NANOGrav limits on gravitational-wave bursts with memory from the nine-year data release

Highly energetic astrophysical phenomena, like mergers of supermassive black hole binary (SMBHB) systems, are predicted to emit potentially detectable amounts of gravitational radiation. Of specific interest is the non-linear effect known as ``memory'': a permanent and non-oscillatory component of the gravitational waveform created primarily during the most violent moments of the SMBHB inspiral. Pulsar timing arrays offer a unique opportunity to detect such burst with memory (BWM) signals, due to their low-frequency sensitivity. In this talk we will present preliminary upper limits on the event rate of such BWM signals using the new 9-year North American NanoHertz Observatory for Gravitational Waves (NANOGrav) data release. We will also discuss the astrophysical implications of these limits, and projected sensitivity for future releases.