A state-dependent influence of the type-I bursts on the accretion in 4U 1608--52?

TL;DR

This study explores how type-I X-ray bursts influence accretion in the neutron star system 4U 1608--52, revealing state-dependent feedback effects linked to radiation interactions with the accretion disc.

Contribution

It provides the first detailed analysis of the state-dependent impact of type-I bursts on accretion processes in 4U 1608--52, considering radiation-disc interactions.

Findings

Persistent flux increases during bursts in the banana state.

In the island state, flux trend depends on burst luminosity.

Radiation interactions may cause observed state-dependent effects.

Abstract

We investigated the possible feedback of type-I burst to the accretion process during the spectral evolution of the atoll source 4U 1608--52. By fitting the burst spectrum with a blackbody and an adjustable, persistent spectral component, we found that the latter is significant state-dependent. In the banana state the persistent flux increases along the burst evolution, while in the island state this trend holds only when the bursts are less luminous and starts to reverse at higher burst luminosities. We speculate that, by taking into account both the Poynting-Robertson drag and radiation pressure, these phenomena may arise from the interactions between the radiation field of the type-I burst and the inner region of the accretion disc.