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Verification of quiescent emission modulation due to disk precession in eRO-QPE1

Determine whether the quiescent X-ray emission of eRO-QPE1 is modulated by rigid accretion disk nodal precession, by obtaining observations sensitive enough to detect quiescent-level variability and confirming (or refuting) the presence of a quiescent quasi-periodic oscillation attributable to disk precession.

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Background

Precession of a misaligned accretion disk can modulate emission and is invoked to explain the observed ∼6-day timing pattern in QPE residuals. The authors note that quiescent-level modulation would be a natural consequence of disk precession and is reported in GSN 069.

For eRO-QPE1, NICER is not sensitive enough to detect quiescent emission, preventing a test of this prediction. Verifying such modulation would strengthen the case for disk precession as the origin of the timing behavior.

References

Another observational consequence of disk precession is modulation of the quiescent emission (it is this reason, for example, that QPOs in accreting stellar-mass black holes are sometimes interpreted in light of rigid precession). However, since the quiescent level of eRO-QPE1 is below NICER\ detectability, we are unable to verify this.

— Testing EMRI models for Quasi-Periodic Eruptions with 3.5 years of monitoring eRO-QPE1 (2402.08722 - Chakraborty et al., 13 Feb 2024) in Discussion, Section 4.3 (Order in the recurrence times)