The NANOGrav 12.5-year data set: A computationally efficient eccentric binary search pipeline and constraints on an eccentric supermassive binary candidate in 3C 66B
Creators: name: Agazie, Gabriella
name: Arzoumanian, Zaven
name: Baker, Paul T.
name: Bécsy, Bence
name: Blecha, Laura
name: Blumer, Harsha
name: Brazier, Adam
name: Brook, Paul R.
name: Burke-Spolaor, Sarah
name: Casey-Clyde, J. Andrew
name: Charisi, Maria
name: Chatterjee, Shami
name: Cheeseboro, Belinda D.
name: Cohen, Tyler
name: Cordes, James M.
name: Cornish, Neil J.
name: Crawford, Fronefield
name: Cromartie, H. Thankful
name: DeCesar, Megan E.
name: Demorest, Paul B.
name: Dey, Lankeswar
name: Dolch, Timothy
name: Ellis, Justin A.
name: Ferdman, Robert D.
name: Ferrara, Elizabeth C.
name: Fiore, William
name: Fonseca, Emmanuel
name: Freedman, Gabriel E.
name: Garver-Daniels, Nate
name: Gentile, Peter A.
name: Glaser, Joseph
name: Good, Deborah C.
name: Gopakumar, Achamveedu
name: Gültekin, Kayhan
name: Hazboun, Jeffrey S.
name: Jennings, Ross J.
name: Johnson, Aaron D.
name: Jones, Megan L.
name: Kaiser, Andrew R.
name: Kaplan, David L.
name: Kelley, Luke Zoltan
name: Key, Joey S.
name: Laal, Nima
name: Lam, Michael T.
name: Lamb, William G.
name: Lazio, T. Joseph W.
name: Lewandowska, Natalia
name: Liu, Tingting
name: Lorimer, Duncan R.
name: Luo, Jing
name: Lynch, Ryan S.
name: Ma, Chung-Pei
name: Madison, Dustin R.
name: McEwen, Alexander
name: McKee, James W.
name: McLaughlin, Maura A.
name: Meyers, Patrick M.
name: Mingarelli, Chiara M. F.
name: Mitridate, Andrea
name: Ng, Cherry
name: Nice, David J.
name: Ocker, Stella Koch
name: Olum, Ken D.
name: Pennucci, Timothy T.
name: Pol, Nihan S.
name: Radovan, Henri A.
name: Ransom, Scott M.
name: Ray, Paul S.
name: Romano, Joseph D.
name: Sardesai, Shashwat C.
name: Schmitz, Kai
name: Siemens, Xavier
name: Simon, Joseph
name: Siwek, Magdalena S.
name: Fiscella, Sophia V. Sosa
name: Spiewak, Renée
name: Stairs, Ingrid H.
name: Stinebring, Daniel R.
name: Stovall, Kevin
name: Susobhanan, Abhimanyu
name: Swiggum, Joseph K.
name: Taylor, Stephen R.
name: Turner, Jacob E.
name: Unal, Caner
name: Vallisneri, Michele
name: Vigeland, Sarah J.
name: Witt, Caitlin A.
name: Young, Olivia
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The radio galaxy 3C 66B has been hypothesized to host a supermassive black hole binary (SMBHB) at its center based on electromagnetic observations. Its apparent 1.05-year period and low redshift ($\sim0.02$) make it an interesting testbed to search for low-frequency gravitational waves (GWs) using Pulsar Timing Array (PTA) experiments. This source has been subjected to multiple searches for continuous GWs from a circular SMBHB, resulting in progressively more stringent constraints on its GW amplitude and chirp mass. In this paper, we develop a pipeline for performing Bayesian targeted searches for eccentric SMBHBs in PTA data sets, and test its efficacy by applying it on simulated data sets with varying injected signal strengths. We also search for a realistic eccentric SMBHB source in 3C 66B using the NANOGrav 12.5-year data set employing PTA signal models containing Earth term-only as well as Earth+Pulsar term contributions using this pipeline. Due to limitations in our PTA signal model, we get meaningful results only when the initial eccentricity $e_0&lt;0.5$ and the symmetric mass ratio $η&gt;0.1$. We find no evidence for an eccentric SMBHB signal in our data, and therefore place 95% upper limits on the PTA signal amplitude of $88.1\pm3.7$ ns for the Earth term-only and $81.74\pm0.86$ ns for the Earth+Pulsar term searches for $e_0&lt;0.5$ and $η&gt;0.1$. Similar 95% upper limits on the chirp mass are $(1.98 \pm 0.05) \times 10^9\,M_{\odot}$ and $(1.81 \pm 0.01) \times 10^9\,M_{\odot}$. These upper limits, while less stringent than those calculated from a circular binary search in the NANOGrav 12.5-year data set, are consistent with the SMBHB model of 3C 66B developed from electromagnetic observations.
description: 27 Pages, 10 Figures, 1 Table, Accepted for publication in ApJ