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33 papers
Relation of cyclotron resonant energy and luminosity in a strongly magnetized neutron star GRO J1008-57 observed by Insight-HXMT
X. Chen, W. Wang, Y. M. Tang +10
Cyclotron line scattering features are detected in a few tens of X-ray pulsars (XRPs) and used as direct indicators of a strong magnetic field at the surface of accreting neutron s…
Accretion Torque Reversals in GRO J1008-57 Revealed by Insight-HXMT
W. Wang, Y. M. Tang, Y. L. Tuo +92
GRO J1008-57, as a Be/X-ray transient pulsar, is considered to have the highest magnetic field in known neutron star X-ray binary systems. Observational data of the X-ray outbursts…
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…
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…
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.…
The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?
A. Shulevski, R. Morganti, P. D. Barthel +85
Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio…
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…
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…
The shape of the radio wavefront of extensive air showers as measured with LOFAR
A. Corstanje, P. Schellart, A. Nelles +78
Extensive air showers, induced by high energy cosmic rays impinging on the Earth's atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emissi…
Discovery of Carbon Radio Recombination Lines in absorption towards Cygnus~A
J. B. R. Oonk, R. J. van Weeren, F. Salgado +100
We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the LOw Frequency ARray in…
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…
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…
Calibrating High-Precision Faraday Rotation Measurements for LOFAR and the Next Generation of Low-Frequency Radio Telescopes
C. Sotomayor-Beltran, C. Sobey, J. W. T. Hessels +77
Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achiev…
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…