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BeppoSAX has been added to the 3rd Interplanetary Network of gamma-ray burst detectors. Of the ≈8 events observed to date by Ulysses and the BeppoSAX Gamma-Ray Burst Monitor (GRBM), four have been localized by triangulation, resulting in annuli whose 3 σ widths are as small as 63″. These data give error boxes whose sizes can be as much as an order of magnitude smaller than those obtained with the SAX Wide Field Camera (WFC). They can be used to confirm the association between fading X-ray and optical sources and gamma-ray bursts.

We describe the analysis of BeppoSAX gamma-ray burst monitor on-ground calibrations performed after the full integration of the spacecraft in order to explore in detail the dependence of the detectors efficiency on the direction and energy of impinging photons. Analytical techniques have been used to determine with reasonable accuracy this function by fitting the angular response at different calibration energies with simple models partially derived from the underlying physics and partially semiempirical. Satisfactory results have been obtained for the two detectors which have almost clean field of view and are co-aligned with the wide field cameras. Work is still in progress for the others. Preliminary results of ground calibration analysis have been already used to derive spectral information on gamma-ray bursts impinging parallel to the axis of the two best performing shields.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The gamma ray burst monitor onboard the BeppoSAX satellite is a secondary function of the anticoincidence shields of the phoswich detection system hard x-ray experiment. For this reason the four CsI slabs operating as gamma ray bursts detectors have a not uniformly clear field of view. Actually the other SAX experiments partially obstruct the GRBM FOV in a way that strongly depends both on direction and energy. This peculiarity makes very hard to build-up a real response matrix of the experiment by simply interpolating the on-ground calibration. Therefore a complex activity of Monte Carlo simulation has been started using the MCNP code, in which the entire SAX satellite is described in a 3D geometrical reconstruction. This code is being used for the simulation of the on-ground calibration set-up, and once a good level of confidence is reached on that, it will be used to reconstruct direction, intensity and spectrum of the cosmic gamma ray bursts. In this paper we present the Monte Carlo set-up, discussing the approach to the work and the approximations that need to be done. Then the first results of the simulations are shown and compared, for some monochromatic energies and for several incoming directions, to the results obtained during the on-ground calibrations.

The phoswich detection system (PDS) is one of the four narrow field experiments on board the x-ray astronomy satellite BeppoSAX. PDS is devoted to deep temporal and spectral studies of celestial x-ray sources in the 15 - 300 keV energy band. It also includes a gamma-ray burst monitor. In this paper we compare the expected and observed in-flight performances. Our estimate of systematic errors in the background subtraction and in the spectral reconstruction are also presented and discussed.

The Italian-Dutch satellite for X-ray Astronomy BeppoSAX is successfully operating on a 600 km equatorial orbit since May 1996. We present here the in-flight performances of the Gamma Ray Burst Monitor experiment during its first year of operation. The GRBM is the secondary function of the four CsI(Na) slabs primarily operating as an active anticoincidence of the PDS hard X-ray experiment.. It has a geometric area of about 4000 cm2 but, due to its location in the core of the satellite its effective area is dependent on the energy and direction of the impinging photons. A dedicated electronics allows to trigger on cosmic gamma-ray bursts. When the trigger condition is satisfied the light curve of the event is recorded from 8 s before to 98 s after the trigger time, with a maximum time resolution of 0.48 ms, in an energy band of 40-700 keV.

The high energy experiment PDS is one of the Narrow Field Instruments aboard the X-ray astronomy satellite BeppoSAX. It covers the energy band from 15 to 300 keV. Here we report results on its in-flight performance and observations of galactic and extragalactic X-ray sources obtained during the Science Verification Phase of the satellite: in particular Crab, Cen X-3, 4U1626-67 and PKS2155-305., 5 pages, 4 PostScript figures, uses aipproc.sty, to appear in Proceedings of Fourth Compton Symposium

During the $BeppoSAX$ survey of the Galactic Center region, we have discovered X-ray emission from the central region of the supernova remnant G0.9+0.1. The high interstellar absorption (N_H about 3 times 10^{23} cm^-2) is consistent with a distance of order of 10 kpc and, correspondingly, an X-ray luminosity of about 10^{35} erg s^{-1}. Although we cannot completely rule out a thermal origin of the X-ray emission, its small angular extent (radius of about 2'), the good fit with a power law, the presence of a flat spectrum radio core, and the estimated SNR age of a few thousand years, favour the interpretation in terms of synchrotron emission powered by a young, energetic pulsar., Comment: 4 pages, 1 figure. Uses espcrc2.sty (included). To appear in The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE, Nuclear Physics B Proceedings Supplements, L. Scarsi, H. Bradt, P. Giommi and F. Fiore (eds.), Elsevier Science B.V

We report on the spectral (pulse averaged) and timing analysis of the ~ 20 ksec observation of the X-ray binary pulsar Vela X-1 performed during the BeppoSAX Science Verification Phase. The source was observed in two different intensity states: the low state is probably due to an erratic intensity dip and shows a decrease of a factor ~ 2 in intensity, and a factor 10 in Nh. We have not been able to fit the 2-100 keV continuum spectrum with the standard (for an X--ray pulsar) power law modified by a high energy cutoff because of the flattening of the spectrum in ~ 10-30 keV. The timing analysis confirms previous results: the pulse profile changes from a five-peak structure for energies less than 15 keV, to a simpler two-peak shape at higher energies. The Fourier analysis shows a very complex harmonic component: up to 23 harmonics are clearly visible in the power spectrum, with a dominant first harmonic for low energy data, and a second one as the more prominent for energies greater than 15 keV. The aperiodic component in the Vela X-1 power spectrum presents a knee at about 1 Hz. The pulse period, corrected for binary motion, is 283.206 +/- 0.001 sec., Comment: 5 pages, 4 PostScript figure, uses aipproc.sty, to appear in Proceedings of Fourth Compton Symposium

We report on the timing analysis of the observation of the X-ray binary pulsar Her X-1 performed during the BeppoSAX Science Verification Phase. The observation covered more that two full orbital cycles near the maximum of the main-on in the 35 day cycle of Her X-1. We present the pulse profiles from 0.1 to 100 keV. Major changes are present below 1 keV, where the appearance of a broad peak is interpreted as re-processing from the inner part of the accretion disk, and above 10 keV, where the pulse profile is less structured and the main peak is appreciably harder. The hardness ratios show complex changes with pulse phase at different energies., 5 pages, 2 PostScript figures, uses aipproc.sty, to appear in Proceedings of Fourth Compton Symposium

Vela X-1 has been observed by the Italian/Dutch X-ray satellite BeppoSAX during its Science Verification Phase. During the ~ 50 ksec observation (orbital phases 0.27-0.34) two different intensity state are present, situation very common in this source. We report results from the pulse phase averaged and pulse phase resolved spectroscopy from the high-energy instrument PDS aboard BeppoSAX., Comment: 4 pages, 2 figures. It uses camera.sty (included). To appear in the Proceedings of "The Cosmic Physics of 2000"

著者人数: 74名, Accepted: 2013-07-11, 資料番号: SA1004571000

The phoswich detection system (PDS) is one of the four narrow field experiments on board the SAX satellite. The PDS will be dedicated to deep temporal and spectral studies of celestial x- ray sources in the 15 - 300 keV energy band. It also includes a gamma-ray burst monitor. The PDS detector is composed of 4 actively shielded NaI(Tl)/CsI(Na) phoswich scintillators with a total geometric area of 795 cm2 and a field of view of 1.3 degrees (FWHM). In this paper we report results of the experiment on-ground calibrations before its integration in the spacecraft and the expected experiment in-flight performance.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We discuss the possibility of detecting the microsecond granularity expected in the flux from wind‐fed x‐ray binary pulsars. This microsecond structure is predicted by the noisy accretion scenario; we derive the physical characteristics of such burst structure in the framework of this model. We investigate the temporal dispersion induced by the scattering of burst photons in their passage through the neutron star magnetosphere and conclude that microsecond structure could indeed by observable for energies less than the cyclotron energy. We show that the coincidence timing mode for the Proportional Counter Array on‐board XTE can be used very effectively to statistically discriminate these microsecond bursts from accidental spurious detections.

We report some comparative results of an investigation devoted to study the spectral evolution of a sample of Gamma-Ray Bursts. They were simultaneously detected with both the Gamma-Ray Burst Monitor and the Wide Field Cameras aboard the BeppoSAX satellite and were reobserved with the Narrow Field Instruments aboard the same satellite.

We report on the operation of the resonant gravitational wave (g.w.) detector Explorer of the Rome group (M = 2300 kg, T =2 :6 K, located at CERN) at the time of the gamma-ray burst GRB 980425 (April 25.90915 UT, 1998), which is probably associated with the supernova SN 1998bw .W e present the data of the detec- tor (with sensitivity hc =8 10 19 for a1m s pulse), and use the BeppoSAX data to estimate the initial time of the GRB: a basic parameter for any correlation analysis. The g.w. data exhibit no signicant time signature around the GRB 980425. We wish to remark the impor- tance to make use, in spite of the present low sensitiv- ity, of the data collected with g.w. detectors, that can be regarded as active observatories, in coincidence with the BeppoSAX data.

The Medium Energy experiment on-board the EXOSAT satellite observed the X-ray binary system 4U 1538-52 on four occasions during 1984 March and August. Observed pulsation periods of 529.97±0.16 s (March 17) and 530.14±0.03 s (August 10) indicate that the neutron star in the 4U 1538-52 system continued to spin down with P p =+3.9×10 −9 s s −1 (P p /P p =+2.3×10 −4 yr −1 ) in the time period of 1976-1988

A phenomenological model of accretion which is applied to the wind-fed X-ray binary pulsar GX 301 - 2 is developed, assuming that the accretion onto the neutron star does not occur from a continuous flux of plasma, but from blobs of matter which are threaded by the magnetic field lines onto the magnetic polar caps of the neutron star. These 'lumps' are produced at the magnetospheric limit by magnetohydrodynamical instability, introducing a 'noise' in the accretion process, due to the discontinuity in the flux of matter onto the neutron star. This model is able to describe the change of slope observed in the continuum component of the power spectra of the X-ray binary pulsar GX 301 - 2, in the frequency range 0.01 - 0.1 Hz. The physical properties of the infalling blobs derived in the model are in agreement with the constraints imposed by observations.

It is shown that, in the case of the interaction between the gravitational waves and the electromagnetic field, the physical system is the Fermi normal co-ordinate and not the currently used transverse traceless system.

This paper reviews the theory of the magnetic monopole as an astrophysical object. In particular we construct a model by which we are able to calculate the mass of the monopole by the unique assumption that the source of energy of quasars is due to monopole-antimonopole annihilation, without referring to particular GUTs. It results that the mass of the monopole must be 1016 GeV, i.e., the monopole predicted by the Georgi-Glashow model.

The co-alignment of two detectors of the BeppoSAX Gamma-Ray Burst Monitor (40–700 keV) with the Wide Field Cameras (2–26 keV) on-board the same satellite has permitted simultaneous detection of several GRBs in X and gamma rays and their localization with high precision. These measurements allow us also to extend the study of GRB spectra down to 2 keV and with good accuracy thanks to the knowledge of source direction. We show and discuss preliminary results of the analysis of X to gamma-rays average spectra based on a sample of 12 BeppoSAX events.

This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of high-mass X-ray binaries and ultra-luminous X-ray sources. For a summary, we refer to the paper., White Paper in Support of the Mission Concept of the Large Observatory for X-ray Timing. (v2 few typos corrected)

The Gamma-Ray Burst Monitor (GRBM) aboard the BeppoSAX satellite has already shown good capabilities in the detection of Gamma-Ray Bursts (GRB). We have also tested its performance as monitor of the hard X-ray flux from strong celestial sources, using the Earth Occultation Technique. A verification of the on-ground calibrations of the instrument was performed deriving the flux of the Crab Nebula. In this paper we report results on Crab and light curves of other sources detected.

We discuss the possibility of detecting the microsecond granularity expected in the flux from wind-fed X-ray binary pulsars. This microsecond structure is predicted by the noisy accretion scenario; we derive the physical characteristics of such burst structure in the framework of this model. We investigate the temporal dispersion induced by the scattering of burst photons in their passage through the neutron star magnetosphere and conclude that microsecond structure could indeed be observable for energies less than the cyclotron energy. We show that the coincidence timing mode for the Proportional Counter Array on-board XTE can be used very effectively to statistically discriminate these microsecond bursts from accidental spurious detections

Lobster-ISS is an X-ray all-sky monitor experiment selected by ESA two years ago for a Phase A study (now almost completed) for a future flight (2009) aboard the Columbus Exposed Payload Facility of the International Space Station. The main instrument, based on MCP optics with Lobster-eye geometry, has an energy passband from 0.1 to 3.5 keV, an unprecedented daily sensitivity of 2x10^{-12} erg cm^{-2}s$^{-1}, and it is capable to scan, during each orbit, the entire sky with an angular resolution of 4--6 arcmin. This X-ray telescope is flanked by a Gamma Ray Burst Monitor, with the minimum requirement of recognizing true GRBs from other transient events. In this paper we describe the GRBM. In addition to the minimum requirement, the instrument proposed is capable to roughly localize GRBs which occur in the Lobster FOV (162x22.5 degrees) and to significantly extend the scientific capabilities of the main instrument for the study of GRBs and X-ray transients. The combination of the two instruments will allow an unprecedented spectral coverage (from 0.1 up to 300/700 keV) for a sensitive study of the GRB prompt emission in the passband where GRBs and X-Ray Flashes emit most of their energy. The low-energy spectral band (0.1-10 keV) is of key importance for the study of the GRB environment and the search of transient absorption and emission features from GRBs, both goals being crucial for unveiling the GRB phenomenon. The entire energy band of Lobster-ISS is not covered by either the Swift satellite or other GRB missions foreseen in the next decade., Comment: 6 pages, 4 figures. Paper presented at the COSPAR 2004 General Assembly (Paris), accepted for publication in Advances in Space Research in June 2005 and available on-line at the Journal site (http://www.sciencedirect.com/science/journal/02731177), section "Articles in press"

We have observed the soft X-ray transient XTE J0421+56 in quiescence with XMM-Newton. The observed spectrum is highly unusual being dominated by a broad feature at 6.5 keV and can be modeled by a strongly absorbed continuum. The spectra of X-ray transients observed so far are normally modeled using Advection Dominated Accretion Flow models, black-bodies, power-laws, or by the thermal emission from a neutron star surface. The strongly absorbed X-ray emission of XTE J0421+56 could result from the compact object being embedded within the dense circumstellar wind emitted from the supergiant B[e] companion star., To appear in the proceedings of the `New Visions of the Universe in the XMM-Newton and Chandra Era' symposium held in ESTEC, The Netherlands, on 26-30 November 2001; ESA SP-488, August 2002, eds F. Jansen

The four Lateral Shields of the PDS experiment aboard the Beppo-SAX satellite are equipped with dedicated electronics and used as a Gamma Ray Burst Monitor (GRBM). On a suitable trigger time histories are recorded and transmitted. The large geometric area and the low background of these detectors provide a remarkable capability which is limited, on the other hand, by the no uniform exposure to different direction, due to the shielding of the other experiments of SAX. Here we discuss the on-ground calibrations and the performance simulations in progress, aimed to reconstruct the cosmic X-ray fluxes impinging on the satellite from the recorded counting rates.

We have observed the X-ray transient XTE J0421+56 in quiescence with XMM-Newton. The observed spectrum is highly unusual being dominated by an emission feature at ~6.5 keV. The spectrum can be fit using a partially covered power-law and Gaussian line model, in which the emission is almost completely covered (covering fraction of 0.98_{-0.06}^{+0.02}) by neutral material and is strongly absorbed with an N_H of (5_{-2}^{+3}) x 10^{23} atom cm^{-2}. This absorption is local and not interstellar. The Gaussian has a centroid energy of 6.4 +/- 0.1 keV, a width < 0.28 keV and an equivalent width of 940 ^{+650}_{-460} eV. It can be interpreted as fluorescent emission line from iron. Using this model and assuming XTE J0421+56 is at a distance of 5 kpc, its 0.5-10 keV luminosity is 3.5 x 10^{33} erg s^{-1}. The Optical Monitor onboard XMM-Newton indicates a V magnitude of 11.86 +/- 0.03. The spectra of X-ray transients in quiescence are normally modeled using advection dominated accretion flows, power-laws, or by the thermal emission from a neutron star surface. The strongly locally absorbed X-ray emission from XTE J0421+56 is therefore highly unusual and could result from the compact object being embedded within a dense circumstellar wind emitted from the supergiant B[e] companion star. The uncovered and unabsorbed component observed below 5 keV could be due either to X-ray emission from the supergiant B[e] star itself, or to the scattering of high-energy X-ray photons in a wind or ionized corona, such as observed in some low-mass X-ray binary systems., 8 pages, 4 postscript figures, accepted for publication in Astronomy and Astrophysics

We present results of a 5.7 day duration BeppoSAX observation of the short-on state of Her X-1 and a short observation during the decline of the preceding main-on state. The 0.1-10 keV spectra can be fit with a power-law and blackbody model together with Fe emission features at 1.0 keV and 6.5 keV. During the later stages of the short-on state there are long intervals when the absorption is $\approxgt$$5 \times 10^{22}$ atom cm$^{-2}$. These intervals become longer and occur ~0.3 day earlier in each orbital cycle as the short-on state progresses. During the intervals of high absorption the 0.1 keV blackbody is still clearly detected. This may indicate the presence of separate scattered and absorbed spectral components, although other explanations such as partial covering or a partially ionized absorber cannot be excluded. During the rest of the short-on state the ratio of flux in the blackbody compared to the power-law is consistent with that in the main-on state. This supports the view that much of the 35 day modulation is caused by an energy independent process, such as electron scattering. The discovery of strong absorption late in the short-on state is consistent with the predictions of the warped disk model (Petterson 1977, see also Schandl & Meyer 1994) where the end of the short-on state is caused by the accretion disk moving into the line of sight to the neutron star. The pulse phase difference between the blackbody and the power-law maxima is 250 +/- 20 degrees in both observations (separated by 0.43 of a 35 day cycle). This constant phase difference is consistent with the blackbody originating at the inner edge of a precessing accretion disk., Accepted by Astronomy and Astrophysics

The X-ray telescopes on board BeppoSAX are an optimal set of instruments to observe bright galactic binary pulsars. These sources emit very hard and quite complex X-ray spectra that can be accurately measured with BeppoSAX between 0.1 and 200 keV. A prototype of this complexity, the source Her X-1, shows at least seven different components in its spectrum. A broad band measure is therefore of paramount importance to have a thorough insight into the physics of the emitting region. Moreover the detection of cyclotron features, when present, allows a direct and highly significant measure of the magnetic field intensity in the emission region. In this paper we briefly report the results obtained with BeppoSAX on this class of sources, with emphasis on the detection and on the measured properties of the cyclotron lines., 10 Latex pages, 4 figures, uses psfig.sty. Accepted for publication in Advances in Space Research, in Proceedings of 32nd Scientific Assembly of COSPAR - Symposium E1.1: "Broad-Band X-ray Spectroscopy of Cosmic Sources"

In about one year, five gamma-ray bursts were simultaneously observed with the Wide Field Cameras and Gamma Ray Burst Monitor aboard the BeppoSAX satellite. From some of them X-ray afterglow emission has been clearly detected with the same satellite. In order to understand how GRB emission is related to the X-ray afterglow, we are performing a systematic study of the spectral properties of these events. We report here preliminary results of this study., Comment: 5 pages, 3 figures. To appear in the Proceedings of the 4th Huntsville Gamma-ray Burst Symposium

The BeppoSAX satellite pointed to the massive X-ray pulsar Cen X-3 for the first time during the Science Verification Phase (SVP). The source was found in a low luminosity state ( L ⋍ 3.8 × 10 36 ergs/s). Cen X-3 was observed again in the Guest Observer Program (GOP) and was found in a much higher luminosity state ( L ⋍ 4.3 × 10 37 ergs/s). This second observation includes also the source eclipse and the eclipse egress. We present the pulse profiles and the average broad-band spectra (0.5 – 80 keV) of the two observations and discuss different overall continuum models to fit these spectra. In particular, we report results on the variation of the iron K-line parameters as a function of the different source states: eclipse, low luminosity state and high luminosity state.

BeppoSAX has been added to the 3rd Interplanetary Network of gamma-ray burst detectors. Of the 8 events observed to date by Ulysses and the BeppoSAX Gamma Ray Burst Monitor (GRBM), four have been localized by triangulation, resulting in annuli whose 3σ widths are as small as 63″. These data give error boxes whose sizes are sometimes smaller than those obtained with the SAX Wide Field Camera (WFC). They can be used to confirm the association between fading X-ray and optical sources and gamma-ray bursts.

BeppoSAX detected a few GRBs with both the GRB Monitor and the Wide Field Cameras. Fast follow-up observation of the field with Narrow Field Instruments of SAX and with other X-ray telescopes has allowed for the detection and monitoring of the GRB afterglows. We discuss the temporal behaviour of the two events better studied both in the whole band and in the band where the Narrow Field Instruments and the Wide Field Cameras overlap.

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., Comment: 6 pages, 2 figures. Uses espcrc2.sty (included).To appear in Proceedings of "The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE"

Fast follow-up observations by BeppoSAX have led so far to the discovery of X-ray afterglows in three GRBs: GRB970228, GRB970402, GRB970508. In this paper we report on the spectral properties, in particular the spectral shape and the spectral variability in the 0.1–10 keV range of GRB970228 and GRB970508, and briefly discuss the implications of these measurements on models and radiative mechanisms of GRBs.

Results of a BeppoSAX observation of Her X-1 in 2000 October during the first main-on state after the longest recorded anomalous low-state are presented. The 0.1-30 keV spectrum, light curve and pulse profile are all consistent with those measured during previous main on-states, indicating that Her X-1 has resumed its regular 35 day cycle with similar on-state properties as before. However, from a comparison of the measured pulse period with that obtained close to the start of the anomalous low-state, it is evident that Her X-1 continued to spin-down strongly during the anomalous low-state such that the pulse period has returned to a similar value as ~15 years ago. Additionally, the occurrence time of the main-on states after the end of the anomalous low-state indicate that a change in the length, or phasing, of the 35-day cycle occurred during the anomalous low-state., Comment: 5 pages, 5 figures, accepted for publication in A&A

We present preliminary results on our campaign of observations of the X-ray binary pulsar GX301-2. BeppoSAX observed this source six times in January/February 1998: at the periastron and apoastron, and at other four, intermediate, orbital phases. We present preliminary results on the GX301-2 spectral and temporal behaviour as a function of orbital phase., 4 pages, 2 figures, to appear in Proc 32nd COSPAR Symposium

The study of the hard (E>10 keV) energy spectra of X-ray binary pulsars can give a wealth of information on the physical processes that occur close to the neutron star surface. Extreme matter regimes are probed, and precious information on how matter and radiation behave and interact in critical conditions can be obtained. We will give an overview on the most recent results obtained by RXTE and BeppoSAX on this class of objects, in order to pass the baton onto just launched experiments, like INTEGRAL, or soon to be launched, like AGILE and ASTRO-E2., 10 Pages, 5 figures. Conference proceedings 4th AGILE Science Workshop "X-ray and Gamma-ray Astrophysics of Galactic Sources", Rome 11-13 June 2003