Deep Synoptic Array Science: Searching for Long Duration Radio Transients with the DSA-110

Abstract We describe the design and commissioning tests for the DSA-110 Not-So-Fast Radio Burst (NSFRB) search pipeline, a 1.4 GHz image-plane single-pulse search sensitive to 134 ms−160.8 s radio bursts. Extending the pulse width range of the Fast Radio Burst search by 3 orders of magnitude, the NSFRB search is sensitive to the recently discovered Galactic Long Period Radio Transients (LPRTs or LPTs). The NSFRB search operates in real-time, utilizing a custom GPU-accelerated search code, cerberus , implemented in Python with JAX. We summarize successful commissioning sensitivity tests with continuum sources and pulsar B0329+54, estimating the 90% completeness 25 σ flux (fluence) limit to be ∼1200 mJy (∼160 Jy ms). Future tests of recovery of longer timescale transients, e.g., CHIME J1634+44, are planned to supplement injection testing and B0329+54 observations. An offline DSA-110 NSFRB Galactic Plane Survey was conducted to search for LPRTs, covering −3 . ° 5 < b < 5 . ° 7 and 141° < l < 225° (∼770 square degrees) in Galactic coordinates. We estimate an upper limit Poissonian burst rate ∼2 hr −1 per square degree (∼17 hr −1 per 3° × 3° survey grid cell) maximized across the inner ∣ b ∣ < 0 . ° 25 of the surveyed region. By imposing the ∼1200 mJy flux limit on two representative models (the magnetar plastic flow model and the White Dwarf-M Dwarf binary model), we reject with 95% confidence the presence of White Dwarf-M Dwarf binary LPRTs (beamed in a detectable direction) with periods between ∼10 and 50 s within ∼95% of the surveyed region. Combined with the prevalence of LPRTs in the Galactic Plane, our results motivate further consideration of both White Dwarf-M Dwarf binary models and isolated magnetar models. We will continue to explore novel LPRT search strategies during real-time operations, such as triggered periodicity searches and additional targeted surveys.