Needle in a Poissonian haystack -- An X-ray astronomer's guide to QPE fishing

TL;DR

This paper discusses new observational strategies and methods for detecting Quasi-Periodic Eruptions (QPEs) in X-ray astronomy, aiming to identify these elusive transients beyond current biased approaches.

Contribution

It introduces two complementary methods for detecting long-term and short-term QPEs, applicable to archival data and real-time follow-ups, expanding search avenues beyond existing strategies.

Findings

Methods enable detection of previously missed QPEs.

Applicable to 25 years of XMM-Newton data and real-time follow-ups.

Help reduce confirmation bias in QPE searches.

Abstract

After six years of studies following the discovery of GSN069, a link is starting to appear between the elusive Quasi-Periodic Eruptions (QPEs) and other types of nuclear transients, among which are Tidal Disruption Events (TDEs). As such, observing strategies are adapting, with a current trend focusing on late-time X-ray follow-ups of (optical) TDEs. While these campaigns are so far proving quite successful, the inherent confirmation bias they introduce in our sample could lead the community to hasty, and perhaps erroneous, conclusions. It is thus important to still pursue the search for nuclear transients in other, more agnostic directions. In this work, we focus on the observational aspects of our field, and lay out two different methods that can be deployed in order to reveal new QPE sources. These complementary methods enable the detection of long-term ($\sim$years) and short term ($\sim$minutes) transient events, that would have otherwise been missed by the standard detection pipelines. Both of these methods can be used either for data mining in the 25 years worth of XMM-Newton archive, or to trigger real-time follow-ups upon a more recent discovery.