A5016574610- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- SAS software applications and methods
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Mechanics and Biomechanics Studies
- Astronomy and Astrophysical Research
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Scientific Measurement and Uncertainty Evaluation
- Geophysics and Sensor Technology
- Particle Detector Development and Performance
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Astrophysics and Star Formation Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Anesthesia and Sedative Agents
- Neuroscience and Neuropharmacology Research
- Cosmology and Gravitation Theories
Astronomical Observatory of Rome
2015-2024
Institute for Space Astrophysics and Planetology
2014-2024
Czech Academy of Sciences, Astronomical Institute
2024
Università Cattolica del Sacro Cuore
2022-2024
Agostino Gemelli University Polyclinic
2024
National Institute for Astrophysics
2012-2023
Istituti di Ricovero e Cura a Carattere Scientifico
1999-2022
Associazione Nazionale Medici Cardiologi Ospedalieri
2017
University of Naples Federico II
1989-2016
Marshall Space Flight Center
2011-2016
The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory gamma-ray burst (GRB) astronomy. It first-of-its-kind autonomous rapid-slewing satellite transient astronomy and pioneers the way future rapid-reaction missions. will be far more powerful than any previous GRB observing 100 bursts yr-1 performing detailed X-ray UV/optical afterglow observations spanning timescales from 1 minute to several days after burst. objectives are (1) determine origin of GRBs, (2)...
The quasi-blackbody plus power-law spectra of many accreting black-hole sources suggests that relatively cold matter is surrounded by hard X-ray emitting plasma. Fluorescent iron lines are produced X-irradiation the gas. shape and variability these can be used to map innermost regions around black hole. In case a disc geometry for gas, effects doppler-broadening gravitational transverse redshifts produce characteristic line profile which depends upon inclination. We show here broad, emission...
Relativistic dragging of inertial frames around fast-rotating collapsed stars is substantial and can give rise to observable effects. We consider kHz quasi-periodic oscillation (QPO) sources, low-mass X-ray binaries (LMXRBs) containing an accreting neutron star. Within beat frequency models, both the Keplerian innermost region accretion disk (~0.3-1.2 kHz) star spin (~0.3-0.4 are directly observed. From these, Lense-Thirring precession (tens Hz) same material as gives QPOs determined within...
A remarkable correlation between the centroid frequencies of quasi-periodic oscillations (or peaked noise components) from low-mass X-ray binaries has been recently discovered by Psaltis, Belloni, & van der Klis. This extends over nearly three decades in frequency and encompasses both neutron star black hole candidate systems. We discuss this result light relativistic precession model, which proposed to interpret kilohertz (QPOs) as well some lower QPOs atoll Z classes. Unlike other models,...
Spinning up an extragalactic neutron star Ultraluminous x-ray sources (ULXs) are strange objects in other galaxies that cannot be explained by conventional accretion onto stellar-mass objects. This has led to exotic interpretations, such as the long-sought intermediate-mass black holes. Israel et al. observed a ULX nearby galaxy NGC 5907 and found it is instead star. The spinning accreting material so fast its spin period quickly accelerating. only way can consume enough explain these...
One of the primary science goals next generation hard X-ray timing instruments is to determine equation state matter at supranuclear densities inside neutron stars, by measuring radius stars with different masses accuracies a few percent. Three main techniques can be used achieve this goal. The first involves waveform modelling. flux we observe from hotspot on star surface offset rotational pole will modulated star's rotation, giving rise pulsation. Information about mass and encoded into...
We have discovered rapid quasi-periodic oscillations (QPOs) in RXTE/PCA measurements of the pulsating tail 2004 December 27 giant flare SGR 1806-20. QPOs at ~92.5 Hz are detected a 50 s interval starting 170 after onset flare. These appear to be associated with increased emission by relatively hard unpulsed component and seen only over phases 7.56 spin period pulsations away from main peak. ~18 ~30 also ~200-300 This is first time that unambiguously flux soft gamma-ray repeater or any other...
view Abstract Citations (402) References (45) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Intermittent Stellar Wind Acceleration and the Long-Term Activity of Population I Binary Systems Containing an X-Ray Pulsar Stella, L. ; White, N. E. Rosner, R. The full range possible regimes for a magnetized neutron star that interacts with stellar wind OB is investigated, results are compared observational data. observed properties system parameters all currently...
We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to September 2009, for total 76 GRBs, and present an additional three pre-Swift not included in earlier sample. Furthermore, we publish 840 new points 42 GRB afterglows, sets 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A 080810. analyzed light curves all derived spectral energy distributions with best quality, allowing us estimate host...
NGC 7793 P13 is a variable (luminosity range ~100) ultraluminous X-ray source (ULX) proposed to host stellar-mass black hole of less than 15 M$_{\odot}$ in binary system with orbital period 64 d and 18-23 B9Ia companion. Within the EXTraS project we discovered pulsations at ~0.42 s two XMM-Newton observations P13, during which was detected $L_{\mathrm{X}}\sim2.1\times10^{39}$ $5\times10^{39}$ erg s$^{-1}$ (0.3-10 keV band). These findings unambiguously demonstrate that compact object neutron...
Soft gamma repeaters and anomalous x-ray pulsars form a rapidly increasing group of sources exhibiting sporadic emission short bursts. They are believed to be magnetars, i.e. neutron stars powered by extreme magnetic fields, B~10^{14}-10^{15} Gauss. We report on soft repeater with low field, SGR 0418+5729, recently detected after it emitted bursts similar those magnetars. X-ray observations show that its dipolar field cannot greater than 7.5x10^{12} Gauss, well in the range ordinary radio...
Gamma-ray bursts (GRBs) have been separated into two classes, originally along the lines of duration and spectral properties, called "short/hard" "long/soft." The latter conclusively linked to explosive deaths massive stars, while former are thought result from merger or collapse compact objects. In recent years, indications accumulating that short/hard versus long/soft division does not map directly onto what would be expected classes progenitors, leading a new classification scheme Type I...
We present a systematic analysis of the fast time variability properties transient black hole binary GRO J1655-40, based on complete set RossiXTE observations. demonstrate that frequencies quasi-periodic oscillations and broad band noise components their variations match accurately strong field general relativistic particle motion in close vicinity innermost stable circular orbit, as predicted by precession model. obtain high precision measurements mass (M = (5.31 +/- 0.07) M solar masses,...
Abstract We discovered 2.8 s pulsations in the X-ray emission of ultraluminous source (ULX) M51 ULX-7 within UNSEeN project, which was designed to hunt for new pulsating ULXs (PULXs) with XMM-Newton. The pulse shape is sinusoidal, and large variations its amplitude were observed even single exposures (pulsed fraction from less than 5% 20%). Source variable, generally at an luminosity between 10 39 40 erg −1 , located outskirts spiral galaxy M51a a distance 8.6 Mpc. According our analysis,...
We consider the interpretation of a pair kHz quasiperiodic oscillations (QPOs) in Fourier spectra two low-mass x-ray binaries, Sco X-1 and 4U1608-52, hosting an old accreting neutron star. The observed frequency difference these QPOs decreases as their increases, contrary to simple beat models. show that behavior is instead well matched terms fundamental frequencies for test particle motion gravitational field star, reasonable star masses, nearly independent spin. These results are not...
Three main types of low-frequency quasi-periodic oscillations (LFQPOs) have been observed in Black Hole Candidates. We re-analyzed RXTE data the bright systems XTE J1859+226, J1550-564 and GX 339-4, which show all three them. review properties these LFQPOs that they follow a well-defined correlation fractional rms vs. softness diagram. frequency behavior through this presents clear analogies with Horizontal-, Normal- Flaring-Branch Oscillations Z sources, inverse being equivalent curvilinear...
Optical and near-infrared observations of the gamma-ray burst GRB 031203, at z = 0.1055, are reported. A very faint afterglow is detected superposed onto host galaxy in our first infrared JHK observations, carried out ~9 hr after burst. Subsequently, a rebrightening all bands, peaking R band about 18 rest-frame days The closely resembles light curve supernova like SN 1998bw, assuming that went off almost simultaneously, but with somewhat slower evolution. Spectra taken close to maximum show...
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We present a scenario ("supranova") for the formation of gamma-ray bursts (GRBs) occurring when supramassive neutron star (SMNS) loses so much angular momentum that centrifugal support against self-gravity becomes impossible, and implodes to black hole. This may be most baryon-clean environment proposed far, because SN explosion in which SMNS forms sweeps medium surrounding remnant, quickly spinning remnant energy through magnetic dipole radiation at rate exceeding its Eddington luminosity...