TITLE: GCN CIRCULAR NUMBER: 40461 SUBJECT: GRB 250424A: COLIBRÍ detection of the associated supernova DATE: 25/05/15 16:39:06 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS adeugartepostigo@gmail.com
Antonio de Ugarte Postigo (LAM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Kin Ocelotl López (UNAM), William H. Lee (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), and Margarita Pereyra (UNAM):
We have continued imaging the field of GRB 250424A (Cenko et al., GCN Circ. 40224 https://gcn.nasa.gov/circulars/40224; Harsha et al. GCN Circ. 40231; Ridnaia et al. GCN Circ. 40243; McKenna et al. GCN Circ. 40249; Zhang et al. GCN Circ. 40252; Nakahira et al. GCN Circ. 40298) at a redshift of z = 0.310 (Saccardi et al. GCN Circ. 40228) to monitor the evolution of the optical transient (Brivio et al. GCN Circ. 40225; Becerra et al. GCN Circ. 40226; de Wet et al. GCN Circ. 40229; Ducoin et al. GCN Circ. 40230; Turpin et al. GCN Circ. 40240; Dutton et al. GCN Circ. 40241; Siegel et al. GCN Circ. 40244; Hu et al. GCN Circ. 40246; Schneider et al. GCN Circ. 40250; Elkabir et al. GCN Circ. 40251; Ghosh et al. GCN Circ. 40263), in search for the possible SN emission, using the DDRAGO wide-field imager on the COLIBRÍ telescope.
The field is covered by the Legacy Survey, which reveals an underlying host galaxy with AB magnitudes g=22.60, r=21.98, i=22.05 (Pérez-Fournon et al. GCN Circ. 40227).
A GRB-SN at that redshift would be expected to reach peak light between the 8th and the 15th of May (Cano et al. 2017). We hereby report two photometric observations of the optical counterpart obtained in the r- and i-bands. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
An r-band observation consisting of 112x60s exposures was obtained with mean epoch 2025-05-11 06:49:32 UTC (16.998 d after the burst, 12.976 d in the rest frame). We measure r = 21.54 +/- 0.21 mag.
An i-band observation consisting of 111x60s exposures was obtained with mean epoch 2025-05-15 06:42:39 UTC (20.993 d after the burst, 16.025 in the rest frame). We measure i = 21.46 +/- 0.12 mag.
Both values are clearly in excess of the underlying host galaxy, and indeed an excess emission is obtained when performing image subtraction with respect to the archival Legacy Survey image.
Subtracting the host contribution we obtain values of r ~ 22.7 mag and i ~ 22.4 mag which are in agreement to the expectations of a GRB-SN at this redshift with a certain amount of extinction. We consequently suggest that COLIBRÍ is currently detecting the supernova associated with GRB 250424A.
Further observations to confirm and monitor the evolution of this GRB-SN are encouraged.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
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