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Results for "R. Riggio"

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Design and Experimental Validation of a Software-Defined Radio Access Network Testbed with Slicing SupportMay 14 2019Network slicing is a fundamental feature of 5G systems to partition a single network into a number of segregated logical networks, each optimized for a particular type of service, or dedicated to a particular customer or application. The realization of ... More
Chandra X-ray spectroscopy of a clear dip in GX 13+1Mar 01 2014Mar 11 2014The source GX 13+1 is a persistent, bright Galactic X-ray binary hosting an accreting neutron star. It shows highly ionized absorption features, with a blueshift of $\sim$ 400 km s$^{-1}$ and an outflow-mass rate similar to the accretion rate. Many other ... More
Discovery of periodic dips in the light curve of GX 13+1: the X-ray orbital ephemeris of the sourceOct 24 2013The bright low-mass X-ray binary (LMXB) GX 13+1 is one of the most peculiar Galactic binary systems. A periodicity of 24.27 d with a formal statistical error of 0.03 d was observed in its power spectrum density obtained with RXTE All Sky Monitor (ASM) ... More
Resolving the Fe xxv Triplet with Chandra in Cen X-3Oct 21 2005We present the results of a 45 ks Chandra observation of the high-mass X-ray binary Cen X--3 at orbital phases between 0.13 and 0.40 (in the eclipse post-egress phases). Here we concentrate on the study of discrete features in the energy spectrum at energies ... More
Precise determination of orbital parameters in system with slowly drifting phases: application to the case of XTE J1807-294Aug 03 2007We describe a timing technique that allows to obtain precise orbital parameters of an accreting millisecond pulsar in those cases in which intrinsic variations of the phase delays (caused e.g. by proper variation of the spin frequency) with characteristic ... More
Spin down during quiescence of the fastest known accretion-powered pulsarJun 07 2010Feb 15 2011We present a timing solution for the 598.89 Hz accreting millisecond pulsar, IGR J00291+5934, using Rossi X-ray Timing Explorer data taken during the two outbursts exhibited by the source on 2008 August and September. We estimate the neutron star spin ... More
Spin up and phase fluctuations in the timing of the accreting millisecond pulsar XTE J1807-294Oct 18 2007Jan 21 2008We performed a timing analysis of the 2003 outburst of the accreting X-ray millisecond pulsar XTE J1807-294 observed by RXTE. Using recently refined orbital parameters we report for the first time a precise estimate of the spin frequency and of the spin ... More
Protein adsorption onto Fe3O4 nanoparticles with opposite surface charge and its impact on cell uptakeMar 16 2014Mar 24 2014Nanoparticles (NPs) engineered for biomedical applications are meant to be in contact with protein-rich physiological fluids. These proteins are usually adsorbed onto the NP surface, forming a swaddling layer called protein corona that influences cell ... More
X-ray spectroscopy of the ADC source X1822-371 with Chandra and XMM-NewtonOct 02 2012The eclipsing low-mass X-ray binary X1822-371 is the prototype of the accretion disc corona (ADC) sources. We analyse two Chandra observations and one XMM-Newton observation to study the discrete features and their variation as a function of the orbital ... More
New ephemeris of the ADC source 2A 1822-371: a stable orbital-period derivative over 30 yearsJun 16 2010We report on a timing of the eclipse arrival times of the low mass X-ray binary and X-ray pulsar 2A 1822-371 performed using all available observations of the Proportional Counter Array on board the Rossi X-ray Timing Explorer, XMM-Newton pn, and Chandra. ... More
Timing of the 2008 Outburst of SAX J1808.4-3658 with XMM-Newton: A Stable Orbital Period Derivative over Ten YearsFeb 12 2009Mar 10 2009We report on a timing analysis performed on a 62-ks long XMM-Newton observation of the accreting millisecond pulsar SAX J1808.4-3658 during the latest X-ray outburst that started on September 21, 2008. By connecting the time of arrivals of the pulses ... More
Charm hadrons and lattice QCDFeb 01 2017We review two lattice calculations involving charm hadrons: a determination of the vector and scalar form factors of the semileptonic $D \to \pi \ell \nu$ decays, which are relevant for the extraction of the CKM matrix element $\lvert V_{cd} \rvert$ from ... More
XMM-Newton detects a relativistically broadened iron line in the spectrum of the ms X-ray pulsar SAX J1808.4-3658Dec 05 2008Dec 22 2008We report on a 63-ks long XMM-Newton observation of the accreting millisecond pulsar SAX J1808.4-3658 during the latest X-ray outburst which started on September 21st 2008. The pn spectrum shows a highly significant emission line in the energy band where ... More
Detailed study of the X-ray and Optical/UV orbital ephemeris of X1822-371Jul 13 2012Recent studies of the optical/UV and X-ray ephemerides of X1822-371 have found some discrepancies in the value of the orbital period derivative. Because of the importance of this value in constraining the system evolution, we comprehensively analyse all ... More
A ionized reflecting skin above the accretion disk of GX 349+2Jun 19 2009The broad emission features in the Fe-Kalpha region of X-ray binary spectra represent an invaluable probe to constrain the geometry and the physics of these systems. Several Low Mass X-ray binary systems (LMXBs) containing a neutron star (NS) show broad ... More
The spin and orbit of the newly discovered pulsar IGR J17480-2446Oct 22 2010Dec 03 2010We present an analysis of the spin and orbital properties of the newly discovered accreting pulsar IGR J17480-2446, located in the globular cluster Terzan 5. Considering the pulses detected by the Rossi X-ray Timing Explorer at a period of 90.539645(2) ... More
Discovery of a new accreting millisecond X-ray pulsar in the globular cluster NGC 2808Nov 09 2016We report on the discovery of coherent pulsations at a period of 2.9 ms from the X-ray transient MAXI J0911-655 in the globular cluster NGC 2808. We observed X-ray pulsations at a frequency of $\sim339.97$ Hz in three different observations of the source ... More
X-ray bursts and burst oscillations from the slowly spinning X-ray pulsar IGR J17480-2446 (Terzan 5)Feb 07 2011Feb 08 2011The newly discovered 11 Hz accreting pulsar, IGR J17480-2446, located in the globular cluster Terzan 5, has shown several bursts with a recurrence time as short as few minutes. The source shows the shortest recurrence time ever observed from a neutron ... More
The X-ray spectrum of the newly discovered accreting millisecond pulsar IGR J17511-3057May 26 2010We report on an XMM-Newton observation of the accreting millisecond pulsar, IGR J17511-3057. Pulsations at 244.8339512(1) Hz are observed with an RMS pulsed fraction of 14.4(3)%. A precise solution for the P_orb=12487.51(2)s binary system is derived. ... More
Secular spin-down of the AMP XTE J1751-305May 10 2011May 11 2011Context. Of the 13 known accreting millisecond pulsars, only a few showed more than one outburst during the RXTE era. XTE J1751-305 showed, after the main outburst in 2002, other three dim outbursts. We report on the timing analysis of the latest one, ... More
Timing of the accreting millisecond pulsar IGR~J17511--3057Oct 29 2010{Timing analysis of Accretion-powered Millisecond Pulsars (AMPs) is a powerful tool to probe the physics of compact objects. The recently discovered \newigrj is the 12 discovered out of the 13 AMPs known. The Rossi XTE satellite provided an extensive ... More
Timing of the accreting millisecond pulsar SAX J1748.9-2021 during its 2015 outburstMar 29 2016We report on the timing analysis of the 2015 outburst of the intermittent accreting millisecond X-ray pulsar SAX J1748.9-2021 observed on March 4 by the X-ray satellite XMM-Newton. By phase-connecting the time of arrivals of the observed pulses, we derived ... More
Timing an Accreting Millisecond Pulsar: Measuring the Accretion Torque in IGR J00291+5934Sep 08 2005We present here a timing analysis of the fastest accreting millisecond pulsar IGR J00291+5934 using RXTE data taken during the outburst of December 2004. We corrected the arrival times of all the events for the orbital (Doppler) effects and performed ... More
Fermat-like equations that are not partition regularMay 24 2016By means of elementary conditions on coefficients, we isolate a large class of Fermat-like Diophantine equations that are not partition regular, the simplest examples being $x^n+y^m=z^k$ with $k\notin\{n,m\}$.
Timing an Accreting Millisecond Pulsar: Measuring the Accretion Torque in IGR J00291+5934Nov 07 2006Nov 13 2006We performed a timing analysis of the fastest accreting millisecond pulsar IGR J00291+5934 using RXTE data taken during the outburst of December 2004. We corrected the arrival times of all the events for the orbital (Doppler) effects and performed a timing ... More
The accretion flow to the intermittent accreting ms pulsar, HETE J1900.1-2455, as observed by XMM-Newton and RXTEDec 11 2012We present a study of the accretion flow to the intermittent accreting millisecond pulsar, HETE J1900.1-2455, based on observations performed simultaneously by XMM-Newton and RXTE. The 0.33-50 keV spectrum is described by the sum of a hard Comptonized ... More
A $N_f = 2 + 1 + 1$ "twisted" determination of the $b$-quark mass, $f_{B}$ and $f_{B_s}$Nov 12 2013We present a lattice QCD determination of the $b$-quark mass and of the $f_{B_s}$ and $f_B$ decay constants performed with $N_f = 2 + 1 + 1$ twisted mass Wilson fermions. We have used simulations at three values of the lattice spacing generated by ETMC ... More
A relativistically smeared spectrum in the neutron star X-ray Binary 4U 1705-44: Looking at the inner accretion disc with X-ray spectroscopyApr 21 2009Jul 09 2009Iron emission lines at 6.4-6.97 keV, identified with fluorescent Kalpha transitions, are among the strongest discrete features in the X-ray band. These are therefore one of the most powerful probes to infer the properties of the plasma in the innermost ... More
A complete X-ray spectral coverage of the 2010 May-June outbursts of Circinus X-1Apr 11 2012May 01 2012Circinus X-1 is a neutron-star-accreting X-ray binary in a wide (P$_{\rm orb}$ = 16.6 d), eccentric orbit. After two years of relatively low X-ray luminosity, in May 2010 Circinus X-1 went into outburst, reaching 0.4 Crab flux. This outburst lasted for ... More
Suzaku broad-band spectrum of 4U 1705-44: Probing the Reflection component in the hard stateFeb 26 2015Iron emission lines at 6.4-6.97 keV, identified with Kalpha radiative transitions, are among the strongest discrete features in the X-ray band. These are one of the most powerful probes to infer the properties of the plasma in the innermost part of the ... More
Testing Rate Dependent corrections on timing mode EPIC-pn spectra of the accreting Neutron Star GX 13+1Sep 24 2014Sep 27 2014When the EPIC-pn instrument on board XMM-Newton is operated in Timing mode, high count rates (>100 cts/s) of bright sources may affect the calibration of the energy scale, resulting in a modification of the real spectral shape. The corrections related ... More
The discovery of the 401 Hz accreting millisecond pulsar IGR J17498-2921 in a 3.8 hr orbitNov 08 2011We report on the detection of a 400.99018734(1) Hz coherent signal in the Rossi X-ray Timing Explorer light curves of the recently discovered X-ray transient, IGR J17498-2921. By analysing the frequency modulation caused by the orbital motion observed ... More
The near-IR counterpart of IGR J17480-2446 in Terzan 5Oct 31 2012Some globular clusters in our Galaxy are noticeably rich in low-mass X-ray binaries. Terzan 5 has the richest population among globular clusters of X- and radio-pulsars and low-mass X-ray binaries. The detection and study of optical/IR counterparts of ... More
Pseudoscalar decay constants $f_K/f_π$, $f_D$ and $f_{D_s}$ with $N_f = 2 + 1 + 1$ ETMC configurationsNov 13 2013We present a lattice QCD calculation of the pseudoscalar decay constants $f_K$, $f_D$ and $f_{D_s}$ performed by the European Twisted Mass Collaboration with $N_f = 2 + 1 + 1$ dynamical fermions. We simulated at three different values of the lattice spacing, ... More
Signature of the presence of a third body orbiting around XB 1916-053Jul 29 2015The ultra-compact dipping source \object{XB 1916-053} has an orbital period of close to 50 min and a companion star with a very low mass (less than 0.1 M$_{\odot}$). The orbital period derivative of the source was estimated to be $1.5(3) \times 10^{-11}$ ... More
The broadband spectral analysis of 4U 1702-429 using XMM-Newton and BeppoSAX dataNov 27 2018Most of the X-ray binary systems containing neutron stars classified as Atoll sources show two different spectral states, called soft and hard. Moreover, a large number of these systems show a reflection component relativistically smeared in their spectra, ... More
Mass of the b-quark and B-decay constants from Nf=2+1+1 twisted-mass Lattice QCDMar 14 2016Jun 10 2016We present precise lattice computations for the b-quark mass, the quark mass ratios mb/mc and mb/ms as well as the leptonic B-decay constants. We employ gauge configurations with four dynamical quark flavors, up/down, strange and charm, at three values ... More
Spectral analysis of the dipping LMXB system XB 1916-053Apr 11 2019Context: XB 1916-053 is a low mass X-ray binary system (LMXB) hosting a neutron star (NS) and showing periodic dips. The spectrum of the persistent emission was modeled with a blackbody component having a temperature between 1.31 and 1.67 keV and with ... More
Discovery of a soft X-ray 8 mHz QPO from the accreting millisecond pulsar IGR J00291+5934Nov 21 2016In this paper, we report on the analysis of the peculiar X-ray variability displayed by the accreting millisecond X-ray pulsar IGR J00291+5934 in a 80 ks-long joint NuSTAR and XMM-Newton observation performed during the source outburst in 2015. The light ... More
A determination of the average up-down, strange and charm quark masses from $N_f=2+1+1$Nov 12 2013Nov 13 2013We present a lattice QCD determination of the average up-down, strange and charm quark masses based on simulations performed by the European Twisted Mass Collaboration with $N_f = 2 + 1 + 1$ dynamical fermions. We simulated at three different values of ... More
Discovery of a soft X-ray 8 mHz QPO from the accreting millisecond pulsar IGR J00291+5934Nov 21 2016Nov 28 2016In this paper, we report on the analysis of the peculiar X-ray variability displayed by the accreting millisecond X-ray pulsar IGR J00291+5934 in a 80 ks-long joint NuSTAR and XMM-Newton observation performed during the source outburst in 2015. The light ... More
SAX J1808.4-3658, an accreting millisecond pulsar shining in gamma rays?Nov 16 2015We report the detection of a possible gamma-ray counterpart of the accreting millisecond pulsar SAX J1808.4-3658. The analysis of ~6 years of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) within a region of ... More
Leptonic decay constants fK, fD and fDs with Nf = 2+1+1 twisted-mass lattice QCDNov 28 2014Feb 25 2015We present a lattice QCD calculation of the pseudoscalar decay constants fK, fD and fDs performed using the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks, which include in the sea, besides ... More
SWIFT J1756.9-2508: spectral and timing properties of its 2018 outburstAug 21 2018Aug 22 2018We discuss the spectral and timing properties of the accreting millisecond X-ray pulsar SWIFT J1756.9-2508 observed by XMM-Newton, NICER and NuSTAR during the X-ray outburst occurred in April 2018. The spectral properties of the source are consistent ... More
XMM-Newton detection of the 2.1 ms coherent pulsations from IGR J17379-3747Jul 23 2018Jul 24 2018We report on the detection of X-ray pulsations at 2.1 ms from the known X-ray burster IGR J17379-3747 using XMM-Newton. The coherent signal shows a clear Doppler modulation from which we estimate an orbital period of ~1.9 hours and a projected semi-major ... More
Updated orbital ephemeris of the ADC source X 1822-371: a stable orbital expansion over 40 yearsMay 08 2019The source X 1822-371 is an eclipsing compact binary system with a period close to 5.57 hr and an orbital period derivative $\dot{P}_{\rm orb}$ of 1.51(7)$\times 10^{-10}$ s s$^{-1}$. The very large value of $\dot{P}_{\rm orb}$ is compatible with a super-Eddington ... More
New orbital ephemerides for the dipping source 4U 1323-619: constraining the distance to the sourceMar 14 20164U 1323-619 is a low mass X-ray binary system that shows type I X-ray bursts and dips. The most accurate estimation of the orbital period is 2.941923(36) hrs and a distance from the source that is lower than 11 kpc has been proposed. We aim to obtain ... More
Study of the reflection spectrum of the LMXB 4U 1702-429Sep 21 2016The source 4U 1702-429 (Ara X-1) is a low-mass X-ray binary system hosting a neutron star. Albeit the source is quite bright ( $\sim10^{37}$ erg s$^{-1}$) its broadband spectrum has never been studied. Neither dips nor eclipses have been observed in the ... More
Heavy flavour precision physics from Nf = 2 + 1 + 1 lattice simulationsNov 03 2014We present precision lattice calculations of the pseudoscalar decay constants of the charmed sector as well as determinations of the bottom quark mass and its ratio to the charm quark mass. We employ Nf=2+1+1 dynamical quark gauge configurations generated ... More
The pulse profile and spin evolution of the accreting pulsar in Terzan 5, IGR J17480-2446, during its 2010 outburstMar 19 2012(abridged) We analyse the spectral and pulse properties of the 11 Hz transient accreting pulsar, IGR J17480-2446, in the globular cluster Terzan 5, considering all the available RXTE, Swift and INTEGRAL observations performed between October and November, ... More
Broadband spectral analysis of MXB 1659-298 in its soft and hard stateJul 30 2018The X-ray transient eclipsing source MXB 1659-298 went in outburst in 1999 and 2015, respectively. During these two outbursts the source was observed by XMM-Newton, NuSTAR and Swift/XRT. Using these observations we studied the broadband spectrum of the ... More
A possible cyclotron resonance scattering feature near 0.7 keV in X1822-371Mar 17 2015We analyse all available X-ray observations of X1822-371 made with XMM-Newton, Chandra, Suzaku and INTEGRAL satellites. The observations were not simultaneous. The Suzaku and INTEGRAL broad band energy coverage allows us to constrain the spectral shape ... More
Subarcsecond location of IGR J17480-2446 with Rossi XTEJun 21 2012On 2010 October 13, the X-ray astronomical satellite Rossi XTE, during the observation of the newly discovered accretion powered X-ray pulsar IGR J17480--2446, detected a lunar occultation of the source. From knowledge of lunar topography and Earth, Moon, ... More
GRO J1744-28: an intermediate B-field pulsar in a low mass X-ray binaryMar 10 2015The bursting pulsar, GRO J1744-28, went again in outburst after $\sim$18 years of quiescence in mid-January 2014. We studied the broad-band, persistent, X-ray spectrum using X-ray data from a XMM-Newton observation, performed almost at the peak of the ... More
Testing reflection features in 4U 1705-44 with XMM-Newton, BeppoSAX and RXTE in the hard and soft stateNov 13 2012We use data of the bright atoll source 4U 1705-44 taken with XMM-Newton, BeppoSAX and RXTE both in the hard and in the soft state to perform a self-consistent study of the reflection component in this source. Although the data from these X-ray observatories ... More
Lattice QCD Study of $B$-meson Decay Constants from ETMCNov 20 2014We discuss a lattice QCD computation of the $B$-meson decay constants by the ETM collaboration where suitable ratios allow to reach the bottom quark sector by combining simulations around the charm-quark mass with an exactly known static limit. The different ... More
A self-consistent approach to the hard and soft states of 4U 1705-44Apr 12 2010Apr 13 2010We analyzed two XMM-Newton observations of the bright atoll source 4U 1705-44, which can be considered a prototype of the class of the persistent NS LMXBs showing both hard and soft states. The first observation was performed when the source was in a ... More
Up, down, strange and charm quark masses with Nf = 2+1+1 twisted mass lattice QCDMar 18 2014Aug 21 2014We present a lattice QCD calculation of the up, down, strange and charm quark masses performed using the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two ... More
$D\toπ$ and $D\to K$ semileptonic form factors with $N_f=2+1+1$ twisted mass fermionsOct 19 2017We present a lattice determination of the vector and scalar form factors of the $D\to\pi(K)\ell\nu$ semileptonic decays, which are relevant for the extraction of the CKM matrix elements $|V_{cd}|$ and $|V_{cs}|$ from experimental data. Our analysis is ... More
Hypercubic effects in semileptonic decays of heavy mesons, toward $B \to π\ell ν$, with $N_f=2+1+1$ Twisted fermionsNov 26 2018We present a preliminary study toward a lattice determination of the vector and scalar form factors of the $B \to \pi \ell \nu$ semileptonic decays. We compute the form factors relative to the transition between heavy-light pseudoscalar mesons, with masses ... More
Tensor form factor of $D \to π(K) \ell ν$ and $D \to π(K) \ell \ell$ decays with $N_f=2+1+1$ twisted-mass fermionsMar 10 2018Jul 17 2018We present the first lattice Nf=2+1+1 determination of the tensor form factor $f_T^{D \pi(K)}(q^2)$ corresponding to the semileptonic and rare $D \to \pi(K)$ decays as a function of the squared 4-momentum transfer $q^2$. Together with our recent determination ... More
Masses and decay constants of $B_c^{(*)}$ mesons with $N_f=2+1+1$ twisted mass fermionsDec 03 2018We present a preliminary lattice determination of the masses and decay constants of the pseudoscalar and vector mesons $B_c$ and $B_c^*$. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with $N_f = ... More
Tensor form factor for the $D \to π(K)$ transitions with Twisted Mass fermionsOct 19 2017We present a preliminary lattice calculation of the $D \to \pi$ and $D \to K$ tensor form factors $f_T(q^2)$ as a function of the squared 4-momentum transfer $q^2$. ETMC recently computed the vector and scalar form factors $f_+(q^2)$ and $f_0(q^2)$ describing ... More
Momentum dependence of kaon semileptonic form factors with Nf=2+1+1 Twisted Mass fermionsNov 16 2015We present a lattice QCD determination of the vector and scalar form factors of the kaon semileptonic decay $K \to \pi \ell \nu$, which is relevant for the determination of the CKM matrix element $|V_{us}|$ from experimental data. Our results are based ... More
Hypercubic Effects in semileptonic $D \to π$ decays on the latticeOct 31 2016We present a lattice determination of the vector and scalar form factors of the semileptonic $D \to \pi \ell \nu$ decays, which are relevant for the extraction of the CKM matrix element $\lvert V_{cd} \rvert$ from experimental data. Our analysis is based ... More
Scalar and vector form factors of $D \to π(K) \ell ν$ decays with $N_f=2+1+1$ twisted fermionsJun 09 2017Sep 22 2017We present a lattice determination of the vector and scalar form factors of the $D \to \pi(K) \ell \nu$ semileptonic decays, which are relevant for the extraction of the CKM matrix elements $|V_{cd}|$ and $|V_{cs}|$ from experimental data. Our analysis ... More
NuSTAR and NICER reveal IGR J17591-2342 as a new accreting millisecond X-ray pulsarAug 30 2018We report on the discovery by the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) of the accreting millisecond X-ray pulsar IGR J17591-2342, detecting coherent X-ray pulsations around 527.4 Hz ... More
Discovery of hard phase lags in the pulsed emission of GRO J1744-28Jun 01 2016Sep 07 2016We report on the discovery and energy dependence of hard phase lags in the 2.14 Hz pulsed profiles of GRO J1744-28. We used data from XMM-Newton and NuSTAR. We were able to well constrain the lag spectrum with respect to the softest (0.3--2.3 keV) band: ... More
Swings between rotation and accretion power in a millisecond binary pulsarMay 16 2013Feb 06 2014It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and ... More
Timing of the Accreting Millisecond Pulsar XTE J1814-338Nov 30 2006We present a precise timing analysis of the accreting millisecond pulsar XTE J1814-338 during its 2003 outburst, observed by RXTE. A full orbital solution is given for the first time; Doppler effects induced by the motion of the source in the binary system ... More
$K \to π$ semileptonic form factors with $N_f=2+1+1$ Twisted Mass fermionsFeb 12 2016Jun 07 2016We present a lattice QCD determination of the vector and scalar form factors of the semileptonic $K \to \pi \ell \nu$ decay which are relevant for the extraction of the CKM matrix element $|V_{us}|$ from experimental data. Our results are based on the ... More
Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658Dec 04 2006We present a timing analysis of the 2002 outburst of the accreting millisecond pulsar SAX J1808.4-3658. A study of the phase delays of the entire pulse profile shows a behavior that is surprising and difficult to interpret: superposed to a general trend, ... More
Pulsating in unison at optical and X-ray energies: simultaneous high-time resolution observations of the transitional millisecond pulsar PSR J1023+0038Apr 23 2019PSR J1023+0038 is the first millisecond pulsar discovered to pulsate in the visible band; such a detection took place when the pulsar was surrounded by an accretion disk and also showed X-ray pulsations. We report on the first high time resolution optical/X-ray/IR/UV ... More
Orbital Evolution of an Accreting Millisecond Pulsar: Witnessing the Banquet of a Hidden Black Widow?Aug 03 2007Jul 10 2008We have performed a timing analysis of all the four X-ray outbursts from the accreting millisecond pulsar SAX J1808.4-3658 observed so far by the PCA on board RXTE. For each of the outbursts we derived the best-fit value of the time of ascending node ... More
K -> pi vector form factor with N_f=2+1+1 Twisted Mass fermionsNov 05 2014We present a lattice QCD determination of the vector form factor of the kaon semileptonic decay K -> pi l nu which is relevant for the extraction of the CKM matrix element |V_{us}| from experimental data. Our result is based on the gauge configurations ... More
D -> πl νand D -> K l νform factors with Nf=2+1+1 Twisted fermionsNov 16 2015We present a lattice QCD determination of the vector and scalar form factors of the semileptonic decays D->\pi l \nu and D -> K l \nu which are relevant for the extraction of the CKM matrix elements |Vcd| and |Vcs| from experimental data. Our analysis ... More
Order in the chaos? The strange case of accreting millisecond pulsarsMay 03 2007Jun 13 2007We review recent results from the X-ray timing of accreting millisecond pulsars in Low Mass X-ray Binaries. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the ... More
Measuring the spin up of the Accreting Millisecond Pulsar XTE J1751-305Oct 05 2007We perform a timing analysis on RXTE data of the accreting millisecond pulsar XTE J1751-305 observed during the April 2002 outburst. After having corrected for Doppler effects on the pulse phases due to the orbital motion of the source, we performed a ... More
Kaon semileptonic vector form factor with $N_f=2+1+1$ Twisted Mass fermionsOct 27 2014We investigate the vector form factor relevant for the $K_{\ell 3}$ semileptonic decay using maximally twisted-mass fermions with 4 dynamical flavours ($N_f=2+1+1$). Our simulations feature pion masses ranging from $210$ MeV to approximately $450$ MeV ... More
Interacting With a Mobile Robot with a Natural Infrastructure-Less InterfaceApr 04 2017In this paper we introduce a novel approach that enables users to interact with a mobile robot in a natural manner. The proposed interaction system does not require any specific infrastructure or device, but relies on commonly utilized objects while leaving ... More
HERMES: An ultra-wide band X and gamma-ray transient monitor on board a nano-satellite constellationDec 06 2018Dec 11 2018The High Energy Modular Ensemble of Satellites (HERMES) project is aimed to realize a modular X/gamma-ray monitor for transient events, to be placed on-board of a CubeSat bus. This expandable platform will achieve a significant impact on Gamma Ray Burst ... More
Study of the reflection spectrum of the accreting neutron star GX 3+1 using XMM-Newton and INTEGRALApr 02 2015Broad emission features of abundant chemical elements, such as Iron, are commonly seen in the X-ray spectra of accreting compact objects and their studies can provide useful information about the geometry of the accretion processes. In this work, we focus ... More
Evolutionary paths of binaries with a neutron star. I. The case of SAX J1808.4-3658Jun 19 2018The evolutionary status of the low mass X-ray binary SAX J1808.4-3658 is simulated by following the binary evolution of its possible progenitor system through mass transfer, starting at a period of $\sim$6.6 hr. The evolution includes angular momentum ... More
Observatory science with eXTPDec 10 2018In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray ... More
Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021Jan 20 2016We analyzed a 115 ks XMM-Newton observation and the stacking of 8 days of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during ... More
X-ray Spectroscopy of MXB 1728-34 with XMM-NewtonApr 04 2011We have analysed an XMM-Newton observation of the low mass X-ray binary and atoll source MXB 1728-34. The source was in a low luminosity state during the XMM-Newton observation, corresponding to a bolometric X-ray luminosity of 5*10E36 d^2 erg/s, where ... More
IGR J17329-2731: The birth of a symbiotic X-ray binaryMar 05 2018We report on the results of the multiwavelength campaign carried out after the discovery of the INTEGRAL transient IGR J17329-2731. The optical data collected with the SOAR telescope allowed us to identify the donor star in this system as a late M giant ... More
Separating Putative Pathogens from Background Contamination with Principal Orthogonal Decomposition: Evidence for Leptospira in the Ugandan Neonatal SeptisomeFeb 01 2016Neonatal sepsis (NS) is responsible for over a 1 million yearly deaths worldwide. In the developing world NS is often treated without an identified microbial pathogen. Amplicon sequencing of the bacterial 16S rRNA gene can be used to identify organisms ... More
Spheroidal galactic halos and mirror dark matterJul 26 2004Mirror matter has been proposed as a dark matter candidate. It has several very attractive features, including automatic stability and darkness, the ability to mimic the broad features of cold dark matter while in the linear density perturbation regime, ... More
New and improved quark-lepton symmetric modelsMay 18 1995We show how the use of a see-saw mechanism based on a $3 \times 3$ neutrino mass matrix texture can considerably simplify Higgs sectors for quark-lepton symmetric models (and for Standard Model extensions generally). The main theory we discuss also incorporates ... More
Natural electroweak symmetry breaking in generalised mirror matter modelsOct 02 2006Nov 28 2006It has recently been pointed out that the mirror or twin Higgs model is more technically natural than the standard model, thus alleviating the ``little'' hierarchy problem. In this paper we generalise the analysis to models with an arbitrary number of ... More
Studies of neutrino asymmetries generated by ordinary-sterile neutrino oscillations in the early universe and implications for big bang nucleosynthesis boundsOct 03 1996Nov 19 1996Ordinary-sterile neutrino oscillations can generate a significant lepton number asymmetry in the early Universe. We study this phenomenon in detail. We show that the dynamics of ordinary-sterile neutrino oscillations in the early Universe can be approximately ... More
Do the SuperKamiokande atmospheric neutrino results explain electric charge quantisation?Aug 24 1998We show that the SuperKamiokande atmospheric neutrino results explain electric charge quantisation, provided that the oscillation mode is $\nu_{\mu} \to \nu_{\tau}$ and that the neutrino mass is of Majorana type.
Neutrino physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experimentMay 23 1995Nov 08 1995Evidence for $\bar \nu_{\mu} \rightarrow \bar \nu_e$ oscillations has been reported at LAMPF using the LSND detector. Further evidence for neutrino mixing comes from the solar neutrino deficit and the atmospheric neutrino anomaly. All of these anomalies ... More
Was ordinary matter synthesised from mirror matter? An attempt to explain why $Ω_{Baryon} \approx 0.2Ω_{Dark}$Apr 28 2003Jun 03 2003The cosmological dust has begun to settle. A likely picture is a universe comprised (predominantly) of three components: ordinary baryons ($\Omega_B \approx 0.05$), non-baryonic dark matter ($\Omega_{Dark} \approx 0.22$) and dark energy ($\Omega_{\Lambda} ... More
How neutrino oscillations can induce an effective neutrino number of less than 3 during Big Bang NucleosynthesisJun 04 1997Ordinary-sterile neutrino oscillations can generate significant neutrino asymmetry in the early Universe. In this paper we extend this work by computing the evolution of neutrino asymmetries and light element abundances during the Big Bang Nucleosynthesis ... More
Maximal neutrino oscillation solution to the solar neutrino problemOct 17 1995We discuss a simple predictive solution to the solar neutrino problem based on maximal vacuum neutrino oscillations. The solution can be motivated by the exact parity symmetric model which predicts that the neutrino mass eigenstates are maximal mixtures ... More
A mirror world explanation for the Pioneer spacecraft anomalies?Aug 06 2001We show that the anomalous acceleration of the Pioneer 10/11 spacecraft can be explained if there is some mirror gas or mirror dust in our solar system.
The exact parity symmetric model and big bang nucleosynthesisDec 04 1996The assumption of exact, unbroken parity symmetry leads directly to a simple predictive resolution of the atmospheric and solar neutrino puzzles. This is because the existence of this symmetry implies the existence of a set of mirror neutrinos which must ... More
Reconciling sterile neutrinos with big bang nucleosynthesisAug 10 1995Nov 08 1995We re-examine the big bang nucleosynthesis (BBN) bounds on the mixing of neutrinos with sterile species. These bounds depend on the assumption that the relic neutrino asymmetry $L_{\nu}$ is very small. We show that for $L_{\nu}$ large enough (greater ... More