A Gamma-ray Pulsar Timing Array Constrains the Nanohertz Gravitational Wave Background

• Published in: arXiv.org 2022-04
• Main Authors: Baldini, L, Ballet, J, Barbiellini, G, Bastieri, D, Bellazzini, R, Blandford, R D, Bloom, E, Bonino, R, Bruel, P, Buehler, R, Burns, E, Buson, S, Cameron, R A, Caraveo, P A, Cavazzuti, E, Cibrario, N, Ciprini, S, Clark, C J, Cognard, I, Crnogorcevic, M, Cutini, S, D'Ammando, F, Gaetano, S D, Digel, S W, Lalla, N D, F Fan Dirirsa, Venere, L D, Domínguez, A, Ferrara, E C, Fiori, A, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Giglietto, N, Giroletti, M, Green, D, Guillemot, L, Guiriec, S, Gustafsson, M, Hays, E, Horan, D, Hou, X, Jóhannesson, G, Keith, M J, Kerr, M, Kramer, M, Kuss, M, Latronico, L, J Li, Longo, F, Loparco, F, Lovellette, M N, Lubrano, P, Manfreda, A, Martí-Devesa, G, Mereu, I, Michelson, P F, Mirabal, N, Mitthumsiri, W, Morselli, A, Negro, M, Ojha, R, Orienti, M, Ormes, J F, Pei, Z, Pesce-Rollins, M, Poon, H, Porter, T A, Principe, G, Racusin, J L, Rainò, S, Rando, R, Ransom, S M, Ray, P S, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Roy, J, Sánchez-Conde, M, Sa Parkinson, P M, Scargle, J, Scotton, L, Serini, D, Sgrò, C, Siskind, E J, Smith, D A, Spandre, G, Spinelli, P, Suson, D J, Tabassum, S, Thayer, J B, Theureau, G, Torres, D F, Troja, E, Wadiasingh, Z, Wood, K, Zaharijas, G
• Format: Article
• Language: English
• Subjects: Arrays; Binary systems; Galaxies; Gamma ray astronomy; Gravitational waves; Millisecond pulsars; Space telescopes; Supermassive black holes
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2204.05226

After large galaxies merge, their central supermassive black holes are expected to form binary systems whose orbital motion generates a gravitational wave background (GWB) at nanohertz frequencies. Searches for this background utilize pulsar timing arrays, which perform long-term monitoring of millisecond pulsars (MSPs) at radio wavelengths. We use 12.5 years of Fermi Large Area Telescope data to form a gamma-ray pulsar timing array. Results from 35 bright gamma-ray pulsars place a 95\% credible limit on the GWB characteristic strain of \(1.0\times10^{-14}\) at 1 yr\(^{-1}\), which scales as the observing time span \(t_{\mathrm{obs}}^{-13/6}\). This direct measurement provides an independent probe of the GWB while offering a check on radio noise models.