James Webb Space Telescope Feed Post

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

(Left:) A 25¨ × 25¨ infrared image from the Digital Sky Survey 2 centered on our NIRCam field of NGC 6397 for JWST program GO-1979 (green box). The image is aligned with North up and East toward the left. The region indicated in red is the archival HST deep field from programs GO-10424 and GO-11633. (Middle:) The entire NIRCam primary field in filter F150W2. (Right:) A zoom-in on a dark sub-region (of ~ 1¨ × 1¨) in the NIRCam image (magenta boxes in the left and center frames), at a scale of 60¨¨ where individual pixels are visible. 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