G. M. Loose
A5079535653- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Antenna Design and Optimization
- Geophysics and Gravity Measurements
- Advanced Frequency and Time Standards
- Distributed and Parallel Computing Systems
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Scientific Computing and Data Management
- Sensor Technology and Measurement Systems
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Non-Invasive Vital Sign Monitoring
- Solar and Space Plasma Dynamics
- Soil Moisture and Remote Sensing
- Embedded Systems Design Techniques
- Radio Wave Propagation Studies
- Advanced MEMS and NEMS Technologies
- Dark Matter and Cosmic Phenomena
Netherlands Institute for Radio Astronomy
2012-2023
Dispersion in the interstellar medium is a well known phenomenon that follows simple relationship, which has been used to predict time delay of dispersed radio pulses since late 1960s. We performed wide-band simultaneous observations four pulsars with LOFAR (at 40-190 MHz), 76-m Lovell Telescope 1400 MHz) and Effelsberg 100-m 8000 test accuracy dispersion law over broad frequency range. In this paper we present results these show accurate better than 1 part 100000 across our observing band....
(abridged). We outline LBCS (the LOFAR Long-Baseline Calibrator Survey), whose aim is to identify sources suitable for calibrating the highest-resolution observations made with International Telescope, which include baselines >1000 km. Suitable must contain significant correlated flux density (50-100mJy) at frequencies around 110--190~MHz on scales of a few hundred mas. At least 200--300-km international baselines, we find 1 calibrator source per square degree over large part northern...
Repeating fast radio bursts (FRBs) present excellent opportunities to identify FRB progenitors and host environments, as well decipher the underlying emission mechanism. Detailed studies of repeating FRBs might also hold clues origin a population. We aim detect first two FRBs: 121102 (R1) 180814.J0422+73 (R2), characterise their repeat statistics. want significantly improve sky localisation R2. use Westerbork Synthesis Radio Telescope conduct extensive follow-up these FRBs. The new...
We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of Westerbork Synthesis Radio Telescope that transforms this telescope into high-sensitivity, wide-field-of-view L -band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams are formed on sky simultaneously, significantly increasing speed telescope. With upgraded instrument, an covering area 2300 deg 2 is being performed will deliver both continuum...
Context. Apertif is a phased-array feed system for the Westerbork Synthesis Radio Telescope, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program utilizing this upgrade started on 1 July 2019, with last observations taken 28 February 2022. The imaging component provides radio continuum, polarization, and spectral line data. Aims. Public release data critical maximizing legacy survey. Toward that end, we describe products from first year operations,...
Fast radio bursts (FRBs) are extragalactic transients of extraordinary luminosity. Studying the diverse temporal and spectral behaviour recently observed in a number FRBs may help to determine nature entire class. For example, fast spinning or highly magnetised neutron star (NS) might generate rotation-powered acceleration required explain bright emission. Periodic, subsecond components suggesting such rotation were reported one FRB, also exist two more. Here we report discovery FRB...
We report the detection of a bright fast radio burst, FRB\,191108, with Apertif on Westerbork Synthesis Radio Telescope (WSRT). The interferometer allows us to localise FRB narrow $5\arcsec\times7\arcmin$ ellipse by employing both multibeam information within phased-array feed (PAF) beam pattern, and across different tied-array beams. resulting sight line passes close Local Group galaxy M33, an impact parameter only 18\,kpc respect core. It also traverses much larger circumgalactic medium...
PSR B0950+08 is a bright non-recycled pulsar whose single-pulse fluence variability reportedly large. Based on observations at two widely separated frequencies, 55 MHz (NenuFAR) and 1.4 GHz (Westerbork Synthesis Radio Telescope), we review the properties of these single pulses. We conclude that they are more similar to ordinary pulses radio emission than special kind short Giant Pulses, observed from only handful pulsars. argue temporal variation interstellar medium along line sight this...
Supermassive black holes at the centres of galaxies can cycle through periods activity and quiescence. Characterising duty active galactic nuclei is crucial for understanding impact energy they release on host galaxy. For radio AGN, this be done by identifying dying (remnant) restarted from their spectral properties. Using combination images 1400 MHz produced Apertif, new phased-array feed receiver installed Westerbork Synthesis Radio Telescope, 150 provided LOFAR, we have derived resolved...
Detection of the electromagnetic emission from coalescing binary neutron stars (BNS) is important for understanding merger and afterglow. We present a search radio counterpart to gravitational-wave source GW190425, BNS merger, using Apertif on Westerbork Synthesis Radio Telescope (WSRT). observe field high probability in associated localisation region 3 epochs at 68, 90 109 days post merger. identify all sources that exhibit flux variations consistent with expected afterglow GW190425. also...
Fast Radio Bursts must be powered by uniquely energetic emission mechanisms. This requirement has eliminated a number of possible source types, but several remain. Identifying the physical nature Burst (FRB) emitters arguably requires good localisation more detections, and broadband studies enabled real-time alerting. We here present Apertif Transient System (ARTS), supercomputing radio-telescope instrument that performs FRB detection on Westerbork Synthesis Telescope (WSRT) interferometer....
We present the serendipitous detection of two main OH maser lines at 1667 and 1665 MHz associated with IRAS 10597+5926 z ⊙ = 0.19612 in untargeted Apertif Wide-area Extragalactic imaging Survey (AWES), subsequent measurement 1612 satellite line same source. With a total luminosity log( L / ) 3.90 ± 0.03, is fourth brightest megamaser (OHM) known. measure lower limit for 1667/1612 ratio R > 45.9, which highest limiting measured to date. measurements provide potentially valuable constraint...
We analyse five early science datasets from the APERture Tile in Focus (Apertif) phased array feed system to verify polarisation capabilities of Apertif view future larger data releases. aim characterise source population polarised sky L-Band using information combination with IR and optical data. use automatic routines generate full field-of-view Q- U-cubes perform RM-Synthesis, finding, cross-matching published radio, optical, catalogues. SED-fitting were used determine photometric...
The first data release of Apertif survey contains 3074 radio continuum images covering a thousand square degrees the sky. observations were performed during August 2019 to July 2020. produced at central frequency 1355 MHz with bandwidth $\sim$150 and angular resolution reaching 10". In this work we introduce apply new method obtain primary beam model using machine learning approach, Gaussian process regression. models obtained are published along products for release. We images, mosaic them...
Context. Apertif is a multi-beam receiver system for the Westerbork Synthesis Radio Telescope that operates at 1.1–1.5 GHz, which overlaps with various radio services, resulting in contamination of astronomical signals radio-frequency interference (RFI). Aims. We analyse approaches to mitigate and design an automated detection procedure its imaging mode. Using this approach, we present long-term RFI results over 300 observations. Methods. Our approach based on AOFlagger approach. introduce...
We present the discovery of a very extended (550 kpc) and low-surface-brightness (3.3 μJy arcsec −2 at 144 MHz) radio emission region in Abell 1318. These properties are consistent with its characterisation as an active galactic nucleus (AGN) remnant plasma, based on morphology spectral properties. performed broad-band (54–1400 index curvature analysis using LOFAR, uGMRT, WSRT-APERTIF data. also derived radiative age detected emission, estimating maximum 250 Myr. The source is remarkably...
The propagation of radio waves from distant compact sources through turbulent interstellar plasma in our Galaxy causes these to twinkle, a phenomenon called scintillation. Such scintillations are unique probe the micro-arcsecond structure as well sub-AU-scale Galactic medium. Weak (i.e. an intensity modulation few percent) on timescales days or longer commonly seen at centimetre wavelengths and thought result line-of-sight integrated turbulence Milky Way. So far, only three were known that...
Context. Phased Array Feeds (PAFs) are multi element receivers in the focal plane of a telescope that make it possible to form simultaneously multiple beams on sky by combining complex gains individual antenna elements. Recently Westerbork Synthesis Radio Telescope (WSRT) was upgraded with PAF and carried out several observing programs including two imaging surveys time domain survey. The Apertif use configuration, where 40 partially overlapping compound (CBs) formed arranged an...
Fast radio bursts (FRBs) are extragalactic transients of extraordinary luminosity. Studying the diverse temporal and spectral behaviour recently observed in a number FRBs may help determine nature entire class. For example, fast spinning or highly magnetised neutron star might generate rotation-powered acceleration required to explain bright emission. Periodic, sub-second components, suggesting such rotation, were reported one FRB, potentially two more. Here we report discovery FRB 20201020A...