A5067538195- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Mechanics and Biomechanics Studies
- Astrophysics and Cosmic Phenomena
- Particle Detector Development and Performance
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Scientific Measurement and Uncertainty Evaluation
- Radiation Detection and Scintillator Technologies
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced X-ray Imaging Techniques
- Statistical and numerical algorithms
- Atomic and Subatomic Physics Research
- Nuclear Materials and Properties
- Nuclear Physics and Applications
- Thermodynamic and Structural Properties of Metals and Alloys
- Galaxies: Formation, Evolution, Phenomena
- Radioactive Decay and Measurement Techniques
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
Osservatorio Astronomico di Cagliari
2022-2024
National Institute for Astrophysics
2004-2022
Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano
1991-2004
Institute for Space Astrophysics and Planetology
1998-2004
Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna
2003
National Academies of Sciences, Engineering, and Medicine
2000
SRON Netherlands Institute for Space Research
2000
Joint Research Centre
1966-1970
We examined the maximum bolometric peak luminosities during type I X-ray bursts from persistent or transient luminous sources in globular clusters. show that for about two thirds of photospheric radius expansion extend to a critical value erg s-1, assuming total burst emission is entirely due black-body radiation and recorded luminosity actual luminosity. This empirical consistent with Eddington limit hydrogen poor material. Since more less always reached (except one source), such may be...
We report on a comprehensive analysis of simultaneous X-ray polarimetric and spectral data the bright atoll source GX 9+9 with Imaging Polarimetry Explorer (IXPE) NuSTAR. The is significantly polarized in 4--8 keV band, degree $2.2\% \pm 0.5\%$ (uncertainty at 68% confidence level). NuSTAR broad-band spectrum clearly shows an iron line, well described by model including thermal disk emission, Comptonized component, reflection. From spectro-polarimetric fit, we obtain upper limit to...
Abstract The launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 2021 December 9 has opened a new window in astronomy. We report here results first IXPE observation weakly magnetized neutron star, GS 1826−238, performed 2022 March 29–31 when source was high soft state. An upper limit (99.73% confidence level) 1.3% for linear polarization degree is obtained over 2–8 keV energy range. Coordinated INTEGRAL and NICER observations were carried out simultaneously with IXPE. spectral...
Abstract The Imaging X-ray Polarimetry Explorer measured with high significance the polarization of brightest Z-source, Sco X-1, resulting in nominal 2–8 keV energy band a degree 1.0% ± 0.2% and angle 8° 6° at 90% confidence level. This observation was strictly simultaneous observations performed by NICER, NuSTAR, Insight-HXMT, which allowed for precise characterization its broadband spectrum from soft to hard X-rays. source has been observed mainly state, short periods flaring. We also...
We report the first high-energy survey catalog obtained with IBIS gamma-ray imager on board INTEGRAL. The analysis has been performed first-year Core Program ISGRI data comprising both Galactic Plane Scan and Centre Deep Exposure pointings for a total exposure time exceeding 5 Ms. This initial revealed presence of ~120 sources detected unprecedented sensitivity ~1 mcrab in energy range 20-100 keV. Each source is located to an accuracy between 1' 3', depending its brightness. outstanding...
ABSTRACT We report spectro-polarimetric results of an observational campaign the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER, and INTEGRAL. Consistently with previous results, broad-band spectrum is characterized a lower-energy component, attributed to accretion disc kTin ≈ 1 keV, plus unsaturated Comptonization in thermal plasma temperature kTe = 3 keV optical depth τ 4, assuming slab geometry. measure polarization degree 2–8 band P 1.8 ± 0.3 per...
Abstract This paper reports the first detection of polarization in X-rays for atoll-source 4U 1820−303, obtained with Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed radio Australia Telescope Compact Array. The IXPE observations 1820−303 coordinated Swift Telescope, Neutron Star Interior Composition Explorer, and Nuclear Spectroscopic Array aiming to obtain an accurate spectral model covering a broad...
We present an overview of BeppoSAX Wide Field Cameras observations the nine most frequent type I X-ray bursters in Galactic center region. Six years (from 1996 to 2002) have amounted 7 Ms and detection 1823 bursts. The 3 are GX 354-0 (423 bursts), KS 1731-260 (339) GS 1826-24 (260). These numbers reflect unique dataset. show that all sources same global burst behavior as a function luminosity. At lowest luminosities () bursts occur quasi-periodically rate increases linearly with accretion...
We have discovered three certain (SAX J1324.5-6313, 2S 1711-339 and SAX J1828.5-1037) two likely J1818.7+1424 J2224.9+5421) new thermonuclear X-ray burst sources with the BeppoSAX Wide Field Cameras, observed a second ever from sixth one (2S 0918-549). Four of them (excluding 0918-549) are newly detected which we single bursts, but no persistent emission. observe first 11 bursts 1711-339; flux was during ten not around last burst. A recently 0918-549 by Jonker et al. (2001); showing radius...
We report on the coordinated observations of neutron star low-mass X-ray binary (NS-LMXB) GX 5−1 in X-rays (IXPE, NICER, NuSTAR , and INTEGRAL), optical (REM LCO), near-infrared (REM), mid-infrared (VLT VISIR), radio (ATCA). This Z-source was observed by IXPE twice March–April 2023 (Obs. 1 2). In band source detected, but only upper limits to linear polarization were obtained at a 3 σ level 6.1% 5.5 GHz 5.9% 9 Obs. 12.5% 20% 2. The mid-IR, near-IR, suggest presence compact jet that peaks...
Data of the 1996 outburst single-known accreting millisecond pulsar SAX J1808.4-3658, taken with Wide Field Cameras (WFCs) on BeppoSAX, are revisited more complete data coverage and comprehensive analysis techniques than in a previous report. An additional type-I X-ray burst was identified which occurred at time when persistent emission is below detection limit, roughly 30 days after maximum. This three times longer first two bursts, 50% brighter. It brightest within ~1700 bursts detected so...
ABSTRACT X-ray polarimetry missions like Imaging Polarimetry Explorer will be able to measure for the first time polarization properties of accreting, weakly magnetized neutron stars in low-mass binaries. In this work, we present simulations expected polarized signal, including coronal emission different geometries corona itself, i.e. a slab above accretion disc and spherical shell around star. The are performed with fully relativistic Monte Carlo code monk capable computing degree angle...
We report on an approximately twelve hour long X-ray flare from the low-mass binary KS 1731-260. The has a rise time of less than 13 min and declines exponentially with decay 2.7 hours. emission is well described by black-body radiation peak temperature 2.4 keV. total energy release event 10^{42} erg (for assumed distance 7 kpc). all characteristics thermo-nuclear bursts (so-called type I bursts), except for its very duration therefore large (factor 1500-4000 longer 250-425 more normal this...
The transient X-ray source GS 1826-238 was monitored during five different observing periods between 1996 August and 1998 October with the BeppoSAX Wide Field Camera instrument in framework of a deep observation Galactic center region. During this time, first detection bursts from occurred, ruling out its previously suggested black hole candidacy strongly suggesting compact object to be weakly magnetized neutron star. 2.5 yr monitoring, corresponding ~2.0 Ms 70 were detected source. Here we...
1RXS J180408.9--342058 is a low mass X-ray binary hosting neutron star, which shows activity at very different mass-accretion regimes, from faint to almost the Eddington luminosity. In this work, we present comprehensive study of source using data Neil Gehrels Swift Observatory, NuSTAR and INTEGRAL/JEM-X. order follow spectral evolution, analysed 2015 outburst three Nustar observations. Besides canonical hard soft states, identified rarely observed intermediate state. This was witnessed by...
SLX 1737-282 is a persistent moderately bright X-ray source 12 from the Galactic center. observations with Wide Field Cameras on BeppoSAX have for first time revealed true nature of 1737-282: 15 min long thermonuclear flash was detected exposing as neutron star in binary system. The Eddington-limited constraining distance to between 5 and 8 kpc. We analyze BeppoSAX, ROSAT, RXTE data 1737-282. 0.5–200 keV luminosity close or less than 1% Eddington limit which implies rarely-seen circumstance activity.
During a 50 ks monitoring observation of the Galactic bulge performed in September 1999 by Wide Field Cameras on board BeppoSAX satellite, an X-ray burst was detected from sky position ~ off centre. No previously known sources are located within error circle observed burst. The new burster, SAX J1752.3-3138, did not show any persistent emission during whole observation. other bursting events, as well steady emission, were reported so far instruments or WFC archive, which covers ~6 Ms and ~4...
Low-mass X-ray binaries hosting weakly magnetized neutron stars (NS-LMXBs) are among the brightest sources in sky. Since 2021, Imaging Polarimetry Explorer (IXPE) has provided new measurements of polarization these sources. IXPE observations have revealed that most NS-LMXBs significantly polarized X-rays, providing unprecedented insight into geometry their accretion flow. In this review paper, we summarize first results obtained by on NS-LMXBs, emerging trends within each class (atoll/Z),...
GX 3+1 is a low-mass X-ray binary that persistently bright since its discovery in 1964.It was found to be an burster twenty years ago proving the compact object this system neutron star.The burst rate so low only 18 bursts were reported prior 1996.The Wide Field Cameras on BeppoSAX have, through dedicated monitoring program Galactic center region, increased number of from by 61.Since exhibits slow (order years) modulation persistent flux about 50%, these observations opens up unique...
Context. The spectroscopic characteristics of GS 1826−238, a neutron star in low-mass X-ray binary system, have already been studied by sensitive, wide band telescopes (e.g. BeppoSAX, RXTE, INTEGRAL). Up to now, the source has always observed low-hard spectral state, with two components typically detected. persistent high-energy (>10 keV) emission is effectively explained thermal Comptonisation hot electron cloud (kTe ~ 20 keV); further low energy component, modelled either pure blackbody or...