Type I X-ray Bursts from the Neutron-star Transient XTE J1701-462

TL;DR

This study reports the discovery of three type-I X-ray bursts from neutron-star transient XTE J1701-462 during its outburst, providing insights into burst behavior across different spectral states and estimating the source distance.

Contribution

First detection of type-I X-ray bursts from XTE J1701-462 across spectral state transitions, challenging previous assumptions about burst occurrence in the flaring branch.

Findings

Bursts observed in both Z-source and atoll-source states.

Photospheric radius expansion indicates a distance of 8.8 kpc.

No significant burst oscillations detected.

Abstract

The neutron-star X-ray transient XTE J1701-462 was observed for $\sim$3 Ms with \xte during its 2006-2007 outburst. Here we report on the discovery of three type-I X-ray bursts from XTE J1701-462. They occurred as the source was in transition from the typical Z-source behavior to the typical atoll-source behavior, at $\sim10%$ of the Eddington luminosity. The first burst was detected in the Z-source flaring branch; the second in the vertex between the flaring and normal branches; and the third in the atoll-source soft state. The detection of the burst in the flaring branch cast doubts on earlier speculations that the flaring branch is due to unstable nuclear burning of accreted matter. The last two of the three bursts show photospheric radius expansion, from which we estimate the distance to the source to be 8.8 kpc with a 15% uncertainty. No significant burst oscillations in the range 30 to 4000 Hz were found during these three bursts.