A Cyclic Burst Rate Behavior of a Persistent X-ray Burster: Recent XMM-Newton and NuSTAR Observations of 4U 1323-62

TL;DR

This study reports recent XMM-Newton and NuSTAR observations of the persistent X-ray burster 4U 1323-62, revealing a cyclic burst rate trend, detection of multiple bursts and dips, and spectral analysis insights.

Contribution

It uncovers a 10-year cyclic pattern in burst rate and provides detailed spectral and timing analysis of bursts and dips in 4U 1323-62.

Findings

Detected 12 unique bursts, including double bursts.

Unveiled a 10-year cyclic trend in burst rate.

Identified a 0.898 Hz QPO during non-bursting, non-dipping periods.

Abstract

In this study, we report partly simultaneous XMM-Newton and NuSTAR observations of the bursting, dipping low mass X-ray binary, 4U 1323-62 obtained in 2024. 4U 1323-62 is one of the well-known persistent bursters, with bursts occurring roughly every three hours. It is also one of the few sources for which the orbital period is known, and shows dips in X-rays. In this paper, we report the detection of 12 unique bursts with XMM-Newton and NuSTAR, 6 of them observed jointly. We detected two double burst events, one with the NuSTAR and another one observed with both missions. Based on the long-term behavior of 4U 1323-62, we unveil a cyclic trend in its burst rate, with a period of about 10 years. During our observations we detected 10 X-ray dips with a periodicity of 2.942 hours, in line with previous measurements. We also present the results of the time resolved X-ray spectral analysis of the bursts and show the limits on the cooling of the corona heated by the burst emission. We also found a 0.898 +/- 0.017 Hz quasi-periodic oscillation (QPO) during the non-bursting and non-dipping times confirming previous detections.