JWST Imaging of the Closest Globular Clusters -- I. Possible Infrared Excess Among White Dwarfs in NGC 6397

TL;DR

This study uses JWST and HST data to analyze white dwarfs in NGC 6397, revealing potential infrared excesses that could indicate the presence of ancient planetary systems, thus extending understanding of WD properties.

Contribution

First infrared characterization of white dwarf cooling sequence in NGC 6397 using JWST, identifying potential IR excesses suggestive of planetary systems.

Findings

Detected IR excess in about 25% of white dwarfs in NGC 6397

Identified a split in the white dwarf cooling sequence

Proposed IR excesses may indicate ancient planetary systems

Abstract

We present James Webb Space Telescope observations of the globular cluster NGC 6397 and use them to extend to infrared wavelengths the characterization of the cluster's entire white dwarf (WD) cooling sequence (CS). The data allows us to probe fundamental astrophysical WD properties and to search for evidence in their colors for (or against) the existence of ancient planetary systems. The existing archival Hubble Space Telescope imaging data obtained ~18 years ago reach ultra-deep optical magnitudes (V~31) and allow us to derive a near-perfect separation between field and cluster members. We detect an apparent split in the lower part of the WD CS of NGC 6397. The red part of the WD CS, containing about 25% of the total, exhibits significant IR-excess of up to Delta m_F322W2 ~ 0.5 mag. These infrared excesses require both theoretical and observational follow-ups to confirm their veracity and to ascertain their true nature.