[en] In this paper we review our current knowledge of the hard X-ray emission properties of accreting X-ray Binary Pulsars and old accreting neutron stars in Low Mass X-ray Binaries in light of 7 years of BeppoSAX and RXTE observations. The paper is divided in two parts. In the first part we review the more recent findings on the phase-dependent broad band continua and cyclotron resonance scattering features observed in many systems of the X-ray Binary Pulsar class. In the second part we review the hard X-ray emission of LMXRB focussing on the hard X-ray components extending up to energies of a few hundred keV that have been clearly detected in sources of both the atoll and Z classes. The presence and characteristics of these hard emission components are then discussed in relation to source properties and spectral state. We, also, briefly mention models that have been proposed for the hard X-ray emission of neutron star X-ray binaries

[en] Scaling relations for the FEL gain, including the e-beam quality effects, have been usefully exploited to design FEL devices. We propose further extension of the above formulae including high gain, inhomogeneous broadening and saturation effects. A crucial role to get these relations is the use of approximant methods generalizing the Pade procedure. We derive gain equations containing the corrections due to energy spread, emittances and field intensity. It is shown that these equations can be exploited to open-quotes simulateclose quotes the FEL evolution with an almost negligible computational effort. Comments on the role of the saturation intensity and its dependence on the e-beam quality, high gain corrections etc. are also presented

[en] The X-ray binary pulsar Cen X-3 was observed with the BeppoSAX satellite on 14/08/96 for about 20 Ks during the Science Verification Phase (SVP). This source is a typical massive X-ray binary with a pulse period of 4.8 s and an orbital period of 2.1 days. In this observation the source was found in a low state with a luminosity, assuming a distance of 8 Kpc, of about 4.6^*10³⁶ ergs/s in the 2-10 keV energy band. In this paper we present the first simultaneous broad band (1.5 - 50 keV) pulse averaged spectrum and discuss two spectral fitting models. The pulsed light curve in the 1.5 - 10 keV energy band is also shown

[en] Two isolated pulsars, the Crab and PSR B0540-69, were observed during the Science Verification Phase with the NFIs on board BeppoSAX. Here we present results from these two observations. In particular, we determine the spectral variations of the phase component P2, P1 and Ip of the Crab light curve using the P1/P2 and Ip/P2 ratio. We also give a brief summary of the spectral and temporal analysis. Moreover, we present the light curve of PSR B0540-69 in different energy bands and, using the best period derived from the BeppoSAX observation together with the previous ones, determine the rotational parameters of the pulsar and the relative breaking index

[en] BeppoSAX observed several galactic binary X-ray pulsars during the Science Verification Phase and in the first year of the regular program. The complex emission spectra of these sources are an ideal target for the BeppoSAX instrumentation, that can measure the emission spectra in an unprecedented broad energy band. Using this capability of BeppoSAX a detailed observational work can be done on the galactic X-ray pulsars. In particular the 0.1-200 keV energy band allows the shape of the continuum emission to be tightly constrained. A better determination of the underlying continuum allows an easier detection of features superimposed onto it, both at low energy (Fe K and L, Ne lines) and at high energies (cyclotron features). We report on the spectral properties of a sample of X-ray pulsars observed with BeppoSAX comparing the obtained results. Some ideas of common properties are also discussed and compared with our present understanding of the emission mechanisms and processes

[en] Broad-band observation of galactic X-ray binary pulsars is one of the main scientific goal of the BeppoSAX mission. In this framework a key role is played by Pulse Phase Resolved Spectroscopy. In the paper we present some preliminary results on both phase-resolved spectra and pulse profile evolution with energy on two sources of this class, Cen X-3 and Her X-1

[en] We report on observations of the low-mass X-ray binary 4U1626-67 performed during the BeppoSAX Science Verification Phase. We present the broad-band 0.1-100 keV pulse averated spectrum, that is well fit by a two-component function: a 0.27 ± 0.02 keV blackbody and an absorbed power law with a photon index of 0.89 ± 0.02. A very deep and narrow absorption feature at 38 keV, attributable to electron cyclotron resonance, is clearly visible in the broad-band spectrum. It corresponds to a neutron star magnetic field strength of 3.3 x 10¹² G. The 4U1626-67 pulse profiles show a dramatic dependence on energy: the transition between the low energy (E < 10 keV) bi-horned shape to the high-energy (E > 10 keV) sinusoidal profile is clearly visible in our data. The modulation index shows a monotonic increase with energy

[en] The Crab Nebula and the Pulsar were observed from 31th to 1st of August and from 6th to 7th September 1996 with the Narrow Field Instruments (NFI's) on board of BeppoSAX, during the Science Verification Phase. The fine time resolution (15 μs) and the high statistic of the data provided phase histogram of very good quality and well suited for phase resolved spectroscopy over the entire energy band (0.1-300 keV) covered by BeppoSAX payload. We present some results of the phase resolved spectral analysis

[en] The transient X-ray pulsar GS 1843+009 was observed by BeppoSAX satellite on 1997 April 4, while it was at flux level of 50 mCrab in the 20-200 keV energy band. Using the MECS and LECS concentrators, the source position was measured with unprecedented accuracy of 30''. In this poster we present results on both spectral and temporal analysis

[en] The ASIC CITIROC is a 32-channel fully analogue front-end ASIC dedicated to the read-out of silicon photo-multiplier (SiPM) sensors that can be used in a variety of experiments with different applications: nuclear physics, medical imaging, astrophysics, etc. For each channel, two parallel AC coupled voltage preamplifiers, one for the high gain and one for the low gain, ensure the read-out of the charge from 160 fC to 320 pC (i.e. from 1 to 2000 photo-electrons with SiPM gain $={10}^6$, with a photo-electron to noise ratio of 10). The signal in each of the two preamplifier chains is shaped and the maximum value is captured by activating the peak detector for an adjustable time interval. In this work, we illustrate the peak detector operation mode and, in particular, how this can be used to calibrate the SiPM gain without the need of external light sources. To demonstrate the validity of the method, we also present and discuss some laboratory measurements.