AstroNote 2025-194

We report the results of a systematic search for transient sources in the first publicly released image from the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), using cross-matching with the Transient Name Server (TNS). The LSST image was taken from the webpage: https://rubinobservatory.org/gallery/collections/first-look-gallery/mli…

After downloading the image, we uploaded it to Astrometry.net to generate an accurate World Coordinate System (WCS) solution for positional cross-matching. The image is centred at coordinates RA =  12:25:27.89, Dec = +06:56:10.5 (J2000), with a field of view of ~ 5.4deg x 2.8deg.

We queried the TNS for all astronomical transients discovered from January 1, 2024, to the present, within the LSST image footprint. Additionally, we included all known superluminous supernovae and Tidal Disruption Events, regardless of discovery year in TNS. Each source was visually inspected in the LSST image to assess detectability. In total, there were 32 transients reported within the image we chose. Details as follows:

Clearly detected (6):
The following six transients are unambiguously detected in the LSST image:
SN 2024kce (Ia-pec), SN 2024adyk (Ia), AT 2025hlg, AT 2025bcu, AT 2025knv, and AT 2025ckp.
The attached Figure 1 includes zoomed-in image cutouts for the six clearly detected transients, showing their visual identification.

Uncertain detection due to near galaxy cores (8):
The following eight targets are located near bright galactic nuclei, making detection ambiguous due to background contamination:
SN 2025npc (Ic), SN 2024lah (Ia), AT 2024orv, AT 2024blp, AT 2024apo, AT 2024bpb, AT 2025mij, and AT 2025iu.

Not detected (18):
No obvious detections were found for the following transients by visual inspection:
SN 2024bhx, AT 2025cur, AT 2025fqa, AT 2024myn, AT 2024ijb, AT 2024hvr, AT 2024ijc, AT 2024jlg, AT 2024fhy, AT 2024cgu, AT 2024fvm, AT 2024gdj, AT 2024chi, AT 2024ckz, AT 2024cbq, AT 2025am, AT 2025ck, and AT 2025oaa.

The attached Figure 2 is the LSST image annotated with the positions of all matched TNS transients.

This work makes use of data products from the Vera C. Rubin Observatory's LSST. We are extremely grateful to the Vera C. Rubin Observatory and its supporting agencies for the images released publicly. We acknowledge that this image material is supported in part by the National Science Foundation through Cooperative Agreement AST-1258333 and Cooperative Support Agreement AST1836783 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory managed by Stanford University.