Observing Gravitational Waves with Advanced LIGO Laura Nuttall on - PowerPoint PPT Presentation

Observing Gravitational Waves with Advanced LIGO Laura Nuttall on behalf of the LIGO Scientific Collaboration and Virgo Collaboration Syracuse University LIGO-G1602189

LIGO Laser Interferometer Gravitational-wave Observatory LIGO-Livingston LIGO-Hanford 2

Weiss’s 1972 design study The design (Weiss, Electromagnetically Coupled Broadband Gravitational Antenna , 1972 Tech. Rep. MIT ) b) T est Mass Differential changes in arm H1 Ly = 4 km 10 ms light length measure strain travel time 𝜀 L = L x - L y = hL a) L1 T est Mass Power Beam Lx = 4 km Recycling Splitter 20 W 100 kW Circulating Power Laser Source T est T est Mass Mass Signal Recycling Photodetector 3 PRL 116, 131103 (2016)

Advanced LIGO Comprehensive upgrade of Initial LIGO instrumentation in the same vacuum system Higher-power laser Improvements Larger mirrors Higher finesse arm cavities Signal recycling cavity Signal recycling mirror Output mode cleaner and more … 4

From iLIGO to aLIGO Better Seismic Isolation 2007 2007 d e s a r e e w r Reduced c o n P I l a r n e Thermal s g a i S L g n d i n l Noise c a y c ~2019 e R 5 https://dcc.ligo.org/LIGO-P1000103/public

Sensitivity: past, present and future Typical range: 
 BNS ~ 70 Mpc BBH ~ 580 Mpc 6 PRL 116, 131103 (2016)

In the early hours of September 14th, 2015… 7

~1/200 th GW150914 proton radius PRL 116, 061102 (2016) • Observed on September 14th, 2015 at 09:40:45 UTC 
 • First observed in LIGO-Livingston then 7ms later at LIGO-Hanford 
 • Over 0.2 seconds the signal increases in frequency and amplitude over ~8 cycles from 35Hz to peak amplitude at 150 Hz 8

~1/200 th GW150914 proton radius PRL 116, 061102 (2016) • Observed on September 14th, 2015 at 09:40:45 UTC 
 • First observed in LIGO-Livingston then 7ms later at LIGO-Hanford 
 • Over 0.2 seconds the signal increases in frequency and amplitude over ~8 cycles from 35Hz to peak amplitude at 150 Hz 9

The big announcement…

GW151226 11 PRL 116, 241103 (2016)

Making a detection 12

Template space • To detect signals from compact-object | χ 1 | < 0 . 9895 , | χ 2 | < 0 . 05 binaries, we construct a bank of | χ 1 , 2 | < 0 . 05 | χ 1 , 2 | < 0 . 9895 template waveforms and matched-filter GW150914 GW151226 the data LVT151012 (gstlal) m 2 [ M � ] 10 1 LVT151012 (PyCBC) � s | h ⇥ ρ = p � h | h ⇥ Z f high a ( f )˜ ˜ b ( f ) � a | b ⇥ = 4Re d f 10 0 S n ( f ) f low 10 0 10 1 10 2 m 1 [ M � ] • An event must match the same waveform template in both detectors H1 within the light travel time between sites 10 ms light travel time • Events are assigned a detection- a) statistic value that ranks their likelihood L1 of being a gravitational wave signal 10 ms + 5 ms for uncertainly in arrival time of weak signals 13

Calculating Significance • Determined by rate at which detector noise produces an event with a detection statistic value equal to or higher than the candidate event • Background set of data is created from coincident data from multiple detectors • Slide the timestamps of one detector’s data by many multiples of 0.1s and computing a new set of coincident events H1 x x x x x x L1 x x xx x x zero lag or foreground events 14 Usman et al., arXiv: 1508.02357 (2015)

Calculating Significance • Determined by rate at which detector noise produces an event with a detection statistic value equal to or higher than the candidate event • Background set of data is created from coincident data from multiple detectors • Slide the timestamps of one detector’s data by many multiples of 0.1s and computing a new set of coincident events H1 H1 x x x x x x L1 L1 x x x x xx x 0.1 s 0.1 s 0.1 s Time shifted data 15 Usman et al., arXiv: 1508.02357 (2015)

Calculating Significance • Determined by rate at which detector noise produces an event with a detection statistic value equal to or higher than the candidate event • Background set of data is created from coincident data from multiple detectors • Slide the timestamps of one detector’s data by many multiples of 0.1s and computing a new set of coincident events H1 x x x x x x L1 x x x xx x background events Time shifted data 16 Usman et al., arXiv: 1508.02357 (2015)

Results from the first observing run 
 (12th Sept 2015 - 19th Jan 2016) 2 σ 3 σ 4 σ 5 σ > 5 σ 2 σ 3 σ 4 σ 5 σ > 5 σ 10 4 Search Result 10 3 Search Background 10 2 Background excluding GW150914 10 1 Number of events 10 0 GW151226 10 − 1 LVT151012 LVT151012 GW151226 10 − 2 GW150914 10 − 3 10 − 4 10 − 5 10 − 6 10 − 7 10 − 8 8 10 12 14 16 18 20 22 24 Detection statistic ˆ ρ c 17 Abbott et al., Phys. Rev. X 6, 041015 (2016)

Results from the first observing run 18 Abbott et al., Phys. Rev. X 6, 041015 (2016)

Parameters of the BBH systems Posterior probability densities of the masses, spins and distance to the three events • Lowest mass is the GW151226 secondary mass • Highest mass is GW150914 remnant • Mass ratios differ: 
 - GW150914 near equal mass 
 - GW151226 and LVT151012 have support for unequal mass ratios 19 Abbott et al., Phys. Rev. X 6, 041015 (2016)

Parameters of the BBH systems Posterior probability densities of the masses, spins and distance to the three events All 3 remnant black holes have spins ~0.7 as expected for the merger of similar mass black holes in a binary 20 Abbott et al., Phys. Rev. X 6, 041015 (2016)

Parameters of the BBH systems Posterior probability densities of the masses, spins and distance to the three events • For GW151226 at least one black hole has spin magnitude > 0.2 • Large spins parallel to angular momentum are disfavoured χ e ff = χ 1 m 1 + χ 2 m 2 M c ~ S 1 , 2 · ˆ � 1 , 2 = L Gm 2 1 , 2 21 Abbott et al., Phys. Rev. X 6, 041015 (2016)

Tests of General Relativity • Allowing deviations in post-Newtonian waveform model • Parameter deviations are reasonably consistent with zero • GW150914 - merger-ringdown regime occurred at best instrument sensitivity. Only several cycles in LIGO sensitivity band. • GW151226 - many cycles in sensitivity band. Signal provides opportunity to probe PN inspiral 22 Abbott et al., Phys. Rev. X 6, 041015 (2016)

Rate of BBH mergers • Knowledge about BBH 0 . 7 Flat merger rates depend Event Based 0 . 6 on the mass Power Law 0 . 5 distribution - which we don’t know very well 0 . 4 R p ( R ) yet! 0 . 3 • Assume a few different 0 . 2 mass distributions 0 . 1 • Infer the BBH merger 0 . 0 rate is in the range 10 0 10 1 10 2 10 3 9-240 Gpc -3 yr -1 R ( Gpc − 3 yr − 1 ) 23 Abbott et al. arXiv: 1606.04856 (2016)

Searching for BNS and NS-BH systems During O1 we looking for gravitational waves from binary neutron star (BNS) and neutron star - black hole (NS-BH) systems O3 O2 O1 • O1 90% upper limit Dominik et al. pop syn BNS rate compared to de Mink & Belczynski pop syn other published rates Vangioni et al. r-process Jin et al. kilonova Petrillo et al. GRB • Constrain the merger Coward et al. GRB rate of BNS systems Siellez et al. GRB with component Fong et al. GRB Kim et al. pulsar masses of 1.35±0.13 aLIGO 2010 rate compendium M ☉ to be less than 10 0 10 1 10 2 10 3 10 4 12,600 Gpc − 3 yr − 1 BNS Rate (Gpc − 3 yr − 1 ) 24 Abbott et al., arXiv: 1607.07456 (2016)

Searching for BNS and NS-BH systems During O1 we looking for gravitational waves from binary neutron star (BNS) and neutron star - black hole (NS-BH) systems • O1 90% upper limit NS-BH rate O3 O2 O1 compared to other published rates Dominik et al. pop syn • Dark blue assumes 1.4-5 M ☉ and de Mink & Belczynski pop syn light blue 1.4-10 M ☉ Vangioni et al. r-process Jin et al. kilonova • Constrain the merger rate of NS- Petrillo et al. GRB BH systems with BH at least 5 M ☉ − 3 yr − 1 to be less than 3,600 Gpc Coward et al. GRB (assuming isotropic distribution of Fong et al. GRB component spins) aLIGO 2010 rate compendium • O2 and O3 BNS ranges are 10 − 2 10 − 1 10 0 10 1 10 2 10 3 10 4 assumed to be 1-1.9 and 1.9-2.7 NSBH Rate (Gpc − 3 yr − 1 ) times larger than O1 25 Abbott et al., arXiv: 1607.07456 (2016)

Future Network 26 Image Credit: Caltech/MIT/LIGO Lab

Future Sensitivity Advanced LIGO's sensitivity was at the upper end of that predicted for the first observing run 27 Abbott et al. Living Reviews in Relativity 19 , 1 (2016)

Future Rates of BBH Mergers • The second 100 % observing run is starting in ~month 
 80 % P ( N > { 2 , 10 , 40 }| h V T i ) • Plan is to run until 60 % christmas followed by a break for the 40 % holidays 20 % • Continue running O2 O3 until early spring 0 % when Virgo will join 1 10 h V T i / h V T i O1 28 Abbott et al. arXiv: 1606.04856 (2016)

LIGO Scientific Collaboration and Virgo Collaboration www.ligo.org 1000+ members, 90 institutions, 16 countries 29 Slide: Gabriela González

Extra Slides

LIGO-G1601165 31

Localisation Sky localization depends on: 
 - the location and orientation of the detectors 
 - time delay between signal arrival at spatially separated sites 32 Abbott et al., Phys. Rev. X 6, 041015 (2016)