U2-2016
Speaker: Serena Valtolina (MPIFR Bonn)
Title: “Pulsar Timing array experiments using gamma-ray photons”
Abstract:
Pulsar Timing Array (PTA) experiments aim at detecting nanohertz gravitational wave (GW) signals hidden as stochastic delays in pulsar observations. The most likely GW source at those frequencies is expected to be a stochastic gravitational wave background (GWB) produced by a superposition of the individual GW emissions from supermassive black hole binaries. In the last few years, the main radio PTA collaborations have announced different levels of evidence for a GWB signal in their respective radio datasets.
It is also possible to time pulsars at higher energies, including with gamma rays. The first gamma-ray PTA (GPTA) study, published in 2022, analyses records of individual photons collected by the Fermi Large Area Telescope (Fermi LAT) and sets an upper limit for the strain amplitude of a possible GWB signal. This result is consistent with the latest estimates from radio PTAs, but it remains a rather loose upper bound.
In this talk, I will show you the unique opportunities and challenges of searching for GWB imprints in pulsar gamma-ray photon observations. In particular, I will focus on explaining how GPTA methods and data differ from those of radio PTA experiments, and what can be learnt exclusively from a GPTA experiment. I will also discuss the improvements and preparation plan for the second GPTA data release, which will be published by the end of this year.
Host: Alberto Sesana