Detecting prompt and afterglow jet emission of gravitational wave events from LIGO/Virgo/KAGRA and next generation detectors

TL;DR

This study quantifies the detectability of prompt jet emission and afterglows from binary neutron star mergers in the LVK O5 era and for next-generation detectors. By combining GW population simulations with afterglow modeling via afterglowpy and a broad suite of current and future telescopes, it highlights how viewing angle and jet opening angle shape multi-wavelength opportunities, predicting a handful of afterglow detections in O5 (optimally in radio with SKA and in the near-IR with JWST) and hundreds of afterglow detections per year in the XG era with facilities like NewAthena and ngVLA. The work also shows prompt gamma-ray detections remain modest in O5 and decline in XG due to distance, though cocoon contributions can boost on-axis detections. Collectively, these results guide planning for rapid, coordinated follow-up of GW events and emphasize the importance of wide-field and deep-imaging capabilities across the EM spectrum for future multimessenger astronomy. The findings are particularly relevant for prioritizing radio and near-IR campaigns and for informing the design and operation of next-generation observatories.

Abstract

Following the wealth of new results enabled by multimessenger observations of the binary neutron star (BNS) merger GW170817, the next goal is increasing the number of detections of electromagnetic (EM) counterparts to gravitational wave (GW) events. We study the detectability of the prompt emission and afterglows produced by the relativistic jets launched by BNS mergers that will be detected by LIGO-Virgo-KAGRA during their fifth observing run (O5), and by next generation (XG) GW detectors (Einstein Telescope and Cosmic Explorer). We quantify the impact of various BNS merger and jet afterglow parameters on the likelihood of detection, focusing on the impact of the observer's viewing angle and the jet's core half-opening angle. We explore detectability over a wide range of current state-of-the-art facilities (e.g., the James Webb Space Telescope, Chandra X-ray Observatory) as well as upcoming next-generation facilities (e.g., AXIS, NewAthena, ngVLA, SKA). We find that a few GW events (~0-4) per year may have a detectable afterglow component in O5, with the largest detection rates expected with SKA in the radio and JWST in the near-infrared. In the XG era, hundreds of multimessenger detections of afterglows per year may be possible with a range of instruments, such as NewAthena in the X-ray and ngVLA in the radio. While zero to a few GW events per year are expected to be accompanied by a detectable prompt emission in O5, dozens per year may be detectable in XG.

Figures (13)

• Figure 1: Redshift distribution of all simulated BNS mergers, where for each GW event we simulated 1,000 afterglows. Events with GW detections are shown in black, and the distribution of those events that had an afterglow detectable in our Run 7 by instruments in X-ray (blue), UVOIR (red), and Radio (green) are shown in the solid lines. Run 1 results are shown in dashed lines. The top figure displays these distributions for O5, and the bottom for XG.
• Figure 2: 100 simulated afterglowpy lightcurves at a frequency of $2.017 \times 10^{14}$ Hz in the near-infrared showing the impact of afterglow parameter assumptions for a simulated GW event with fixed $d_\textrm{L}$$=$$130$ Mpc, $_\textrm{v}$$=$$0.36$ rad (20 deg). The afterglow parameters are sampled from Case 1. Run 1 is shown on the left in cyan, and Run 7, using the very narrow distribution for $_\textrm{C}$, is shown on the right in pink. A lightcurve simulated from the best-fit GW170817 afterglow parameters is shown by a thick black line Ryan2023. The sensitivities of a few instruments, Roman, HST, and JWST, are shown by the dashed horizontal lines.
• Figure 3: Total percent of afterglows detectable by each instrument for O5 (top) and XG (bottom) over all simulated times between $10^{-2}$ d and 6.5 yr after the merger. We show how these detections change based on each run (different color lines; shown in label).
• Figure 4: Percent of afterglows detectable by each instrument for O5 (top) and XG (bottom) as a function of time after the event (observer frame). We show how many afterglows are detectable after 12 hours, 1 day, 10 days, 100 days, and 1000 days after the event. Here we consider only our fiducial run: simulation Run 7.
• Figure 5: Percent of prompt GRB emission detectable in gamma-rays by each instrument for O5 (left) and XG (right). We show how these detections change based on each run and are corrected for the field of view and duty cycle of each instrument.