LOFAR 144-MHz follow-up observations of GW170817

Abstract

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 13.7 degrees 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 days after the merger event, we obtain 3$\sigma$ 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 ${\alpha }_{144}^{610}\gtrsim -2.5$. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.

9 pages, 2 figures, accepted for publication in MNRAS

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Cited by in corpus (7)

• Electromagnetic precursors to black hole - neutron star gravitational wave events: Flares and reconnection-powered fast-radio transients from the late inspiral
• Electromagnetic precursor flares from the late inspiral of neutron star binaries
• The Panchromatic Afterglow of GW170817: The full uniform dataset, modeling, comparison with previous results and implications
• Limits on long-time-scale radio transients at 150 MHz using the TGSS ADR1 and LoTSS DR2 catalogues
• Searching for low radio-frequency gravitational wave counterparts in wide-field LOFAR data
• LOFAR observations of gravitational wave merger events: O3 results and O4 strategy
• RADAR-Radio Afterglow Detection and AI-driven Response: A Federated Framework for Gravitational Wave Event Follow-Up