isolated Galaxies, Spiral-Spiral Pairs, and Mergers: The Robustness of Galaxy Morphology during Secular Evolution
Conselice, C. J.; Hernández-Toledo, H. M.; Avila-Reese, V. +1 more
We present a structural analysis of nearby galaxies in spiral-spiral pairs in optical BVRI bands and compare them with the structures of isolated spiral galaxies and galaxies in ongoing mergers. We use these comparisons to determine how galaxy structure changes during galaxy interactions and mergers. We analyze light concentration (C), asymmetry (…
The Gamma-Ray Giant Flare from SGR 1806-20: Evidence of Crustal Cracking via Initial Timescales
Kataria, D. O.; Zane, Silvia; Schwartz, Steven J. +6 more
Soft γ-ray repeaters (SGRs) are neutron stars that emit short (<~1 s) and energetic (<~1042 ergs s-1) bursts of soft γ-rays. Only four of them are currently known. Occasionally, SGRs have been observed to emit much more energetic ``giant flares'' (~1044-1045 ergs s-1). These are exceptio…
XMM-Newton study of the two-dimensional structure of the REFLEX-DXL galaxy clusters
Zhang, Y. -Y.; Finoguenov, A.; Böhringer, H.
We carry out a two-dimensional study of temperature, entropy, and pressure distributions in a nearly volume-limited subsample of REFLEX clusters at redshift 0.3, the REFLEX-DXL. We use the observations gained by XMM-Newton, which cover the central 1{-}2× r500. We define the substructure in both entropy and pressure as a deviation from t…
Old Globular Clusters Masquerading as Young in NGC 4365?
Forbes, Duncan A.; Brodie, Jean P.; Beasley, Michael A. +5 more
High signal-to-noise ratio, low-resolution spectra have been obtained for 22 globular clusters (GCs) in NGC 4365. Some of these were selected as probable representatives of an intermediate-age (2-5 Gyr), extremely metal-rich GC subpopulation. The presence of such a subpopulation had been inferred from the unusual optical and near-infrared color di…