GRB250402A

This page lists all entries on GRB250402A in GRBweb

Summary Fermi GBM GCN 40014 GCN 40015 GCN 40019 GCN 40021 GCN 40022 GCN 40023 GCN 40027 GCN 40030 GCN 40033 GCN 40047 GCN 40049 GCN 40062 GCN 40082

Summary table
Variable Value Source
GRB_name_Fermi GRB250402964
T0 23:08:06.787 UTC Fermi_GBM
ra 213.4089° GCN_circulars,Swift-XRT Other
decl -5.9302° GCN_circulars,Swift-XRT Other
T90 44.288 s Fermi_GBM
T90_error 1.864 s Fermi_GBM
T90_start 23:08:06.787 UTC Fermi_GBM
fluence 3.64e-06 erg/cm² Fermi_GBM
fluence_error 2.46e-08 erg/cm² Fermi_GBM
redshift 2.8230 GCN_circulars,Other
T100 44.288 s
GBM_located False
mjd 60767.96396744213 Fermi_GBM
Fermi GBM table
GRB_name_Fermi GRB250402964
trigger_name bn250402964
ra 213.4092°
decl -5.9300°
datum 2025-04-02
t_trigger 23:08:09.091 UTC
T90 44.288 s
T90_error 1.864 s
T90_start 23:08:06.787 UTC
fluence 3.64e-06 erg/cm²
fluence_error 2.46e-08 erg/cm²
flux_1024 2.39e+00 erg/cm²/s
flux_1024_error 2.14e-01 erg/cm²/s
flux_1024_time 2.27e+01 erg/cm²/s
flux_64 4.41e+00 erg/cm²/s
flux_64_error 1.04e+00 erg/cm²/s
GCN 40014 table
GRB_name GRB250402A
GCN_number 40014
Detection_method Optical
ra 213.3783°
decl -5.9457°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40014 SUBJECT: GRB 250402A: SVOM detection of a burst DATE: 25/04/03 00:15:14 GMT FROM: SVOM_group X. Chen(YNU), Y. Hu(GXU), H. Yang(IRAP), B. Cordier (CEA), L. Zhang(IHEP), P. Maggi (ObAS) on behalf of the SVOM mission team. At 2025-04-02T23:07:56 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250402A (SVOM burst-id sb25040203). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 15 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 27.79 in the [8-120] keV energy band over a time window of 40.96 seconds starting at Tb. The light curve showed a long GRB with a T90 duration of about 35 (+/-3) s. The localization of the best alert is R.A., Dec 213.3783, -5.9457 degrees (J2000) with a 90% C.L. radius of 3.42 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. MXT began observing the field at 2025-04-02T23:10:58 UTC, 183 seconds after Tb. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec 213.3893, -5.9468 degrees: RA (J2000) = 14h13m33.44s DEC (J2000) = -5d56m48.59s with a 90% C.L. radius of 45 arcseconds(including 25 arcseconds systematic error added in quadrature). This location is 0.66 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocate (BA) on shift for this burst is X. Chen: xlchen@stu.ynu.edu.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
GCN 40015 table
GRB_name GRB250402A
GCN_number 40015
Detection_method Optical
ra 213.4092°
decl -5.9301°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40015 SUBJECT: GRB 250402A: SVOM/VT optical counterpart DATE: 25/04/03 00:26:36 GMT FROM: Liping Xin at NAOC, SVOM L.P. Xin, Y. L. Qiu, C. Wu, H. L. Li, J . Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, Y. N. Yi, J. Y. Wei (NAOC), J. T. Palmerio(CEA/Irfu), T. Sadibekova(CEA) report on behalf of the SVOM team: SVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Chen et al., GCN 40014). SVOM/VT began observing the field automatically with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With VHF downlinked data, a bright uncatalogued source was found in both channels in the first sequence, and brightening with about 0.2 mag in the second sequence, compared to DESI catalog. The coordinates are RA, Dec = 213.40915, -5.93013 which is equivalent to: R.A.(J2000) = 14:13:38.20, DEC.(J2000)= -05:55:48.5 Error=0.5 arcseconds. The brightness are VT_B ~21.53 mag(AB) and VT_R ~20.61 mag(AB) in the first sequence with the mid time of 443 seconds after the burst. We proposed that this is the optical counterpart of the burst. Given the VT color, it is likely a low/medium redshift burst. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.
GCN 40019 table
GRB_name GRB250402A
GCN_number 40019
Detection_method Other
ra 213.4042°
decl -5.9436°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40019 SUBJECT: GRB 250402A: refined SVOM/MXT data analysis DATE: 25/04/03 07:20:33 GMT FROM: SVOM_group P. Maggi (ObAS), D. Götz (CEA), H. Goto (Kanazawa University/CEA), M. Moita (CEA), C. Plasse (CEA), F. Robinet (IJCLab), C. Van Hove (IJCLab) report of behalf of the SVOM/MXT Team: GRB 250402A (Chen et al. GCN 40014) was observed by SVOM/MXT after an automatic SVOM slew starting at T0 = 2025-04-02T23:10:59.278 (183s after trigger time Tb). MXT observed for 4.3 ks effective exposure. Using the full X band dataset, we find a rapidly fading uncatalogued source with a light curve temporal index of -0.75+/-0.02. At times T0>500s the source is no longer detected and hence we restricted the analysis to the first 500s of data. Its position is RA=213.4051, Dec=-5.94374 RA (J2000) = 14h13m37s Dec (J2000) = -05d56m37s with a statistical 90% C.L. radius of 38". The position is 51" away from, but consistent with, the one reported for the SVOM/VT afterglow candidate (Xin et al. GCN 40015) when including a 35" systematic uncertainty. The X-ray spectrum (t
GCN 40021 table
GRB_name GRB250402A
GCN_number 40021
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40021 SUBJECT: GRB 250402A: REM optical/NIR upper limits DATE: 25/04/03 09:46:37 GMT FROM: Riccardo Brivio at INAF-OAB R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of the SVOM/ECLAIRs GRB 250402A (Chen et al., GCN 40014) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 April 03 at 00:50:28 UT (i.e. 1.7 hr after the burst), and lasted for about 2 hours. From preliminary inspection, we do not find any counterpart at the position of the reported optical afterglow candidate (Xin et al., GCN. 40015; Pérez-Fournon et al., GCN 40020) down to the following 3sigma limits: r > 20.3 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 2.8 hours after the trigger, H > 16.1 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 2.2 hours after the trigger.
GCN 40022 table
GRB_name GRB250402A
GCN_number 40022
Detection_method Other
redshift 2.8230
Circular_text TITLE: GCN CIRCULAR NUMBER: 40022 SUBJECT: GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823 DATE: 25/04/03 09:52:28 GMT FROM: luca.izzo@inaf.it B. Schneider (LAM), A. Saccardi (CEA/Irfu), A. de Ugarte Postigo (LAM), L. Izzo (INAF-OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (U. Leicester), A. Martin-Carrillo (UCD) report on behalf of the Stargate collaboration: We observed the afterglow of the SVOM/ECLAIRs GRB 250402A (Chen et al., GCN 40014; Xin et al., GCN 40015, Maggi et al., GCN 40019; Pérez-Fournon et al., GCN 40020) using the ESO/VLT UT1 (Antu) equipped with the FORS2 spectrograph. Observations started on April 3 at 05:54:45 UT (6.78 hr after the SVOM trigger). Four exposures of 600 s were obtained. From a 60 s acquisition image obtained on April 3 at 05:43:17 UT (6.59 hr after the SVOM trigger), we measure r ~ 21.1 +/- 0.2 (AB). From a preliminary reduction of the 300V spectrum, a trough due to Lya absorption is visible at 4645 AA. From the detection of multiple absorption features, which we interpret as due to Si II, O I, C II, Si IV, Si II*, C IV, Fe II, and Al II, we infer a redshift of z = 2.823. Additionally, we note the presence of an intervening absorber at z = 1.409 with multiple Fe II absorption lines. We acknowledge excellent support from the ESO observing staff in Paranal.
GCN 40023 table
GRB_name GRB250402A
GCN_number 40023
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40023 SUBJECT: GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart DATE: 25/04/03 10:48:39 GMT FROM: Francesco Magnani at Aix-Marseille Université, CPPM/CNRS Francesco Magnani (CPPM), Camila Angulo (UNAM), Damien Dornic (CPPM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), William H. Lee (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), , Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and X. Chen (YNU) report: We imaged the field of the SVOM/ECLAIRs GRB 250402A (sb25040203, Chen et al. GCN 40014) with the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-04-03 04:37 to 06:49 UTC (between 5.49 and 7.69 hours after the trigger) and obtained 43 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. At the position of the previously reported optical afterglow (Xin et al., GCN 40015; Pérez-Fournon et al. GCN 40020; Schneider et al. GCN 40022), we detect a source with a magnitude of i = 21.22 +/- 0.11 Further observations are ongoing. 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 40027 table
GRB_name GRB250402A
GCN_number 40027
Detection_method Swift-XRT Other
ra 213.4089°
decl -5.9302°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40027 SUBJECT: GRB 250402A: Swift-XRT observations DATE: 25/04/03 16:01:19 GMT FROM: Simone Dichiara at Pennsylvania State University S. Dichiara (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB), K.L. Page and P.A. Evans (U.Leicester) reports on behalf of the Swift-XRT team: We have analysed 2.4 ks of XRT data for the SVOM/ECLAIRs-detected burst GRB 250402A (SVOM trigger sb25040203; Chen et al., GCN circ. 40014), from T0+49.2 ks to T0+51.5 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. We find an uncatalogued X-ray source consistent with the X-ray counterpart identified by SVOM/MXT (Maggi et al., GCN circ. 40019) and the optical counterpart (Xin et al., GCN 40015, Pérez-Fournon et al., GCN 40020, Schneider et al., GCN 40022, Magnani et al., GCN 40023). We note that the source is fading compared to the flux reported by previous MXT observations (Maggi et al., GCN circ. 40019). Details of this source are given below: Source 1: RA (J2000): 213.4089 = 14:13:38.13 Dec (J2000): -5.9302 = -05:55:48.5 Error: 3.4 arcsec (radius, 90% conf. [Enhanced position]) Count-rate:0.045 (±0.012) ct s-1 Flux: 1.9 (±0.5) ×10-12 erg cm-2 s-1 (observed, 0.3-10 keV) This XRT position is 1.07 arcsec away from the optical position. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00009/. This circular is an official product of the Swift-XRT team.
GCN 40030 table
GRB_name GRB250402A
GCN_number 40030
Detection_method Fermi GBM Det
t_trigger 23:08:09.090 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 40030 SUBJECT: GRB 250402A: Fermi GBM Observation DATE: 25/04/03 17:29:10 GMT FROM: Matt Godwin Jacob Smith (UAH), Utkarsh Pathak(IIT Bombay), and Matt Godwin (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 23:08:09.09 UT on 02 April 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250402A (trigger 765328094/250402964). which was also detected by SVOM (Chen et al. 2025, GCN 40014). The Fermi GBM on-ground location is consistent with the SVOM position. The angle from the Fermi LAT boresight is 57 degrees. The GBM light curve consists of a double peak with a duration (T90) of about 44 s (50-300 keV). The time-averaged spectrum from T0-5.1 to T0+45.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 115 +/- 10 keV. The event fluence (10-1000 keV) in this time interval is (4.1 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+23 s in the 10-1000 keV band is 2.4 +/- 0.2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 60 +/- 10 keV, alpha = -0.4 +/- 0.3 and beta = -2.1 +/- 0.1. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN 40033 table
GRB_name GRB250402A
GCN_number 40033
Detection_method correction
Circular_text TITLE: GCN CIRCULAR NUMBER: 40033 SUBJECT: GRB 250402A: NUTTelA-TAO Early Optical Limits DATE: 25/04/03 19:02:42 GMT FROM: Toktarkhan Komesh at Nazarbayev University T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), D. Berdikhan (NU), B. Grossan (UCB, NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB250402A on receipt of an automated GCN / SVOM position alert, observing in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We started observations at 23:10:30 UT on 2025-04-02, 154 seconds after the SVOM/ECLAIRs trigger (X. Chen et al., GCN 40014). Observations were made in partially cloudy conditions. No source consistent with the SVOM/VT (L. P. Xin et al., GCN 40015) was detected. We report the following results: start time t-t0(s) end time UL g' UL r' exposure_time (s) -------------------------------------------------------------- 23:10:30 154 23:11:30 18.01 18.35 60 23:12:13 257 23:22:13 18.58 18.67 600 t is the middle time, t0 is the SVOM/ECLAIRs trigger time, t-t0 is given in seconds. UL gives the 5 sigma upper limit sensitivity in magnitudes, for images of the given exposure time. Calibration was done with 4 Pan-STARRS catalog stars on our images. No color or other corrections were applied to the values above. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.
GCN 40047 table
GRB_name GRB250402A
GCN_number 40047
Detection_method Swift-UVOT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 40047 SUBJECT: GRB 250402A: Swift/UVOT Upper Limits DATE: 25/04/04 12:51:00 GMT FROM: Sam Shilling at Lancaster University S. P. R. Shilling (Lancaster U.) and S. R. Oates (Lancaster U.) report on behalf of the Swift UVOT team: Swift/UVOT observed the field of SVOM/ECLAIRs GRB 250402A (Chen et al. GCN Circ. 40014) for 2521 seconds in the U-band starting at 12:48:12 UT on 25/04/03, ~13 hours after the detection by SVOM/ECLAIRs. No optical afterglow is detected within a 5" radius of the position of the uncatalogued X-ray source detected by Swift/XRT (Dichiara et al., GCN Circ. 40027) and SVOM/MXT (Maggi et al., GCN circ. 40019) or the optical afterglow detected by SVOM/VT (Xin et al., GCN Circ. 40015), LCOGT (Pérez-Fournon et al., GCN Circ. 40020), and the SVOM/COLIBRÍ (Magnani et al., GCN Circ. 40023). The Swift/UVOT non-detection in the U-band has a preliminary 3-sigma upper limit of >21.1, calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373).
GCN 40049 table
GRB_name GRB250402A
GCN_number 40049
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40049 SUBJECT: GRB 250402A: Mondy optical observations DATE: 25/04/04 14:24:06 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), E. Klunko (ISTP), N. Pankov (HSE), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed GRB 250402A (Chen et al. GCN 40014) with the AZT-33IK telescope starting on 2025-04-03 (UT) 18:11:28. We found the optical counterpart (Xin et al., GCN 40015; Pérez-Fournon et al., GCN 40020; Schneider et al., GCN 40022; Magnani et al., GCN 40023) at the position reported by Xin et al., GCN 40015. Preliminary photometry of the optical counterpart is the following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2025-04-03 18:11:28 0.81567 R 29*120 21.9 0.2 22.3 The photometry is based on the nearby PS1 stars (R mag by Lupton transformations).
GCN 40062 table
GRB_name GRB250402A
GCN_number 40062
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 40062 SUBJECT: GRB 250402A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/04/04 18:11:36 GMT FROM: Jimmy DeLaunay at Penn State James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250402A onboard (T0: 2025-04-02T23:08:01.467 UTC, SVOM trig sb25040203, Fermi trig 765328094) The Fermi and SVOM notices, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 8.2 in a 4.096 s analysis time bin, starting at T0 + 7.168 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 5,905 deg2 and the 50% credible area is 1,632 deg2. The integrated probability inside the coded field of view is 1%. The NITRATES skymap is consistent with the SVOM/ECLAIRS position (GCN 40014), and the afterglow position (SVOM/VT GCN 40015, SVOM/MXT GCN 40019, LCO GCN 40020, SVOM/COLIBRI GCN 40023, Swift/XRT GCN 40027, EP/FXT GCN 40040, Mondy GCN 40049) A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=765328116/#:~:text=Probability%20Skymap) The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/765328116/0_n_PROBMAP) Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=765328116 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
GCN 40082 table
GRB_name GRB250402A
GCN_number 40082
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40082 SUBJECT: GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations. DATE: 25/04/05 22:22:30 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250402A (SVOM burst-id sb25040203, Chen et al., GCN 40014) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-04-02 23:57 UT (approximately 49 min after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and fair visibility conditions. The OT was detected at the following position (+/- 0.3 arcsec): RA (J2000) 14h 13m 38.17s Decl. (J2000) -05° 55' 48.8" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-03 01:39:02 UT 2.52 180x60s CR 21.6 +/- 0.4 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported L.P. Xin et al. (GCN 40015), Pérez-Fournon et al. (GCN 40020), Brivio et al. (GCN 40021), Schneider et al. (GCN 40022), Magnani et al. (GCN 40023), Komesh et al. (GCN 40033), Shilling et al. (GCN 40047), Mazaeva et al. (GCN 40049). The message may be cited.