Issue |
A&A
Volume 669, January 2023
|
|
---|---|---|
Article Number | A36 | |
Number of page(s) | 18 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202142974 | |
Published online | 03 January 2023 |
Central engine of GRB170817A: Neutron star versus Kerr black hole based on multimessenger calorimetry and event timing
1
Department of Physics and Astronomy, Sejong University, 209 Neungdong-ro, Gwangin-gu, Seoul 05006, Republic of Korea
e-mail: mvp@sejong.ac.kr
2
INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
3
Department of Physics, Ariel University, Ariel 40700, Israel
Received:
22
December
2021
Accepted:
25
September
2022
Context. LIGO–Virgo–KAGRA observations may identify the remnant of compact binary coalescence and core-collapse supernovae associated with gamma-ray bursts. The multimessenger event GW170817–GRB170817A appears ripe for this purpose thanks to its fortuitous close proximity at 40 Mpc. Its post-merger emission, ℰGW, in a descending chirp can potentially break the degeneracy in spin-down of a neutron star or black hole remnant by the relatively large energy reservoir in the angular momentum, EJ, of the latter according to the Kerr metric.
Aims. The complex merger sequence of GW170817 is probed for the central engine of GRB170817A by multimessenger calorimetry and event timing.
Methods. We used model-agnostic spectrograms with equal sensitivity to ascending and descending chirps generated by time-symmetric butterfly matched filtering. The sensitivity was calibrated by response curves generated by software injection experiments, covering a broad range in energies and timescales. The statistical significance for candidate emission from the central engine of GRB170817A is expressed by probabilities of false alarm (PFA; type I errors) derived from an event-timing analysis. Probability density functions (PDF) were derived for start-time ts, identified via high-resolution image analyses of the available spectrograms. For merged (H1,L1)-spectrograms of the LIGO detectors, a PFA p1 derives from causality in ts given GW170817–GRB17081A (contextual). A statistically independent confirmation is presented in individual H1 and L1 analyses, quantified by a second PFA p2 of consistency in their respective observations of ts (acontextual). A combined PFA derives from their product since the mean and (respectively) the difference in timing are statistically independent.
Results. Applied to GW170817–GRB170817A, PFAs of event timing in ts produce p1 = 8.3 × 10−4 and p2 = 4.9 × 10−5 of a post-merger output ℰGW ≃ 3.5% M⊙c2 (p1p2 = 4.1 × 10−8, equivalent Z-score 5.48). ℰGW exceeds EJ of the hyper-massive neutron star in the immediate aftermath of GW170817, yet it is consistent with EJ rejuvenated in gravitational collapse to a Kerr black hole. Similar emission may be expected from energetic core-collapse supernovae producing black holes of interest to upcoming observational runs by LIGO–Virgo–KAGRA.
Key words: methods: statistical / methods: data analysis / methods: numerical / black hole physics / gravitational waves / relativistic processes
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe-to-Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.