[Paper Review] Perspectives for multi-messenger astronomy with the next generation of gravitational-wave detectors and high-energy satellites

S. Ronchini, M. Branchesi+7 more|arXiv (Cornell University)|Jan 1, 2022

Pulsars and Gravitational Waves Research107 references69 citations

TL;DR

This paper investigates the synergy between third-generation gravitational-wave detectors (like the Einstein Telescope) and future high-energy satellites for multi-messenger astronomy. Using a physically motivated model of short gamma-ray burst (SGRB) emission, it predicts that joint GW and high-energy detections of binary neutron star mergers will approach 100% efficiency in a network of 3G detectors, with wide-field X-ray monitors crucial for detecting off-axis and low-luminosity SGRBs and enabling precise source localization for follow-up.

ABSTRACT

The Einstein Telescope (ET) is going to bring a revolution for the future of multimessenger astrophysics. In order to detect the counterparts of binary neutron star (BNS) mergers at high redshift, the high-energy observations will play a crucial role. Here, we explore the perspectives of ET, as a single observatory and in a network of gravitational-wave (GW) detectors, operating in synergy with future γ-ray and X-ray satellites. We predict the high-energy emission of BNS mergers and its detectability in a theoretical framework which is able to reproduce the properties of the current sample of observed short GRBs (SGRBs). We estimate the joint GW and high-energy detection rate for both the prompt and afterglow emissions, testing several combinations of instruments and observational strategies. We find that the vast majority of SGRBs detected in γ-rays have a detectable GW counterpart; the joint detection efficiency approaches 100% considering a network of third-generation GW observatories. The probability of identifying the electromagnetic counterpart of BNS mergers is significantly enhanced if the sky localization provided by GW instruments is observed by wide-field X-ray monitors. We emphasize that the role of the future X-ray observatories will be very crucial for the detection of the fainter emission outside the jet core, which will allow us to explore the population of low-luminosity SGRBs in the nearby Universe, as well as to unveil the nature of the jet structure and the connections with the progenitor properties.

Motivation & Objective

• To assess the joint detection efficiency of binary neutron star (BNS) mergers in gravitational waves and high-energy emissions (γ-ray and X-ray) using next-generation instruments.
• To evaluate the role of wide-field X-ray monitors in detecting faint, off-axis SGRB emission and improving sky localization for follow-up observations.
• To quantify the scientific potential of joint detections for probing jet structure, progenitor properties, and cosmological parameters.
• To optimize observational strategies for future high-energy satellites by prioritizing GW triggers based on sky localization, distance, and viewing angle.
• To establish requirements for future instruments—especially wide-field X-ray telescopes—enabling detection of low-luminosity SGRBs and high-redshift counterparts.

Proposed method

• Develops a theoretical framework based on astrophysically motivated BNS populations and SGRB emission models that reproduce observed short GRB properties.
• Simulates high-energy emission (prompt γ-ray and X-ray afterglow) from BNS mergers using a structured jet model with variable luminosity and viewing angle dependence.
• Estimates joint detection rates by cross-correlating simulated GW signals from the Einstein Telescope (ET) with high-energy satellite response functions for γ-ray and X-ray instruments.
• Evaluates detection efficiency under various observational strategies: survey mode vs. pointed observations, and different response times (tresp) from 100 s to 1 hr.
• Models sky localization performance of ET alone and in network with Cosmic Explorer (CE), using low-latency parameter estimation to inform satellite repointing.
• Assesses the capability of future instruments—such as THESEUS, Athena WFI, and X-IFU—to detect and localize X-ray afterglows, especially off-axis and faint signals.

Experimental results

Research questions

• RQ1 What is the expected joint detection rate of BNS mergers in gravitational waves and high-energy emissions (γ-ray and X-ray) with next-generation detectors and satellites?
• RQ2 How does the inclusion of wide-field X-ray monitors improve the detection of off-axis and low-luminosity short GRBs?
• RQ3 What is the optimal observational strategy for high-energy satellites to maximize joint detection efficiency given limited observing time?
• RQ4 How do sky localization accuracy and response time affect the probability of detecting X-ray afterglows from BNS mergers?
• RQ5 To what extent can joint detections at high redshift enable cosmological parameter estimation and tests of general relativity?

Key findings

• The joint detection efficiency of BNS mergers in GW and high-energy emissions approaches 100% when using a network of third-generation GW detectors such as ET+CE.
• A delay of just one hour in starting X-ray monitoring after merger reduces detection probability by a factor of 10 or more compared to a 100-second response time.
• The Einstein Telescope alone can localize a few percent of BNS events within ∆Ω < 100 deg², increasing to tens of percent in a network with CE, enabling effective satellite follow-up.
• Wide-field X-ray monitors (e.g., Athena WFI) can detect a significant fraction of BNS mergers that are too off-axis for γ-ray detection, enabling the study of low-luminosity SGRBs.
• Mosaic observations with Athena WFI over one month can cover up to a few dozen BNS events localized within 100 deg², especially when prioritizing sources with favorable viewing angles and distances.
• The X-IFU instrument on Athena will be able to detect and characterize X-ray afterglows from all jointly detected sources, enabling detailed studies of jet structure and progenitor properties.