LIGO SCIENTIFIC COLLABORATION VIRGO COLLABORATION KAGRA COLLABORATION Technical Document LIGO-T2000424-v2 VIR-0666B-20 JGW-T2011802-v2 The LSC-Virgo-KAGRA Observational Science White Paper (Summer 2020 edition) The LSC-Virgo-KAGRA Observational Science Working Groups http://www.ligo.org http://www.virgo-gw.eu https://gwcenter.icrr.u-tokyo.ac.jp Processed with LATEX on 2020/08/07 LSC-Virgo-KAGRA Observational Science White Paper Contents 1 Overview and Executive Summary 5 1.1 Searches for Generic Transients, or Bursts . .9 1.2 Searches for Signals from Compact Binary Coalescences . 11 1.3 Searches for Continuous-Wave Signals . 16 1.4 Searches for Stochastic Backgrounds . 19 1.5 Working Group Leadership Roles . 22 2 Burst Group Activity Plans 23 Op-2.1 Search for short-duration GW bursts . 23 LT-2.1 Search for short-duration GW bursts R&D (Long Term) . 25 Op-2.2 Search for long-duration GW bursts . 25 LT-2.2 Search for long-duration GW bursts R&D (Long Term) . 27 Op-2.3 Search without templates for GWs from binary stellar mass black holes . 27 LT-2.3 Search without templates for GWs from binary stellar mass black holes R&D (Long Term) . 29 Op-2.4 GW burst signal characterization . 29 LT-2.4 GW burst signal characterization R&D (Long Term) . 31 Op-2.5 Search for GWs from core-collapse supernova . 31 LT-2.5 Search for GWs from core-collapse supernova R&D (long term) . 33 3 CBC Group Activity Plans 34 Op-3.1 CBC Parameter Estimation R&D (Short Term) . 34 LT-3.1 CBC Parameter Estimation R&D (Long Term) . 37 Op-3.2 Tests of General Relativity R&D (Short Term) . 38 LT-3.2 Tests of General Relativity R&D (Long Term) . 40 Op-3.3 Studies of Extreme Matter R&D (Short Term) . 41 LT-3.3 Studies of Extreme Matter R&D (Long Term) . 42 Op-3.4 CBC Waveform Models R&D (Short Term) . 43 LT-3.4 CBC Waveform Models R&D (Long Term) . 45 Op-3.5 Binary Coalescence Rates and Population R&D (Short Term) . 46 LT-3.5 Binary Coalescence Rates and Population R&D (Long Term) . 50 Op-3.6 CBC Cosmology R&D (Short Term) . 51 LT-3.6 CBC Cosmology R&D (Long Term) . 53 Op-3.7 CBC All Sky Search InfraOps R&D . 56 LT-3.7 CBC All Sky Search R&D (Long Term) . 59 Op-3.8 O3b Catalog of Compact Binaries . 60 Op-3.9 O3b Astrophysical Distribution of Compact Binaries . 64 Op-3.10 O3b Strong-Field Tests of General Relativity . 67 Op-3.11 O3 Hubble Constant Measurements . 70 Op-3.12 O3 Search for Lensed Gravitational Waves . 72 Op-3.13 O3a Sub-Threshold Search for Compact Binaries . 75 Op-3.14 O3b Sub-Threshold Search for Compact Binaries . 78 Op-3.15 Search for sub-solar-mass compact binary coalescences . 81 Op-3.16 Characterizing exceptional CBC events . 83 2 LSC-Virgo-KAGRA Observational Science White Paper 4 CW Group Activity Plans 84 Op-4.1 Targeted searches for known pulsars . 84 Op-4.2 Narrow-band searches for known pulsars . 86 Op-4.3 Targeted searches for non-tensorial emission from known pulsars . 88 Op-4.4 Directed searches targeting Cassiopeia A and other Galactic supernova remnants . 89 Op-4.5 Directed searches targeting Scorpius X-1 and other low-mass X-ray binaries . 90 Op-4.6 Directed searches targeted the Galactic center . 92 Op-4.7 All-sky searches for isolated sources . 92 Op-4.8 All-sky searches for unknown sources in binaries . 94 Op-4.9 Searches for long-transient emission from a post-merger neutron star . 96 Op-4.10 Searches for long-transient emission following a pulsar glitch . 97 Op-4.11 Searches for continuous emission from ultra-light boson clouds around black holes 99 Op-4.12 Support for continuous wave searches: Follow-up of interesting candidates . 101 Op-4.13 Support for continuous wave searches: Detector characterization . 102 Op-4.14 Support for continuous wave searches: Data preparation . 104 Op-4.15 Support for continuous wave searches: Scientific software maintenance . 105 LT-4.16 Further improvement and optimization of existing data analysis pipelines . 106 LT-4.17 Development of model-robust/agnostic data analysis methods . 108 LT-4.18 Development of new and potentially more sensitive data analysis methods . 108 LT-4.19 Use mock data challenges to compare data analysis pipelines . 110 5 Stochastic Group Activity Plans 111 Op-5.1 Search for an isotropic stochastic gravitational-wave background (short term) . 111 LT-5.1 Search for an isotropic stochastic gravitational-wave background (long term) . 112 Op-5.2 Directional searches for persistent gravitational waves (short term) . 113 LT-5.2 Directional searches for persistent gravitational waves (long term) . 115 Op-5.3 Search for very-long transient gravitational-wave signals . 115 LT-5.3 Search for very-long transient gravitational-wave signals (Long Term) . 116 Op-5.4 Data Folding for Efficient Searches of Stochastic Gravitational-Wave Background 117 6 Burst+CBC Joint Activity Plans 119 Op-6.1 Search for GWs from intermediate mass black hole binaries . 119 LT-6.1 Search for GWs from intermediate mass black hole binaries R&D . 120 Op-6.2 Multimessenger search for GWs and GRBs . 120 LT-6.2 Multimessenger search for GWs and GRBs R&D . 122 Op-6.3 Multimessenger search for GWs and fast radio bursts . 123 Op-6.4 Search for GW transients from magnetar flares and neutron star glitches . 124 LT-6.4 Search for GW transients from isolated neutron stars R&D (Long Term) . 125 Op-6.5 O3GK Observation Paper . 125 Op-6.6 Multimessenger search for GWs and high-energy neutrinos . 127 LT-6.6 Multimessenger search for GWs and high-energy neutrinos R&D . 128 7 Burst+Stochastic Joint Activity Plans 129 Op-7.1 Search for GWs from cosmic strings . 129 LT-7.1 Search for GWs from cosmic strings R&D (Long Term) . 130 8 Stochastic+CBC Joint Activity Plans 131 LT-8.1 Search for the stochastic background from unresolvable binary black hole mergers 131 3 LSC-Virgo-KAGRA Observational Science White Paper 9 Stochastic+DetChar Joint Activity Plans 133 Op-9.1 Data quality investigations for stochastic searches . 133 LT-9.1 Data quality investigations for stochastic searches (long term) . 134 10 Stochastic+CW Joint Activity Plans 135 Op-10.1 Identification and follow-up of outliers in All-Sky All-Frequency (ASAF) skymaps 135 References 137 4 LSC-Virgo-KAGRA Observational Science White Paper 1 Overview and Executive Summary Gravitational wave (GW) searches and astrophysics in the LIGO Scientific Collaboration (LSC), Virgo Col- laboration and KAGRA Collaboration are organized into four working groups. The Compact Binary Co- alescence (CBC) group searches for and studies signals from merging neutron stars and black holes by filtering the data with waveform templates. The Burst group searches for generic gravitational wave tran- sients with minimal assumption on the source or signal morphology. The Continuous Waves (CW) group targets periodic signatures from rotating neutron stars. The Stochastic Gravitational-Wave Background (SGWB) group looks for a gravitational wave background of cosmological or astrophysical origin. These groups also collaborate with the Detector Characterization (DetChar) group, which interfaces with the detector commissioning teams and works to improve GW signal searches by identifying and mitigating noise sources that limit sensitivity to astrophysical signals, as well as with the Calibration and Computing & Software teams. The LSC, Virgo Collaboration and KAGRA Collaboration are separate entities but work together closely, especially on data analysis. We often refer to the LSC and Virgo together as ‘LVC’, and refer to the LSC- Virgo-KAGRA combination as ‘LVK’. This LSC-Virgo-KAGRA Observational Science White Paper, which is updated yearly (and was formerly called the LSC-Virgo White Paper on Gravitational Wave Data Analysis and Astrophysics), describes the planned activities of the members of the four astrophysical search working groups, including science goals and methods. The subsections in sections 2 through 10 contain “activity plans” with a wide range of themes. Each activity plan has a prefix which associates it with either Section 2 or Section 4 of the LIGO Scientific Collaboration Program 2020-2021: • Section 2, Scientific Operations and Scientific Results (prefix “Op-”), includes activities to produce and publish observational results from the most recent observing run (O3), as well as some critical infrastructure preparations for the next observing run (O4). • Section 4, Advancing Frontiers of GW Astrophysics, Astronomy and Fundamental Physics: Enhanced Analysis Methods (prefix “LT-”) includes longer-term developments which we will pursue to advance the scientific frontiers of GW observational science. The LSC Program Committee and Virgo Core Program Committee set specific goals for collaboration work on an annual basis, using this white paper and other inputs. While this white paper concerns the activities of the four astrophysical search groups, LSC and Virgo activities in the domains of Commissioning, Calibra- tion, Computing, Detector Characterization, LSC Fellows program, and Run Planning can be found in the LSC-Virgo Operations White Paper (LIGO-T2000294, VIR-0551A-20). Direct detection of gravitational waves was the result of decades of development of both instrumentation and data analysis methods. Substantial advances were made using data collected by the initial LIGO detectors (2002–2010) and the initial Virgo detector (2007–2011), but no GW signals were detected. The era of GW detection, GW astronomy and astrophysics was enabled by the Advanced LIGO and Advanced Virgo upgrades. The first Advanced LIGO observing run, O1, began in September 2015 and immediately yielded the first detected event, GW150914.