LIGO-Virgo Searches for Periodic Gravitational Waves from Rapidly Rotating Neutron Stars

Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors

John T. Whelan john.whelan@ligo.org

School of Mathematical Sciences & Center for Computational Relativity & Gravitation Rochester Institute of Technology

on behalf of the LIGO Scientiﬁc Collaboration and the Virgo Collaboration NCRA Neutron Star Workshop 2016 January 15 LIGO-G1600077-v2

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 1/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Outline

1 Periodic Gravitational Waves

2 Periodic GW Searches and Initial Detector Results Targeted Searches for GWs from Known Pulsars Directed Searches for GWs from Known Sky Positions All-Sky (“Blind”) Searches for Unknown Neutron Stars

3 Prospects and Plans with Advanced Detectors

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 2/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Outline

1 Periodic Gravitational Waves

3 Prospects and Plans with Advanced Detectors

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 3/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Gravitational Waves from Neutron Stars

Focus on observation of GW from NS w/ground-based detectors

10 Hz . fgw . 4000 Hz (NOT use of Pulsar Timing Array as nanohertz GW detector) Two kinds of GW from neutron stars: Transient signal from binary inspiral (or glitch): talk by Anuradha Gupta Long-lived periodic signal from rapid rotation (P . 0.2 s) Continuous Wave (“CW”) Generations of ground-based interferometric GW detectors Initial detector era: null results & upper limits Initial LIGO 2002-2010; design sensitivity from 2006 Initial Virgo 2007-2011; design sensitivity from 2010 Advanced detector era: 10 improvement in design sens Advanced LIGO from 2015;× design sens expected 2019 Advanced Virgo from 2016? design sens expected 2021 KAGRA & LIGO India in construction & planning stages

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 4/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Advanced Detector Timeline

−19 10 Initial LIGO Initial Virgo Advanced LIGO −20 10 Advanced Virgo LIGO Early

Hz −21 Mid √ 10 / 1 , ) Late f ( n S Design

p −22 10 Virgo

−23 10

1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 Jan 1 2 3 10 10 10 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 f, Hz Time Advanced LIGO Advanced Virgo 21 21 10− 10− Early (2015–16, 40–80 Mpc) Early (2016–17, 20–60 Mpc) Mid (2016–17, 80–120 Mpc) Mid (2017–18, 60–85 Mpc) 2 2

/ Late (2017–18, 120–170 Mpc) / Late (2018–20, 65–115 Mpc) 1 1 − Design (2019, 200 Mpc) − Design (2021, 130 Mpc) BNS-optimized (215 Mpc) BNS-optimized (145 Mpc) 22 22 10− 10− LVC, arXiv:1304.0670

23 23 10− 10− Strain noise amplitude/Hz Strain noise amplitude/Hz

24 24 10− 10− 101 102 103 101 102 103 Frequency/Hz Frequency/Hz

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 5/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Periodic GW Sources

Image Credits (clockwise): Hubble/Chandra; Chandra; Spitzer/Hubble/Chandra; Fahad Sulehria, http://www.novacelestia.com/; http://www.einsteinathome.org/ G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 6/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Continuous Wave Signals

Rotating NS w/deformation or long-lived oscillation emits nearly sinusoidal signal; two polarization states 1 + cos2 ι h+ = h0 cos Φ(τ(t)) h = h0 cos ι sin Φ(τ(t)) 2 × Φ(τ) ≡ phase evolution in inertial frame: f , f˙, ¨f ,... τ(t) ≡ Doppler modulation from detector motion (& binary orbit) Note since gravity couples so weakly, only have to worry about lowest harmonic; No complicated “pulse proﬁle” Don’t need to search over amplitude params (extrinsic) 4π2G I I f 2 = | xx − yy | gw ι ψ φ h0 c4d , spin orientation ( , ), 0 (can analytically maximize likelihood over them) Templates parameterized by phase params (intrinsic) f , f˙, sky position (α, δ), orbital params (if NS in binary) Broad antenna pattern; sky position primarily from Doppler modulation

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 7/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Computing Cost Motivates Search Strategies

All-sky coherent search of full phase param space infeasible: # of templates skyrockets w/increasing integration time E.g, for all-sky search with one spindown,

1 1 1 2 2 5 Ntmplts T T (fT ) T ∼ ∆f ∆f˙ ∆sky ∼ · · ∝ Different strategies depending on knowledge of object: Known pulsars: all phase parameters known, can do fully coherent Targeted Search Note fgw = 2frot for triaxial ellipsoid rotating about principal axis Unknown objects: need to use semi-coherent methods for Blind Search Known objects not seen as pulsars (e.g., SN remnants, LMXBs): can do Directed Search but need to cope w/uncertain remaining phase parameters

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 8/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Outline

1 Periodic Gravitational Waves

3 Prospects and Plans with Advanced Detectors

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 9/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Periodic GW Sources – Known Pulsars

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 10/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches LSC-Virgo Targeted CW Searches

1 “Setting upper limits on the strength of periodic gravitational waves from PSR J1939+2134 using the ﬁrst science data from the GEO 600 and LIGO detectors.” 2 “Limits on gravitational wave emission from selected pulsars using LIGO data.” 3 “Upper Limits on Gravitational Wave Emission from 78 Radio Pulsars.” 4 “Beating the spin-down limit on gravitational wave emission from the Crab pulsar” 5 “Searches for gravitational waves from known pulsars with S5 LIGO data” 6 “Beating the spin-down limit on gravitational wave emission from the Vela pulsar” 7 “Gravitational-waves from known pulsars: results from the initial detector era” 8 “Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data” Pulsar ephemeris means phase model known Searches not computationally bound

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 11/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Known pulsar upper limits from initial detector era

23 10−

S3/S4

VSR2/4

S6 24 10− AdV/aLIGO

25 10− Strain Sensitivity

26 10−

10 27 − 101 102 103 Gravitational-wave Frequency (Hz)

LVC, arXiv:1309.4027; ApJ 785, 119 (2014) 4π2GεI f 2 h = zz gw ; ε = I I /I 0 c4d | xx − yy | zz

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 12/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Periodic GW Sources – Known Neutron Stars

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 13/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches LSC-Virgo Directed CW Searches

1 “Coherent searches for periodic gravitational waves from unknown isolated sources and Scorpius X-1: results from the second LIGO science run.” 2 “Upper limit map of a background of gravitational waves.” 3 “First search for gravitational waves from the youngest known neutron star” 4 “A directed search for continuous Gravitational Waves from the Galactic Center” 5 “Directional limits on persistent gravitational waves using LIGO S5 science data” 6 “A directed search for gravitational waves from Scorpius X-1 with initial LIGO” 7 “Searches for continuous gravitational waves from nine young supernova remnants” Sco X-1, SN Remnants, Galactic Center

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 14/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Directed Searches in Supernova Remnants , 39 (2015) 813 LVC, arXiv:1412.5942 ; ApJ

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 15/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Periodic GW Sources – Unknown Neutron Stars

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 16/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches LSC-Virgo Blind CW Searches

1 “First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform.” 2 “Coherent searches for periodic gravitational waves from unknown isolated sources and Scorpius X-1: results from the second LIGO science run.” 3 “All-sky search for periodic gravitational waves in LIGO S4 data” 4 “The Einstein@Home search for periodic gravitational waves in LIGO S4 data” 5 “All-sky LIGO Search for Periodic Gravitational Waves in the Early S5 Data” 6 “Einstein@Home search for periodic gravitational waves in early S5 LIGO data” 7 “All-sky search for periodic gravitational waves in the full S5 LIGO data” 8 “Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data” 9 “Application of a Hough search for continuous gravitational waves on data from the 5th LIGO science run” 10 “Implementation of an F-statistic all-sky search for continuous gravitational waves in Virgo VSR1 data” 11 “First all-sky search for continuous gravitational waves from unknown sources in binary systems.” 12 “A search of the Orion spur for continuous gravitational waves using a "loosely coherent" algorithm on data from LIGO interferometers” 13 “First low frequency all-sky search for continuous gravitational wave signals”

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 17/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches One All-Sky Tool: Einstein@Home

Volunteer distributed computing project Also used to search radio & gamma-ray data for binary pulsars

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 18/22 Periodic Gravitational Waves Targeted Searches Searches and Initial Detector Results Directed Searches Prospects and Plans with Advanced Detectors Blind Searches Blind “Spotlight” Search LVC arXiv:1510.03474 Blind but not all-sky; focus on Orion spur

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 19/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Outline

1 Periodic Gravitational Waves

3 Prospects and Plans with Advanced Detectors

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 20/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Plans for Advanced Detector Era

Search plans in LVC Data Analysis White Paper LIGO-T1500055 Targeted searches for known pulsars (radio, X-ray, γ-ray) Depends on ephemeris from electromagnetic observations Beneﬁts to AMXP searches from ASTROSAT: Arunava Mukherjee’s talk Directed searches for SN remnants and LMXBs Cas A, Sco X-1& J1751-305 highest priority All-sky searches w/LVC clusters & Einstein@Home

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 21/22 Periodic Gravitational Waves Searches and Initial Detector Results Prospects and Plans with Advanced Detectors Prospects for Sco X-1 w/Advanced Detectors

Detections in 1st Sco X-1 MDC 24 24 10− 3 10− HL × HLV 24 10− Torque balance 25 3 10− × 25 3 10− × 25 10− (strain) 25 0 10− h

sensitivity (strain) 26 cc,ts,rm,sb,pn cc,rm 0 3 10− 26 3 10− h × × cc,ts,rm,sb cc,ts cc,ts,rm cc 26 26 10− 10− 10 20 50 100 200 500 1000 2000 50 100 200 500 1000 2000 Frequency (Hz) Frequency (Hz)

Whelan et al arXiv:1504.05890; PRD 91, 102005 (2015) Messenger et al arXiv:1504.05889; PRD 92, 023006 (2015) Leaci & Prix arXiv:1502.00914; PRD 91, 102003 (2015)

G1600077-v2 John T. Whelan for the LSC & Virgo LVC Searches for Periodic GW from NS 22/22