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Large amplitude solitary waves in and near the EarthÂ’s magnetosphere, magnetopause and bow shock: Polar and Cluster observations
André, M.; Cattell, C.; Dombeck, J. +6 more
Solitary waves with large electric fields (up to 100's of mV/m) have been observed throughout the magnetosphere and in the bow shock. We discuss observations by Polar at high altitudes ( ~ 4-8 RE ), during crossings of the plasma sheet boundary and cusp, and new measurements by Polar at the equatorial magnetopause and by Cluster near the bow shock…
INTEGRAL/SPI ground calibration
Knödlseder, J.; von Kienlin, A.; Bouchet, L. +30 more
Three calibration campaigns of the spectrometer SPI have been performed before launch in order to determine the instrument characteristics, such as the effective detection area, the spectral resolution and the angular resolution. Absolute determination of the effective area has been obtained from simulations and measurements. At 1 MeV, the effecti…
A Hubble Space Telescope Search for Lyman Continuum Emission from Galaxies at 1.1 < z < 1.4
Malkan, Matthew; Webb, Wayne; Konopacky, Quinn
If enough of their Lyman-limit continuum escapes, star-forming galaxies could be significant contributors to the cosmic background of ionizing photons. To investigate this possibility, we obtained the first deep imaging in the far-ultraviolet of 11 bright blue galaxies at intermediate redshift (1.1<z<1.4) with the Space Telescope Imaging Spe…
Solar and Heliospheric Observatory/Coronal Diagnostic Spectrograph and Ground-based Observations of a Two-Ribbon Flare: Spatially Resolved Signatures of Chromospheric Evaporation
Andretta, V.; Teriaca, L.; Falchi, A. +3 more
During a coordinated observing campaign (Solar and Heliospheric Observatory, SOHO JOP 139), we obtained simultaneous spectroheliograms of a solar active region in several spectral lines, sampling levels from the chromosphere to the corona. Ground-based spectroheliograms were acquired at the Dunn Solar Tower of the National Solar Observatory/Sacram…
X-Ray Absorption by the Low-Redshift Intergalactic Medium: A Numerical Study of the Λ Cold Dark Matter Model
Davé, Romeel; Weinberg, David H.; Chen, Xuelei +1 more
Using a hydrodynamic simulation of a cold dark matter universe with a cosmological constant, we investigate the ``X-ray forest'' absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM), at redshift z~0. In agreement with previous studies, we find that O VII and O VIII produce the strongest absorption…
Observation of coronal loop torsional oscillation
Zaqarashvili, T. V.
We suggest that the global torsional oscillation of solar coronal loop may be observed by the periodical variation of a spectral line width. The amplitude of the variation must be maximal at the velocity antinodes and minimal at the nodes of the torsional oscillation. Then the spectroscopic observation as a time series at different heights above t…
The Contribution of Polar Plumes to the Fast Solar Wind
Lemaire, P.; Gabriel, A. H.; Bely-Dubau, F.
The Doppler dimming technique is used for the first time to study ultraviolet polar plumes in the height range of 1.05-1.35 Rsolar, using observations from the spectrometer SUMER on the Solar and Heliospheric Observatory. It is found that, contrary to a number of published suggestions, outflow velocities in the plumes exceed those in th…
Ram pressure stripping and the formation of cold fronts
Churazov, E.; Forman, W.; Heinz, S. +2 more
Chandra and XMM-Newton observations of many clusters reveal sharp discontinuities in the surface brightness, which, unlike shocks, have lower gas temperature on the X-ray brighter side of the discontinuity. For this reason, these features are called `cold fronts'. It is believed that some cold fronts are formed when a subcluster merges with anothe…
The extra-galactic Cepheid distance scale from LMC and Galactic period-luminosity relations
Tanvir, N. R.; Kanbur, S. M.; Ngeow, C. +2 more
In this paper, we recalibrate the Cepheid distance to some nearby galaxies observed by the HST Key Project and the Sandage-Tammann-Saha group. We use much of the Key Project methodology in our analysis but apply new techniques, based on Fourier methods to estimate the mean of a sparsely sampled Cepheid light curve, to published extra-galactic Ceph…
Observability of Scattered-Light Echoes around Variable Stars and Cataclysmic Events
Sugerman, Ben E. K.
Scattered-light echoes from variable and cataclysmic stars offer one of the most effective means to probe the structure and composition of circumstellar and interstellar media. I build a simple model of light-echo surface brightness by considering the source spectrum and the dust density, geometry, and scattering efficiency. I use this model to in…