Swift Follow-up Observations of Gravitational-wave and High-energy Neutrino Coincident Signals

Azadeh Keivani,Imre Bartos,Derek B Fox,Doğa Veske,Riki Rapisura,Jamie A Kennea,Phil A Evans,Zsuzsa Márka,Aaron Tohuvavohu,Samantha R Oates,Stefan Countryman,Szabolcs Márka

doi:10.3847/1538-4357/abdab4

Abstract

Abstract Electromagnetic observations of gravitational-wave and high-energy neutrino events are crucial in understanding the physics of their astrophysical sources. X-ray counterparts are especially useful in studying the physics of the jet, the energy of the outflow, and the particle acceleration mechanisms in the system. Ultraviolet and optical observations can help us constrain the mass and velocity of the outflow and provide hints on the viewing angle. We present the Neil Gehrels Swift Observatory prompt searches for X-ray and UV/optical counterparts to the joint gravitational-wave and high-energy neutrino coincident events that happened during the third observing run of LIGO/Virgo. Swift observed the overlap between gravitational-wave and neutrino error regions for three of the considerable (p-value < 1%) joint gravitational-wave and high-energy neutrino coincident alerts, which were generated by the IceCube Neutrino Observatory in real time after triggering by the LIGO/Virgo gravitational-wave public alerts. The searches did not associate any X-ray or UV/optical counterparts with any of the joint gravitational-wave and high-energy neutrino coincident events; however, the follow-up of these alerts significantly improved the tiling techniques covering regions between the gravitational-wave sky maps and the neutrino’s error regions, making the real-time system ready for future potential discoveries. We discuss the details of each follow-up procedure, the results of each search, and the plans for future searches.

Highlights

Multi-messenger searches have opened up new doors to astrophysical source discoveries, which result in understanding the physics of the sources and the underlying mechanisms that produce the messenger particles and waves
We present the Neil Gehrels Swift Observatory prompt searches for X-ray counterparts to the joint gravitational wave and high-energy neutrino coincident events that happened during the third observing run of LIGO/Virgo
The GW170817 event (Abbott et al 2017a) which was detected by the LIGO and Virgo detectors (Abbott et al 2015; Acernese et al 2015) and was immediately found to be in coincidence with the gamma-ray bursts (GRB)-170817A (Goldstein et al (2017); Savchenko et al (2017)), started an extensive multi-messenger search resulting in the discovery of a kilonova and in expanding our knowledge about binary neutron star systems (Abbott et al 2017b)

Summary

INTRODUCTION

Multi-messenger searches have opened up new doors to astrophysical source discoveries, which result in understanding the physics of the sources and the underlying mechanisms that produce the messenger particles and waves. The IceCube-170922A neutrino candidate detected by the IceCube Neutrino Observatory found to be associated with a flaring blazar, TXS 0506+056, which initiated broad follow-up observations in different wavelengths (Aartsen et al 2018). The Neil Gehrels Swift Observatory followed up three of the coincident GW+neutrino candidates during O3 under our Swift Cycle 15 guest investigator program. The goal of these observations were to identify electromagnetic counterparts to GW+neutrino events. We will discuss the likelihood of these GW+neutrino alerts to be real coincident events based on different possible source scenarios capable of producing joint GW+neutrino alerts, in the last section (Sec. 4)

OBSERVATIONS

TECHNIQUES

Findings

DISCUSSION