LIGO observation of a binary neutron star merger.Merger product and rate estimate If merger resulted...
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LIGO observation of a binary neutron star merger. Cody Messick for the LIGO Scientific Collaboration
Transcript of LIGO observation of a binary neutron star merger.Merger product and rate estimate If merger resulted...
LIGO observation of a binary neutron star merger.
Cody Messick for the LIGO Scientific Collaboration
LIGO NSF Proposal
● “The most certain of the sources is coalescence of neutron-star binaries.”
● Length of arms chosen to maximize chance of observing neutron star mergers
Evidence for binary neutron stars
Distribution of neutron stars
2010 Predictions for compact binary merger rates
LIGO Scientific Collaboration, Virgo Collaboration, Classical and Quantum Gravity, Volume 27, Number 17 (2010)
Binary neutron star motivation
● Equation of state
● Short gamma-ray bursts
● Multi-messenger astrophysics
Figure credit: NSF/LIGO/Sonoma State University/Aurore Simonnet
Multi-messenger Astrophysics
● Event that can be detected through multiple channels; e.g. light, neutrinos, GWs
● Classic example: the Sun
● Modern example: binary neutron stars
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Importance of Multi-messenger Astrophysics
● Different emissions provide different information about the source
● Can raise significance of quiet events
Neutron star summary
● Indirect evidence of GWs from a binary neutron star
● Have good handle on population statistics of neutron stars
● Important to multi-messenger astrophysics
A worrisome start?
Figure credit: LSC/Sonoma State University/Aurore Simonnet
August 17th, 2017 Timeline
● 12:41:04 UTC - Gravitational waves from binary neutron star merger reaches LIGO detectors
● 12:41:06 UTC - GRB reaches Fermi GBM
● 12:47:18 UTC - Single detector candidate identified with FAR 1 in 10,000 years LSC/Duncan Brown/Geoffery Lovelace/Duncan Macleod
August 17th, 2017 Timeline
● 13:21:42 UTC - Initial GCN sent out
● 14:09:25 UTC - GCN sent out with Fermi skymap
● 17:54:51 UTC - First three-instrument LIGO/Virgo skymap sent out
https://gcn.gsfc.nasa.gov/gcn3/21505.gcn3
Offline Analysis Results
● Found by two independent matched-filter searches with false alarm rates of
○ 1 in 1.1M years
○ < 1 in 80k years
Searching for Gravitational Waves
Figure credit: Leslie Wade
Source Properties (Masses)
: dimensionless spin parameter, defined such that 1 corresponds to the max spin of a black hole
Image credit: B.P. Abbot et al., PRL 119, 161101 (2017)
Sources Properties
Table credit: B.P. Abbot et al., PRL 119, 161101 (2017)● Assuming low spin, upper bound of Λ for 1.4 M
☉ NS is 970, compared to
1000 derived from X-rays
Localization
Localization
Image credit: LVC/Greco, Arnaud, Vicerè (background image:HEASARC/Skyview)
Localization
Image credit: LVC/Greco, Arnaud, Vicerè (background image:HEASARC/Skyview)
Merger product and rate estimate
● If merger resulted in black hole, GWs would be emitted around 6kHz
● Saw no evidence of GWs up to 4kHz after detection
● 1540+3200-1220 Gpc-3 yr-1
○ O1 Upper Limit: 12600 Gpc-3 yr-1 Image credit: NASA/AEI/ZIB/M. KOPPITZ AND L. REZZOLLA
What can we do better next time?
● Lower search and skymap generation latency
● Low latency data quality
● Automated alerts, remove the human element
● Early warning system
Questions?
Frank Elavsky/Northwestern/LIGO-Virgo
