Abstract
The International Pulsar Timing Array (IPTA)'s second data release (IPTA DR2)
combines observations of 65 millisecond pulsars from 7 radio telescopes
spanning decades, aiming to detect nanohertz gravitational waves (GWs). IPTA
datasets are complex and take years to assemble, often excluding recent data
crucial for low-frequency GW searches. To address this, we introduce the
``Lite'' analysis, a framework that informs the full data combination process.
Using a Figure of Merit, we first select individual PTA datasets per pulsar,
enabling immediate access to new data and providing an early estimate of fully
combined dataset results. Applying this method to IPTA DR2, we create an
uncombined dataset (DR2 Lite) and an early-combined subset (EDR2) before
constructing the final Full DR2 dataset (IPTA DR2). We find that DR2 Lite can
detect the common red noise process seen in Full DR2 but overestimates the
amplitude as $A = 5.2^{+1.8}_{-1.7} \times 10^{-15}$ at $\gamma = 13/3$, likely
due to unmodeled noise. In contrast, the combined datasets improve spectral
characterization, with Full DR2 yielding an amplitude of $A = 4.0^{+1.0}_{-0.9}
\times 10^{-15}$ at $\gamma = 13/3$. Furthermore, combined datasets yield
higher, albeit small, detection statistics for Hellings-Downs correlations.
Looking ahead, the Lite method will enable rapid synthesis of the latest PTA
data, offering preliminary GW constraints before full dataset combinations are
available while also motivating their construction.