TITLE: GCN CIRCULAR NUMBER: 36706 SUBJECT: GRB 240615A: possible transient detection from Wendelstein observations DATE: 24/06/19 22:11:12 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de> Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.), Antonella Palmese (Carnegie Mellon U.), Christoph Ries (LMU), Arno Riffeser (LMU/MPE) report: With the 3KK optical-NIR imager at the 2m Fraunhofer telescope at Wendelstein Observatory, Germany, we have followed up the GRB 240615A reported by GCN 36671, 36672. Our observations began at ~3.2 days after the GRB. We detect one source at 10sigma significance that is consistent with the location (90% error of ~9") of the Swift-XRT uncatalogued X-ray source reported in GCN 36683. We report the following photometric measurements and 3-sigma upper limits for this source (hereafter referred to as Source 1): Name RA(J2000) dec(J2000) UTC mag_r mag_i mag_J Source 1 21:44:23.63 +38:34:08.89 2024-06-18T22:44:19 >24.0 24.0 +/- 0.5 20.36 +/- 0.09 We also obtained a tentative detection of Source 1 in images taken about 22 h before this detection (~2.3 days after the GRB). There is evidence at the 3sigma level that Source 1 was brightening between the two epochs. We note that Source 1 is extremely red in color with i-J>3 mag. A second source (Source 2) is marginally detected at RA, dec (J2000) = 21:44:23.8, +38:34:03.4 in both r and i-bands. We note the marginal detection of an underlying source in PS1 imaging at both of these locations (Source 1 and Source 2). Further observations are scheduled and additional follow-up is encouraged. Magnitudes are in the AB system and not corrected for the significant Milky Way extinction along this line of sight. View this GCN Circular online at https://gcn.nasa.gov/circulars/36706. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...