A5006626904- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Mechanics and Biomechanics Studies
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- High-pressure geophysics and materials
- Manufacturing Process and Optimization
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Radio Astronomy Observations and Technology
- Anesthesia and Neurotoxicity Research
- Additive Manufacturing Materials and Processes
- Additive Manufacturing and 3D Printing Technologies
- Tryptophan and brain disorders
- Evaluation of Teaching Practices
- Vibrio bacteria research studies
- Salmonella and Campylobacter epidemiology
- Innovations in Concrete and Construction Materials
- Spacecraft Design and Technology
- Aluminum Alloy Microstructure Properties
United States Air Force Research Laboratory
2024-2025
U.S. Air Force Research Laboratory Munitions Directorate
2024-2025
UK Astronomy Technology Centre
2020-2024
Columbia University Irving Medical Center
2023
European Southern Observatory
2023
Royal Observatory
2020
European Southern Observatory
2017-2020
University of Cape Town
2014-2017
Southern Cross University
2016
University of Southampton
2010-2013
The mechanism by which supergiant (sg)B[e] stars support cool, dense dusty discs/tori and their physical relationship with other evolved, massive such as luminous blue variables is uncertain. In order to investigate both issues we have analysed the long term behaviour of canonical sgB[e] star LHA 115-S 18. We employed OGLE II-IV lightcurve search for (a-)periodic variability supplemented these data new historic spectroscopy. contrast historical expectations stars, S18 photometrically...
We present a multi-wavelength analysis of the very fast X-ray transient MAXI J0158-744, which was detected by MAXI/GSC on 2011 November 11. The subsequent exponential decline flux followed with Swift observations, all revealed spectra low temperatures (~100eV) indicating that J0158-744 is new Supersoft Source (SSS). near maximum show features around 0.8 keV we interpret as possible absorption from OVIII, and emission O, Fe, Ne lines. obtained SAAO ESO optical counterpart early in outburst...
On MJD 56590-1 (2013 Oct 25-26) observations of the Magellanic Clouds by INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observatory discovered a previously-unreported bright, flaring X-ray source.This source was initially given identification IGR J00569-7226.Subsequent multi-wavelength identified system as new Be/X-ray binary in Small Cloud.Follow-up Swift and XMM-Newton revealed an pulse period 5.05s that underwent regular occulation/eclipse behaviour every 17d.This is first...
We observed the newly discovered X-ray source Swift J053041.9-665426 in and optical regime to confirm its proposed nature as a high mass binary. obtained XMM-Newton data, along with observations ESO Faint Object Spectrograph, investigate spectral temporal characteristics of J053041.9-665426. The data show coherent pulsations period 28.77521(10) s (1 sigma). spectrum can be modelled by an absorbed power law photon index within range 0.76 0.87. addition black body component increases quality...
In the course of XMM-Newton survey Small Magellanic Cloud (SMC), two new bright X-ray sources were discovered exhibiting spectral characteris- tics High Mass Binaries - but revealing only weak evidence for pulsations in just one objects(at 153s XMMUJ010743.1-715953). The accurate X- ray source locations permit identification these with Be stars, thereby strongly suggesting systems are Be/X-ray binaries. From blue spectra proposed classification XMMUJ010633.1-731543 is B0.5-1Ve and...
To better understand the LBV phenomenon, we analyze multi-epoch and multi-wavelength spectra photometry of R71. Pre-outburst are analyzed with radiative transfer code CMFGEN to determine star's fundamental stellar parameters. During quiescence, R71 has an effective temperature $T_\mathrm{{eff}} = 15\,500~K$ a luminosity log$(L_*/L_{\odot})$ 5.78 is thus classical LBV, but at lower end this group. We its mass-loss rate $4.0 \times 10^{-6}~M_{\odot}~$yr$^{-1}$. present R71's spectral energy...
The Galactic supergiant B[e] star CI Camelopardalis (CI Cam) was the first sgB[e] detected during an X-ray outburst. brightened to $\sim$2 Crab in regime within hours before decaying a quiescent level less than 2 weeks, clearly indicative of binarity. Since outburst Cam, number stars have been identified as overluminous for single (i.e. $L_X > 10^{-7}~L_{bol}$). This small population has recently expanded include two Ultra Luminous sources (ULX), Holmberg II X-1 and NGC300 ULX-1/supernova...
We present a detailed X-ray study of the 2003 XMM–Newton observation high-mass binary XTE J0421+560/CI Camelopardalis. The continuum spectrum is well described by flat power law (Γ = 1.0 ± 0.2) with large intrinsic absorbing column (NH (4.4 0.5) × 1023 cm−2). have decomposed broad iron line into three separate components: Fe i-Kα, i-Kβ and xxiv-xxvKα. It unclear how both neutral almost fully ionized can exist simultaneously; however, we suggest that this could be evidence compact object...
In the course of XMM-Newton survey Small Magellanic Cloud (SMC), a region to east emission nebula N19 was observed in November 2009. To search for new candidates high mass X-ray binaries EPIC PN and MOS data detected point sources were investigated their spectral temporal characteristics identified. A transient (XMMUJ005011.2-730026= SXP214) with pulse period 214.05 s discovered; source had hard spectrum power-law index ~0.65. The accurate location permits identification ~15th magnitude Be...
Several persistent, low luminosity (L_X 10^{34} erg s^{-1}), long spin period (P>100 s) High Mass X-ray Binaries have been reported with blackbody components temperatures >1 keV. These hot thermal excesses correspondingly small emitting regions (<1 km^2) and are attributed to the neutron star polar caps. We present a recent XMM-Newton target of opportunity observation newest member this class, Swift J045106.8-694803. The was determined be 168.5+/-0.2 s as 17 July 2012 (MJD = 56125.0). At...
The stellar population of the 30 Doradus star-forming region in Large Magellanic Cloud contains a subset apparently single, rapidly rotating O-type stars. physical processes leading to formation this cohort are currently uncertain. One member group, late star VFTS 399, is found be unexpectedly X-ray bright for its bolometric luminosity - study we aim determine nature and cause behaviour. We find 399 an aperiodic photometric variable with apparent near-IR excess. Its optical spectrum...
We present X-ray and optical data on the Be/X-ray binary (BeXRB) pulsar IGR J01054-7253 = SXP11.5 in Small Magellanic Cloud (SMC). Rossi Timing Explorer (RXTE) observations of this source a large outburst reveal an 11.483 +/- 0.002s pulse period show both accretion driven spin-up neutron star motion around companion through Doppler shifting spin period. Model fits to these suggest orbital 36.3 0.4d Pdot (4.7 0.3) x 10^{-10} ss^{-1}. solution for system, making it one best described BeXRB...
The number of known Be/X-ray binaries in the Large Magellanic Cloud is small compared to observed population Galaxy or Small Cloud. discovery a system outburst provides rare opportunity measure its X-ray properties detail. IGR J05414-6858 was discovered 2010 by INTEGRAL and found another with Swift satellite 2011. In order characterise system, we analysed data from follow-up XMM-Newton target observation 2011 investigate stellar counterpart photometry spectroscopy. We modelled spectra EPIC...
The Observatory Science Operations (OSO) subsystem of the SKAO consists a range complex tools which will be used to propose, design, schedule and execute observations. Bridging gap between science telescope domains is key responsibility OSO, requiring considerations usability, performance, availability accessibility, amongst others. This paper describes state observatory software as we approach construction milestones, how applications meet these requirements using modern technology...
We report the analysis of a highly magnetized neutron star in Large Magellanic Cloud (LMC). The high-mass X-ray binary pulsar Swift J045106.8−694803 has been observed with telescope (XRT) 2008, Rossi Timing Explorer (RXTE) 2011 and Multi-Mirror Mission–Newton (XMM–Newton) 2012. change spin period over these four years indicates spin-up rate −5.01 ± 0.06 s yr−1, amongst highest for an accreting pulsar. This can be accounted using Ghosh & Lamb accretion theory assuming it magnetic field (1.2...
One of the goals XMM-Newton survey Small Magellanic Cloud is study Be/X-ray binary population. During one our first observations a bright new transient - XMMUJ004814.0-732204 was discovered. We present analysis EPIC X-ray data together with optical observations, to investigate spectral and temporal characteristics XMMUJ004814.0-732204. found coherent pulsations in period (11.86642 +/- 0.00017) s. The spectrum can be modelled by an absorbed power-law indication for soft excess. Depending on...
We identify a new candidate for Be/X-ray binary in the XMM–Newton slew survey and archival Swift observations that is located transition region of Wing Small Magellanic Cloud Bridge. investigated classified this source with follow-up optical observations. model X-ray spectra search periodicities variability Optical Gravitational Lensing Experiment I-band light curve. The counterpart has been spectroscopically, data obtained at South African Astronomical Observatory 1.9 m telescope,...
An exceptionally bright new X-ray source in the Large Magellanic Cloud was discovered by Swift/BAT telescope on MJD 54923 (2009 April 2), and shown to have a pulse period of 27 s using follow-up observations RXTE/PCA (Krimm et al. 2009). We report here detailed timing taken over following weeks Fermi/Gamma Ray Burst Monitor (GBM) which reveal an excellent orbital solution indicate that flux is peaked at ∼1038 erg s−1. In addition, we optical (spectroscopic photometric) permit classification...
The X-ray binary population of the Small Magellanic Cloud (SMC) contains a large number massive binaries, and recent survey SMC by XMM–Newton has resulted in almost 50 more tentative high-mass (HMXB) candidates. Using probability parameters from Haberl Sturm together with optical spectra timing this work, we confirm six new binaries SMC. We also report two very probable periods 36.4 d XMM 1859 72.2 2300. These Be are likely part general population, which rarely undergoes an outburst.
We present 5 years of optical and infrared data the black hole candidate MAXI J1659-152 covering its 2010 outburst, decay quiescence. Combining taken during outburst decay, we obtain an orbital period 2.414 $\pm$ 0.005 h, in perfect agreement with value previously measured from X-ray dips. In addition, detect a clear H$α$ excess decay. also single hump modulation most likely produced by irradiation. Assuming that maximum occurs at phase 0.5, constrain dips to be ~ 0.65. quiescent counterpart...