Effects of oxygen-rich disc composition on reflection diagnostics

Determine the extent to which the oxygen-rich disc composition of 4U 0614+091 affects the reliability of standard reflection diagnostics and establish whether its fast-timing behaviour tracks the spectral-state changes inferred from reflection-based models.

Background

Previous studies of 4U 0614+091 reported oxygen, neon, and iron reflection features, but generally applied reflection models calibrated for solar-abundance, hydrogen-rich accretion discs. Because 4U 0614+091 is believed to contain an oxygen-rich disc associated with a white-dwarf donor, the applicability and reliability of those standard reflection diagnostics remain unresolved.

The same paragraph also identifies an unresolved relationship between the source’s rapid X-ray variability and the spectral-state changes inferred from these models. These issues motivate simultaneous broadband spectral and timing observations.

References

Despite this comparatively rich spectral characterisation, these reflection studies have generally relied on models calibrated for solar-abundance, hydrogen-rich discs, leaving open the extent to which oxygen-rich disc composition affects the reliability of standard reflection diagnostics in this source, and whether the fast-timing behaviour tracks the spectral-state changes inferred from these models.

— Comparative spectro-temporal study between 1A 1246$-$588 and 4U 0614$+$091 using AstroSat  (2609.29316 - Chattopadhyay et al., 24 Sep 2026) in Section 1, Introduction, paragraph discussing 4U 0614+091