LOFAR 144-MHz follow-up observations of GW170817

J. W. Broderick, T. W. Shimwell, K. Gourdji, A. Rowlinson, S. Nissanke, K. Hotokezaka, P. G. Jonker, C. Tasse, M. J. Hardcastle, J. B. R. Oonk, R. P. Fender, R. A. M. J. Wijers, A. Shulevski, A. J. Stewart, S. ter Veen, V. A. Moss, M. H. D. van der Wiel, D. A. Nichols, A. Piette, M. E. BellD. Carbone, S. Corbel, J. Eislöffel, J.-M. Grießmeier, E. F. Keane, C. J. Law, T. Muñoz-Darias, M. Pietka, M. Serylak, A. J. van der Horst, J. van Leeuwen, R. Wijnands, P. Zarka, J. M. Anderson, M. J. Bentum, R. Blaauw, W. N. Brouw, M. Brüggen, B. Ciardi, M. de Vos, S. Duscha, R. A. Fallows, T. M. O. Franzen, M. A. Garrett, A. W. Gunst, M. Hoeft, J. R. Hörandel, M. Iacobelli, E. Jütte, L. V. E. Koopmans, A. Krankowski, P. Maat, G. Mann, H. Mulder, A. Nelles, H. Paas, M. Pandey-Pommier, R. Pekal, W. Reich, H. J. A. Röttgering, D. J. Schwarz, O. Smirnov, M. Soida, M. C. Toribio, M. P. van Haarlem, R. J. van Weeren, C. Vocks, O. Wucknitz, P. Zucca

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Samenvatting

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 Advanced LIGO-Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13 ${_{.}^{\circ}}$ 7 when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130-138 and 371-374 d after the merger event, we obtain 3σ upper limits for the afterglow component of 6.6 and 19.5 mJy beam-1, respectively. Using our best upper limit and previously published, contemporaneous higher frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index $\alpha ^{610}_{144} \gtrsim$ -2.5. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.
Originele taal-2English
Pagina's (van-tot)5110-5117
Aantal pagina's8
TijdschriftMonthly Notices of the Royal Astronomical Society
Volume494
Nummer van het tijdschrift4
DOI's
StatusPublished - 1-jun-2020

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