Abstract for Proposal 094261

Late-time follow-up of the QPE candidate XMMSL1 J0249

We propose for an anticipated Target-of-Opportunity XMM-Newton observation, joint with Swift, of XMMSL1 J024916.6-041244 (hereafter J0249). J0249 wasr ecently identified as a strong candidate source of Quasi-Periodic Eruptions (QPEs), thanks to the detection of 1.5 QPE-like flares by XMM in 2006. Subsequent observations taken in 2021 did not detect QPEs, although quiescence was still detected, and had developed a notable hard powerlaw component akin to the corona of AGN. Our recent re-analysis of existing and newly taken Swift XRT data reveal that the source has rebrightened, perhaps with high-amplitude variability suggestive of QPEs. Our goal is to determine whether QPEs are really persisting in J0249, and even if they are not detected, to track the evolution of the quiescent hard component.

Details on Observing Strategy and Trigger Criteria
We propose a Anticipated TOO joint with Swift. We request 20 ks total of Swift time, split into two 10x1 ks campaigns each spaced over ~few days shortly before each of the two XMM visibility windows (July-August 2024, Jan-Feb 2025). If any Swift snapshots result in a detection, we will trigger a 120 ks XMM exposure (25% probability). If both Swift campaigns pass with no detections, we instead request a 30 ks XMM exposure (100% probability) in the second observing window. In either case the weight is 30 ks.