A5089922553- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Mechanics and Biomechanics Studies
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Electrical and Bioimpedance Tomography
- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Magnetic confinement fusion research
- Particle Detector Development and Performance
- Scientific Measurement and Uncertainty Evaluation
- Semiconductor Lasers and Optical Devices
- Superconducting and THz Device Technology
- X-ray Spectroscopy and Fluorescence Analysis
- Superconducting Materials and Applications
- Radio Wave Propagation Studies
- Marine and Coastal Research
University of Oxford
2014-2022
University of Southampton
2009-2021
National Air Traffic Services (United Kingdom)
2020
Rhodes University
2015
Science Oxford
2015
European Southern Observatory
2010-2012
Swedish Institute of Space Physics
2010-2012
University of Manchester
2006-2011
University of Cambridge
2009
SKA Observatory
2006-2007
A heavy black hole in an x-ray binary If a interacts with companion star, the system emits x-rays and can form radio jet. The masses of holes these binaries are all lower than those detected using gravitational waves, challenging models formation from massive stars. Miller-Jones et al. used astrometry to refine distance Cygnus X-1, well-studied binary. They found larger previous estimates, raising mass 21 solar masses. results challenge wind loss rates implemented stellar evolution models....
Opening the sky to new classes of airspace user is a political and economic imperative for European Union. Drone industries have significant potential economical growth according latest estimations. To enable this safely efficiently, CORUS project has developed concept operations drones flying in Europe very low-level airspace, which they share that space with manned aviation, quite soon urban air mobility aircraft as well. U-space services development smart, automated, interoperable,...
We report new observations with the Very Large Array, Atacama Millimeter and Submillimeter Array at frequencies from 1.0 to 355 GHz of Galactic Center black hole, Sagittarius A*. These were conducted between October 2012 November 2014. While we see variability over whole spectrum an amplitude as large a factor 2 millimeter wavelengths, find no evidence for change in mean flux density or Sgr A* that can be attributed interaction G2 source. The absence bow shock low is consistent...
We present simultaneous radio through sub-mm observations of the black hole X-ray binary (BHXB) V404 Cygni during most active phase its June 2015 outburst. Our $4$ hour long set overlapping with Very Large Array, Sub-millimeter and James Clerk Maxwell Telescope (SCUBA-2), covers 8 different frequency bands (including first detection a BHXB jet at $666 \,{\rm GHz}/450\mu m$), providing an unprecedented multi-frequency view extraordinary flaring activity seen this period In particular, we...
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...
Radio and mm-wavelength observations of Sagittarius A* (Sgr A*), the radio source associated with supermassive black hole at center our Galaxy, show that it behaves as a partially self-absorbed synchrotron-emitting source. The measured size Sgr shows emission comes from small region consists inner accretion flow possible collimated outflow. Existing have revealed time lag between light curves 43 GHz 22 GHz, which is consistent rapidly expanding plasma supports presence outflow environment an...
We measure the proper motion of pulsar PSR J1745-2900 relative to Galactic center massive black hole, Sgr A*, using Very Long Baseline Array (VLBA). The has a transverse velocity 236 ± 11 km s−1 at position angle 22 2 deg east north projected separation 0.097 pc from A*. Given unknown radial velocity, this measurement does not conclusively prove that is bound A*; however, probability chance alignment very small. do show and are consistent with orbit originating in clockwise disk stars...
AX J1745.6-2901 is a high-inclination (eclipsing) neutron star low-mass X-ray binary (LMXB) located less than ∼1.5 arcmin from Sgr A⋆. Ongoing monitoring campaigns have targeted A⋆ frequently and these observations also cover J1745.6-2901. We present here an analysis of using large data set 38 XMM–Newton observations, including 11 which caught in outburst. Fe K absorption clearly seen when the soft state, but disappears during hard state. The variability features does not appear to be due...
In order to test the recently proposed classification of radio/X-ray states X-ray binary Cyg X-3, we present an analysis radio data available for system at much higher spatial resolutions than used defining states. The set consists archival VLBA 5 or 15 GHz and new e-EVN GHz. We also MERLIN observations outburst X-3. regime use quasi-simultaneous with radio, monitoring pointed RXTE observations. find that when emission from both jet core is globally considered, behaviour X-3 milliarcsecond...
Recent studies of different X-ray binaries (XRBs) have shown a clear correlation between the radio and emission. We present evidence close relationship found emission at epochs for GRS1915+105, using observations from Ryle Telescope Rossi Timing Explorer satellite. The strongest was during hard state (also known as `plateau' state), where steady AU-scale jet is to exist. Both were decay start most plateau states, with decaying faster. An empirical $S_{\rm{radio}}\propto S_{\rm{X-ray}}^{\xi}$...
We present evidence for the presence of a weak compact jet during soft X-ray state Cygnus X-1. Very-high-resolution radio observations were taken with VLBA, EVN and MERLIN hard-to-soft spectral change, showing hard to be suppressed by factor about 3-5 in flux unresolved direct imaging (i.e. < 1 mas at 4 cm). High time-resolution RXTE-PCA also monitoring period, source make transition from softer (via an intermediate state), although may never have reached canonical state. Using astrometric...
Black hole X-ray binaries undergo occasional outbursts caused by changing inner accretion flows.Here we report high angular resolution radio observations of the 2013 outburst black candidate binary system XTE J1908+094, using data from Very Long Baseline Array and European VLBI Network.We show that following a hard-to-soft state transition, detect moving jet knots appear asymmetric in morphology brightness, expand to become laterally resolved as they move away core, along an axis aligned...
ThunderKAT is the image-plane transients programme for MeerKAT. The goal as outlined in 2010, and still today, to find, identify understand high-energy astrophysical processes via their radio emission (often concert with observations at other wavelengths). Through a comprehensive complementary of surveying monitoring Galactic synchrotron (across range compact accretors explosive phenomena) exploring distinct populations extragalactic (microquasars, supernovae possibly yet unknown transient -...
We present coordinated multiwavelength observations of the high Galactic latitude (b=+50 deg) black hole X-ray binary (XRB) J1357.2-0933 in quiescence. Our broadband spectrum includes strictly simultaneous radio and observations, near-infrared, optical, ultraviolet data taken 1-2 days later. detect Swift at all wavebands except for (f_5GHz < 3.9 uJy/beam). Given current constraints on distance (2.3-6.3 kpc), its 0.5-10 keV flux corresponds to an Eddington ratio Lx/Ledd = 4e-9 -- 3e-8...
We report on radio and X-ray monitoring observations of the BHC Swift J1753.5−0127 taken over a ∼10 yr period. Presented are daily at 15 GHz with Arcminute Microkelvin Imager Large Array (AMI-LA) data from Telescope Burst Alert Telescope. Also presented is deep 2 h JVLA observation in an unusually low-luminosity soft-state (with low disc temperature). show that although source has remained relatively radio-quiet compared to XRBs similar luminosity hard-state, power-law relationship scales as...
Adding VLBI capability to the SKA arrays will greatly broaden science of SKA, and is feasible within current specifications.SKA-VLBI can be initially implemented by providing phased-array outputs for SKA1-MID SKA1-SUR using these extremely sensitive stations with other radio telescopes, in SKA2 realising a distributed configuration baselines up thousands km, merging it existing networks.The motivation possible realization SKA-VLBI described this paper.
Abstract The ejection of a relativistic jet has been observed in the luminous Galactic low-mass X-ray binary Cygnus X-2. Using high-resolution radio observations, directly resolved event discovered while source was on horizontal branch Z-track. Contemporaneous and observations were made with European VLBI Network at 6 cm Swift observatory 0.3–10 keV band. This difficult to achieve because previous inability predict formation. Two sets ∼10 h spaced 12 apart, apparently switching during Day 1....
High-resolution long-slit Hα spectra of the shell old nova DQ Herculis have been obtained with William Herschel Telescope using ISIS spectrograph. An equatorial expansion velocity 370 ± 14 km s−1 is derived from which, in conjunction a narrow-band image remnant, allows distance estimate 525 28 pc. ring which exhibits enhanced [N ii] emission has also detected and inclination angle found to be respect line sight. The reveal tails extending clumps shell, radial increasing along their length....
XTE J1908+094 is an X-ray transient black hole candidate in the Galactic plane that was observed outburst 2002 and 2013. Here we present multifrequency radio data, including polarimetry, spanning entire period of 2013 outburst. We find behaviour traces standard hardness–intensity path, evolving from a hard state, through soft before returning to state quiescence. Its typical compact jet becomes quenched discrete ejecta are launched during late stages softening. The fluxes, as well...
We present the results of our observations early stages 2012--2013 outburst transient black hole X-ray binary (BHXRB), Swift J1745$-$26, with VLA, SMA, and JCMT (SCUBA--2). Our data mark first multiple-band mm & sub-mm a BHXRB. During system was in hard accretion state producing steady, compact jet. The unique combination radio mm/sub-mm allows us to directly measure spectral indices between regimes, including index measured for Spectral fitting revealed that both (230 GHz) (350 measurements...
There is currently a clear discrepancy in the proper motions measured on different angular scales approaching radio jets of black hole X-ray binary GRS1915+105. Lower velocities were with Very Large Array (VLA) prior to 1996 than subsequently found from higher-resolution observations made Long Baseline and Multi-Element Radio Linked Interferometer Network. We initiated an observing campaign use all three arrays attempt track motion jet knots 2006 February outburst source, giving us...
We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. performed optical imaging and longslit spectroscopy 12 using Manchester echelle spectrometer with 2.1m San Pedro Martir telescope. reveal, for first time, presence end caps (or knots) aligned bipolar lobes shell in deep [NII]6584 image measured from our radial velocities 120 km/s these knots. have derived inclination angle hourglass shaped nebular to be 65 degrees line sight. It has been...
The radio emitting X-ray binary GRS 1915+105 shows a wide variety of and states. We present decade monitoring observations, with the RXTE-ASM Ryle Telescope, in conjunction high-resolution observations using MERLIN VLBA. Linear polarisation at 1.4 1.6 GHz has been spatially resolved jets, on scale ~150 mas flux densities few mJy. Depolarisation core occurs during flaring, associated ejection relativistic knots emission. have identified four epochs flaring. Assuming no deceleration, proper...
We report results of one-day simultaneous multiwavelength observations CygnusX-2 using XMM, Chandra, the European VLBI Network and XMM Optical Monitor. During observations, source did not exhibit Z-track movement, but remained in vicinity soft apex. It was a radio quiescent/quiet state <150 μJy. Strong dip events were seen as 25% reductions X-ray intensity. The use broadband CCD spectra combination with narrow-band grating has now demonstrated for first time that these dipping are caused by...