EP250321A
GCN Circular 40054
Subject
EP250321A: J band upper limit by SYSU 80cm telescope
Date
2025-04-04T15:32:10Z (a year ago)
From
Yan Yu <yuyan35@mail2.sysu.edu.cn>
Via
Web form
Yan Yu, Jin-Ji Li, Jia-Qi Lin, Wei-Sen Huang, Zhong-Nan Dong, Pu Lin, Hao-Nan Yang, Hao-Ran Zhang, Chun Chen, P H Thomas Tam, Rong-Feng Shen, Bin Ma(Sun Yat-sen University) report on behalf of the SYSU 80cm telescope team:
We observed the field of EP250321A (EP GCN 39800; MASTER-OAFA GCN 39803; Zhu et al., GCNs 39809; Swift-XRT GCN 39811) using the Sun Yat-sen University 80cm infrared telescope with 90 x 20 s exposures in J band. The calculated position is RA. = 179.2625 deg, DEC = 17.3628 deg J2000, from EP observation. Our observations began at 2025-3-22 13:25:00 UTC, 31.25 hours after the EP trigger.
We do not detect any counterpart at the position of the optical afterglow (Fu et al., GCN 39804; Perez-Garcia et al., GCNs 39805; Brivio et al., GCNs 39807; Becerra et al., GCNs 39810; Pérez-Fournon et al., GCN 39812; Lee et al., GCN 39815; Ghosh et al., GCN 39816; Han et al., GCN 39817; Jin et al., GCN 39822; Zhu et al., GCN 39827; Gill et al., GCN 39831; Zheng et. al, GCN 39832; Pankov et al., GCN 39836; Bochenek et. al, GCN 7939837; Zhu et. al, GCN 39854), down to a 5-sigma depth of J~ 17.6 Vega magnitudes.
GCN Circular 39831
Subject
EP250321A: COLIBRÍ Continuing Optical Observations
Date
2025-03-22T05:50:58Z (a year ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
Web form
Ramandeep Gill (UNAM), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM) and Antonio de Ugarte Postigo (LAM), and report:
We continued our observations of the field of EP250321A (Hu et al., GCN Circ. 39800) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We observed from 2025-03-22 03:55 to 05:25 UTC (21.75 to 23.26 hours after the trigger). The data were coadded with the custom software and analysed with STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
We detect the optical counterpart (Fu et al. 2025, GCN Circ. 39804; Perez-Garcia et al. 2025, GCN Circ. 39805; Brivio et al. 2025, GCN Circ. 39807; Zhu et al. 2025, GCN Circ. 39809; Becerra et al. 2025, GCN Circ. 39810; Pérez-Fournon et al. 2025, GCN Circ. 39812; Lee et al. 2025, GCN Circ. 39815; Han et al. 2025, GCN Circ. 39817; Sharma et al. 2025, GCN Circ. 39822) with a magnitude of:
i = 22.5 +/- 0.1
Compared to the latest reported measurement in i (Lee et al, GCN Circ. 39815), this corresponds to a decay with a power-law index of approximately -1.3.
Further observations are planned.
We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir
GCN Circular 39816
Subject
EP 250321A: Optical counterpart detection by LCO.
Date
2025-03-21T15:19:10Z (a year ago)
From
ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994@gmail.com>
Via
Web form
Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration.
We observed the field of the GRB 250321A triggered by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hu et al., GCN 39800) in the r, V filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Siding Spring is near Coonabarabran, New South Wales, Australia . The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel).
Observations began on March 21, 2025, starting 5.46 hours after the GRB trigger.
We clearly detect the optical transient (OT) reported by GCNs (Fu et al. GCN 39804, Perez-Garcia et al al., GCN 39805; Brivio et al., GCN 39807; Zhu et al., GCN 39809; Becerra et al., GCN 39810; Pérez-Fournon et al., GCN 39812, Lee et al., GCN 39815) in our r, V band image.
|Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude|
----------------------------------------------------------------------------------------------
2025-03-21 11:38:04.13 5.468 1 x 900 r r = 21.40 +/- 0.07
2025-03-21 11:38:20.54 5.472 1 x 900 V V = 21.76 +/- 0.09
The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.
GCN Circular 39810
Subject
EP250321A: COLIBRÍ Optical Observations
Date
2025-03-21T10:50:05Z (a year ago)
From
Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>
Via
Web form
Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Benjamin Schneider (LAM), Ny Avo Rakotondrainibe (LAM), Ramandeep Gill (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), William H. Lee (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM) and Antonio de Ugarte Postigo (LAM), and report:
We imaged the field of EP250321A (Hu et al., GCN Circ. 39800) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We started observing at 2025-03-21 07:42 UTC (1.54 hours after the trigger). The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is in the AB system and is not corrected for Galactic extinction.
At a mid-time T+1.9 h after the trigger, we detect the optical counterpart (Fu et al. 2025, GCN Circ. 39804; Perez-Garcia et al. 2025, GCN Circ. 9805; Brivio et al. 2025, GCN Circ. 39807; Zhu et al. 2025, GCN Circ. 39809) with AB magnitudes of:
r = 20.69 +/- 0.05
i = 19.12 +/- 0.04
Further analysis of the additional images is ongoing.
Further observations are planned.
We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.