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Electron temperature anisotropy constraints in the solar wind
Maksimovic, Milan; Marsch, Eckart; Scime, Earl E. +3 more
We have performed a statistical study of a substantial amount of electron data acquired in the solar wind to understand the constraints on electron temperature anisotropy by plasma instabilities and Coulomb collisions. We use a large data set of electron measurements from three different spacecraft (Helios I, Cluster II, and Ulysses) collected in …
Evidence of Cosmic Evolution of the Stellar Initial Mass Function
van Dokkum, Pieter G.
Theoretical arguments and indirect observational evidence suggest that the stellar IMF may evolve with time, such that it is more weighted toward high-mass stars at higher redshift. Here we test this idea by comparing the rate of luminosity evolution of massive early-type galaxies in clusters at 0.02 <= z<= 0.83 to the rate of their color ev…
CoRoT sounds the stars: p-mode parameters of Sun-like oscillations on HD 49933
Auvergne, M.; Baudin, F.; Jiménez-Reyes, S. J. +19 more
Context: The first asteroseismology results from CoRoT are presented, on a star showing Sun-like oscillations. We have analyzed a 60 day lightcurve of high-quality photometric data collected by CoRoT on the F5 V star HD 49933. The data reveal a rich spectrum of overtones of low-degree p modes.
Aims: Our aim was to extract robust estimates of t…
Observation of energetic electrons within magnetic islands
Daly, P. W.; Khotyaintsev, Y.; Vaivads, A. +10 more
Magnetic reconnection is the underlying process that releases impulsively an enormous amount of magnetic energy in solar flares , flares on strongly magnetized neutron stars and substorms in the Earth's magnetosphere. Studies of energy release during solar flares, in particular, indicate that up to 50% of the released energy is carried by accelera…
The Low-z Intergalactic Medium. III. H I and Metal Absorbers at z < 0.4
Shull, J. Michael; Danforth, Charles W.
We conduct an ultraviolet (HST and FUSE) spectroscopic survey of H I (Lyman lines) and seven metal ions (O VI, N V, C IV, C III, Si IV, Si III, Fe III) in the low-redshift IGM at z < 0.4. We analyzed 650 Lyα absorbers over redshift path length Δ z = 5.27, detecting numerous absorbers: 83 O VI systems, 39 C III, 53 Si III, 24 C IV, 24 N V, and s…
Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity
Faucher-Giguère, Claude-André; Hernquist, Lars; Lidz, Adam +1 more
We investigate the implications of the intergalactic opacity for the evolution of the cosmic UV luminosity density and its sources. Our main constraint is our measurement of the Lyα forest opacity at redshifts 2 <= z <= 4.2 from 86 high-resolution quasar spectra. In addition, we impose the requirements that H I must be reionized by z = 6 and…
A model of Titan's aerosols based on measurements made inside the atmosphere
Tomasko, M. G.; Doose, L.; Engel, S. +5 more
The descent imager/spectral radiometer (DISR) instrument aboard the Huygens probe into the atmosphere of Titan measured the brightness of sunlight using a complement of spectrometers, photometers, and cameras that covered the spectral range from 350 to 1600 nm, looked both upward and downward, and made measurements at altitudes from 150 km to the …
Meeting the Cool Neighbors. X. Ultracool Dwarfs from the 2MASS All-Sky Data Release
Kirkpatrick, J. Davy; Reid, I. Neill; Lowrance, Patrick +5 more
Using data from the 2 Micron All Sky Survey All-Sky Point Source Catalogue, we have extended our census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitude of 15°. Starting with an initial catalog of 2,139,484 sources, we have winnowed the sample to 467 candidate late-type M or L dwarfs within 20 pc of the Sun. Fi…
The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei
Maiolino, Roberto; Brandt, W. N.; Kaspi, Shai +2 more
We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3-3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/LEdd) and the hard X-ray photon index (Γ) for 35 moderate- to high-lum…
The EPIC-MOS particle-induced background spectra
Kuntz, K. D.; Snowden, S. L.
Context: To analyze diffuse emission that fills the field of view, one must accurately characterize the instrumental backgrounds. For the XMM-Newton EPIC-MOS instrument these backgrounds include a temporally variable “quiescent” component, as well as the strongly variable soft proton contamination.
Aims: We have characterized the spectral and …