TITLE: GCN CIRCULAR NUMBER: 39969 SUBJECT: GRB20250327B: 45th Parallel Observatory upper limit DATE: 25/03/31 12:21:20 GMT FROM: Vincenzo Della Vecchia v.dellavecchia@uai.it
Vincenzo della Vecchia (45th Parallel Observatory, Italy)
Member of: AAVSO - American Association of Variable Star Observers UAI - Unione Astrofili Italiani - Gamma Ray Burst Section
In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report:
We imaged the field of GRB 250327B detected by SVOM (burst-id sb25032706, GCN Circular 39888) and Swift XRT (GCN circ. 39895) with the 0.25-m f/5.6 Ritchey-Chrétien telescope of the 45th Parallel Observatory (IAU code D43).
The observation started 22.33 hours after the GRB trigger, with acceptable sky transparency and seeing. A series of 10 sec observations has been added for a total integration time of approximately 30 minutes.
Start T0+ End T0+ CR lim 22.33 hour 22.83 hour 19.5
CR as unfiltered with R zero point.
No optical counterpart has been detected at the position expected for the GRB.
Limit magnitudes are estimated with the Pan-STARSS DR1 catalogue and are not corrected for galactic dust extinction. I am grateful to Ulisse Quadri (Bassano Bresciano Astronomical Observatory) for his support.
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