- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 40729] GRB 251112A: Swift-XRT refined Analysis
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42665 SUBJECT: GRB 251112A: Swift-XRT refined Analysis DATE: 25/11/13 10:27:12 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 847 s of XRT data for GRB 251112A, from 90 s to 939 s after the Swift trigger. The data comprise 64 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 274.0697, +24.1535 which is equivalent to: RA (J2000): 18h 16m 16.72s Dec(J2000): +24d 09' 12.5" with an uncertainty of 4.1 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=3.14 (+0.34, -0.30). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 3.3 (+/-0.4). The best-fitting absorption column is 4.9 (+1.3, -1.1) x 10^21 cm^-2, in excess of the Galactic value of 1.8 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 2.2 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 4.9 (+1.3, -1.1) x 10^21 cm^-2 Galactic foreground: 1.8 x 10^21 cm^-2 Excess significance: 4.6 sigma Photon index: 3.3 (+/-0.4) If the light curve continues to decay with a power-law decay index of 3.14, the count rate at T+24 hours will be 7.8 x 10^-9 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-19 (8.4 x 10^-19) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01413695. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42665. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40728] GRB 251108C: AstroSat CZTI detection
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42664 SUBJECT: GRB 251108C: AstroSat CZTI detection DATE: 25/11/13 09:10:52 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 251108C. This burst was also detected by the Konus-Wind team (priv. comm.) T0(KW) = 23:08:03.415 UT. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-11-08 23:07:57.38 UTC. The measured peak count rate associated with the burst is 250 (+36, -38) counts/s above the background in the combined data of all quadrants, with a total of 630 (+121, -124) counts. We caution that there is a 0.3 s readout dead time in CZT data during the burst which affects the calculated total counts. The local mean background count rate was 257 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 7.0 (+1.8, -1.6) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-11-08 23:07:56.96 UTC The measured peak count rate associated with the burst is 660 (+49, -53) counts/s above the background in the combined data of all quadrants, with a total of 3568 (+326, -374) counts. The local mean background count rate was 1128 (+7, -7) counts/s. Using cumulative rates, we measure a T90 of 10.9 (+3.2, -3.0) s. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42664. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40727] LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42663 SUBJECT: LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq DATE: 25/11/13 08:46:10 GMT FROM: Paul Groot at Radboud University Nijmegen <p.groot(a)astro.ru.nl> P.J. Groot (Radboud/UCT/SAAO) , H. Tranin (Barcelona), J. van Roestel (ISTA), P.M. Vreeswijk (Radboud), D. Pieterse (Radboud), G. Leloudas (DTU Space), N. Blagorodnova (Barcelona), S. Bloemen (Radboud), G. Ramsay (Armagh), S. Scaringi (Durham) report on behalf of the BlackGEM and MeerLICHT consortia: "The BlackGEM and MeerLICHT telescopes (Groot et al., 2024) reacted to the LVK-announced gravitational wave event S251112cm (LVK2025, GCN Circ. 42650). Both telescope systems covered about 50% of the 90% error box, primarily the part located in the Southern Hemisphere. A detailed overview of observations will be given in a subsequent report. Here we report the detection of AT2025adgp (BGEM J014746.20-514925.5), and AT2025adgq (MLT J002931.8-393051.6) as two newly detected transients in the BlackGEM/MeerLICHT footprint, which, on average, had a limiting magnitude for new transients of q~19.8. AT2025adgp is located at RA, Dec (ICRS) = 01:47:46.202 -51:49:25.52 (26.942508d, -51.823756d) with an uncertainty of 0.1" in each coordinate. It was detected on 2025-11-13 03:09:48 and 03:25:29 UT in the BlackGEM q-band (440-720 nm) filter using the BG-2 telescope, at, respectively, q=19.31+/-0.12 and q=19.29+/-0.12. The first detection was 11h50m after the LVK Trigger time. The transient is located in the southern outskirts of a face-on spiral galaxy WISExSCOS J014746.23-514922.5, listed in the Regalade catalog (Tranin et al., 2025) at a luminosity distance of D_L =246 Mpc with a large standard deviation, and in the GLADE+ (Dalya et al., 2020) catalog at D_L = 250 +/- 45 Mpc. If the galaxy is the host of AT2025adgp this would put its distance at the upper edge of consistency with the distance to S251112cm as announced by the LVK collaboration at D_S251112cm = 96 +/- 29 Mpc. AT2025adgq is located at RA,Dec (ICRS) = 00:29:31.8, -39:30:51.6 (7.38245842d, -39.5143190d) with an uncertainty of 0.1” in each coordinate. It was detected on 2025-11-13 00:03:38 and 00:04:43 UT in the BlackGEM q-band (440-720 nm) filter using the MeerLICHT telescope at, q=19.28+/-0.10 in each exposure. The first detection was 08h44m after the LVK trigger. The BlackGEM array also detected AT2025adgq on 2025-11-13 01:05:23 UT and 01:22:00 UT using the BG-2 telescope at q=19.28 +/- 0.10 and q=19.41 +/- 0.1, respectively. The transient is located in the north-eastern elongation of an oblated galaxy, WISExSCOS J002932.49-393059.7, listed in the Regalade catalog at a luminosity distance of D_L = 279 +/- 130 Mpc, and in the GLADE+ catalog at D_L = 300 +/- 68 Mpc. If the galaxy is the host of AT2025adqp this would put its distance at the upper edge of consistency with the distance to S251112cm as announced by the LVK collaboration. We encourage spectroscopic classification of AT2025adgp and AT2025adgq to confirm their nature and distance, and therefore the possibility of them being a counterpart to S251112cm." References: Groot et al., 2024, PASP 136, 5003, Tranin et al., 2025, arXiv250813267T, Dalya et al., 2020, VizieR On-line Data Catalog: VII/275; LVK2025, 2025, GCN 42650 View this GCN Circular online at https://gcn.nasa.gov/circulars/42663. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40726] GRB 251112B: MAXI/GSC detection
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42662 SUBJECT: GRB 251112B: MAXI/GSC detection DATE: 25/11/13 03:24:59 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> T. Kawamuro (Osaka U.), M. Nakajima (Nihon U.), Y. Kawakubo, M. Serino (AGU), H. Negoro, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), S. Yamada (Tohoku U) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 20:54:12 UT on November 12, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (278.962 deg, 18.196 deg) = (18 35 50, +18 11 45) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.30 deg and 0.26 deg, respectively. The roll angle of long axis from the north direction is 99.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 146 +- 34 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (277.696, 16.760) deg = (18 30 47, +16 45 36) (J2000) (R.A., Dec) = (278.212, 16.464) deg = (18 32 50, +16 27 50) (J2000) (R.A., Dec) = (279.748, 18.876) deg = (18 38 59, +18 52 33) (J2000) (R.A., Dec) = (279.227, 19.177) deg = (18 36 54, +19 10 37) (J2000) There was no significant excess flux in the previous transit at 19:21 UT and in the next transit at 22:27 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/42662. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40725] Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42661 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB DATE: 25/11/13 02:41:40 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 784687703/251113034 at 00:48:18.02 UT on 13 November 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to distant particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/42661. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40724] Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42660 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB DATE: 25/11/13 02:40:53 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 784687099/251113027 at 00:38:14.12 UT on 13 November 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to distant particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/42660. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40723] LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
by GCN Circulars 13 Nov '25

13 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42659 SUBJECT: LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations DATE: 25/11/13 02:29:27 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> H. Hiramatsu, S. Sugita, M. Serino, Y. Kawakubo, Y. Kondo (AGU) H. Negoro, M. Nakajima, K. Takagi (Nihon U.), N. Kawai, T. Mihara, (RIKEN), report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after compact binary merger candidate S251112cm at 2025-11-12 15:18:45.362 UTC (GCN #42650). At the trigger time of S251112cm, the high-voltage of MAXI/GSC was on. The instantaneous field of view of GSC at the GW trigger time covered 1% of the 90% credible region of the bayestar sky map, in which we found no significant new X-ray source. The first one-orbit (92 min) scan observation with GSC after the event covered 72% of the 90% credible region of the bayestar skymap from 15:18:45 to 16:50:09 UTC (T0+0 to T0+5484 sec). No significant new source was found in the region in the one-orbit scan observation. A typical 1-sigma averaged upper limit obtained in one scan observation is 20 mCrab at 2-20 keV. If you require information about X-ray flux by MAXI/GSC at specific coordinates, please contact the submitter of this circular by email. View this GCN Circular online at https://gcn.nasa.gov/circulars/42659. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40722] LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
by GCN Circulars 12 Nov '25

12 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42658 SUBJECT: LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations DATE: 25/11/12 22:47:23 GMT FROM: kendall.ackley(a)warwick.ac.uk K. Ackley, B. Godson, D. O'Neill, B. P. Gompertz, M. Dyer, J. Lyman, K. Ulaczyk, S. Belkin, T. Killestein, A. Kumar, M. Pursiainen, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, J. Casares Velásquez, L. K. Nuttall, report on behalf of the GOTO collaboration: We carried out optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al 2024) in response to the LIGO/Virgo/KAGRA gravitational wave candidate event S251112cm (GCN 42650). Targeted observations were performed by GOTO-South (Siding Spring, Australia) starting at 2025-11-12 16:09:51 UT, (+0.85h post trigger) and continued through to 2025-11-12 17:51:21 UT (+2.54h post trigger). A total of 39 image sets with exposures of 4x60s and 4x90s were taken across 6 unique pointings, covering 250.5 sq. degrees within the 90% localisation contour of the initial skymap. We covered approximately 14.6% of the total 2D localisation probability with an average 5-sigma depth of L~19.9 mag (AB). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. Within the initial skymap, we identify 2 optical sources within the 90% contour and 1 optical source within the 99% probability contour. We find no convincing evidence of excess flux in either GOTO25jyg/AT2025addc or GOTO25jya/AT2025adcv prior to the GW trigger time in previous GOTO observations or the ZTF observations provided by the Lasair broker (Smith et al. 2019). The ATLAS forced photometry server (Shingles et al. 2021) returns recent detections for GOTO25jyg and GOTO25jya, albeit at low significance. We encourage further analysis to confirm these pre-detections. We note that GOTO25jya appears to be associated with a GLADE+ galaxy HyperLEDA 422311 with zphot~0.01 (D_L~474 Mpc) which, if correct, would put it outside the nominal luminosity distance estimates of S251112cm. We do not find a host galaxy underlying GOTO25jyg. There is a galaxy located 9.27 arcsec from the candidate’s position within the Legacy DR10 photometric redshift catalog with zphot ~ 0.3 (Dey et al. 2019). GOTO25jye/AT2025adcy is located outside of the 90% probability contour of the initial skymap and is potentially associated with a GLADE+ galaxy HyperLEDA 389528 at zphot ~ 0.13 (D_L~664 Mpc). This association would make this candidate unlikely to be related to S251112cm. | Internal name | IAU name | RA(J2000) | Dec(J2000) | Mag(AB) | | ------------- | ---------- | ----------- | ------------ |--------------- | | GOTO25jyg | AT2025addc | 04:55:26.13 | -53:09:43.61 | 19.93 +/- 0.20 | | GOTO25jya | AT2025adcv | 03:05:58.60 | -54:09:06.60 | 19.30 +/- 0.10 | | GOTO25jye | AT2025adcy | 04:35:28.56 | -57:28:31.64 | 19.71 +/- 0.12 | Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction. Continued observations are planned from both GOTO sites, weather permitting. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/42658. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40721] GRB 251108B: Glowbug gamma-ray detection
by GCN Circulars 12 Nov '25

12 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42657 SUBJECT: GRB 251108B: Glowbug gamma-ray detection DATE: 25/11/12 22:29:39 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251108B, which was also detected by Konus-Wind (Trig_Time = 03:59:31.499 UT). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-08 03:59:18.952 with a duration of 15.4 s and a total significance of about 40 sigma. The light curve comprises two primary peaks at ~T0+7s and T0+13s. Note that data from ~T0-1s to T0+3s suffered from deadtime in various detectors. The best-fit localization is RA, Decl. (J2000, deg) = 283.3, 48.0 with a radius of 7.8 deg (95% confidence), with a highly uncertain systematic uncertainty. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42657. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40720] Swift Trigger 1413695: a possible GRB 251112A
by GCN Circulars 12 Nov '25

12 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42656 SUBJECT: Swift Trigger 1413695: a possible GRB 251112A DATE: 25/11/12 22:04:25 GMT FROM: James DeLaunay at PSU <jjd330(a)psu.edu> A. Mei (INAF-OAB), J. J. DeLaunay (PSU), M. Ferro (INAF-OAB), R. Gupta (NASA GSFC) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 21:28:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible GRB 251112A (trigger=1413695). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 274.019, +24.226 which is RA(J2000) = 18h 16m 05s Dec(J2000) = 24d 13' 32" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 60 sec. The peak count rate was ~600 counts/sec (15-350 keV), at ~25 sec after the trigger. The XRT began observing the field at 21:30:22.7 UT, 86.9 seconds after the BAT trigger. No source was detected in 782 s of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 91 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.161. Due to no credible afterglow candidate in the initial XRT and UVOT data, we for now call this a possible GRB while we wait for additional data for further inspection. Burst Advocate for this burst is A. Mei (alessio.mei AT inaf.it). 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/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42656. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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