Observational evidence for extended emission to GW170817
Abstract
The recent LIGO event GW170817 is the merger of a double neutron star system with an associated short GRB170817A with 2.9 ± 0.3 s soft emission over 8-70 keV. This association has a Gaussian equivalent level of confidence of 5.1σ. The merger produced a hypermassive neutron star or stellar mass black hole with prompt or continuous energy output powering GRB170817A. Here, we report on a possible detection of extended emission (EE) in gravitational radiation during GRB170817A: a descending chirp with characteristic time-scale τ_s=3.01± 0.2 s in a (H1,L1)-spectrogram up to 700 Hz with Gaussian equivalent level of confidence greater than 3.3σ based on causality alone following edge detection applied to (H1,L1)-spectrograms merged by frequency coincidences. Additional confidence derives from the strength of this EE. The observed frequencies below 1 kHz indicate a hypermassive magnetar rather than a black hole, spinning down by magnetic winds and interactions with dynamical mass ejecta.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2019
- DOI:
- 10.1093/mnrasl/sly166
- arXiv:
- arXiv:1806.02165
- Bibcode:
- 2019MNRAS.482L..46V
- Keywords:
-
- gravitational waves;
- methods: data-analysis;
- stars: neutron;
- gamma-ray bursts: individual: GRB170817A;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- talk at KAGRA f2f, Osaka (May 20 2018)