The second data release from the European Pulsar Timing Array

Abstract

Pulsar timing arrays offer a probe of the low-frequency gravitational wave spectrum (1–100 nHz), which is intimately connected to a number of markers that can uniquely trace the formation and evolution of the Universe. We present the dataset and the results of the timing analysis from the second data release of the European Pulsar Timing Array (EPTA). The dataset contains high-precision pulsar timing data from 25 millisecond pulsars collected with the five largest radio telescopes in Europe, as well as the Large European Array for Pulsars. The dataset forms the foundation for the search for gravitational waves by the EPTA, presented in associated papers. We describe the dataset and present the results of the frequentist and Bayesian pulsar timing analysis for individual millisecond pulsars that have been observed over the last ~25 yr. We discuss the improvements to the individual pulsar parameter estimates, as well as new measurements of the physical properties of these pulsars and their companions. This data release extends the dataset from EPTA Data Release 1 up to the beginning of 2021, with individual pulsar datasets with timespans ranging from 14 to 25 yr. These lead to improved constraints on annual parallaxes, secular variation of the orbital period, and Shapiro delay for a number of sources. Based on these results, we derived astrophysical parameters that include distances, transverse velocities, binary pulsar masses, and annual orbital parallaxes.

NANOGrav results and dark first order phase transitions

“…In addition to previous analyses [6][7][8][9], the recent NANOGrav 15-year data also reports the evidence for quadrupolar correlations that follow the signature described by Hellings and Downs [10] and is then conclusive with regard to the nature of the detection. Similar evidences have been independently reported by the European Pulsar Timing Array (EPTA) [11][12][13][14][15][16], the Parkes Pulsar Timing Array (PPTA) [17][18][19], and the Chinese Pulsar Timing Array (CPTA) [20], pointing at a broadly consistent picture.…”

Inflationary interpretation of the stochastic gravitational wave background signal detected by pulsar timing array experiments

“…Very recently, in June 2023, various PTA experiments, including NANOGrav, EPTA, PPTA, and the Chinese Pulsar Timing Array (CPTA), in the case of EPTA including also data from the Indian PTA (InPTA), reported on the analyses of their latest datasets, which all confirm the presence of excess red common-spectrum signals, with strain amplitude of order O(10 −15 ) at the reference frequency f = 1 yr −1 [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Importantly, all analyses report evidence (with varying strength) for HD correlations, which point to a genuine GW origin for the signals, in turn making these the first convincing detections of a SGWB signal in the nHz range.…”

The NANOGrav 15 yr Data Set: Bayesian Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries

“…With recent results reporting evidence for the presence of a GWB in PTA data sets (Agazie et al 2023b;Antoniadis et al 2023b;Reardon et al 2023), searches for individual binaries are becoming more and more important. Assuming the GWB is due to a population of SMBHBs, we can reasonably expect to also see an individual binary within the next decade (Rosado et al 2015;Mingarelli et al 2017;Kelley et al 2018).…”

“…Nanohertz gravitational waves (GWs) can be probed by regularly monitoring millisecond-pulsars and measuring the times-of-arrival of their radio pulses (for a review, see, e.g., Burke-Spolaor et al 2019;Taylor 2021). Three such pulsar timing arrays (PTAs) have the required decade-long data sets to probe the nanohertz band: the North American Nanohertz Observatory for Gravitational Waves (NANOGrav; Agazie et al 2023a), the European Pulsar Timing Array (EPTA; Antoniadis et al 2023a), and the Parkes Pulsar Timing Array (PPTA; Zic et al 2023). All three of these collaborations found a low-frequency stochastic process in their data (Agazie et al 2023b;Antoniadis et al 2023b;Reardon et al 2023).…”

“…Three such pulsar timing arrays (PTAs) have the required decade-long data sets to probe the nanohertz band: the North American Nanohertz Observatory for Gravitational Waves (NANOGrav; Agazie et al 2023a), the European Pulsar Timing Array (EPTA; Antoniadis et al 2023a), and the Parkes Pulsar Timing Array (PPTA; Zic et al 2023). All three of these collaborations found a low-frequency stochastic process in their data (Agazie et al 2023b;Antoniadis et al 2023b;Reardon et al 2023). They also found various levels of evidence for Hellings-Downs (HD;Hellings & Downs 1983) spatial correlations between pulsars, which points to the origin of this process being a stochastic gravitational-wave background (GWB).…”