A5003765624- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Mechanics and Biomechanics Studies
- High-pressure geophysics and materials
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Higher Education Learning Practices
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Gastrointestinal Tumor Research and Treatment
- Gastrointestinal disorders and treatments
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Atomic and Subatomic Physics Research
- Advanced X-ray and CT Imaging
- Streptococcal Infections and Treatments
- Scientific Measurement and Uncertainty Evaluation
- Helicobacter pylori-related gastroenterology studies
- Optical Systems and Laser Technology
Cardiff University
2015-2024
Liverpool John Moores University
2015-2024
Netherlands Institute for Radio Astronomy
2009-2019
University of South Wales
2010-2014
The Open University
2008-2013
University of Southampton
2007-2011
University of Groningen
2011
European Southern Observatory
2011
University of Amsterdam
2009-2011
Hong Kong Metropolitan University
2008-2011
Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of entire sky. Aims. We present Science Alerts project, which operation since 1 June 2016. describe system developed to enable discovery publication transient events as seen by . Methods. outline data handling, timings, performances, we detection algorithms filtering procedures needed manage high false alarm rate. identify two classes...
Abstract We present a comprehensive analysis of the optical and infrared (IR) properties high-mass X-ray binary (HMXB) IC 10 X-2, classified as supergiant HMXB superfast transient by previous work. Our regular (daily weekly) observations both Zwicky Transient Facility Las Cumbres Observatory over 5 yr period indicates periodic flares variations in apparent magnitude color with ∼26.5 days—likely orbital this system. The flaring suggests stellar companion is Be star, resulting from increased...
We present ultradeep radio observations with the Expanded Very Large Array of 4U 1957+11, a Galactic black hole candidate X-ray binary known to exist in persistent soft state. derive stringent upper limit 11.4 micro-Jy beam^-1 (3 sigma) at 5-7 GHz, which provides most rigorous date on presence jets state binary. X-ray, UV and optical fluxes obtained within few weeks data can be explained by thermal emission from disk. At this luminosity, hard that follows established empirical radio--X-ray...
Many X-ray binaries remain undetected in the mid-infrared, a regime where emission from their compact jets is likely to dominate. Here, we report detection of black hole binary GX 339-4 with Wide-field Infrared Survey Explorer (WISE) during very bright, hard accretion state 2010. Combined rich contemporaneous multiwavelength dataset, clear spectral curvature found infrared, associated peak flux density expected jet. An optically-thin slope ~-0.7 and jet radiative power >6x10^{35} erg/s (d/8...
We present phase resolved optical spectroscopy and photometry of V4580 Sagittarii, the counterpart to accretion powered millisecond pulsar SAX J1808.4−3658, obtained during 2008 September/October outburst. Doppler tomography N iiiλ4640.64 Bowen blend emission line reveals a focused spot at location consistent with secondary star. The velocity this occurs 324 ± 15 km s−1; applying 'K-correction', we find star projected on sight be 370 40 s−1. Based existing pulse timing measurements,...
Abstract Black hole (BH) X-ray binaries (XRBs) are ideal targets to study the connection between accretion inflow and jet outflow. Here we present quasi-simultaneous, multiwavelength observations of Galactic BH system MAXI J1820+070, throughout its 2018–2019 outburst. Our data set includes coverage from radio through bands 17 different instruments/telescopes, encompasses 19 epochs over a 7 month period, resulting in one most well-sampled sets XRB outburst date. With our data, compile model...
We report striking changes in the broadband spectrum of compact jet black hole transient MAXI J1836−194 over state transitions during its discovery outburst 2011. A fading optical–infrared (IR) flux occurred as source entered hard–intermediate state, followed by a brightening it returned to hard state. The optical–IR was consistent with power law from optically thin synchrotron emission, except when X-ray softest. By fitting radio optical spectra broken law, we constrain frequency and...
In outburst, neutron star X-ray binaries produce less powerful jets than black holes at a given luminosity. This has made them more difficult to study as they fade towards quiescence. To explore whether stars power low accretion rates (LX ≲ 1036 erg s−1), we investigate the radio and properties of three accreting millisecond pulsars (IGR J17511−3057, SAX J1808.4−3658 IGR J00291+5934) during their outbursts in 2015, non-pulsing Cen X−4 quiescence (2015) outburst (1979). We did not detect...
ABSTRACT PSR J2129−0429 is a “redback” eclipsing millisecond pulsar binary with an unusually long 15.2 hr orbit. It was discovered by the Green Bank Telescope in targeted search of unidentified Fermi gamma-ray sources. The companion optically bright (mean m R = 16.6 mag), allowing us to construct longest baseline photometric data set available for such system. We present 10 years archival and new photometry from Lincoln Near-Earth Asteroid Research Survey, Catalina Real-time Transient...
On 2015 June 15 the burst alert telescope (BAT) on board {\em Swift} detected an X-ray outburst from black hole transient V404 Cyg. We monitored Cyg for last 10 years with 2-m Faulkes Telescope North in three optical bands (V, R, and i$^{'}$). found that, one week prior to this outburst, flux was 0.1--0.3 mag brighter than quiescent orbital modulation, implying precursor outburst. There is also a hint of gradual decay (years) followed by rise lasting two months fortuitously obtained spectrum...
Abstract We present a comprehensive multiwavelength spectral analysis of the black hole (BH) X-ray binary MAXI J1820+070 during its 2018 outburst, utilizing AstroSat far-UV, soft X-ray, and hard data, along with (quasi-)simultaneous optical data from Las Cumbres Observatory NICER, respectively. In state, we detect UV/optical excess components over above intrinsic accretion disk emission ( kT in ∼ 0.58 keV) steep power-law component. The is consistent high-temperature blackbody 0.79 keV),...
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...
Disc instability models predict that for X-ray binaries in quiescence, there should be a brightening of the optical flux prior to an outburst. Tracking variations quiescence is generally not possible, so monitoring provides best means measure mass accretion rate variability between outbursts, and identify beginning stages new outbursts. With our regular Faulkes Telescope/Las Cumbres Observatory (LCO) we are routinely detecting rise binary outbursts before they detected by all-sky monitors....
We present contemporaneous X-ray, ultraviolet (UV), optical, and near-infrared observations of the black hole binary system Swift J1753.5−0127 acquired in 2012 October. The UV observations, obtained with Cosmic Origins Spectrograph on Hubble Space Telescope, are first spectra this system. dereddened spectrum is characterized by a smooth, blue continuum broad emission lines C iv He ii. was stable to <10% during our observations. estimated interstellar reddening fitting 2175 Å absorption...
The microquasar GX 339-4 experienced a new outburst in 2010: it was observed simultaneously at various wavelengths from radio up to soft gamma-rays. We focused on observations that are quasi-simultaneous with those made the INTEGRAL and RXTE satellites: these were collected 2010 March-April during our Target of Opportunity program, some other observing programs field-of-view. X-ray transients extreme systems often harbour black hole, known emit throughout whole electromagnetic spectrum when...
We report on quasi-simultaneous observations from radio to X-ray frequencies of the neutron star binary Aql X-1 over accretion state transitions during its 2016 outburst. All show millimetre spectra consistent with emission a jet, spectral break optically thick thin synchrotron that decreases ~100 GHz <5.5 transition hard soft state. The 5.5 flux density as source reaches state, 0.82$\pm$0.03 mJy, is highest recorded date for this source. During decay outburst, jet detected again at...
We present results of the detailed dust energy balance study for seven large edge-on galaxies in HEROES sample using 3D radiative transfer (RT) modelling. Based on available optical and near-infrared observations galaxies, we derive distribution stars these galaxies. For sake uniformity, apply same technique to retrieve galaxy properties entire sample: use a stellar model consisting S\'ersic bulge three double-exponential discs (a superthin disc young population thin thick old populations)....
We investigate the dust energy balance for edge-on galaxy IC 2531, one of seven galaxies in HEROES sample. perform a state-of-the-art radiative transfer modelling based, first time, on set optical and near-infrared images. show that taking into account imaging significantly improves constraints retrieved parameters content. confirm result from previous studies including young stellar population is important explaining observed distribution. However, discrepancy between modelled thermal...
Optical time series photometry of the short-period magnetic white dwarf + probable brown binary SDSS J121209.31+013627.7 reveals pulse-like variability in all bands from i′ to u′, increasing towards bluer wavelengths and peaking at u′. These modulations are most likely due a self-eclipsing accretion hot spot on dwarf, rotating into view every 88.43 min. This period is commensurate with Hα radial velocity ≈90 min, consistent rotation accretor being equal orbital period. We combine our...
We present the results of radio observations black hole binaries GRO J1655−40 and XTE J1550−564 in quiescence, with upgraded Australia Telescope Compact Array. Neither system was detected. Radio flux density upper limits (3σ) 26 μJy (at 5.5 GHz), 47 9 GHz) for 1.4 mJy 1.75 27 were measured. In conjunction quasi-simultaneous Chandra X-ray (in case J1655−40) Faulkes optical (XTE J1550−564) we find that these systems provide first evidence relatively ‘radio-quiet’ at low luminosities,...
<i>Context. <i/>In August 2008, the accreting milli-second X-ray pulsar (AMXP), IGR J00291+5934, underwent an outburst lasting ~100 days, first since its discovery in 2004.<i>Aims. <i/>We present data from 2008 double-peaked of J00291+5934 Faulkes Telescope North, Isaac Newton Telescope, Keck PAIRITEL, Westerbork Synthesis Radio and Swift, XMM-Newton RXTE missions. We study outburst's evolution at various wavelengths, allowing us to probe accretion physics this AMXP.<i>Methods. light curve...
We present optical monitoring of the black hole candidate XTE J1752-223 during its 2009 - 2010 outburst and decay to quiescence. The light curve can be described by an exponential followed a plateau, then more rapid fade towards plateau appears due extra component emission that brightens fades over ~ 40 days. show evidence for origin this 'flare' synchrotron jet decaying hard state, we identify isolate both disc components in spectral energy distributions. flare has same morphology amplitude...
We report on the results of optical, near-infrared (NIR) and mid-infrared observations black hole X-ray binary candidate (BHB) MAXI J1535-571 during its 2017/2018 outburst. During first part outburst (MJD 58004-58012), source shows an optical-NIR spectrum that is consistent with optically thin synchrotron power-law from a jet. After MJD 58015, however, faded considerably, drop in flux being much more evident at lower frequencies. Before fading, we measure de-reddened density $\gtrsim$100 mJy...