Combining the second data release of the European Pulsar Timing Array with low-frequency pulsar data
Abstract
Low-frequency radio data improve the sensitivity of pulsar timing arrays (PTAs) to propagation effects such as dispersion measure (DM) variations, enabling better noise characterization essential for detecting the stochastic gravitational wave background (GWB). We combined LOFAR (100-200 MHz) and NenuFAR (30-90 MHz) observations with the recent European and Indian PTA release (DR2new+) into a new dataset, DR2low, spanning ~11 years for 12 pulsars. DR2low allows updated noise models, increasing PTA sensitivity to the GWB. Using Libstempo and Enterprise, we applied standard noise models including red noise (RN) and time-variable DM (DMv) as power laws, and performed Bayesian model selection over RN, DMv, and an additional chromatic noise term (CN4). Compared to DR2new+, DR2low improves DM constraints and separates DM and RN contributions. We found that the RN is required in the final model for 10 out of 12 pulsars, compared to only 5 in the DR2new+ dataset. The improved sensitivity to plasma effects provided by DR2low also favors the identification of significant CN4 in eight pulsars, while none showed such evidence in DR2new+. The analysis also reveals unmodelled solar wind effects, particularly near solar conjunction, with residual delays absorbed into the DM component, highlighting the importance of accurately modelling the solar wind in PTA datasets.
Cite
@article{arxiv.2510.04639,
title = {Combining the second data release of the European Pulsar Timing Array with low-frequency pulsar data},
author = {F. Iraci and A. Chalumeau and C. Tiburzi and J. P. W. Verbiest and A. Possenti and S. C. Susarla and M. A. Krishnakumar and G. M. Shaifullah and J. Antoniadis and M. Bagchi and C. Bassa and R. N. Caballero and B. Cecconi and S. Chen and S. Chowdhury and B. Ciardi and I. Cognard and S. Corbel and S. Desai and D. Deb and J. Girard and A. Golden and J-M. Grießmeier and L. Guillemot and M. Hoeft and H. Hu and F. Jankowski and G. Janssen and B. C. Joshi and S. Kala and E. Keane and K. Nobelson and A. Konovalenko and I. Kravtsov and M. Kramer and K. Liu and A. Parthasarathy and P. Rana and D. Schwarz and J. Singha and A. Srivastava and K. Takahashi and P. Tarafdar and G. Theureau and O. Ulyanov and C. Vocks and J. Wang and V. Zakharenko and P. Zarka},
journal= {arXiv preprint arXiv:2510.04639},
year = {2025}
}