A5082180400- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- High-pressure geophysics and materials
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Mechanics and Biomechanics Studies
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Superconducting Materials and Applications
- Astronomy and Astrophysical Research
- Geophysics and Sensor Technology
- Particle Detector Development and Performance
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Space Technology and Applications
- Statistical and numerical algorithms
- Relativity and Gravitational Theory
- Fluid Dynamics Simulations and Interactions
- Fluid Dynamics and Vibration Analysis
- Crystallography and Radiation Phenomena
Universitat Politècnica de Catalunya
2017-2025
Norwegian University of Science and Technology
2022-2025
Institut d'Estudis Espacials de Catalunya
2018-2021
NTNU Samfunnsforskning
2016-2021
Instituto de Astrofísica de Canarias
2012-2018
Universidad de La Laguna
2013-2017
University of Amsterdam
2005-2016
Vassar College
2010-2016
Massachusetts Institute of Technology
2010-2016
Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata
2016
Abstract New millisecond pulsars (MSPs) in compact binaries provide a good opportunity to search for the most massive neutron stars. Their main-sequence companion stars are often strongly irradiated by pulsar, displacing effective center of light from their barycenter and making mass measurements uncertain. We present series optical spectroscopic photometric observations PSR J2215+5135, “redback” binary MSP 4.14 hr orbit, measure drastic temperature contrast between dark/cold ( T N = 5660...
We report on the first 180 days of Rossi X-Ray Timing Explorer observations outburst black hole candidate IGR J17091–3624. This source exhibits a broad variety complex light curve patterns including periods strong flares alternating with quiet intervals. Similar in X-ray curves have been seen (up to now) unique system GRS 1915+105. In context variability classes defined by Belloni et al. for 1915+105, we find that J17091–3624 shows ν, ρ, α, λ, β, and μ as well which resemble χ class, all...
Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks," constitute the long-sought link between low-mass X-ray binaries and radio offer a unique probe of interaction pulsar winds accretion flows. We present systematic study eight nearby redbacks, using more than 100 observations obtained Swift's Telescope. distinguish three main states: pulsar, disk, outburst states. find mode switching in disk state PSR J1023+0038 XSS J12270–4859, similar what was...
The X-ray transient IGR J18245-2452 in the globular cluster M28 contains first neutron star (NS) seen to switch between rotation-powered and accretion-powered pulsations. We analyse its 2013 March-April 25d-long outburst as observed by Swift, which had a peak bolometric luminosity of ~6% Eddington limit (L$_{E}$), give detailed properties thermonuclear burst on April 7. also present analysis new archival Chandra data, we use study quiescent emission from 2002 2013. Together, these...
We search the literature for reports on spectral properties of neutron star low-mass X-ray binaries when they have accretion luminosities between 1034 and 1036 erg s−1, corresponding to roughly 0.01–1 per cent Eddington rate a star. found that in this luminosity range photon index (obtained from fitting simple absorbed power law 0.5–10 keV range) increases with decreasing (i.e. spectrum softens). Such behaviour has been reported before individual sources, but here we demonstrate very likely...
ABSTRACT In this paper, we study compact binary millisecond pulsars with low- and very low-mass companion stars (spiders) in the Galactic field, using data from latest Gaia release (DR3). We infer parallax distances of optical counterparts to spiders, which use estimate X-ray luminosities. compare those derived radio pulse dispersion measures find that they have systematically larger values, by 40 per cent on average. also test correlation between spin-down luminosities, finding most...
We present Chandra and XMM-Newton X-ray observations that monitor the neutron star cooling of quasi-persistent transients KS 1731-260 MXB 1659-29 for approximately 4 years after these sources returned to quiescence from prolonged outbursts. In both outbursts were long enough significantly heat crust out thermal equilibrium with core. analyse spectra by fitting absorbed atmosphere models observations. The results our analysis strengthen preliminary findings Wijnands et al. in cools down very...
During the September-October 2008 outburst of accreting millisecond pulsar SAX J1808.4-3658, source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe K-alpha emission line which is present in data-sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties K during each observation are very similar. From modeling line, we determine inner accretion disk radius to be 13.2 +/- 2.5...
We have discovered a new transient low-mass X-ray binary, NGC 6440 X-2, with Chandra/ACIS, RXTE/PCA, and Swift/XRT observations of the globular cluster 6440. The discovery outburst (2009 July 28–31) peaked at LX ∼ 1.5 × 1036 erg s−1 lasted for <4 days above = 1035 s−1. Four other outbursts May 29–June 4, August 29–September 1, October 1–3, been observed RXTE/PCA (identifying millisecond pulsations) (confirming positional association X-2), similar peak luminosities decay times. Optical...
[abridged] The LMXB 4U 0614+091 is a source of sporadic thermonuclear (type I) X-ray bursts. We find bursts with wide variety characteristics in serendipitous wide-field observations by EURECA/WATCH, RXTE/ASM, BeppoSAX/WFC, HETE-2/FREGATE, INTEGRAL/IBIS/ISGRI, and Swift/BAT, as well pointed RXTE/PCA HEXTE. Most them reach peak flux ~15 Crab, but few only below Crab. One the shows very strong photospheric radius-expansion phase. This allows us to evaluate distance source: 3.2 kpc. burst...
We report and study the outburst of a new transient X-ray binary (XRB) in Terzan 5, third detected this globular cluster, Swift J174805.3-244637 or 5 X-3. find clear spectral hardening Swift/XRT data during rise to hard state, thanks our early coverage (starting at LX ∼ 4 × 1034 erg s−1) outburst. This appears be due decline relative strength soft thermal component from surface neutron star (NS) rise. identify Type I burst with long (16 s) decay time, indicative hydrogen burning on NS. use...
We present a comprehensive study of the thermonuclear bursts and millihertz quasi-periodic oscillations (mHz QPOs) from neutron star (NS) transient 11 Hz X-ray pulsar IGR J17480−2446, located in globular cluster Terzan 5. The increase burst rate that we found during its 2010 outburst, when persistent luminosity rose 0.1 to 0.5 times Eddington limit, is qualitative agreement with burning theory yet contrary all previous observations bursts. Thermonuclear gradually evolved into mHz QPO...
We present Chandra, XMM-Newton, and Swift observations of the quiescent neutron star in transient low-mass X-ray binary MAXI J0556–332. Observations source made during outburst (with Rossi Timing Explorer) reveal tracks its color–color hardness–intensity diagrams that closely resemble those neutron-star Z sources, suggesting J0556–332 had near- or super-Eddington luminosities for a large part ∼16 month outburst. A comparison these with other sources suggests distance 46 ± 15 kpc. Fits to...
Abstract We present the discovery of variable optical counterpart to PSR J2055+1545, a redback millisecond pulsar, and first radial velocity curve its companion star. The multi-band light curves this system show 0.4–0.6 mag amplitude modulation with single peak per orbit colours, suggesting that is mildly irradiated by pulsar wind. find flux maximum asymmetric occurs at orbital phase ≃ 0.4, anticipating superior conjunction (where emission companions typically brightest). ascribe asymmetry,...
Abstract Understanding the formation and properties of relativistic jets from accreting compact objects has far-reaching implications in astrophysics. Transitional millisecond pulsars (tMSPs) – a class neutron stars transitioning between radio pulsar accretion states offer unique opportunity to study jet behavior within low-level regime around fast-spinning, magnetized stars. We analyzed archival spectral energy distributions (SEDs) for both confirmed candidate tMSPs literature various...
The 2009 November outburst of the neutron star X-ray binary Aquila X-1 was observed with unprecedented radio coverage and simultaneous pointed observations, tracing emission around full hysteresis loop for first time. We use these data to discuss disc-jet coupling, finding be consistent being triggered at state transitions, both from hard soft spectral vice versa. Our appear confirm previous suggestions quenching in above a threshold luminosity about 10% Eddington luminosity. also present...
We report the discovery of second accreting millisecond X-ray pulsar (AMXP) in globular cluster NGC 6440. Pulsations with a frequency 205.89 Hz were detected Rossi X-Ray Timing Explorer on August 30th, October 1st and 28th, 2009, during decays ~4 day outbursts newly transient source By studying Doppler shift pulsation frequency, we find that system is an ultra-compact binary orbital period 57.3 minutes projected semi-major axis 6.22 light-milliseconds. Based mass function, estimate lower...
We study the accretion/ejection processes (i.e. disc/jet coupling) in neutron star X-ray binary Aquila X-1 via a multi-wavelength approach. use radio band publicly available VLA archive containing observations of object between 1986-2005, archival RXTE data (PCA and HEXTE) 1997-2008, optical (R band) with SMARTS recorded 1998-2007. In combined set we find three outbursts for which quasi-simultaneous radio, exist focus on them to some extent. provide evidence that coupling is similar what has...
In studies of accreting black holes in binary systems, empirical relations have been proposed to quantify the coupling between accretion processes and ejection mechanisms. These are probed respectively by means X-ray radio/optical-infrared observations. The predict, given certain conditions, expected energy output form a jet. We investigated this studying hole candidate Swift J1753.5-0127, via multiwavelength coordinated observations over period ~4 years. present results our campaign showing...
We present time-resolved optical photometry of the binary millisecond `redback' pulsar PSR J1023+0038 (=AY Sex) during its low-mass X-ray phase. The light curves taken between 2014 January and April show an underlying sinusoidal modulation due to irradiated secondary star accretion disc. also observe superimposed rapid flaring on time-scales as short ~20 s with amplitudes ~0.1-0.5 mag additional large flare events ~5-60 min ~0.5-1.0 mag. power density spectrum is dominated by a red-noise...
Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are result of cooling or due to continued low-level remains unclear. In this work we use Swift data obtained after long and bright 2011 2013 outbursts, as well short faint 2015 outburst, investigate hypothesis accretion-heated crust dominates emission X-1. We demonstrate light curves...
We report the detection of 15 X-ray bursts with RXTE and Swift observations peculiar binary Circinus X-1 (Cir X-1) during its 2010 May re-brightening. These are first observed from source after initial discovery by Tennant collaborators, 25 years ago. By studying their spectral evolution, we firmly identify nine as type I (thermonuclear) bursts. obtain an arcsecond location that confirms once for all identification Cir a burst source, therefore low magnetic field accreting neutron star. The...
We present our monitoring campaign of the outburst black hole candidate Swift J1753.5−0127, observed with Rossi X-ray Timing Explorer and satellites. After ∼4.5 yr since its discovery, source had a transition to hard intermediate state. performed spectral timing studies showing that, unlike majority transient holes, system did not go soft states but it returned state after few months. During this J1753.5−0127 features properties which are similar those displayed by Cygnus X-1. compared one...