Multi-Messenger Astronomy of Gravitational-Wave Sources With Flexible Wide-Area Radio Transient Surveys

Abstract

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of gravitational waves and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, LOFAR and MWA. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ∼30 second time window and ∼200-500 deg 2 sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ∼2. For some models, we also map the parameter space that may be constrained by non-detections.

Constraining coherent low-frequency radio flares from compact binary mergers

“…The first station of the Long Wavelength Array (LWA1) operates in the 10-88 MHz frequency range and has two all-sky modes, the transient-buffer narrow and the transient-buffer wide (Yancey et al 2015), the latter of which allows for continuous data recording with a bandwidth of 70 kHz, which is tunable within the observing band. LWA1 is also equipped with the Prototype All Sky Imager (PASI) backend, which performs all-sky imaging in near real time on the native time resolution of 5 s (Obenberger et al 2015).…”

“…However, LWA1 has had two rapid-response triggering modes commissioned, including the Burst Early Response Triggering system and the Heuristic Automation for LWA1 (HAL) system, the latter of which can respond to triggers within 2 mins (Yancey et al 2015). These modes trigger the full LWA1 beam facility, which has a bandwidth of 19.6 MHz and up to four pointed synthesised beams that can be used to tile portions of large positional uncertainty regions, such as those of Fermi-detected GRBs and gravitational wave events detected by aLIGO/Virgo.…”

“…These modes trigger the full LWA1 beam facility, which has a bandwidth of 19.6 MHz and up to four pointed synthesised beams that can be used to tile portions of large positional uncertainty regions, such as those of Fermi-detected GRBs and gravitational wave events detected by aLIGO/Virgo. While the additional dispersion delay afforded by the lower observing frequency of LWA1 means there is more time to repoint the telescope at a transient before any prompt radio emission arrives, the 2 min response time of HAL means that it will not be able to sample prompt, coherent emission produced prior or during the merger from the SGRB population below a DM of 200 pc cm −3 (between a redshift of 0.1 and 0.2; Yancey et al 2015). However, the impressive temporal resolution of LWA1 (microsecond timescales; e.g.…”

Science with the Murchison Widefield Array: Phase I results and Phase II opportunities

“…Along with the VOEvent triggering mechanism discussed in Section 2.3, an optimal strategy for MWA followup of prompt emission from GW transients has been implemented (Kaplan et al, 2016). This is complementary to approaches taken with other facilities (e.g., Yancey et al, 2015) where the wide FoV, rapid response, and Southern location of the MWA give it an advantage (Chu et al, 2016;Howell et al, 2015). Kaplan et al (2016) used simulated GW events from Singer et al (2014) to compute the expected fraction of events that the MWA would observe and the sensitivity to them, given the optimized pointing strategy.…”

LOFAR 144-MHz follow-up observations of GW170817

“…Therefore, there is the interesting potential to use low-frequency aperture arrays to search for prompt, coherent radio emission from a compact binary merger (e.g. Callister et al 2019; also see Obenberger et al 2014, Yancey et al 2015, Kaplan et al 2015, Chu et al 2016, Anderson et al 2018, Rowlinson & Anderson 2019, James et al 2019.…”