119467249
BeppoSAX observations of GRB970402
GRB970402 is the fourth gamma-ray burst detected by BeppoSAX simultaneously in the Gamma Ray Burst Monitor (GRBM) and one of the two Wide Field Cameras (WFCs). A rapid pointing of the BeppoSAX Narrow Field Instruments (NFIs) 8 hours after the GRB led to the identification of an unknown weak X-ray source: 1SAX J1450.1-6920. Its position was approximately at the center of the 3 arcmin error circle derived from the WFC image. Both the Medium Energy (MECS, 2-10 keV) and Low Energy (LECS, 0.1-10 keV) concentrators detected the source. A follow-up observation performed 1.5 days later and lasting 54 ks showed that the source had faded almost to, but not below the detectability threshold. The flux decrease between the two observations was a factor ~= 2.5. 1SAX J1450.1-6920 was the second X-ray afterglow associated with a GRB. Searches promptly started at other wavelengths (optical, IR, radio) did not reveal any transient event within the 3 arcmin error circle.
121516202
An inexpensive spectroscopic beam monitor for hard X-ray synchrotron applications
We describe an inexpensive beam monitor for hard X-ray synchrotron applications which has good spectroscopic abilities and can operate without cooling. The device is centred on an inexpensive, commercial off-the-shelf, large area (1.2 × 1.2 mm2) Si photodiode operated in single counting mode. Measurements carried out at the HASYLAB synchrotron research facility have shown that it is fully spectroscopic across the energy range 8 keV to 100 keV with a measured energy resolution of ~ 1.2 keV FWHM at room temperature. The measured resolutions were found to be the same under pencil-beam and full-area illumination, indicating uniform crystallinity and stoichiometry of the bulk. The low cost, simplicity and performance of the detector make it suitable for a wider range of applications, e.g., in undergraduate laboratory experiments.
12042223
THE COMPLEX X-RAY SPECTRUM OF THE LOW-MASS X-RAY BINARY 4U 1626-67
We report on observations of the X-ray pulsar 4U 1626-67 by the LECS instrument on-board Bepposax. We confirm the recent ASCA discovery of excess emission near 1 keV (Angelini et al. 1995). The pulse period of 7.66794 +/- 0.00004 s indicates that the source continues to spin-down. The phase averaged spectrum is well fit by an absorbed power-law of photon index 0.61 +/- 0.02 and a blackbody of temperature 0.33 +/- 0.02 keV, together with an emission feature at 1.05 +/- 0.02 keV. This spectral shape is similar to that observed by ASCA during the spin-down phase, but significantly different from measurements during spin-up. This suggests that the change in spectrum observed by ASCA may be a stable feature during spin-down intervals. The source intensity is a factor ~2 lower than observed by ASCA three years earlier, confirming that 4U 1626-67 continues to become fainter with time.
7722527
Low-energy line emission from Cygnus X-2 observed by the BeppoSAX LECS
We present a 0.2–10 keV spectrum of the low-mass X-ray binary Cygnus X-2 obtained using the Low Energy Concentrator Spectrometer on-board BeppoSAX. The spectrum can be described by a cut-off power-law model with absorption of (2.28±0.07)×1021 atoms cm−2, a power-law index of 0.78±0.02 and a cut-off energy of 4.30±0.08 keV (68% confidence errors), except at energies near ∼1 keV where excess emission is present. This can be modeled by a broad Gaussian line feature with an energy of 1.02±0.04 keV, a full width half-maximum of 0.47±0.07 keV and an equivalent width of 74±1125 eV. This result confirms earlier reports of line emission near 1 keV and shows the intensity and structure of the feature to be variable. For a more detailed account of these observations we refer to Kuulkers et al. [4].
115557306
SLAC Linac Preparations for FACET
The SLAC 3km linear electron accelerator has been cut at the two-thirds point to provide beams to two independent programs. The last third provides the electron beam for the Linac Coherent Light Source (LCLS), leaving the first two-thirds available for FACET, the new experimental facility for accelerator science and test beams. In this paper, we describe this separation and projects to prepare the linac for the FACET experimental program.
13928123
Soft X-ray observations of the complex warm absorber in MCG-6-30-15 with BeppoSAX
We report on soft X-ray observations of the Seyfert 1 galaxy MCG-6-30-15 with the Low and Medium Energy Concentrator Spectrometers on board BeppoSAX. The time averaged 0.1-4 keV spectrum shows evidence for a complex warm absorber. K-edges of highly ionized oxygen (O vii and O viii) can only partly describe the soft X-ray spectrum below 2 keV. A spectral variability study reveales large and rapid changes in absorption at the energy of the O viii K-edge and in the continuum shape and count rate. These fluctuations are not simply correlated.
118212086
A Simple Model for Galactic Cosmic Rays which is Consistent with Age and Anisotropy Data
121784430
Simple technique for determining the mean lifetime of the cosmic ray μ meson
A single scintillation counter is used for determining the lifetime of cosmic ray μ mesons. The experimental arrangement has a greater detection rate and a higher detection efficiency than the conventional multidetector delayed coincidence technique.
123383571
The interplanetary transport of solar cosmic rays
Numerical solutions are presented for the propagation of solar cosmic rays in interplanetary space, including the effects of pitch-angle scattering and adiabatic focusing. The intensity-time profiles can be well fitted by a simple radial spatial diffusion equation with scattering mean-free path lambda/sub fit/. The radial mean-free path so obtained is significantly larger than the true scattering mean-free path for low-rigidity particles due to both adiabatic focusing and the inapplicability of the diffusive approximation early in the event. The well-known discrepancy between lambda/sub fit/ and the theoretical predictions may be resolved by these calculations.
121844770
The age distribution of galactic cosmic rays
The general solution for the distribution of ages for primary galactic cosmic rays is given for a class of steady-state, bounded models of cosmic-ray diffusion in the Galaxy. Both one-and threedimensional models are considered, with point sources and distributed sources. In all models, the age distribution, is approximately exponential for ages longer than the average age, although for shorter ages the distribution depends on the details of the model. The leaky-box model, with an exponential age distribution, is thus a good approximation to most diffusive models. It is shown that one-dimensional (‘disk’) models are consistent with both age and anisotropy data for galactic cosmic rays regardless of whether production takes place near the galactic center or throughout the disk.
117706405
Two-component model for cosmic-ray fluctuations at neutron monitor energies