The broad band X-ray spectrum of the lowmass X-ray binary (LMXB) GS 1826-238 was measured with the narrow-field instruments on BeppoSAX on April 6 and 7, 1997. The spectrum is consistent with the Comptonization of a 0.6 keV thermal spectrum by a hot cloud of temperature equivalent kT = 20 keV. During the observation two type I X-ray bursts were detected. From the bursts an upper limit to the di...

We demonstrate highly broad-band frequency conversion via four-wave mixing in silicon nanowaveguides. Through appropriate engineering of the waveguide dimensions, conversion bandwidths greater than 150 nm are achieved and peak conversion efficiencies of -9.6 dB are demonstrated. Furthermore, utilizing fourth-order dispersion, wave-length conversion across four telecommunication bands from 1477 ...

In this theoretical paper, the wide-band low-gain feature of a tapered smooth wall gyro-traveling wave tube (gyro-TWT) was combined with the low beam energy, low magnetic field, and high gain, though narrow band, feature of a vane loaded nontapered gyro-TWT, to propose a distributed, tapered vane loaded gyro-TWT for both high gains and wide bandwidths. The device was analyzed for the tapering o...

The contributions of different radiation mechanisms to the diffuse γ-ray emission of the galactic disk are studied in a broad energy region from 104 to 1014 eV. Our analysis shows that at energies between 1 and 100 MeV the radiation is dominated by the bremsstrahlung of relatively low energy, typically less than 1 GeV electrons, but with a non-negligible contribution from the inverse Compton (I...

An obvious issue with a low-frequency broad-band receiver is the degree to which the science data are affected by radio-frequency interference (RFI). RFI comes in two main classes: a) relatively narrow-band quasi-steady transmissions and b) broad-band transient signals. Very strong narrowband signals can result in non-linear responses which dramatically spread the signal in frequency. Transient...

Within the sample of unidentified γ-ray sources found in the first survey of our Galaxy, AX J1838.0-065 is particularly interesting due to its likely physical association with the newly discovered TeV source HESS J1837-069 (Aharonian et al. 2005a). In fact, its position coincides with the center of gravity of the TeV emission and therefore has been suggested by Aharonian et al. (2005a) as the m...

High power, broad bandwidth, high linearity, and low noise are among the most important features in amplifier design. The broad-band spatial power-combining technique addresses all these issues by combining the output power of a large quantity of microwave monolithic integrated circuit (MMIC) amplifiers in a broad-band coaxial waveguide environment, while maintaining good linearity and improvin...

The pertinent lack of a standard calibration procedure for UV filter radiometers introduces unknown and potentially large uncertainties in their measurement products. Although most UV calibration facilities take into account many instrument properties that affect the measurement quality of UV filter radiometers, some instrument characteristics that are difficult to determine present substantial...

We present the results of UBV imaging of a large sample of irregular galaxies: 94 Im systems, 24 Blue Compact Dwarfs (BCDs), and 18 Sm galaxies. We also include JHK imaging of 41 of these galaxies. The sample spans a large range in galactic parameters. Ellipse fit axial ratios, inclinations, and position angles are derived, integrated photometry and azimuthally-averaged surface photometry profi...

Microquasars (MQs) are galactic objects with relativistic jets that constitute a source population which can be responsible for production of a non-negligible fraction of the observed galactic cosmic rays. These relativistic protons, associated with the termination of the jet, interact with the interstellar medium and, at certain surrounding conditions, may lead to production of detectable flux...