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30 papers
A large light-mass component of cosmic rays at 10^{17} - 10^{17.5} eV from radio observations
S. Buitink, A. Corstanje, H. Falcke +101
Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whet…
Low-radio-frequency eclipses of the redback pulsar J2215+5135 observed in the image plane with LOFAR
J. W. Broderick, R. P. Fender, R. P. Breton +30
The eclipses of certain types of binary millisecond pulsars (i.e. `black widows' and `redbacks') are often studied using high-time-resolution, `beamformed' radio observations. Howe…
LOFAR MSSS: Detection of a low-frequency radio transient in 400 hrs of monitoring of the North Celestial Pole
A. J. Stewart, R. P. Fender, J. W. Broderick +99
We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Mult…
Wide-Band, Low-Frequency Pulse Profiles of 100 Radio Pulsars with LOFAR
M. Pilia, J. W. T. Hessels, B. W. Stappers +84
LOFAR offers the unique capability of observing pulsars across the 10-240 MHz frequency range with a fractional bandwidth of roughly 50%. This spectral range is well-suited for stu…
The LOFAR Multifrequency Snapshot Sky Survey (MSSS) I. Survey description and first results
G. H. Heald, R. F. Pizzo, E. Orrú +147
We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and de…
A LOFAR census of millisecond pulsars
V. I. Kondratiev, J. P. W. Verbiest, J. W. T. Hessels +29
We report the detection of 48 millisecond pulsars (MSPs) out of 75 observed thus far using the LOFAR in the frequency range 110-188 MHz. We have also detected three MSPs out of nin…
LOFAR discovery of a quiet emission mode in PSR B0823+26
C. Sobey, N. J. Young, J. W. T. Hessels +91
PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing.…
Measuring a Cherenkov ring in the radio emission from air showers at 110-190 MHz with LOFAR
A. Nelles, P. Schellart, S. Buitink +66
Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic tim…
The LOFAR long baseline snapshot calibrator survey
J. Moldón, A. T. Deller, O. Wucknitz +82
Aims. An efficient means of locating calibrator sources for International LOFAR is developed and used to determine the average density of usable calibrator sources on the sky for s…
LOFAR low-band antenna observations of the 3C295 and Bootes fields: source counts and ultra-steep spectrum sources
R. J. van Weeren, W. L. Williams, C. Tasse +98
We present LOFAR Low Band observations of the Bootes and 3C295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam, making them the dee…
LOFAR observations of PSR B0943+10: profile evolution and discovery of a systematically changing profile delay in Bright mode
A. Bilous, J. Hessels, V. Kondratiev +10
We present broadband, low-frequency (25-80 MHz and 110-190 MHz) LOFAR observations of PSR B0943+10, with the goal of better illuminating the nature of its enigmatic mode-switching…
The LOFAR Pilot Surveys for Pulsars and Fast Radio Transients
Thijs Coenen, Joeri van Leeuwen, Jason W. T. Hessels +87
We have conducted two pilot surveys for radio pulsars and fast transients with the Low-Frequency Array (LOFAR) around 140 MHz and here report on the first low-frequency fast-radio…
LOFAR tied-array imaging of Type III solar radio bursts
D. E. Morosan, P. T. Gallagher, P. Zucca +82
The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<…
Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz
H. K. Vedantham, L. V. E. Koopmans, A. G. de Bruyn +91
We present radio observations of the Moon between and MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far bey…
Initial LOFAR observations of Epoch of Reionization windows: II. Diffuse polarized emission in the ELAIS-N1 field
V. Jelic, A. G. de Bruyn, M. Mevius +106
This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal…
LOFAR Sparse Image Reconstruction
H. Garsden, J. N. Girard, J. L. Starck +77
Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of F…
Detecting cosmic rays with the LOFAR radio telescope
P. Schellart, A. Nelles, S. Buitink +102
The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferom…
Detecting highly-dispersed bursts with next-generation radio telescopes
T. E. Hassall, E. F. Keane, R. P. Fender
Recently, there have been reports of six bright, dispersed bursts of coherent radio emission found in pulsar surveys with the Parkes Multi-beam Receiver. Not much is known about th…
Studying Galactic interstellar turbulence through fluctuations in synchrotron emission: First LOFAR Galactic foreground detection
M. Iacobelli, M. Haverkorn, E. Orrú +85
The characteristic outer scale of turbulence and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the i…
The brightness and spatial distributions of terrestrial radio sources
A. R. Offringa, A. G. de Bruyn, S. Zaroubi +75
Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obs…
LOFAR: The LOw-Frequency ARray
M. P. van Haarlem, M. W. Wise, A. W. Gunst +197
LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR…
LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A
Ashish Asgekar, J. B. R. Oonk, S. Yatawatta +89
Cassiopeia A was observed using the Low-Band Antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) a…
Differential Frequency-dependent Delay from the Pulsar Magnetosphere
T. E. Hassall, B. W. Stappers, P. Weltevrede +60
Some radio pulsars show clear drifting subpulses, in which subpulses are seen to drift in pulse longitude in a systematic pattern. Here we examine how the drifting subpulses of PSR…
Initial deep LOFAR observations of Epoch of Reionization windows: I. The North Celestial Pole
S. Yatawatta, A. G. de Bruyn, M. A. Brentjens +86
The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitu…