The NANOGrav 15-year Data Set

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a project using high-precision radio timing observations of a set of millisecond spin-period pulsars (MSPs) to detect gravitational waves (GW) in the nHz frequency range. This approach is complementary to higher-frequency GW experiments as it is sensitive to different sources. The strongest expected GW source in this band is a stochastic background (GWB) of binary supermassive black holes; other more exotic cosmological or astrophysical sources may also exist. Our most recent published results, the 12.5-year Data Set, included 47 MSPs and showed evidence for a common noise process affecting their timing. This was consistent with a GWB signal but not significant enough to detect the expected inter-pulsar correlations that are the unique signature of GW. We have recently updated our analysis to incorporate additional newer data. The new 15-year Data Set includes timing data on 68 MSPs taken with the Arecibo, Green Bank, and Very Large Array radio telescopes. In addition to new data, this effort includes significant improvements to software pipelines, new analyses of binary and astrometric parameters, and detailed noise modelling for all pulsars. Here we present an overview of NANOGrav’s observing program and the new data set, highlighting recent improvements. We will also discuss the status of our ongoing GW analyses that incorporate the new data.