A5048946636- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Astro and Planetary Science
- High-pressure geophysics and materials
- Geophysics and Sensor Technology
- Astronomy and Astrophysical Research
- Superconducting Materials and Applications
- Molecular Spectroscopy and Structure
- GNSS positioning and interference
- Galaxies: Formation, Evolution, Phenomena
- Radiomics and Machine Learning in Medical Imaging
- Computational Physics and Python Applications
- Adaptive optics and wavefront sensing
- Medical Imaging Techniques and Applications
- Advanced Chemical Physics Studies
- Particle Detector Development and Performance
- Cosmology and Gravitation Theories
- Medical Imaging and Analysis
University of Oxford
2020-2025
Pennsylvania State University
2015-2025
Friedrich Schiller University Jena
2002-2011
Center for Astrophysics Harvard & Smithsonian
2009-2011
Institute of Applied Astronomy
2011
University of Alicante
2011
Moscow Engineering Physics Institute
2011
Sabancı Üniversitesi
2011
Max Planck Institute for Radio Astronomy
2011
Max Planck Institute for Extraterrestrial Physics
2003-2010
Abstract We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. is a high-gain ( ${\sim}2.8\,\mbox{K Jy}^{-1}$ ) low-system temperature ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ array that currently operates 580–1 670 MHz can produce tied-array beams suitable observations. This paper presents MeerTime Large Survey Project commissioning with PTUSE. Highlights include...
We perform population synthesis studies of different types neutron stars (thermally emitting isolated stars, normal radio pulsars, magnetars) taking into account the magnetic field decay and using results from most recent advances in star cooling theory. For first time, we confront our with observations {\it simultaneously} Log N -- S distribution for nearby L magnetars, pulsars $P$ $\dot P$ diagram. this purpose, fix a baseline model (all microphysics input), other relevant parameters to...
We present the largest single survey to date of average profiles radio pulsars, observed and processed using same telescope data reduction software. Specifically, we measurements for 1170 by Thousand Pulsar Array (TPA) programme at 64-dish SARAO MeerKAT telescope, in a frequency band from 856 1712 MHz. provide rotation measures (RM), dispersion measures, flux densities polarization properties. The catalogue includes 254 new RMs that substantially increase total number known pulsar RMs. Our...
Abstract We present initial results from a James Webb Space Telescope (JWST) survey of the youngest Galactic core-collapse supernova remnant, Cassiopeia A (Cas A), made up NIRCam and MIRI imaging mosaics that map emission main shell, interior, surrounding circumstellar/interstellar material (CSM/ISM). also four exploratory positions Medium Resolution Spectrograph integral field unit spectroscopy sample ejecta, CSM, associated dust representative shocked unshocked regions. Surprising...
We report on six new Chandra observations of the Geminga pulsar wind nebula (PWN). The PWN consists three distinct elongated structures - two $\approx 0.2 d_{250}$ pc long lateral tails and a segmented axial tail 0.05 length, where $d_{250}=d/(250 {\rm pc})$. photon indices power law spectra tails, $\Gamma \approx 1$, are significantly harder than those ($\Gamma 1.5$) 1.6$). There is no significant diffuse X-ray emission between -- ratio surface brightness south this sky area at least 12....
ABSTRACT We report on the subpulse modulation properties of 1198 pulsars using Thousand-Pulsar-Array programme MeerKAT. About 35 per cent analysed exhibit drifting subpulses that are more pronounced towards death line, consistent with previous studies. estimate this common phenomenon is detectable in 60 overall pulsar population if high-quality data were available for all. This large study reveals evolution across unprecedented detail. In particular, we find period P3 follows a V-shaped...
We present extensive spectral and photometric observations of the recycled pulsar/white dwarf binary containing PSR J0437−4715, which we analyzed together with archival X-ray gamma-ray data, to obtain complete mid-infrared spectrum. first fit each part spectrum separately, then whole multi-wavelength find that optical–infrared is well by a cool white atmosphere model pure hydrogen composition. The (Teff = 3950 ± 150 K, log g 6.98 0.15, RWD (1.9 0.2) × 109 cm) fits our data remarkably for...
To examine the previously claimed fast cooling of Central Compact Object (CCO) in Cas A supernova remnant (SNR), we analyzed two Chandra observations this CCO, taken a setup minimizing instrumental spectral distortions. We fit CCO X-ray spectra from 2006 and 2012 with hydrogen carbon neutron star atmosphere models. The temperature flux changes 5.5 yr between epochs depend on adopted constraints fitting parameters uncertainties effective area calibrations. If allow change equivalent emitting...
We report here on initial results from the Thousand Pulsar Array (TPA) programme, part of Large Survey Project "MeerTime" MeerKAT telescope. The interferometer is used in tied-array mode band 856 to 1712~MHz, and wide coupled with large collecting area low receiver temperature make it an excellent telescope for study radio pulsars. TPA a 5 year project which aims observe (a) more than 1000 pulsars obtain high-fidelity pulse profiles, (b) some 500 these over multiple epochs, (c) long...
We describe the ongoing Relativistic Binary programme (RelBin), a part of MeerTime large survey project with MeerKAT radio telescope. RelBin is primarily focused on observations relativistic effects in binary pulsars to enable measurements neutron star masses and tests theories gravity. selected 25 as an initial high priority list targets based their characteristics observational history other telescopes. In this paper, we provide outline programme, present polarisation calibrated pulse...
We present initial results from a JWST survey of the youngest Galactic core-collapse supernova remnant Cassiopeia A (Cas A), made up NIRCam and MIRI imaging mosaics that map emission main shell, interior, surrounding circumstellar/interstellar material (CSM/ISM). also four exploratory positions MIRI/MRS IFU spectroscopy sample ejecta, CSM, associated dust representative shocked unshocked regions. Surprising discoveries include: 1) web-like network ejecta filaments resolved to 0.01 pc scales...
Abstract We present pulse width measurements for a sample of radio pulsars observed with the MeerKAT telescope as part Thousand-Pulsar-Array (TPA) programme in MeerTime project. For centre frequency 1284 MHz, we obtain 762 W10 across total bandwidth 775 where is at 10 per cent level peak. also measure about 400 values each four or eight sub-bands. Assuming, function rotation period P, this relationship can be described power law index μ = −0.29 ± 0.03. However, using orthogonal distance...
ABSTRACT We have measured the scattering time-scale, τ, and spectral index, α, for 84 single-component pulsars. Observations were carried out with MeerKAT telescope as part of Thousand-Pulsar-Array programme in MeerTime project at frequencies between 0.895 1.670 GHz. Our results give a distribution values α (defined terms τ frequency ν ∝ ν−α) which, upon fitting Gaussian, we obtain mean standard deviation 〈α〉 = 4.0 ± 0.6. This is due to our identification possible causes inaccurate...
Far-ultraviolet (FUV) observations of pulsars allow us to measure surface temperatures neutron stars and study their thermal evolution. Some can exhibit FUV bow-shock nebulae (BSNe), providing an additional tool for probing the interstellar medium studying pulsar's properties. The nearby middle-aged gamma-ray pulsar J1741--2054 its wind nebula (PWN) have been studied in X-rays, BSN has investigated Balmer lines, but they never observed FUV. To further magnetospheric emission from PSR...
Abstract Measuring the magnetic field of Milky Way reveals structure and evolution galaxy. Pulsar rotation measures (RMs) provide a means to probe this Galactic (GMF) in three dimensions. We use largest single-origin data set pulsar measurements, from MeerKAT Thousand-Pulsar-Array, map out GMF components parallel lines sight. also present these measurements for easy integration into consolidated RM catalogue, RMTable. Focusing on disk, we investigate competing theories how relates spiral...
We present multi-wavelength observations of the radio magnetar PSR J1622-4950 and its environment. Observations with Chandra (in 2007 2009) XMM 2011) show that X-ray flux has decreased by a factor ~50 over 3.7 years, decaying exponentially characteristic time 360 +/- 11 days. This behavior identifies as possible addition to small class transient magnetars. The decay likely indicates is recovering from an outburst occurred earlier in 2007, before observations. Australia Telescope Compact...
ABSTRACT We present the detection of 107 pulsars with interstellar scintillation arcs at 856–1712 MHz, observed MeerKAT Thousand Pulsar Array Programme. Scintillation appear to be ubiquitous in clean, high S/N observations, their mainly limited by short observing durations and coarse frequency channel resolution. This led survey sensitive nearby, lightly scattered effective velocity – from a large proper motion, screen nearby pulsar, or near Earth. measure arc curvatures all our sources,...
We report on the study of six Chandra observations (four epochs) Central Compact Object (CCO) in Cassiopeia A supernova remnant with ACIS instrument subarray mode. This mode minimizes spectrum-distorting instrumental effects such as pileup. The data were taken over a time span ~ 14 years. If non-magnetic carbon atmosphere is assumed for this youngest known CCO, then temperature change constrained to be $\dot{T}=-2900\pm 600$ K yr$^{-1}$ or $\dot{T}=-4500\pm 800 $ ($1\sigma$ uncertainties)...
ABSTRACT We report here on the timing of 597 pulsars over last four years with MeerKAT telescope. provide times arrival, pulsar ephemeris files, and per-epoch measurements flux density, dispersion measure (DM), rotation (RM) for each pulsar. In addition, we use a Gaussian process to model residuals spin frequency derivative at epoch. also detection 11 glitches in nine individual pulsars. find significant DM RM variations 87 76 pulsars, respectively. that scale approximately linearly DM,...
Abstract JWST observed the magnetar 4U 0142+61 with Mid-Infrared Instrument (MIRI) and Near Infrared Camera (NIRCam) instruments within a 77 minute time interval on 2022 September 20–21. The low-resolution MIRI spectrum NIRCam photometry show that in wavelength range 1.4–11 μ m can be satisfactorily described by an absorbed power-law (PL) model, f ν ∝ − α , spectral slope = 0.96 ± 0.02, interstellar extinction A V 3.9 0.2, normalization 0 59.4 0.5 Jy at λ 8 m. These observations do not...
Our search for the earliest stages of massive star formation turned up 12 pre-protocluster candidates plus a few protoclusters. For this search, we selected 47 FIR-bright IRAS sources in outer Galaxy. We mapped regions several square arcminutes around source millimeter continuum order to find cold cloud cores possibly being very early stage formation. Masses and densities are derived 128 molecular found obtained maps. present these maps together with near-infrared, mid-infrared, radio data...
PSR J1509-5850 is a middle-aged pulsar with the period P ~ 89 ms, spin-down power Edot = 5.1 x 10^35 erg/s, at distance of about 3.8 kpc. We report on deep Chandra X-ray Observatory observations this and its wind nebula (PWN). In addition to previously detected tail extending up 7' southwest from (the southern outflow), images reveal similarly long, faint diffuse emission stretched toward north northern outflow) fine structure compact (CN) in vicinity. The CN resolved into two lateral tails...