New candidates for magnetar counterparts from a deep search with the Hubble Space Telescope

TL;DR

This study identifies six new magnetar counterpart candidates using deep near-infrared imaging from the Hubble Space Telescope, expanding the known population and providing insights into their properties.

Contribution

It presents the discovery of new magnetar counterparts and compares their properties with existing counterparts, highlighting potential candidates and the need for further confirmation.

Findings

Six new magnetar counterpart candidates identified.

Two candidates for AXJ1818.8-1559 are consistent with known counterparts.

Most new candidates are likely chance alignments or have different origins.

Abstract

We report the discovery of six new magnetar counterpart candidates from deep near-infrared Hubble Space Telescope imaging. The new candidates are among a sample of nineteen magnetars for which we present HST data obtained between 2018-2020. We confirm the variability of previously established near-infrared counterparts, and newly identify candidates for PSRJ1622-4950, SwiftJ1822.3-1606, CXOUJ171405.7-381031, SwiftJ1833-0832, SwiftJ1834.9-0846 and AXJ1818.8-1559 based on their proximity to X-ray localisations. The new candidates are compared with the existing counterpart population in terms of their colours, magnitudes, and near-infrared to X-ray spectral indices. We find two candidates for AXJ1818.8-1559 which are both consistent with previously established counterparts. The other new candidates are likely to be chance alignments, or otherwise have a different origin for their near-infrared emission not previously seen in magnetar counterparts. Further observations and studies of these candidates are needed to firmly establish their nature.