55 research outputs found
Shared and distinct pathways and networks genetically linked to coronary artery disease between human and mouse
LOFAR 144-MHz follow-up observations of GW170817
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 4, June 2020, Pages 5110â5117, ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO-Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13.7 degrees when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130-138 and 371-374 days after the merger event, we obtain 3 upper limits for the afterglow component of 6.6 and 19.5 mJy beam, respectively. Using our best upper limit and previously published, contemporaneous higher-frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index . We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.Peer reviewe
Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies
Context. The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (< 100 MHz) can reach several thousands of janskys, and they often contaminate observations of the low-frequency sky by interfering with image processing. Furthermore, these sources are foreground objects for all-sky observations hampering the study of faint signals, such as the cosmological 21 cm line from the epoch of reionisation. Aims. We aim to produce robust models for the surface brightness emission as a function of frequency for the A-team sources at ultra-low frequencies. These models are needed for the calibration and imaging of wide-area surveys of the sky with low-frequency interferometers. This requires obtaining images at an angular resolution better than 15\u2033 with a high dynamic range and good image fidelity. Methods. We observed the A-team with the Low Frequency Array (LOFAR) at frequencies between 30 MHz and 77 MHz using the Low Band Antenna system. We reduced the datasets and obtained an image for each A-team source. Results. The paper presents the best models to date for the sources Cassiopeia A, Cygnus A, Taurus A, and Virgo A between 30 MHz and 77 MHz. We were able to obtain the aimed resolution and dynamic range in all cases. Owing to its compactness and complexity, observations with the long baselines of the International LOFAR Telescope will be required to improve the source model for Cygnus A further
Chemical and physical fertility indicators of a weakly-structured Ultisol after liming and mulching
DFT studies on thiophene acetylide Ru(II) complexes for nonlinear optics: Structureâfunction relationships and solvent effects
Participatie: De kunst van het verbinden
Na een beknopt overzicht van participatie in de afgelopen decennia, geeft de auteur een schets van burgerparticipatie in de huidige context, waarbij overheid, markt en âcivil societyâ gezamenlijk invulling moeten geven aan de betekenis ervan. Dit essay sluit af met wat dit betekent voor de vaardigheden van de nieuwe gebiedsontwikkelaar.Real Estate and HousingArchitectur
Herbestemming vraagt om kansrijke programmering
Restauratie en herbestemming van industriële monumenten vereisen een bijzondere aanpak. Cultuurhistorische, economische en belevingswaarden moeten gerespecteerd worden. Dit vraagt om moed bij de opdrachtgevers.Real Estate and HousingArchitecture and The Built Environmen
Bouwen in de binnenstad
Als de crisis voor een ding heeft gezorgd in het ruimtelijke domein is het de confrontatie met de dagelijkse realiteit. Sinds de Woningwet in 1901heeft de overheid langs de lijn van het volkshuisvestingsbeleid een belangrijke rol gespeeld in het plannen van de stedelijke ontwikkeling. Een eeuw lang was het oog op de toekomstige groei gericht. De Vinex markeert de overgang van een dominante overheids-sturing naar een sturing met meer ruimte voor âde marktâ. Vandaag de dag ligt er een wens vanuit het Rijk om de komende jaren binnenstedelijk te verdichten. De vraag is hoe deze ambitie gerealiseerd kan worden in een decentraal planningsstelsel, met zeer beperkte middelen.Real Estate and HousingArchitectur
Terug naar de fabriek: met nieuwe energie
artikel op gebiedsontwikkeling.nu, 2 feb 2016Practice Chair Urban Area Developmen
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