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@ARTICLE{deGasperin:453899,
      author       = {de Gasperin, F. and Vink, J. and McKean, J. P. and Asgekar,
                      A. and Bentum, M. J. and Blaauw, R. and Bonafede, A. and
                      Bruggen, M. and Breitling, F. and Brouw, W. N. and Butcher,
                      H. R. and Ciardi, B. and Cuciti, V. and de Vos, M. and
                      Duscha, S. and Eisloffel, J. and Engels, D. and Fallows, R.
                      A. and Franzen, T. M. O. and Garrett, M. A. and Gunst, A. W.
                      and Horandel, J. and Heald, G. and Koopmans, L. V. E. and
                      Krankowski, A. and Maat, P. and Mann, G. and Mevius, M. and
                      Miley, G. and Nelles, A. and Norden, M. J. and Offringa, A.
                      R. and Orrú, E. and Paas, H. and Pandey-Pommier, M. and
                      Pizzo, R. and Reich, W. and Rowlinson, A. and Schwarz, D. J.
                      and Shulevski, A. and Smirnov, O. and Soida, M. and Tagger,
                      M. and Toribio, M. C. and van Ardenne, A. and van der Horst,
                      A. J. and van Haarlem, M. P. and van Weeren, R. J. and
                      Vocks, C. and Wucknitz, O. and Zarka, P. and Zucca, P.},
      title        = {{C}assiopeia {A}, {C}ygnus {A}, {T}aurus {A}, and {V}irgo
                      {A} at ultra-low radio frequencies},
      journal      = {Astronomy and astrophysics},
      volume       = {635},
      issn         = {1432-0746},
      address      = {Les Ulis},
      publisher    = {EDP Sciences},
      reportid     = {PUBDB-2021-00259, arXiv:2002.10431},
      pages        = {A150},
      year         = {2020},
      note         = {© ESO 2020 7 pages, 2 figures, accepted $A\&A,$ online
                      data on $A\&A$ website},
      abstract     = {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″ 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.},
      keywords     = {radio continuum: general (autogen) / techniques:
                      interferometric (autogen)},
      cin          = {HUB / Z-RAD},
      ddc          = {520},
      cid          = {I:(DE-H253)HUB-20140108 / I:(DE-H253)Z-RAD-20210408},
      pnm          = {613 - Matter and Radiation from the Universe (POF3-613)},
      pid          = {G:(DE-HGF)POF3-613},
      experiment   = {EXP:(DE-MLZ)External-20140101},
      typ          = {PUB:(DE-HGF)16},
      eprint       = {2002.10431},
      howpublished = {arXiv:2002.10431},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2002.10431;\%\%$},
      UT           = {WOS:000525646400001},
      doi          = {10.1051/0004-6361/201936844},
      url          = {https://bib-pubdb1.desy.de/record/453899},
}