Publications (110)
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…
Detecting and characterising the magnetic field of exoplanets
A. Strugarek, S. V. Berdyugina, V. Bourrier +25
Magnetic fields play a crucial role in planetary evolution and habitability. While the intrinsic magnetic fields of solar system planets are relatively well understood, the magneti…
Predicting low-frequency radio fluxes of known extrasolar planets
J. -M. GrieÃmeier, P. Zarka, H. Spreeuw
Context. Close-in giant extrasolar planets (''Hot Jupiters'') are believed to be strong emitters in the decametric radio range. Aims. We present the expected characteristics of the…
MHD study of extreme space weather conditions for exoplanets with Earth-like magnetospheres: On habitability conditions and radio-emission
J. Varela, A. S. Brun, P. Zarka +3
The present study aims at characterizing the habitability conditions of exoplanets with an Earth-like magnetosphere inside the habitable zone of M stars and F stars like tau Boo, c…
Simulating Jupiter-satellite decametric emissions with ExPRES: a parametric study
C. K. Louis, L. Lamy, P. Zarka +3
The high latitude radio emissions produced by the Cyclotron Maser Instability (CMI) in Jupiter's magnetosphere extend from a few kHz to 40 MHz. Part of the decametric emissions is…
New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR
D. Carbone, A. J. van der Horst, R. A. M. J. Wijers +23
We report on the results of a search for radio transients between 115 and 190\,MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 mi…
A broadband radio study of PSR J0250+5854: the slowest-spinning radio pulsar known
C. H. Agar, P. Weltevrede, L. Bondonneau +19
We present radio observations of the most slowly rotating known radio pulsar PSR J0250+5854. With a 23.5 s period, it is close, or even beyond, the - diagram region tho…
ExPRES: a Tool to Simulate Exoplanetary and Planetary Radio Emissions
C. K. Louis, S. L. G. Hess, B. Cecconi +4
All magnetized planets are known to produce intense non thermal radio emissions through a mechanism known as Cyclotron Maser Instability (CMI), requiring the presence of accelerate…
Dual-frequency single-pulse study of PSR B0950+08
A. V. Bilous, J. M. Griessmeier, T. Pennucci +33
PSR B0950+08 is a bright non-recycled pulsar whose single-pulse fluence variability is reportedly large. Based on observations at two widely separated frequencies, 55 MHz (NenuFAR)…
Calibrating the absolute amplitude scale for air showers measured at LOFAR
A. Nelles, J. R. Hörandel, T. Karskens +74
Air showers induced by cosmic rays create nanosecond pulses detectable at radio frequencies. These pulses have been measured successfully in the past few years at the LOw Frequency…
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…
Low-frequency monitoring of flare star binary CR Draconis: Long-term electron-cyclotron maser emission
J. R. Callingham, B. J. S. Pope, A. D. Feinstein +12
Recently detected coherent low-frequency radio emission from M dwarf systems shares phenomenological similarities with emission produced by magnetospheric processes from the gas gi…
RFI Flagging Implications for Short-Duration Transients
Y. Cendes, P. Prasad, A. Rowlinson +24
With their wide fields of view and often relatively long coverage of any position in the sky in imaging survey mode, modern radio telescopes provide a data stream that is naturally…
A LOFAR census of non-recycled pulsars: average profiles, dispersion measures, flux densities, and spectra
A. Bilous, V. Kondratiev, M. Kramer +24
We present first results from a LOFAR census of non-recycled pulsars. The census includes almost all such pulsars known (194 sources) at declinations and Galac…
LOFAR 150-MHz observations of SS 433 and W 50
J. W. Broderick, R. P. Fender, J. C. A. Miller-Jones +28
We present LOFAR high-band data over the frequency range 115-189 MHz for the X-ray binary SS 433, obtained in an observing campaign from 2013 February - 2014 May. Our results inclu…
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…
LOFAR imaging of Cygnus A -- Direct detection of a turnover in the hotspot radio spectra
J. P. McKean, L. E. H. Godfrey, S. Vegetti +75
The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termin…
Sub-arcsecond imaging with the International LOFAR Telescope I. Foundational calibration strategy and pipeline
L. K. Morabito, N. J. Jackson, S. Mooney +71
[abridged] The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2,000 km, LOFAR has the unique capability of achievin…
The "SPectrogram Analysis and Cataloguing Environment" (SPACE) Labelling Tool
C. K. Louis, C. M. Jackman, S. W. Mangham +6
The SPectrogram Analysis and Cataloguing Environment (SPACE) tool is an interactive python tool designed to label radio emission features of interest in a time-frequency map (calle…
PALANTIR: an updated prediction tool for exoplanetary radio emissions
E. Mauduit, J. -M. Griessmeier, P. Zarka +1
In the past two decades, it has been convincingly argued that magnetospheric radio emissions, of cyclotron maser origin, can occur for exoplanetary systems, similarly as solar plan…
The LOFAR radio environment
A. R. Offringa, A. G. de Bruyn, S. Zaroubi +93
Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analys…
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…
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…
MOVES V. Modelling star-planet magnetic interactions of HD 189733
A. Strugarek, R. Fares, V. Bourrier +10
Magnetic interactions between stars and close-in planets may lead to a detectable signal on the stellar disk. HD 189733 is one of the key exosystems thought to harbor magnetic inte…
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…
Long term monitoring of FRB~20121102 with the Nançay Radio Telescope and multi-wavelength campaigns including INTEGRAL
C. Gouiffés, C. Ng, I. Cognard +12
The origin(s) of Fast Radio Bursts (FRBs), mysterious radio bursts coming from extragalactic distances, remains unknown. Multi-wavelength observations are arguably the only way to…
Radio Burst from a Stellar Coronal Mass Ejection
J. R. Callingham, C. Tasse, R. Keers +15
Coronal mass ejections (CMEs) are massive expulsions of magnetised plasma from a star, and are the largest contributors to space weather in the Solar System. CMEs are theorized to…
Improved upper limits on the 21-cm signal power spectrum at and from an optimal field observed with NenuFAR
S. Munshi, F. G. Mertens, J. K. Chege +19
We report the deepest upper limits to date on the power spectrum of the 21-cm signal during the Cosmic Dawn (redshifts: ), using four nights of observations with NenuFAR. The…
Pulsars with NenuFAR: backend and pipelines
L. Bondonneau, J. -M. GrieÃmeier, G. Theureau +27
NenuFAR (New extension in Nançay upgrading LoFAR) is a new radio telescope developed and built on the site of the Nançay Radio Observatory. It is designed to observe the largely…
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…
Overview of Saturn lightning observations
G. Fischer, U. A. Dyudina, W. S. Kurth +8
The lightning activity in Saturn's atmosphere has been monitored by Cassini for more than six years. The continuous observations of the radio signatures called SEDs (Saturn Electro…
Sub-arcsecond imaging with the International LOFAR Telescope: II. Completion of the LOFAR Long-Baseline Calibrator Survey
Neal Jackson, Shruti Badole, John Morgan +69
The Low-Frequency Array (LOFAR) Long-Baseline Calibrator Survey (LBCS) was conducted between 2014 and 2019 in order to obtain a set of suitable calibrators for the LOFAR array. In…
Jupiter radio emission induced by Ganymede and consequences for the radio detection of exoplanets
P. Zarka, M. S. Marques, C. Louis +4
By analysing a database of 26 years of observations of Jupiter with the Nancay Decameter Array, we unambiguously identify the radio emissions caused by the Ganymede-Jupiter interac…
M87 at metre wavelengths: the LOFAR picture
F. de Gasperin, E. Orru', M. Murgia +92
M87 is a giant elliptical galaxy located in the centre of the Virgo cluster, which harbours a supermassive black hole of mass 6.4x10^9 M_sun, whose activity is responsible for the…
Coherent radio emission from a population of RS Canum Venaticorum systems
S. E. B. Toet, H. K. Vedantham, J. R. Callingham +5
Coherent radio emission from stars can be used to constrain fundamental coronal plasma parameters, such as plasma density and magnetic field strength. It is also a probe of chromos…
Shock location and CME 3D reconstruction of a solar type II radio burst with LOFAR
P. Zucca, D. E. Morosan, A. P. Rouillard +62
Type II radio bursts are evidence of shocks in the solar atmosphere and inner heliosphere that emit radio waves ranging from sub-meter to kilometer lengths. These shocks may be ass…
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…
Effect of a magnetosphere compression on Jovian radio emissions: in situ case study using Juno data
C. K. Louis, C. M. Jackman, G. Hospodarsky +13
During its 53-day polar orbit around Jupiter, Juno often crosses the boundaries of the Jovian magnetosphere (namely the magnetopause and bow shock). From the boundary locations, th…
LOFAR tied-array imaging and spectroscopy of solar S bursts
D. E. Morosan, P. T. Gallagher, P. Zucca +50
Context. The Sun is an active source of radio emission that is often associated with energetic phenomena ranging from nanoflares to coronal mass ejections (CMEs). At low radio freq…
LBCS: the LOFAR Long-Baseline Calibrator Survey
N. Jackson, A. Tagore, A. Deller +76
(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 the…
LOFAR Observations of Swift J1644+57 and Implications for Short-Duration Transients
Y. Cendes, R. A. M. J. Wijers, J. D. Swinbank +25
Aims: We have analyzed low frequency radio data of tidal disruption event (TDE) Swift J1644+57 to search for a counterpart. We consider how brief transient signals (on the order of…
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 (<…
Properties of Saturn Kilometric Radiation measured within its source region
L. Lamy, P. Schippers, P. Zarka +9
On 17 October 2008, the Cassini spacecraft crossed the southern sources of Saturn kilometric radiation (SKR), while flying along high-latitude nightside magnetic field lines. In si…
Effect of the exoplanet magnetic field topology on its magnetospheric radio emission
J. Varela, V. Réville, A. S. Brun +2
The magnetized wind from stars that impact exoplanets should lead to radio emissions. According to the scaling laws derived in the solar system, the radio emission should depend on…
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.…
Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT
V. Zakharenko, A. Konovalenko, P. Zarka +49
This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. This paper describes digital radio astronomical receivers used for d…
On Earth's habitability over the Sun's main-sequence history: joint influence of space weather and Earth's magnetic field evolution
J. Varela, A. S. Brun, A. Strugarek +3
The aim of this study is to analyze the Earth habitability with respect to the direct exposition of the Earth atmosphere to the solar wind along the Suns evolution on the main sequ…
1977-2017: 40 years of decametric observations of Jupiter and the Sun with the Nancay Decameter Array
L. Lamy, P. Zarka, B. Cecconi +5
The Nancay Decameter Array (NDA) routinely observes low frequency (10-100 MHz) radio emissions of Jupiter and the Sun since 4 decades. The NDA observations, acquired with a variety…
Constraining the magnetic field geometry of the millisecond pulsar PSR~J0030+0451 from joint radio, thermal X-ray and -ray emission
J. Pétri, S. Guillot, L. Guillemot +13
With the advent of multi-wavelength electromagnetic observations of neutron stars, spanning many decades in photon energies, from radio wavelengths up to X-rays and -rays, it b…
Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers
P. Schellart, T. N. G. Trinh, S. Buitink +71
We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radical…
LOFAR 144-MHz follow-up observations of GW170817
J. W. Broderick, T. W. Shimwell, K. Gourdji +66
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 A…
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…
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…
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…
The Search for Signatures Of Transient Mass Loss in Active Stars
M. K. Crosley, R. A. Osten, J. W. Broderick +7
The habitability of an exoplanet depends on many factors. One such factor is the impact of stellar eruptive events on nearby exoplanets. Currently this is poorly constrained due to…
The LOFAR LBA Sky Survey II. First data release
F. de Gasperin, H. W. Edler, W. L. Williams +27
The Low Frequency Array (LOFAR) is the only existing radio interferometer able to observe at ultra-low frequencies (<100 MHz) with high resolution (<15") and high sensitivity (<1 m…
Cassini observations of Saturn's southern polar cusp
C. S. Arridge, J. M. Jasinski, N. Achilleos +15
The magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground- and space-based observations at Earth have enab…
The LOFAR LBA Sky Survey I. survey description and preliminary data release
F. de Gasperin, W. L. Williams, P. Best +38
LOFAR is the only radio telescope that is presently capable of high-sensitivity, high-resolution (<1 mJy/b and <15") observations at ultra-low frequencies (<100 MHz). To utilise th…
Atmospheric Electricity at the Ice Giants
K. L. Aplin, G. Fischer, T. A. Nordheim +3
Lightning was detected by Voyager 2 at Uranus and Neptune, and weaker electrical processes also occur throughout planetary atmospheres from galactic cosmic ray (GCR) ionisation. Li…
Searching for Star-Planet interactions within the magnetosphere of HD 189733
R. Fares, J. -F. Donati, C. Moutou +7
HD 189733 is a K2 dwarf, orbited by a giant planet at 8.8 stellar radii. In order to study magnetospheric interactions between the star and the planet, we explore the large-scale m…
The population of M dwarfs observed at low radio frequencies
J. R. Callingham, H. K. Vedantham, T. W. Shimwell +12
Coherent low-frequency ( MHz) radio emission from stars encodes the conditions of the outer corona, mass-ejection events, and space weather. Previous low-frequency se…
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…
GMRT search for 150 MHz radio emission from the transiting extrasolar planets HD189733b and HD209458b
A. Lecavelier des Etangs, S. K. Sirothia, Gopal-Krishna +1
We report a sensitive search for meter-wavelength emission at 150 MHz from two prominent transiting extrasolar planets, HD189733b and HD209458b. To distinguish any planetary emissi…
Determining the beaming of Io decametric emissions : a remote diagnostic to probe the Io-Jupiter interaction
L. Lamy, L. Colomban, P. Zarka +8
We investigate the beaming of 11 Io-Jupiter decametric (Io-DAM) emissions observed by Juno/Waves, the Nan\c cay Decameter Array and NenuFAR. Using an up-to-date magnetic field mode…
The Association of a J-burst with a Solar Jet
D. E. Morosan, P. T. Gallagher, R. A. Fallows +56
Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections and numerous smaller-scale events such as solar jets.…
Orbital and superorbital variability of LS I +61 303 at low radio frequencies with GMRT and LOFAR
B. Marcote, M. Ribó, J. M. Paredes +23
LS I +61 303 is a gamma-ray binary that exhibits an outburst at GHz frequencies each orbital cycle of 26.5 d and a superorbital modulation with a period of 4.6…
Radio emission in Mercury magnetosphere
J. Varela, V. Reville, A. S. Brun +2
Context: Active stars possess magnetized wind that has a direct impact on planets that can lead to radio emission. Mercury is a good test case to study the effect of the solar wind…
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…
Imaging Jupiter's radiation belts down to 127 MHz with LOFAR
J. N. Girard, P. Zarka, C. Tasse +71
Context. Observing Jupiter's synchrotron emission from the Earth remains today the sole method to scrutinize the distribution and dynamical behavior of the ultra energetic electron…
Magnetospheric Emission from Extrasolar Planets
J. Lazio, T. Bastian, G. Bryden +12
The magnetospheric emissions from extrasolar planets represent a science frontier for the next decade. All of the solar system giant planets and the Earth produce radio emissions a…
Periodicities in radio emissions from the Jupiter's magnetosphere and consequences for radio emissions from star-exoplanet systems
C. K. Louis, A. Loh, P. Zarka +7
The search for radio signals from exoplanets or star-planet interactions is a topic of major scientific interest, as it is likely the best way to detect and measure a planetary mag…
GMRT radio observations of the transiting extrasolar planet HD189733b at 244 and 614 MHz
A. Lecavelier des Etangs, S. K. Sirothia, Gopal-Krishna +1
We report a sensitive search for meter-wavelength emission at 244 and 614 MHz from HD189733b, the nearest known extrasolar transiting planet of `hot-Jupiter' type. To discriminate…
The UTR-2 decametre pulsar and transient survey I. Transient detection
V. V. Zakharenko, I. P. Kravtsov, I. Y. Vasylieva +6
Context. This paper presents a detailed description of the Decametre Pulsar and Transient Survey of the Northern Sky that was carried out in 2012-2017 using the world's largest rad…
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…
Observing pulsars and fast transients with LOFAR
B. W. Stappers, J. W. T. Hessels, A. Alexov +91
Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in…
Near-field imaging of local interference in radio interferometric data: Impact on the redshifted 21 cm power spectrum
S. Munshi, F. G. Mertens, L. V. E. Koopmans +24
Radio-frequency interference (RFI) is a major systematic limitation in radio astronomy, particularly for science cases requiring high sensitivity, such as 21 cm cosmology. Traditio…
Polarised radio pulsations from a new T dwarf binary
H. K. Vedantham, Trent J. Dupuy, E. L. Evans +6
Brown dwarfs display Jupiter-like auroral phenomena such as magnetospheric H emission and coherent radio emission. Coherent radio emission is a probe of magnetospheric accelera…
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…
Radio Signatures of Star-Planet Interactions, Exoplanets, and Space Weather
J. R. Callingham, B. J. S. Pope, R. D. Kavanagh +22
Radio detections of stellar systems provide a window onto stellar magnetic activity and the space weather conditions of extrasolar planets, information that is difficult to attain…
Large closed-field corona of WX UMa evidenced from radio observations
I. Davis, H. K. Vedantham, J. R. Callingham +5
The space-weather conditions that result from stellar winds significantly impact the habitability of exoplanets. The conditions can be calculated from first principles if the neces…
First upper limits on the 21 cm signal power spectrum from cosmic dawn from one night of observations with NenuFAR
S. Munshi, F. G. Mertens, L. V. E. Koopmans +24
The redshifted 21 cm signal from neutral hydrogen is a direct probe of the physics of the early universe and has been an important science driver of many present and upcoming radio…
MHD study of planetary magnetospheric response during extreme solar wind conditions: Earth and exoplanet magnetospheres applications
J. Varela, A. S. Brun, A. Strugarek +3
Context: The stellar wind and the interplanetary magnetic field modify the topology of planetary magnetospheres. Consequently, the hazardous effect of the direct exposition to the…
Pulsar polarisation below 200 MHz: Average profiles and propagation effects
A. Noutsos, C. Sobey, V. I. Kondratiev +52
We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Base…
Emission and propagation of Saturn kilometric radiation: magneto-ionic modes, beaming pattern and polarization state
L. Lamy, B. Cecconi, P. Zarka +7
The Cassini mission crossed the source region of the Saturn kilometric radiation (SKR) on 17 October 2008. On this occasion, the Radio and Plasma Wave Science (RPWS) experiment det…
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…
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…
Decameter Type III Bursts with Changing Frequency Drift-Rate Signs
V. N. Melnik, A. I. Brazhenko, A. A. Konovalenko +10
We discuss properties of type III bursts which change sign of their drift rate from negative to positive and vice versa. Moreover such bursts may change sign of their drift rates m…
A circularly polarized low-frequency radio burst from the exoplanetary system HD 189733
X. Zhang, P. Zarka, J. N. Girard +17
We aim to detect low-frequency radio emission from exoplanetary systems, which can provide insights into planetary magnetic fields, star-planet interactions, stellar activity, and…
Wide-band Simultaneous Observations of Pulsars: Disentangling Dispersion Measure and Profile Variations
T. E. Hassall, B. W. Stappers, J. W. T. Hessels +91
Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since t…
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…
Broadband Polarized Radio Emission Detected from Starlink Satellites Below 100 MHz with NenuFAR
X. Zhang, P. Zarka, C. Viou +16
This study evaluates the impact of Starlink satellites on low-frequency radio astronomy below 100 MHz, focusing on challenges on data processing and scientific goals. We conducted…
MOVES I. The evolving magnetic field of the planet-hosting star HD189733
R. Fares, V. Bourrier, A. A. Vidotto +9
HD189733 is an active K dwarf that is, with its transiting hot Jupiter, among the most studied exoplanetary systems. In this first paper of the Multiwavelength Observations of an e…
Combining the second data release of the European Pulsar Timing Array with low-frequency pulsar data
F. Iraci, A. Chalumeau, C. Tiburzi +46
Low-frequency radio data improve the sensitivity of pulsar timing arrays (PTAs) to propagation effects such as dispersion measure (DM) variations, enabling better noise characteriz…
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…
Saturn northern aurorae at solstice from HST observations coordinated with Cassini Grand Finale
L. Lamy, R. Prangé, C. Tao +8
Throughout 2017, the Hubble Space Telescope (HST) observed the northern far-ultraviolet aurorae of Saturn at northern solstice, during the Cassini Grand Finale. These conditions pr…
V-LoTSS: The Circularly-Polarised LOFAR Two-metre Sky Survey
J. R. Callingham, T. W. Shimwell, H. K. Vedantham +44
We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We use the second data release of the 144 MHz LOFAR Two-metr…
Radio emission from satellite-Jupiter interactions (especially Ganymede)
P. Zarka, M. S. Marques, C. Louis +4
Analyzing a database of 26 years of observations of Jupiter from the Nançay Decameter Array, we study the occurrence of Io-independent emissions as a function of the orbital phase…
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…
Magnetic Fields of Extrasolar Planets: Planetary Interiors and Habitability
J. Lazio, G. Hallinan, V. Airapetian +13
Jupiter's radio emission has been linked to its planetary-scale magnetic field, and spacecraft investigations have revealed that most planets, and some moons, have or had a global…
Direct radio discovery of a cold brown dwarf
H. K. Vedantham, J. R. Callingham, T. W. Shimwell +9
Magnetospheric processes seen in gas-giants such as aurorae and circularly-polarized cyclotron maser radio emission have been detected from some brown dwarfs. However, previous rad…