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Now showing items 13028-13047 of 24190

    • LOFAR early-time search for coherent radio emission from GRB 180706A 

      Rowlinson, A.; Gourdji, K.; Meulen, K. van der; Meyers, Z. S.; Shimwell, T. W.; Veen, S. ter; Wijers, R. A. M. J.; Kuiack, M. J.; Shulevski, A.; Broderick, J. W.; Horst, A. J. van der; Tasse, C.; Hardcastle, M. J.; Mechev, A. P.; Williams, W. L. (2019-10-21)
      The nature of the central engines of gamma-ray bursts (GRBs) and the composition of their relativistic jets are still under debate. If the jets are Poynting flux dominated rather than baryon dominated, a coherent radio ...

    • LOFAR facet calibration 

      Van Weeren, R. J.; Williams, W. L.; Hardcastle, M.J.; Shimwell, T. W.; Rafferty, D. A.; Sabater, J.; Heald, G.; Sridhar, S. S.; Dijkema, T. J.; Brunetti, G.; Brüggen, M.; Andrade-Santos, F.; Ogrean, G. A.; Röttgering, H. J. A.; Dawson, W. A.; Forman, W.R.; Gasperin, F. de; Jones, C.; Miley, G.K.; Rudnick, L.; Sarazin, C.L.; Bonafede, A.; Best, P. N.; Bîrzan, L.; Cassano, R.; Chyży, K. T.; Croston, J. H.; Ensslin, T.; Ferrari, C.; Hoeft, M.; Horellou, C.; Jarvis, M.J.; Kraft, R.P.; Mevius, M.; Intema, H. T.; Murray, S. S.; Orrú, E.; Pizzo, R.; Simionescu, A.; Stroe, A.; Tol, S. van der; White, G.J. (2016-03-07)
      LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides ...

    • LOFAR first look at the giant radio galaxy 3C 236 

      Shulevski, A.; Barthel, P. D.; Morganti, R.; Harwood, J. J.; Brienza, M.; Shimwell, T. W.; Röttgering, H. J. A.; White, G. J.; Callingham, J. R.; Mooney, S.; Rafferty, D. A. (2019-07-28)
      We have examined the giant radio galaxy 3C~236 using LOFAR at 143 MHz down to an angular resolution of 7", in combination with observations at higher frequencies. We have used the low frequency data to derive spectral index ...

    • LOFAR HBA observations of the Euclid Deep Field North (EDFN) 

      Bondi, M.; Scaramella, R.; Zamorani, G.; Ciliegi, P.; Vitello, F.; Arias, M.; Best, P.N.; Bonato, M.; Botteon, A.; Brienza, M.; Brunetti, G.; Hardcastle, M. J.; Magliocchetti, M.; Massaro, F.; Morabito, L. K; Pentericci, L.; Prandoni, I.; Röttgering, H. J. A.; Shimwell, T. W.; Tasse, C.; Weeren, R. J. van; White, G. J. (2024-03-18)
      We present the first deep (72 h of observations) radio image of the Euclid Deep Field North (EDFN) obtained with the LOw-Frequency ARray (LOFAR) High Band Antenna (HBA) at 144 MHz. The EDFN is the latest addition to the ...

    • LOFAR imaging of Cygnus A - direct detection of a turnover in the hotspot radio spectra 

      McKean, J. P.; Godfrey, L. E H; Vegetti, S.; Wise, Michael W.; Morganti, R.; Hardcastle, M. J.; Rafferty, D.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bemmel, I. M. van; Bentum, M. J.; Bernardi, G.; Best, Philip; Blaauw, R.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brüggen, Marcus; Cerrigone, L.; Ciardi, B.; De Gasperin, Francesco; Deller, A.; Duscha, S.; Engels, D.; Falcke, H.; Fallows, R. A.; Frieswijk, W.; Garrett, M.A.; Grießmeier, J. -M.; Haarlem, M. P. van; Heald, G.; Hoeft, Matthias; van der, HorstA J.; Iacobelli, M.; Interna, H.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Koopmans, L. V E; Kuniyoshi, M.; Kuper, G.; Van Leeuwen, J.; Maat, P.; Mann, R. G.; Markoff, S.; McFadden, R.; McKay-Bukowski, D.; Mulcahy, D. D.; Munk, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pietka, M.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rottgering, H. J. A.; Rowlinson, A.; Scaife, A. M M; Serylak, M.; Shulevski, Alexander; Sluman, J.; Smirnov, O.; Steinmetz, M.; Stewart, A. J.; Swinbank, J.; Tagger, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Van Weeren, R. J.; Wucknitz, O.; Yatawatta, S.; Zarka, P. (2016-12-01)
      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 termination. These processes are responsible for ...

    • The LOFAR LBA Sky Survey I. survey description and preliminary data release 

      Gasperin, F. de; Williams, W. L.; Best, P.; Bruggen, M.; Brunetti, G.; Cuciti, V.; Dijkema, T. J.; Hardcastle, M. J.; Norden, M. J.; Offringa, A.; Shimwell, T.; Weeren, R. van; Bomans, D.; Bonafede, A.; Botteon, A.; Callingham, J. R.; Cassano, R.; Chyzy, K. T.; Emig, K. L.; Edler, H.; Haverkorn, M.; Heald, G.; Heesen, V.; Iacobelli, M.; Intema, H. T.; Kadler, M.; Malek, K.; Mevius, M.; Miley, G.; Mingo, B.; Morabito, L. K.; Sabater, J.; Morganti, R.; Orru, E.; Pizzo, R.; Prandoni, I.; Shulevski, A.; Tasse, C.; Vaccari, M.; Zarka, P.; Rottgering, H. (2021-02-17)
      Context. The LOw Frequency ARray (LOFAR)istheonlyradiotelescopethatispresentlycapableofhigh-sensitivity,high-resolution (i.e. < 1mJybeam−1 and < 1500) observations at ultra-low frequencies(< 100MHz). To utilise these ...

    • The LOFAR LBA Sky Survey II. First data release 

      Gasperin, F. de; Edler, H. W.; Williams, W. L.; Callingham, J. R.; Asabere, B.; Bruggen, M.; Brunetti, G.; Dijkema, T. J.; Hardcastle, M. J.; Iacobelli, M.; Offringa, A.; Norden, M. J.; Rottgering, H. J. A.; Shimwell, T.; Weeren, R. J. van; Tasse, C.; Bomans, D. J.; Bonafede, A.; Botteon, A.; Cassano, R.; Chyzy, K. T.; Cuciti, V.; Emig, K. L.; Kadler, M.; Miley, G.; Mingo, B.; Oei, M. S. S. L.; Prandoni, I.; Schwarz, D. J.; Zarka, P. (2023-05-26)
      Context. 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 mJy beam−1 ). To exploit these ...

    • The LOFAR LBA Sky Survey: Deep Fields I. The Boötes Field 

      Williams, W. L.; Gasperin, F. de; Hardcastle, M. J. H.; Weeren, R. van; Tasse, C.; Shimwell, T. W.; Best, P. N.; Bonato, M.; Bondi, M.; Brüggen, M.; Röttgering, H. J. A.; Smith, D. J. B. (2021-11-10)
      We present the first sub-mJy ($\approx0.7$ mJy beam$^{-1}$) survey to be completed below 100 MHz, which is over an order of magnitude deeper than previously achieved for widefield imaging of any field at these low frequencies. ...

    • Lofar low-band antenna observations of the 3C 295 and boötes fields : Source counts and ultra-steep spectrum sources 

      Van Weeren, R. J.; Williams, W. L.; Tasse, C.; Röttgering, H. J.A.; Rafferty, D. A.; Van Der Tol, S.; Heald, G.; White, G. J.; Shulevski, A.; Best, P.; Intema, H. T.; Bhatnagar, S.; Reich, W.; Steinmetz, M.; Van Velzen, S.; Enßlin, T. A.; Prandoni, I.; De Gasperin, F.; Jamrozy, M.; Brunetti, G.; Jarvis, M. J.; McKean, J. P.; Wise, M. W.; Ferrari, C.; Harwood, J.; Oonk, J. B.R.; Hoeft, M.; Kunert-Bajraszewska, M.; Horellou, C.; Wucknitz, O.; Bonafede, A.; Mohan, N. R.; Scaife, A. M.M.; Klöckner, H. R.; Van Bemmel, I. M.; Merloni, A.; Chyzy, K. T.; Engels, D.; Falcke, H.; Pandey-Pommier, M.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Breitling, F.; Broderick, J.; De Vos, M. (2014-10-01)
      We present Low Frequency Array (LOFAR) Low Band observations of the Boötes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam-1, making them the deepest images ever obtained ...

    • A LOFAR mini-survey for low-frequency radio emission from the nearest brown dwarfs 

      Burningham, Ben; Hardcastle, Martin; Nichols, Jonathan; Casewell, Sarah; Littlefair, Stuart; Stark, Craig; Burleigh, Matthew; Metchev, Stanimir; Tannock, Megan; van Weeren, Reinout; Williams, Wendy Louise; Wynn, Graham (2016-12-01)
      We have conducted a mini-survey for low-frequency radio emission from some of the closest brown dwarfs to the Sun with rapid rotation rates: SIMP J013656.5+093347, WISEPC J150649.97+702736.0, and WISEPA J174124.26+255319.5. ...

    • LOFAR MSSS: Detection of a low-frequency radio transient in 400 hrs of monitoring of the North Celestial Pole 

      Stewart, A. J.; Fender, R.P.; Broderick, J. W.; Hassall, T. E.; Muñoz-Darias, T.; Rowlinson, A.; Swinbank, J. D.; Staley, T. D.; Molenaar, G. J.; Scheers, B.; Grobler, T. L.; Pietka, M.; Heald, G.; McKean, J. P.; Bell, M. E.; Bonafede, A.; Breton, R. P.; Carbone, D.; Cendes, Y.; Clarke, A. O.; Corbel, S.; Gasperin, F. de; Eislöffel, J.; Falcke, H.; Ferrari, C.; Grießmeier, J. -M.; Hardcastle, M.J.; Heesen, V.; Hessels, J. W. T.; Horneffer, A.; Iacobelli, M.; Jonker, P.; Karastergiou, A.; Kokotanekov, G.; Kondratiev, V. I.; Kuniyoshi, M.; Law, C. J.; Leeuwen, J. van; Markoff, S.; Miller-Jones, J. C. A.; Mulcahy, D.; Orru, E.; Pandey-Pommier, M.; Pratley, L.; Rol, E.; Röttgering, H. J. A.; Scaife, A. M. M.; Shulevski, A.; Sobey, C. A.; Stappers, B. W.; Tasse, C.; van der Horst, A.J.; Velzen, S. van; Weeren, R. J. van; Wijers, R.A.M.J.; Wijnands, R.; Wise, M.; Zarka, P.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bentum, M. J.; Bernardi, G.; Best, P.; Breitling, F.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; Corstanje, A.; Geus, E. de; Deller, A.; Duscha, S.; Frieswijk, W.; Garrett, M.A.; Gunst, A. W.; Haarlem, M. P. van; Hoeft, M.; Hörandel, J.; Juette, E.; Kuper, G.; Loose, M.; Maat, P.; McFadden, R.; McKay-Bukowski, D.; Moldon, J.; Munk, H.; Norden, M. J.; Paas, H.; Polatidis, A. G.; Schwarz, D.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Wijnholds, S. J.; Wucknitz, O.; Yatawatta, S. (2016-03-01)
      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 Multifrequency Snapshot Sky Survey (MSSS). The ...

    • LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group 

      Clarke, A. O.; Heald, G.; Jarrett, T.; Bray, J. D.; Hardcastle, Martin; Cantwell, T. M.; Scaife, A. M. M.; Brienza, M.; Bonafede, A.; Breton, R. P.; Broderick, J. W.; Carbone, D.; Croston, J. H.; Farnes, J. S.; Harwood, J. J.; Heesen, V.; Horneffer, A.; Horst, A. J. van der; Iacobelli, M.; Jurusik, W.; Kokotanekov, G.; McKean, J. P.; Morabito, L. K.; Mulcahy, D. D.; Nikiel-Wroczynski, B. S.; Orru, E.; Paladino, R.; Pandey-Pommier, M.; Pietka, M.; Pizzo, R.; Pratley, L.; Riseley, C. J.; Rottgering, H. J. A.; Rowlinson, A.; Sabater, J.; Sendlinger, K.; Shulevski, A.; Sridhar, S. S.; Stewart, A. J.; Tasse, C.; Velzen, S. van; Weeren, R. J. van; Wise, M. W. (2017-05-01)
      We report on the discovery in the LOFAR Multifrequency Snapshot Sky Survey (MSSS) of a giant radio galaxy (GRG) with a projected size of $2.56 \pm 0.07$ Mpc projected on the sky. It is associated with the galaxy triplet ...

    • LOFAR MSSS: Flattening low-frequency radio continuum spectra of nearby galaxies 

      Chyży, K. T.; Jurusik, W.; Piotrowska, J.; Nikiel-Wroczyński, B.; Heesen, V.; Vacca, V.; Nowak, N.; Paladino, R.; Surma, P.; Sridhar, S. S.; Heald, G.; Beck, R.; Conway, J.; Sendlinger, K.; Curyło, M.; Mulcahy, D.; Broderick, J. W.; Hardcastle, M. J.; Callingham, J. R.; Gürkan, G.; Iacobelli, M.; Röttgering, H. J. A.; Adebahr, B.; Shulevski, A.; Dettmar, R. -J.; Breton, R. P.; Clarke, A. O.; Farnes, J. S.; Orrú, E.; Pandey, V. N.; Pandey-Pommier, M.; Pizzo, R.; Riseley, C. J.; Rowlinson, A.; Scaife, A. M. M.; Stewart, A. J.; Horst, A. J. van der; Weeren, R. J. van (2018-11-07)
      Aims. The shape of low-frequency radio continuum spectra of normal galaxies is not well understood, the key question being the role of physical processes such as thermal absorption in shaping them. In this work we take ...

    • LOFAR MSSS: The Scaling Relation between AGN Cavity Power and Radio Luminosity at Low Radio Frequencies 

      Kokotanekov, G.; Wise, Michael; Heald, G. H.; McKean, J. P.; Bîrzan, L.; Rafferty, D. A.; Godfrey, L. E H; Vries, M. de; Intema, Huib T.; Broderick, J. W.; Hardcastle, M. J.; Bonafede, A.; Clarke, A. O.; Weeren, R. J. van; Röttgering, H.~J.~A.; Pizzo, R.; Iacobelli, M.; Orrú, E.; Shulevski, Alexander; Riseley, C. J.; Breton, R. P.; Nikiel-Wroczyński, B.; Sridhar, S. S.; Stewart, A. J.; Rowlinson, A.; Horst, A. J. van der; Harwood, J. J.; Gürkan, G.; Carbone, D.; Pandey-Pommier, M.; Tasse, C.; Scaife, A. M. M.; Pratley, L.; Ferrari, Chiara; Croston, J. H.; Pandey, V. N.; Jurusik, W.; Mulcahy, D. D. (2017-09-07)
      We present a new analysis of the widely used relation between cavity power and radio luminosity in clusters of galaxies with evidence for strong AGN feedback. We study the correlation at low radio frequencies using two new ...

    • The LOFAR Multifrequency Snapshot Sky Survey (MSSS) : I. Survey description and first results 

      Heald, G. H.; Pizzo, R. F.; Orrú, E.; Breton, R. P.; Carbone, D.; Ferrari, C.; Hardcastle, M.J.; Jurusik, W.; Macario, G.; Mulcahy, D.; Rafferty, D.; Asgekar, A.; Brentjens, M.; Fallows, R. A.; Frieswijk, W.; Toribio, M. C.; Adebahr, B.; Arts, M.; Bell, M. R.; Bonafede, A.; Bray, J.; Broderick, J.; Cantwell, T.; Carroll, P.; Cendes, Y.; Clarke, A. O.; Croston, J. H.; Daiboo, S.; De Gasperin, F.; Gregson, J.; Harwood, J.; Hassall, T.; Heesen, V.; Horneffer, A.; van der Horst, A.J.; Iacobelli, M.; Jelić, V.; Jones, D.; Kant, D.; Kokotanekov, G.; Martin, P.; McKean, J. P.; Morabito, L. K.; Nikiel-Wroczyński, B.; Offringa, A.; Pandey, V. N.; Pandey-Pommier, M.; Pietka, M.; Pratley, L.; Riseley, C.; Rowlinson, A.; Sabater, J.; Scaife, A. M. M.; Scheers, L. H. A.; Sendlinger, K.; Shulevski, A.; Sipior, M.; Sobey, C.; Stewart, A. J.; Stroe, A.; Swinbank, J.; Tasse, C.; Trüstedt, J.; Varenius, E.; Van Velzen, S.; Vilchez, N.; Van Weeren, R. J.; Wijnholds, S.; Williams, W. L.; de Bruyn, A. G.; Nijboer, R.; Wise, M.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Van Bemmel, I.; Bentum, M. J.; Bernardi, G.; Best, P.; Breitling, F.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; De Geus, E.; De Jong, A.; De Vos, M.; Deller, A.; Dettmar, R. J.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fender, R.; Garrett, M.A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Holties, H. A.; Intema, H.; Jackson, N. J.; Jütte, E.; Karastergiou, A.; Klijn, W. F. A.; Kondratiev, V. I.; Koopmans, L. V. E.; Kuniyoshi, M.; Kuper, G.; Law, C.; Van Leeuwen, J.; Loose, M.; Maat, P.; Markoff, S.; McFadden, R.; McKay-Bukowski, D.; Mevius, M.; Miller-Jones, J. C A; Morganti, R.; Munk, H.; Nelles, A.; Noordam, J. E.; Norden, M. J.; Paas, H.; Polatidis, A. G.; Reich, W.; Renting, A.; Röttgering, H.; Schoenmakers, A.; Schwarz, D.; Sluman, J.; Smirnov, O.; Stappers, B. W.; Steinmetz, M.; Tagger, M.; Tang, Y.; Ter Veen, S.; Thoudam, S.; Vermeulen, R.; Vocks, C.; Vogt, C.; Wijers, R.A.M.J.; Wucknitz, O.; Yatawatta, S.; Zarka, P. (2015-10-01)
      We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky Low Frequency Array (LOFAR) imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. ...

    • LOFAR observations of the XMM-LSS field 

      Hale, C. L.; Williams, W.; Jarvis, M. J.; Hardcastle, M. J.; Morabito, Leah K.; Shimwell, T. W.; Tasse, C.; Best, P. N.; Harwood, J. J.; Heywood, I.; Prandoni, I.; Röttgering, H. J. A.; Sabater, J.; Smith, D. J. B.; Weeren, R. J. van (2018-11-19)
      We present observations of the XMM Large-Scale Structure (XMM-LSS) field observed with the LOw Frequency ARray (LOFAR) at 120-168 MHz. Centred at a J2000 declination of $-4.5^{\circ}$, this is a challenging field to observe ...

    • A LOFAR prompt search for radio emission accompanying X-ray flares in GRB 210112A 

      Hennessy, A.; Starling, R. L. C.; Rowlinson, A.; Ruiter, I. de; Kumar, A.; Eyles-Ferris, R. A. J.; Ror, A. K.; Anderson, G. E.; Gourdji, K.; Horst, A. J. van der; Pandey, S. B.; Shimwell, T. W.; Steeghs, D.; Stylianou, N.; Veen, S. ter; Wiersema, K.; Wijers, R. A. M. J. (2023-11-01)
      The composition of relativistic gamma-ray burst (GRB) jets and their emission mechanisms are still debated, and they could be matter or magnetically dominated. One way to distinguish these mechanisms arises because a ...

    • LOFAR Properties of SILVERRUSH Lya emitter candidates in the ELAIS-N1 Field 

      Gloudemans, A. J.; Duncan, K. J.; Kondapally, R.; Sabater, J.; Cochrane, R. K.; Röttgering, H. J. A.; Best, P. N.; Bonato, M.; Bondi, M.; Malek, K.; McCheyne, I.; Smith, D. J. B.; Prandoni, I.; Wang, L. (2021-04-07)
      Lyman alpha emitters (LAEs) in the Epoch of Reionization (EoR) offer valuable probes of early galaxy evolution and the process of reionization; however, the exact evolution of their abundance and the nature of their emission ...

    • LOFAR reveals the giant : A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31 

      Heesen, V.; Croston, J. H.; Morganti, R.; Hardcastle, M. J.; Stewart, A. J.; Best, P. N.; Broderick, J. W.; Brüggen, M.; Brunetti, G.; Chyzy, K. T.; Harwood, J. J.; Haverkorn, M.; Hess, K. M.; Intema, H. T.; Jamrozy, M.; Kunert-Bajraszewska, M.; McKean, J. P.; Orrú, E.; Röttgering, H. J.A.; Shimwell, T. W.; Shulevski, A.; White, G. J.; Wilcots, E. M.; Williams, W. L. (2018-03-11)
      We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 ...

    • The LOFAR Two Meter Sky Survey : Deep Fields Data Release 1, I -- Direction-dependent calibration and imaging 

      Tasse, C.; Shimwell, T.; Hardcastle, M. J.; O'Sullivan, S. P.; Weeren, R. van; Best, P. N.; Bester, L.; Hugo, B.; Smirnov, O.; Sabater, J.; Calistro-Rivera, G.; Gasperin, F. de; Morabito, L. K.; Röttgering, H.; Williams, W. L.; Bonato, M.; Bondi, M.; Botteon, A.; Brüggen, M.; Brunetti, G.; Chyży, K. T.; Garrett, M. A.; Gürkan, G.; Jarvis, M. J.; Kondapally, R.; Mandal, S.; Prandoni, I.; Repetti, A.; Retana-Montenegro, E.; Schwarz, D. J.; Shulevski, A.; Wiaux, Y. (2021-04-07)
      The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and is sensitive to large scale and compact emission. It is, however, very challenging to synthesize ...