Abstract for Proposal 096454

Resolving the relativistic shock breakout in the brightest, longest QPE

We recently discovered Quasi-Periodic Eruptions (QPEs) in a tenth galaxy, SDSS1335+0728. They are extreme: they rise to peak amplitudes of 500x quiescence, last 1.5 days, and reach fluxes >1.5e-11 erg/cm2/s. With eruptions 4x longer and peak flux 2.5x higher than any other QPE source, SDSS1335 provides 10x more counts per flare, allowing phase-resolved high-resolution spectroscopy for the first time. We uncovered a rapidly evolving spectral feature suggesting a relativistic outflow of 0.06-0.15c; this is the first detection of such a feature in a QPE, and tracing its evolution will be an extremely powerful model constraint. We propose 440ks XMM+50ks Swift monitoring to resolve the properties of the ionizing continuum in unprecedented detail and constrain the putative shock-breakout powering QPEs.



Details on Observing Strategy and Trigger Criteria
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