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X-ray facility for the ground calibration of the X-ray monitor JEM-X on board INTEGRAL
Frontera, F.; Westergaard, N. J.; Lund, N. +12 more
We describe the X-ray facility developed for the calibration of the X-ray monitor JEM-X on board the INTEGRAL satellite. The apparatus allowed the scanning of the detector geometric area with a pencil beam of desired energy over the major part of the passband of the instrument. The monochromatic radiation is obtained with the use of a double cryst…
Free-Free Emission in the Far-Ultraviolet Spectral Range: A Resource for Diagnosing Solar and Stellar Flare Plasmas
Curdt, W.; Landi, E.; Doschek, G. A. +2 more
We report the detection of free-free (bremsstrahlung) emission near 1200 Å from a flare at the solar limb observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecraft. The observations consist of a time series of slit spectra at a fixed pointing that lasted a…
The sensitivity of the seismic solar model to Newton's constant
Silk, Joseph; Lopes, Ilídio P.
New experimental determinations of Newton's gravitational constant have been recently given. There are significant disagreements between these new measurements. We show that the high accuracy obtained with current standard solar models is such that the uncertainties in core temperature profiles arising from the uncertainties in G can be comparable…
VLF wave activity in the solar wind and the photoelectron effect in electric field measurements: Ulysses observations
Balogh, A.; McComas, D. J.; Lin, Naiguo +2 more
We present observations of very low frequency (VLF) waves (0.2 to 448 Hz) made by Ulysses during the solar maximum and compare the observations with those obtained when the solar activity was approaching a minimum. The occurrences and properties of the waves are found to be similar during the solar maximum and solar minimum periods for slow and in…
The RCW 114 nebula: An old supernova remnant or a WR wind-blown bubble?
Lallement, R.; Welsh, B. Y.; Sallmen, S. +1 more
We present medium resolution spectra (R ~ 7 km s-1) of the interstellar NaI D1 & D2 absorption lines observed towards 7 early-type stars with distances ranging from 221 to ~ 1.5 kpc in the line-of-sight to the RCW 114 nebula. Our observed pattern of absorption is in conflict with the findings of Bedford et al. (1984) who placed an u…
Probing the extended emission-line region in 3C 171 with high-frequency radio polarimetry
Hardcastle, M. J.
I present high-frequency polarimetric radio observations of the radio galaxy 3C 171, in which depolarization is associated with an extended emission-line region. The radio hotspots, known to be depolarized at low radio frequencies, become significantly polarized above (observer's frame) frequencies of 15 GHz. There is some evidence that some of th…
The Nature of the Ultraviolet/X-Ray Absorber in PG 2302+029
Hamann, Fred; Shields, Joseph C.; Jannuzi, Buell T. +2 more
We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029. This quasar has a rare system of ultra-high-velocity (-56,000 km s-1) UV absorption lines that form in an outflow from the active nucleus. The Chandra data indicate that soft X-ray absorption is also present. We perform a joint UV and X-ray analysis, using photoio…
Technique for Detecting Warm-Hot Intergalactic Gas in Quasar Ultraviolet Spectra
Binette, Luc; Rodríguez-Martínez, Mario; Haro-Corzo, Sinhue +1 more
The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution shortward of ~1200 Å. The change of the power-law index from approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being intrinsic to quasars. We consider the possibility that the steepening may result from a tenuous absorption compone…
Flare characteristics: Properties of eruptive and non-eruptive events and their associations
Culhane, J. L.; Harra, L. K.; Kay, H. R. M. +1 more
The complex: relationship between solar flares and coronal mass ejections is investigated using a comparison of flare parameters for a total of 69 ejective and non-ejective flares. In the case of solar flares which do not show mass ejection there seems to be a clear relationship between the peak intensity and duration, with higher intensity events…
The Hubble Deep Field South Flanking Fields
Ferguson, Henry C.; Lucas, Ray A.; Baum, Stefi A. +22 more
As part of the Hubble Deep Field South program, a set of shorter two-orbit observations were obtained of the area adjacent to the deep fields. The WFPC2 flanking fields cover a contiguous solid angle of 48 arcmin2. Parallel observations with the STIS and NICMOS instruments produce a patchwork of additional fields with optical and near-i…