Exploring LSST's capabilities for early detection of outbursts in low-mass X-ray binaries

TL;DR

This paper assesses LSST's potential to detect early optical signals of X-ray binary outbursts, finding current survey plans limit early detection but enabling population inference.

Contribution

It develops an extended metric for outburst detectability and evaluates LSST's capabilities for early detection of low-mass X-ray binary outbursts.

Findings

LSST's planned cadence limits early detection of XRB outbursts.

An extended metric for outburst detectability was developed.

The method can help infer the Galactic LMXB population.

Abstract

Following long periods of quiescence, low-mass X-ray binaries can exhibit intense X-ray outbursts triggered by instabilities within the accretion disk. These outbursts can sometimes be detected in optical wavelengths before being detected in X-rays, acting as an early onset warning and enabling a deep study of accretion disk properties informed by the lag between optical and X-ray rise. We explore the potential of Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) to detect these outbursts early through optical observations. We evaluate the capabilities of LSST based on currently planned survey cadence, filter-specific depth, and other observational factors that affect early detection. We develop and apply an extended metric to assess outburst detectability and recovery fraction. We find that despite inherent potential for early detection of XRB outbursts, the currently planned survey strategy makes it challenging to detect early onset of XRBs. Lastly, we demonstrate how this estimate can be used to infer the wider LMXB population in the Galaxy as the LSST progresses.