GRB250430A

This page lists all entries on GRB250430A in GRBweb

Summary Swift GCN 40292 GCN 40294 GCN 40295 GCN 40299 GCN 40302 GCN 40303 GCN 40304 GCN 40305 GCN 40307 GCN 40308 GCN 40310 GCN 40311 GCN 40312 GCN 40316 GCN 40318 GCN 40321 GCN 40323

Summary table
Variable Value Source
T0 17:31:21 UTC GCN_circulars,Swift Det
ra 233.3869° Swift
decl -18.1184° Swift
pos_error 1.42e-04° Swift
GBM_located False
mjd 60795.730104166665 GCN_circulars,Swift Det
Swift table
GRB_name GRB250430A
t_trigger 17:31:21 UTC
ra 233.3869°
decl -18.1184°
pos_error 1.42e-04°
GCN 40292 table
GRB_name GRB250430A
GCN_number 40292
Detection_method Swift Det
t_trigger 17:31:21 UTC
ra 233.4280°
decl -18.0830°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40292 SUBJECT: GRB 250430A: Swift detection of a burst with optical counterpart DATE: 25/04/30 18:07:07 GMT FROM: Tyler Parsotan at NASA GSFC T. M. Parsotan (GSFC), C. Gronwall (PSU), R. Gupta (NASA GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), M. J. Moss (GSFC), K. L. Page (U Leicester), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 17:31:21 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250430A (trigger=1308754). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 233.428, -18.083 which is RA(J2000) = 15h 33m 43s Dec(J2000) = -18d 04' 59" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi peak structure with a duration of about 20 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 17:33:37.5 UT, 157.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 233.38611, -18.11784 which is equivalent to: RA(J2000) = 15h 33m 32.67s Dec(J2000) = -18d 07' 04.2" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 190 arcseconds from the BAT onboard position, outside the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (9.57 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.5 (+2.62/-2.27) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 161 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at RA(J2000) = 15:33:32.85 = 233.38688 DEC(J2000) = -18:07:06.2 = -18.11840 with a 90%-confidence error radius of about 1.10 arc sec. This position is 3.65 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.44 with a 1-sigma error of about 0.35. No correction has been made for the expected extinction corresponding to E(B-V) of 0.092. Burst Advocate for this burst is T. M. Parsotan (tyler.parsotan AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN 40294 table
GRB_name GRB250430A
GCN_number 40294
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40294 SUBJECT: GRB 250430A: Kanata optical upper limit DATE: 25/04/30 18:52:29 GMT FROM: Koji Kawabata at HASC,Hiroshima U K. S. Kawabata, T. Hori, T. Nakaoka (Hiroshima Univ.) report on behalf of Kanata team: We performed optical imaging polarimetry to the field of the GRB 180720B (Parsotan et al. GCN 40292; Lipunov et al. GCN 40291) from 2025-04-30 17:34:03 UT (162 seconds after the trigger) with HONIR attached to the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Japan. We did not detect any new optical source up to a limiting magnitude of Rc = 16.0 (3-sigma; Vega mag) at the position of the UVOT source in our first 30 second exposure.
GCN 40295 table
GRB_name GRB250430A
GCN_number 40295
Detection_method Swift-BAT Det
ra 233.3873°
decl -18.1183°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40295 SUBJECT: GRB 250430A: AKO Optical Afterglow Detection DATE: 25/04/30 19:20:09 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of GRB 250430A detected by Swift/BAT (Parsotan et al., GCN 40292), using our 0.36m f/7.7 robotic telescope. The observation session began on 30 April 2025 at 17:52 UT, 21 minutes after the trigger. We obtained multiple 180-second exposures using the Ic filter. An uncatalogued object is faintly visible at the location below, which could be the optical afterglow: R.A. (J2000): 15:33:32.95 Dec. (J2000): -18:07:05.9 The following observation was calculated using the Atlas catalogue as a reference: ---------------------------------------------------------------------------- - ObsTime (mid), Exposure (sec), Filter, Mag ---------------------------------------------------------------------------- - 2025-04-30T18:29:42Z, 15 x 180s (stacked), Ic, 18.6 +/- 0.22 ---------------------------------------------------------------------------- - The magnitude is not corrected for galactic extinction.
GCN 40299 table
GRB_name GRB250430A
GCN_number 40299
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 40299 SUBJECT: EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission DATE: 25/05/01 08:11:44 GMT FROM: EP Team at NAOC/CAS C. Y. Wang (THU), H. L. Peng (NJNU), Y. Q. Zhao (USTC, PRIC), W. Yuan (NAO, CAS), behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250430a. The WXT detection was not triggered onboard due to the closeness of the source position to the bright X-ray source Sco X-1, but was made in the onground analysis of the telemetry data later. No automated follow-up X-ray observation was performed. The WXT position of the source is R.A. = 233.399 deg, DEC = -18.130 deg (J2000) with an uncertainty of 2.9 arcmin in radius (90% C.L. statistical and systematic), which is offset by 1.0 arcmin from the Swift/XRT position of the likely long GRB 250430A (Lipunov et al., GCN 40291; Parsotan et al., GCN 40292; Kawabata et al., GCN 40294; Odeh et al., GCN 40295). The X-ray rise time precedes the GRB trigger time by approximately 23 seconds, and the X-ray duration is longer than that of the GRB by about 30 seconds. The X-ray emission peaked at 2025-04-30T17:31:05.5 (UTC). The consistency of EP250430a and GRB 250430A in position and time suggests EP250430a to be the X-ray counterpart of GRB 250430A. Note that the source parameters given above are only approximate and detailed analysis is onging. The averaged WXT spectrum in 0.5-4 keV can be fitted by an absorbed power law model with a photon index of 2.37 (+0.61, -0.54) and a column density of 3.80 (+1.50, -1.31) x 10^21 cm^-2. The average unabsorbed 0.5-4 keV flux is about 1.63 (+0.69, -0.36) x 10^-10 erg/cm^2/s. These parameters derived are at the 1-sigma confidence level. Further observations with the Follow-up X-ray Telescope (FXT) on board EP may be considered at a later stage. Contact transient advocate (TA) for EP250430a is C. Y. Wang (wang-cy22@mails.tsinghua.edu.cn) and please contact the TA for information regarding the EP observation of this source. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN 40302 table
GRB_name GRB250430A
GCN_number 40302
Detection_method MITSuME
Circular_text TITLE: GCN CIRCULAR NUMBER: 40302 SUBJECT: GRB 250430A : MITSuME Akeno optical upper limits DATE: 25/05/01 11:06:05 GMT FROM: hagio.h.ffca@m.isct.ac.jp H. Hagio, I. Takahashi, M. Sasada, H. Seki, S. Joshima, Y. Kubo, A. Ochi, R. Kato, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration: We observed the field of GRB 240430A detected by Swift/BAT (Parsotan et al. GCN 40292) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. The observation started at 2025-04-30 17:31:53 UT (32 seconds after the Swift/BAT trigger). We stacked the images with good conditions. We did not detect any obvious point sources at the position reported by Parsotan et al., GCN 40292, Odeh et al., GCN 40295, Wang et al., GCN 40299, and Garnichey et al., GCN 40301. We obtained the 5-sigma limits of the stacked images as follows: T0+[min] | MID-UT | T-EXP[sec] | 5-sigma limits ------------------------------------------------------------------------------------------------ 15.1 | 2025-04-30 17:46:27 | 620 | g'>18.2, Rc>18.2, Ic>17.8 78.5 | 2025-04-30 18:29:51 | 2880 | g'>19.3, Rc>19.6, Ic>19.0 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the trigger T-EXP: Total Exposure time We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire).
GCN 40303 table
GRB_name GRB250430A
GCN_number 40303
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40303 SUBJECT: GRB 250430A: Bassano Bresciano Observatory upper limit DATE: 25/05/01 13:33:33 GMT FROM: Ulisse Quadri at Bassano Bresciano Observatory U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory) Members of: GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani. AAVSO - American Association of Variable Star Observers. GAC - Gruppo Astrofili Cremonesi. 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), B. De Simone (Universita' degli Studi Di Salerno) report: We imaged the field of GRB 250430A detected by Swift with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy. The observations started 5h 01m after the GRB trigger with our Newton telescope D=250 mm F/D=4.8. We co-added 2 series of 150 exposures of 30 sec each. Start T0+ End T0+ Rc lim. Err. 5h 01m 6h 30m 20.3 +/- 0.2 6h 31m 8h 01m 20.3 +/- 0.2 We did not found any optical uncatalogued object within the Swift error circle. Our upper limit is consistent with other observations reported by K. S. Kawabata et al. (GCN Circular 40294), Mohammad Odeh et al. (GCN Circular 40295), Andrea Saccardi et al (GCN Circular 40301), H. Hagio et al. (GCN Circular 40302). Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations. Not corrected for galactic dust extinction. Reference: http://www.osservatoriobassano.altervista.org The message may be cited.
GCN 40304 table
GRB_name GRB250430A
GCN_number 40304
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40304 SUBJECT: GRB 250430A: Leavitt Observatory optical upper limit DATE: 25/05/01 14:02:45 GMT FROM: leavittob@gmail.com L. Moretti, E. Pavoni (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia 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 observed the field of the GRB 250430A / EP250430a (Parsotan et al., GCN 40292; Wang et al., GCN 40299) with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Manciano, Italy. The observations started approximately 6 hours after the Swift/BAT trigger time, with good weather conditions. We utilized the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A) to align and stack 25 individual frames of 120 sec each, with a median time of 2025-04-30T23:29:41 (UTC). All images are unfiltered and were processed by a single data processing pipeline based on astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). In the stacked frame, we did not found any optical uncatalogued object within the Swift error circle. Mid-Time (UTC) Rc limit Error 2025-04-30T23:29:41 >20.32 +/- 0.01 This upper limit is consistent with other observations reported by K. S. Kawabata et al. (GCN Circular 40294), Mohammad Odeh et al. (GCN Circular 40295), Andrea Saccardi et al (GCN Circular 40301), H. Hagio et al. (GCN Circular 40302), Quadri et al. (GCN 40303). Our photometry is in the AB system and is not corrected for galactic dust extinction. Magnitudes were estimated with the Pan-STARRS cat. and converted using Lupton (2005) equations. The message may be cited. Reference: https://leavittobservatory.altervista.org
GCN 40305 table
GRB_name GRB250430A
GCN_number 40305
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40305 SUBJECT: GRB 250430A: DDOTI Optical Observations DATE: 25/05/01 14:06:36 GMT FROM: sahil.atri@students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), and Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of the Swift/BAT GRB 250430A (Parsotan et al., GCN Circ. 40292) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-05-01 UTC. DDOTI observed the Swift/UVOT error region (Parsotan et al., GCN Circ. 40292) from 05:23 UTC to 10:43 UTC (from T+11.9 h to T+17.4 h after the trigger) with a total exposure of 2.3 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no any uncatalogued source at the position reported by Parsotan et al., (GCN Circ. 40292); Odeh et al., (GCN Circ. 40295); Wang et al., (GCN Circ. 40299); Garnichey et al., (GCN Circ. 40301); Hagio et al., (GCN Circ. 40302); Quadri (GCN Circ. 40303) and Moretti (GCN Circ. 40304) down to a 3-sigma limiting AB magnitude of: w > 20.6 We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir.
GCN 40307 table
GRB_name GRB250430A
GCN_number 40307
Detection_method correction
Circular_text TITLE: GCN CIRCULAR NUMBER: 40307 SUBJECT: GRB 250430A: NUTTelA-TAO Early Measurements DATE: 25/05/01 17:08:43 GMT FROM: Toktarkhan Komesh at Nazarbayev University T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), B. Grossan (UCB, NU), D. Berdikhan (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 GRB 250430A on receipt of an automated GCN / BAT 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 17:31:53 UT on 2025-04-30, 32 s after the BAT trigger. Observations were made in clear conditions for the first ~1 hour, followed by cloudy weather. Note that these observations provide essentially full-time coverage, simultaneous in two bands. A new and changing source consistent with the XRT/EP position (T. M. Parsotan et al., GCN 40292; C. Y. Wang et al., GCN 40299) was detected. We report the results for the earliest co-added images, without color corrections or corrections for galactic reddening, as following: filter tc-t0(s) mag err exposure_time (s) ------------------------------------------------------------------------------- r' 59 18.44 0.13 54 g' 55 UL18.10 45 r’ 162 18.56 0.14 120 g’ 227 19.23 0.11 300 … … … … tc-t0 = image center time minus trigger time. Calibration was done with 4 bright Pan-STARRS catalog stars on our images. A light curve of the optical transient is presented in Figure 1: https://ecl.nu.edu.kz/research/observations/gamma-ray-bursts/grb250430a We welcome opportunities for collaboration and data-sharing. ---------------------------------- 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 40308 table
GRB_name GRB250430A
GCN_number 40308
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40308 SUBJECT: GRB 250430A / EP250430a: J-band upper limits with WINTER DATE: 25/05/01 17:50:27 GMT FROM: Geoffrey Mo at MIT Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Benjamin Schneider (LAM), Viraj Karambelkar (Caltech), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 250430A / EP250430a (Parsotan et al., GCN 40292; Wang et al., GCN 40299) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2025-05-01T08:49:52 UTC (15.3 hours after the GRB), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565). We do not detect a source at the optical and X-ray counterpart position (Parsotan et al., GCN 40292; Kawabata et al., GCN 40294; Odeh et al., GCN 40295; Garnichey et al., GCN 40301; Hagio et al., GCN 40302; Quadri et al., GCN 40303; Moretti et al., GCN 40304; Atri et al., GCN 40305; Komesh et al., GCN 40307). We obtain the following 5-sigma upper limit: J ~ 19.7 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN 40310 table
GRB_name GRB250430A
GCN_number 40310
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40310 SUBJECT: GRB 250430A: KAIT optical observations DATE: 25/05/01 21:27:09 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 250403A (Parsotan et al., GCN 40292; Wang et al., GCN 40299) with a set of 120x60s images in the clear (roughly R) filters, at a mid time of 13.9 hours after the trigger. We marginally detected the optical afterglow (Parsotan et al., GCN 40292; Odeh et al., GCN 40295; Garnichey et al., GCN 40301; Komesh et al., GCN 40307) in the coadd image with a brightness of 21.7 +/- 0.3 mag (Vega).
GCN 40311 table
GRB_name GRB250430A
GCN_number 40311
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40311 SUBJECT: GRB 250430A: SVOM/VT optical observations DATE: 25/05/02 03:29:23 GMT FROM: SVOM_group H. L. Li, , L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), L. Zhang(IHEP), W. K. Zheng (UCB) report on behalf of the SVOM/VT team: SVOM/VT conducted ToO follow-up observations for GRB 250430A. The observation started on 2025 Apr 24 04:54:31 UT in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. The optical counterpart (Parsotan et al., GCN 40292; Odeh et al., GCN 40295;Garnichey et al., GCN 40301; Komesh et al., GCN 40307; Zheng et al., GCN 40310) was clearly detected in our observations. The afterglow was fading during our observations and the brightness was estimated to be 21.69+/-0.05 mag in VT_R, and 22.96+/-0.10 mag in VT_B, at the mid time of 13.39 hours post the burst. The photometry was estimated in AB magnitude and not corrected for Galactic extinction. Considering the host galaxy's brightness and red color (Garnichey et al., GCN 40301)，the photometry might be contaminated by the host galaxy's light, particularly in the VT_R band. 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 40312 table
GRB_name GRB250430A
GCN_number 40312
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40312 SUBJECT: GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit DATE: 25/05/02 06:35:58 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 imaged the field of GRB 250430A detected by Swift/BAT (Parsotan et al. GCN 40292), with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-04-30 21:32 UT (approximately 4.02 hours after burst) stacking a set of unfiltered CCD image. We co-added 80 exposures of 60 sec each. Start T0+ End T0+ CR lim 4.02 hour 6.85 hour 19.9 We did not found any optical uncatalogued object within the Swift error circle. Magnitudes were estimated with the PanSTARRS cat. and are not corrected for galactic dust extinction. Our upper limit is consistent with other observations reported by Kawabata et al. (GCN 40294), Odeh et al. (GCN 40295), Saccardi et al. (GCN 40301), Hagio et al. (GCN 40302), Quadri et al. (GCN 40303), Moretti et al. (GCN 40304), Atri et al. (GCN 40305), Komesh et al. (GCN 40307), Mo et al. (GCN 40308), Zheng et al. (GCN 40310), Li et al. (GCN 40311). The message may be cited.
GCN 40316 table
GRB_name GRB250430A
GCN_number 40316
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40316 SUBJECT: GRB 250430A: Optical Observations via Virtual Telescope Project, Italy DATE: 25/05/02 11:22:42 GMT FROM: Gianluca Masi at Virtual Telescope Project Gianluca Masi, Virtual Telescope Project (Italy), reports: We attempted to observe the optical counterpart (Parsotan et al., GCN 40292; Odeh et al., GCN 40295) of GRB 250430A with the 14” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-3200E based CCD camera, its QE peaking (90%) in the red part of the spectrum. We collected 7, 300-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 30 April, 22:19 UTC, that is about 4.75 hours after the burst. We detected a faint object at the following position (J2000): RA: 15 33 32.94s Decl.: -18 07 06.5 R= 20.8 (assuming R-mags from Gaia DR2 for the reference stars). This position is consistent with Odeh et al., GCN 40295. At the position above, there is a very faint source on Panstarrs DR1 images, as well as on DESI Legacy DR10 images (the latter mentioned by Garnichey et al., GCN 40301), likely the host galaxy of GRB 250430A. The image is available here: https://www.virtualtelescope.eu/2025/05/02/grb-250430a-detection-of-the-optical-afterglow-30-apr-2025/
GCN 40318 table
GRB_name GRB250430A
GCN_number 40318
Detection_method Swift-XRT Det
ra 233.3870°
decl -18.1185°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40318 SUBJECT: GRB 250430A: Enhanced Swift-XRT position DATE: 25/05/02 11:57:52 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 1722 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250430A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 233.38699, -18.11851 which is equivalent to: RA (J2000): 15h 33m 32.88s Dec (J2000): -18d 07' 06.6" with an uncertainty of 2.3 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN 40321 table
GRB_name GRB250430A
GCN_number 40321
Detection_method Swift-UVOT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40321 SUBJECT: GRB 250430A: Swift/UVOT Detection DATE: 25/05/02 12:22:02 GMT FROM: Alice Breeveld at MSSL-UCL A.A. Breeveld (UCL-MSSL) and T. M. Parsotan (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250430A 118 s after the BAT trigger (Parsotan et al., GCN Circ. 40292). The optical source detected in the UVOT white filter reported in that circular (and also detected by Oden & Guessoum, GCN Circ. 40295; Garnichy et al., GCN Circ. 40301; Komesh et al., GCN Circ. 40307; Zheng et al., GCN Circ. 40310 and Li et al., GCN Circ. 40311) was also detected in the UVOT U-band filter, but has since faded. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 141 291 147 19.08 ± 0.1 white 843 1856 264 19.40 ± 0.1 v 118 1733 169 >18.9 b 473 1831 156 >19.8 u 448 468 20 17.91 ± 0.3 u 621 1117 59 18.67 ± 0.3 w1 424 1782 156 >19.0 m2 1393 1413 19 >17.3 w2 696 1364 58 >18.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.092 in the direction of the burst (Schlegel et al. 1998).
GCN 40323 table
GRB_name GRB250430A
GCN_number 40323
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 40323 SUBJECT: GRB 250430A: Swift-XRT refined Analysis DATE: 25/05/02 13:27:07 GMT FROM: Phil Evans at U of Leicester R. Brivio (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 1.4 ks of XRT data for GRB 250430A, from 166 s to 1.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=0.37 (+0.13, -0.14). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.89 (+0.26, -0.24). The best-fitting absorption column is 1.7 (+0.9, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 9.6 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.7 (+0.9, -0.8) x 10^21 cm^-2 Galactic foreground: 9.6 x 10^20 cm^-2 Excess significance: 1.7 sigma Photon index: 1.89 (+0.26, -0.24) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01308754. This circular is an official product of the Swift-XRT team.