Binary Neutron Star Merger – GW170817 Thomas Dent Galician Gravitational Wave Week 2019 Lecture 4 Plan of lecture Detection and sky localization of GW170817 with �–ray space detectors & LIGO–Virgo Followup by optical telescopes and discovery of ‘kilonova’ source of many heavy elements via ‘r–process nucleosynthesis’ Bounds on deviations from GR Hubble constant estimate from host galaxy Measured properties of the binary, NS deformability and equation of state 2 Detection of GW170817/ GRB 170817A 3 GW signal Slower waveform evolution than all BBH systems we observed Implies much lower chirp mass Signal spends ~100 sec in the LIGO sensitive band (>20 Hz) Clear signals in LIGO detectors, not obvious in Virgo BNS horizon distances (Mpc) 218 (L1), 107 (H1), 58 (V1) In Virgo’s blind spot triangulation is still possible Total SNR: 32.4 Loudest GW signal detected! 4 GammaRayBurst detection Fermi GBM: 90% of burst fluence observed over T90 = 2.0 ± 0.5 s Fast main pulse – ~0.5 sec long – Comptonized spectrum (power law + exponential) – peak energy 185 ± 62 keV Followed by a weak tail – ~1 sec long – 10 keV – blackbody spectrum Integral observation consistent 3:1 odds for ‘short’ vs. ‘long’ GRB 5 Glitch removal & triangulation Problem : low latency data contained loud transient (glitch) in LLO reprocess ‘by hand’ to window out & filter data again 6 Sky map comparisons GBM map from directional sensitivity Fermi/Integral band from time delay GW map uses H–L time delay and H/L/V signal amplitudes https://dcc.ligo.org/DocDB/0146/G1702012/003/antenna-patterns.mp4 7 Probability of chance coincidence Rate of sGRBs detected by GBM ~0.1/day Probability that unrelated sGRB detected with peak within ±1.74 ~ 5×10−6 Probability that GW/Fermi–GBM sky maps are as consistent for unrelated sGRB ~ 0.01 Chance probability for both time and direction : 5×10−8 ~ “5.3 �” ⇒ Clear association of BNS merger with (one) sGRB 8 Followup campaign with optical telescopes 9 Optical counterpart & host Campaign by dozens of observatories New source seen within a few hours Host galaxy NGC 4993 − distance ~40Mpc � = 0.0097 10 ‘Kilonova’ emission Early ‘blue’ emission quickly transitions to ‘red’ Large number of ‘light’ / ‘heavy’ element nuclear transitions Material travelling with high velocity 11 ‘r-process’ nucleosynthesis Large fraction of heavier metal elements made in BNS mergers 12 Bounds on non‐GR theories GRB recorded ~2s after BNS merger time GW and light travel at the same average speed ! GW and light experience same delay travelling through gravitational potential ! LVC+Fermi-GBM+INTEGRAL ApJL (2017) Rules out many non‐GR theories proposed to avoid dark matter/dark energy 13 Ezquiaga & Zumalacárregui PRL (2017) Hubble constant measurement Luminosity distance determined from GW amplitude “standard siren” �H ‘Hubble flow velocity’ : average recession velocity of galaxies at given distance estimated via redshifts of surrounding group & bulk flow peculiar velocity 14 GW as tie‐breaker on H0 ? ) Inclination is largest � uncertainty on H0 measurement Inclinationcos( Hubble constant H0 ) Consistent with both 0 CMB-based and distance ladder determinations Probability p(H Probability 15 NS masses from the GW signal Assume NS spins are � < 0.05 (weaker bounds if high spin allowed) 16 NS tidal deformability NS in (static) tidal field will develop a nonzero quadrupole moment Λ : dimensionless deformability Affects evolution of orbit and GW emission when NS approach close to each other Leading contribution to GW phase prop. to 17 Bounds for ‘independent’ Λ’s low spins assumed 18 Parameterized EOS bounds ‘Spectral model’ of NS energy & density as functions of pressure (Lindblom et al.) polynomials in � imposing physical constraints must allow � ≥ 1.97 M☉ 19 NS mass and radius For parameterized EOS find & same constraint for R2 20 Desmorest et al. 2010 21 The next few years LVCK, Living Rev. Relativity 2018 22 Upcoming science runs Projections from Living Rev. Relativity vol.19 (2016) 1 O3 run to start ~early 2019, duration ~1 year Advanced LIGO design sensitivity by 2021-22 23 Extending the network ~ 2017+ 2022+ with LIGO-India 24 ‘A+’ aLIGO mid scale upgrade ● Upgrade to aLIGO that leverages existing technology and infrastructure, with minimal new investment and moderate risk ● Target: average 1.7x increase in range over aLIGO è ~ 5x greater event rate than Advanced LIGO ~ 40 times greater than current Advanced LIGO sensitivity ● Stepping stone to future detector technologies ● Two year down time; back online by A+ key parameters 2023 12 dB injected squeezing 15% readout loss 100 m filter cavity (FC) 20 ppm round trip FC loss Coating Thermal Noise half of aLIGO 25 Further on: Voyager, Einstein Telescope, Cosmic Explorer Longer Arm Length Interferometers LIGO Voyager – exploiting the LIGO Observatory facility limits Einstein Telescope A future GW observatory in the EU λ = 2 µm Cosmic Explorer – A future GW observatory in the US 26 .