[en] In this paper we present some preliminary result on the spectral and timing analysis of the X-ray pulsed emission from the 16 ms pulsar PSR J0537-6910 in the energy range 0.1-30 keV, based on archival BeppoSAX and RossiXTE observations. This pulsar, discovered by Marshall et al. [ApJ 499 (1998) L179] in the LMC field with RXTE, is the fastest spinning pulsar associated with a supernova remnant. It is characterized by strong glitch activity with the highest rate of all known Crab-like system

[en] We propose a two component model for the emission of PSR B0531+21 (Crab pulsar) to describe the energy dependence of the pulse profile and, in particular, of the relative peak (and interpeak) intensities. We show that the energy change of the X-ray pulse profile can be well reproduced by adding to the optical profile a unique broad pulse component whose intensity scales with the energy

[en] We report the current status of the analysis of the MECS background using the entire dataset of the BeppoSAX Science performance Verification Phase. We have collected 360 ks of dark Earth instrumental background, 470 ks of bright Earth background and 1100 ks of blank field data. We are attempting to model the instrumental background in terms of its various components (in particular the spatial modulation of the residual contamination by the built-in Fe calibration sources), and then use this model, and the information on the vignetting and the PSF to derive the cosmic background in the 2-10 keV range

[en] We present preliminary results of BeppoSAX and ASCA observations of the Galactic field containing the unidentified γ-ray transient GRO J1838-04. Several weak X-ray sources are detected within the EGRET error box. No obvious counterpart of GRO J1838-04 is evident from these observations. More multiwavelength observations are necessary to identify the nature of this non-blazar γ-ray transient

[en] We report the results of the temporal and spectral analysis of the longest BeppoSAX pointing (about 770 ks) of the microquasar GRS 1915+105, performed in October 2000. For the largest fraction of the observation GRS 1915+105 was in the so called ρ-mode, characterized by series of sharp pulses with a typical recurrence time of about 50 s, well detectable in the energy range 2-10 keV. This quasi-periodic behaviour was generally quite stable but, occasionally, it changed to a more irregular state in which the pulses are broader and their recurrence time is highly fluctuating. We found that this irregular ρ-mode is associated with an enhanced emission at energies greater than 15 keV. Wavelet analysis of the (2-10 keV) light curves is used to study the time evolution of the ρ-mode

[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] We present some results of an RXTE observation on PSR B1937+21, the fastest known millisecond pulsar (P≅1.56 ms). The pulse profile, detected up to ∼20 keV, shows a double peak, with the main component much stronger than the other. The peak phase separation is 0.526±0.002 and the pulsed spectrum over the energy range 2-25 keV is well described by a power law with a photon index equal to 1.14±0.07. We find that the X-ray pulses are closely aligned in phase with the giant pulses observed in the radio band. This result suggest that giant radio pulses and X-ray pulses originate in the same region of the magnetosphere due to a high and fluctuating electron density that occasionally emits coherently in the radio band. The X-ray events, however, do not show any clustering in time indicating that no X-ray flares are produced

[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] The unique pulsar/Be star system PSR B1259-63/SS2883 had their second 'usable' periastron fly-by on May 29 ∼ 19:00 UT (T). The original plan of observing the pulsar with the BeppoSAX NFIs some two months before and after periastron and to monitor it during the passage with five, one week interleaved observations, could not be accomplished. PSR B1259-63 was instead observed five times by BeppoSAX during 1997: on March 22 (T-68 days) and on September 2, 8, 17, 25 (T +96, 102, 111, 118 days) for a total exposure time of 178.7 ks for each MECS and 36.1 ks for the LECS. Here we present the preliminary results from the spectral and temporal analysis and compare them with previous ROSAT and ASCA observations

[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