Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 1518)
Virtual (Apr 2426); Time Zone: Central Time
Session T08: Gravitational Wave Searches: Continuous Sources 
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Sponsoring Units: DGRAV Chair: M. Alessandra Papa, Max Planck Inst Room: Symphony III  2nd Floor 
Tuesday, April 18, 2023 10:45AM  10:57AM 
T08.00001: Einstein@Home allsky search for continuous gravitational waves in LIGO O3a public data Benjamin Steltner, M. Alessandra Papa We present the results of the volunteer computing project Einstein@Home allsky search for continuous gravitational waves in the LIGO O3 public data. This is the most sensitive search to date for the probed waveforms, with frequencies in the 20800 Hz range and spindowns between 2.6 x 10^9 Hz s^1 and 2.6 x 10^10 Hz s^1. 
Tuesday, April 18, 2023 10:57AM  11:09AM 
T08.00002: Probing More Deeply in an AllSky Search for Continuous Gravitational Waves in the LIGO O3 Data Set Aashish Tripathee, Keith Riles The LIGOVirgo O3 data set offers not only detection of nowfamiliar compact binary mergers of distant black holes and neutron stars, but potentially the detection of much weaker but continuous radiation from nearby rapidly spinning, nonaxisymmetric neutron stars in the galaxy. Allsky searches for such radiation from previously unknown stars using necessarily long data sets are computationally challenging and have given rise to several different approaches. We describe here the application of the well established PowerFlux program to a new allsky search of the LIGO data from the O3 observing run. In order to probe the O3 data more deeply than in a previously published O3 PowerFlux search, we apply loose coherence and coherent summing of LIGO Hanford and Livingston data in the first stage of the hierarchical search. The status of the search and its chosen parameters will be presented. 
Tuesday, April 18, 2023 11:09AM  11:21AM 
T08.00003: Results from an Einstein@Home deep search for continuous gravitational waves from G347.3 and Vela Jr in LIGO O2 data Jing Ming

Tuesday, April 18, 2023 11:21AM  11:33AM 
T08.00004: Falcon continuous gravitational wave atlas and large scale data analysis using MVL. Vladimir Dergachev Continuous waves from nonaxisymmetric neutron stars are orders of magnitude weaker than transient events from black hole and neutron star collisions. However, because continuous waves persist, it is possible to improve sensitivity by integrating months of data at a great computational cost. The latest Falcon search has produced an atlas containing results of such integrations for every direction on the sky and every analyzed band. Both upper limits and signaltonoise ratios are provided. Some of the results have been followed up, but the majority are unexplored. 
Tuesday, April 18, 2023 11:33AM  11:45AM 
T08.00005: Constraining asteroidmass primordial black hole abundance using continuous gravitational waves Andrew Miller We present new constraints on the merging rates of planetarymass and asteroidmass primordial black hole binaries using limits on continuous gravitational waves (quasimonochromatic, quasiinfinite duration signals) derived from an allsky search for isolated compact objects in the third observing run of LIGO/Virgo. We calculate the merging rates of these binaries in a modelindependent way, and convert them to constraints on the primordial black hole abundance with minimal modelling assumptions. Our results show that we are sensitive to sources at most O(10 pc) away for systems with chirp masses of O(10^{−5}M_{?}) at gravitationalwave frequencies around 3040 Hz. These results also show that continuouswave searches could in the future directly probe the existence of planetarymass and asteroidmass primordial black holes, especially those in binaries with asymmetric mass ratios. Furthermore, they demonstrate that new methods accounting for the full nonlinear gravitationalwave frequency evolution are needed to improve constraints on primordial black holes. 
Tuesday, April 18, 2023 11:45AM  11:57AM 
T08.00006: The NANOGrav 12.5year Data Set: Bayesian Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries Caitlin A Witt Pulsar timing array collaborations, such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), are seeking nanohertz gravitational waves emitted by supermassive black hole binaries formed in the aftermath of galaxy mergers. We have searched for continuous waves from individual circular supermassive black hole binaries using NANOGrav's recent 12.5year data set. We created new methods to accurately model the uncertainties on pulsar distances in our analysis, and we implemented new techniques to account for a common red noise process in pulsar timing array data sets while searching for deterministic gravitational wave signals, including continuous waves. As we found no evidence for continuous waves in our data, we placed 95\% upper limits on the strain amplitude of continuous waves emitted by these sources. On behalf of the NANOGrav collaboration, I will describe our upper limits on continuous waves for the entire sky across the nanohertz frequency band, limits for particular supermassive black hole binary candidates, and astrophysical interpretations of our results. 
Tuesday, April 18, 2023 11:57AM  12:09PM 
T08.00007: Exploring Continuous Waves for Pulsar Timing Arrays in a Parameterized PostEinsteinian Formalism Alexander G Saffer, Kent Yagi, Stephen R Taylor, Sarah J Vigeland Pulsar timing arrays have the ability to detect the gravitational waves emitted by supermassive black hole binaries. These gravitational waves carry with them the information of the spacetime surrounding the compact objects, as well as information about the dynamical processes dictating the evolution of the system. As this system is slowly evolving, the gravitational radiation is expected to be seen as a continuous wave emanating from the direction of the sky that the binary system is in. Modified theories of gravity allow for this emission to carry with it additional effects which are not present in general relativity. As there are a number of various theories of gravity, a detailed study for all of their modifications would be a tedious endeavor. Rather than looking at a particular modified theory of gravity, we here discuss a theoryagnostic approach to parameterizing modifications to general relativity. In particular, we investigate the effects of a parameterized postEinsteinian formalism on a gravitational system emitting continuous waves, similar to those expected from supermassive black hole binaries. Our approach modifies existing code within the enterprise and enterprise_extensions packages to work with pulsar timing data from the NANOGrav collaboration. The goal of this approach is to determine what, if any, limits can be placed on the coupling parameters of the formalism that can aid in constraining modified effects of gravity not present in general relativity. 
Tuesday, April 18, 2023 12:09PM  12:21PM 
T08.00008: Efficient Gravitational Wave Searches with Pulsar Timing Arrays using Hamiltonian Monte Carlo Gabriel Freedman, Sarah J Vigeland, Aaron Johnson, Rutger van Haasteren Pulsar timing arrays (PTAs) aim to detect lowfrequency gravitational waves (GWs) by looking for correlated deviations in pulse arrival times. Current Bayesian searches using Markov Chain Monte Carlo (MCMC) methods struggle to sample the large number of parameters needed to model PTA GW signals. This imposes limits on the complexity of models available for study and poses future problems with scalability as the data span increases. Hamiltonian Monte Carlo (HMC) is a Monte Carlo algorithm that utilizes Hamiltonian dynamics to make wellinformed sample proposals via gradients of the model likelihood. This in turn allows it to converge faster to high dimensional and highly correlated distributions. We benchmark HMC as an alternative sampling method by performing a Bayesian analysis for the stochastic gravitational wave background, and compare the accuracy and efficiency of this method against similar analyses run with standard MCMC techniques. We also investigate the capability and performance of HMC when sampling PTA models containing both stochastic and deterministic signals. 
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