TITLE: GCN CIRCULAR NUMBER: 39909 SUBJECT: FRB 20250316A: FTW optical observations DATE: 25/03/28 16:50:28 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München m.busmann@physik.lmu.de
Malte Busmann, Jennifer Fabà, Daniel Gruen, Mathias Mucke, Xiaoxiong Zuo (LMU), Brendan O'Connor, and Antonella Palmese (CMU) report on behalf of a larger collaboration:
We observed the localization of FRB 20250316A (Ng et al., ATel #17081; Andrew et al., GCN 39886). With the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the g and i band on multiple nights. Observations started 2.53d after the FRB or 5.8h after the discovery of an uncataloged X-ray source EP J120944.2+585060 by Einstein Probe (GCN 39834).
| Time (UT) | t - t0 (d) | Band | Exposures | Depth (3 sigma, AB mag) | Depth Diff (3 sigma, AB mag) | |---------------------|------------|------|-----------|-------------------------|------------------------------| | 2025-03-18T21:14:03 | 2.53 | g | 10x 180 s | 24.3 | Used as Reference | | 2025-03-18T21:14:03 | 2.53 | i | 10x 180 s | 23.7 | Used as Reference | | 2025-03-22T20:05:28 | 6.48 | g | 16x 180 s | 21.9 | - | | 2025-03-22T20:05:28 | 6.48 | i | 16x 180 s | 21.6 | - | | 2025-03-23T23:11:05 | 7.61 | g | 15x 180 s | 24.4 | 23.5 | | 2025-03-23T23:11:05 | 7.61 | i | 15x 180 s | 23.8 | 23.0 | | 2025-03-28T03:33:48 | 11.79 | g | 10x 180 s | 23.0 | 22.9 | | 2025-03-28T03:33:48 | 11.79 | i | 10x 180 s | 22.5 | 22.5 |
We performed difference imaging against templates from the LegacySurvey (g) and PS1 (i). We also used our first observation as a template and do not detect any excess flux at the FRB location in either case. This is consistent with the observations of Becerra et al. (ATel #17082, GCN 39843, 39853), Niino et al.(ATel #17084), Hashimoto (ATel #17095), Yang et al. (ATel #17101), Troja et al. (ATel #17109, GCN 39869), Dong et al. (ATel #17112), Aryan et al. (GCN 39839), Pereyra et al. (GCN 39858), Jiang et al. (GCN 39864), Gillanders et al. (GCN 39883), and Simha et al. (ATel #17116, GCN 39887).
The magnitudes are calibrated against the PS1 catalog and are not corrected for galactic extinction.
We thank Christoph Ries and Michael Schmidt from the Wendelstein Observatory staff for obtaining these observations.
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