A gamma-ray pulsar timing array constrains the nanohertz gravitational wave background
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2022-04-07
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Citation of Original Publication
Fermi-LAT Collaboration. "A gamma-ray pulsar timing array constrains the nanohertz gravitational wave background." SCIENCE, 376, no. 6592 (7 Apr 2022): 521-523. DOI: 10.1126/science.abm3231
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
After large galaxies merge, their central supermassive black holes are expected to form binary systems. Their orbital motion should generate a gravitational wave background (GWB) at nanohertz frequencies. Searches for this background use pulsar timing arrays, which perform long-term monitoring of millisecond pulsars at radio wavelengths. We used 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 × 10−14 at a frequency of 1 year–1. The sensitivity is expected to scale with tobs, the observing time span, as t−13/6obs. This direct measurement provides an independent probe of the GWB while offering a check on radio noise models.