TITLE: GCN CIRCULAR NUMBER: 39904 SUBJECT: GRB 250327B: further optical observations by LCOGT DATE: 25/03/28 12:22:25 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK amitkundu515@gmail.com
Amit Kumar (RHUL/Warwick), Raya Dastidar (UNAB), Giuliano Pignata (UTA), Danny Steeghs, Thomas Killestein (Warwick), David O’Neill (Birmingham), Jonathan Andrés Pineda García (UNAB) and Mauricio Ramirez (UNAB) report on behalf of the wider collaboration:
We conducted optical follow-up observations of the optical counterpart to the SVOM/ECLAIRs-detected GRB 250327B (Bouchet et al., GCN 39888) using the LCOGT 0.4-m telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Teide Observatory, Tenerife, Spain, equipped with the SCICAM-QHY600 camera. Observations were carried out on 2025-03-28 between 02:18:54 UT and 03:34:29 UT, corresponding to approximately 5.1 to 6.4 hours post-burst.
Each epoch comprised a series of 6 × 300 sec exposures in the B-band. In the stacked image, we clearly detect the optical counterpart with a B-band magnitude of ~21.9 ± 0.2. The detected position is consistent with the location of the optical counterpart reported by Moskvitin et al. GCN 39889 (a.k.a. GOTO25bhx, AT 2025gcz), with supporting detections from Xin et al. (GCN 39890), O’Neill et al. (GCN 39891), Malesani et al. (GCN 39893), Lian et al. (GCN 39894), Shrestha et al. (GCN 39896), Ducoin et al. (GCN 39897), and Perley & Bochenek (GCN 39902).
The reported magnitude is calibrated against the USNO-B1 catalog and is not corrected for Galactic extinction in the direction of the event.
Further analysis and follow-up observations are ongoing. This circular may be cited.
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