AT2026jpw
GCN Circular 44385
Subject
GOTO26djh/AT2026jpw: ATCA radio detection
Date
2026-04-22T00:39:54Z (5 days ago)
From
James Leung at U. Toronto / HUJI <jamesk.leung@utoronto.ca>
Via
Web form
J. K. Leung (U. Toronto/HUJI)
We observed the field of the transient GOTO26djh/AT2026jpw (O'Neill et al., GCN 44301) with the Australia Telescope Compact Array (ATCA). We conducted the observation on 2026 April 19 at 15:30 - 16:30 UT. In our preliminary analysis, we detect an unresolved radio source coincident with the position of the transient (Rhodes et al., GCN 44379). The unresolved radio source had a flux density of ~0.2mJy at 10 GHz and a self-absorbed spectrum at and around this frequency.
We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.
GCN Circular 44379
Subject
GOTO26djh/AT2026jpw: radio detection at 15GHz
Date
2026-04-21T15:44:07Z (6 days ago)
Edited On
2026-04-21T17:00:37Z (6 days ago)
From
Lauren Rhodes at McGill <lauren.rhodes@mcgill.ca>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Lauren Rhodes at McGill <lauren.rhodes@mcgill.ca>
Via
Web form
Lauren Rhodes (McGill), Andrew Hughes, Rob Fender (Oxford), Dave Green, Dave Titterington (Cambridge) report:
We observed the position of GOTO26djh/AT2026jpw (GCN 44301) with the Arcminute Microkelvin Imager Large-Array (AMI-LA) at 15.5 GHz beginning for three epochs starting 2026-04-16 22:18UTC; 2026-04-17 21:14UTC and 2026-04-18 21:38UTC, each epoch lasting 5, 6.5, and 7 hours, respectively.
We detect an unresolved source, in each epoch with coordinates consistent with those of GOTO26djh/AT2026jpw. We measure a peak flux density of 0.28±0.07, 0.44±0.08, and 0.36±0.09mJy//beam in epochs 1, 2 and 3, respectively.
We thank the staff at the Mullard Radio Astronomy Observatory for carrying out these observations and operating the AMI-LA.
GCN Circular 44353
Subject
GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
Date
2026-04-20T06:51:39Z (7 days ago)
From
Nicolai Pankov at IKI <colinsergesen@gmail.com>
Via
Web form
N. Pankov (IKI), V. Rumyantsev (CrAO), E. Klunko (ISTP), A. Pozanenko (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We continued optical observations of the field of AT2026jpw (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303; Moskvitin and Spiridonova, GCN 44304; Xu et al., GCN 44305; The COLIBRÍ team, GCN 44306; Sosnovskij et al., GCN 44309; Ma et at., GCN 44314; Pankov et al., GCN 44316) in the R band with the Shajn 2.6-meter telescope (ZTSh) of the Crimean Astrophysical Observatory (CrAO) and the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations began on 2026-04-16 20:53 UT, i.e. ~2.92 days since GOTO detection at CrAO and on 2026-04-18 14:47 UT (~4.67 days since GOTO detection) at Mondy. The series of 38x120s exposures were taken by ZTSh/CrAO and 35x120s exposures were taken by AZT-33IK/Mondy. The optical counterpart is clearly detected in the co-add image from CrAO, but not detected by AZT-33IK.
The preliminary photometry and observation details are provided below:
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) Telescope/Site
(mid, days) (s)
2026-04-16 20:53:30 2.92638 38x120 R 22.11 0.02 23.7 ZTSH/CrAO
2026-04-18 14:47:18 4.66999 35x120 R n/d n/d 22.8 AZT-33IK/Mondy
The photometry is calibrated using nearby stars from USNO-B1.0 (see Moskvitin and Spiridonova, GCN 44304) and has not been corrected for the Galactic extinction.
GCN Circular 44316
Subject
GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
Date
2026-04-16T15:00:15Z (11 days ago)
From
Nicolai Pankov at IKI <colinsergesen@gmail.com>
Via
Web form
N. Pankov (IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of AT2026jpw (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303; Moskvitin and Spiridonova, GCN 44304; Xu et al., GCN 44305; The COLIBRÍ team, GCN 44306; Sosnovskij et al., GCN 44309; Ma et at., GCN 44314) in the R- and I-bands with the Shajn 2.6-meter telescope (ZTSh) of the Crimean Astrophysical Observatory (CrAO). The observations began on 2026-04-15 19:17 UT, i.e. ~1.84 days since GOTO detection. The series of 15x120s exposures were taken in the R-band and 21x120s exposures were taken in the I-band. The optical counterpart is clearly detected.
The preliminary photometry and observation details are provided below:
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2026-04-15 19:17:42 1.84388 15x120 R 21.49 0.05 23.6
2026-04-15 19:56:05 1.87469 21x120 I 21.59 0.08 23.3
The photometry is calibrated using nearby stars from USNO-B1.0 (see Moskvitin and Spiridonova, GCN 44304) and has not been corrected for the Galactic extinction.
GCN Circular 44314
Subject
GOTO26djh/AT2026jpw: SVOM/VT optical observation
Date
2026-04-16T13:55:26Z (11 days ago)
From
Yinuo Ma <mayn@bao.ac.cn>
Via
Web form
Y. N. Ma, H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, J. R. Xu, 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), J. Palmerio (CEA), W. L. Zhang (PMO), W. K. Zheng (UCB) report on behalf of the SVOM/VT team.
SVOM/VT performed a Target of Opportunity observation of the transient GOTO26djh/AT2026jpw detected by GOTO (O'Neill et al., GCN 44301). SVOM/VT began observing the field at 2026-04-16T06:11:26 UTC, 54.9 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With X-band data available, the OT (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303; Moskvitin & Spiridonova, GCN 44304; Xu et al., GCN 44305; Sosnovskij et al., GCN 44306; Méndez et al., GCN 44309) was clearly detected in VT_R band. The magnitude is:
mid time (h) | exposure time (s) | band | mag (AB) | mag err
-------------|-------------------|------|----------|--------
54.918 | 3*70 | VT_R | 21.5 | 0.2
Our photometry was not corrected for Galactic extinction.
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 Circular 44309
Subject
COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
Date
2026-04-16T06:26:13Z (11 days ago)
From
enriquemm@astro.unam.mx
Via
Web form
GOTO26djh/AT2026jpw: COLIBRÍ optical observations.
Enrique Moreno Méndez (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Ramandeep Gill (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the orphan afterglow candidate GOTO26djh/AT2026jpw reported by O'Neill et al., (GCN Circ. 44301) and also observed by Corcoran et al. (GCN Circ. 44303), Moskvitin et al. (GCN Circ. 44304), Xu et al. (GCN Circ. 44305), and Sosnovskij et al. (GCN Circ. 44306) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope.
We observed from 2026-04-16 03:47:39 to 04:44:41 (from 52.50 to 53.45 hours after the trigger) and obtained 15/15/15/45 minutes of simultaneous exposure in the g/r/i/z filters.
The data were reduced and coadded with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detected the optical counterpart reported by D. O'Neill et al., GCN Circ. 44301 at preliminary magnitudes of:
g = 22.51 +/- 0.06
r = 22.10 +/- 0.06
i = 21.87 +/- 0.08
z = 21.55 +/- 0.07
Comparing our values with the reported by NOT (Corcoran et al. GCN Circ. 44303), we estimate an optical decay alpha 1.6. Moreover, the detection in the four filters suggests a photo-z < 2.7 using typical IGM absorption.
Further observations and analysis are ongoing.
We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.
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.
GCN Circular 44306
Subject
GOTO26djh/AT2026jpw : MASTER OT observation
Date
2026-04-16T01:58:03Z (11 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
A.Sosnovskij, V.Lipunov, A.Kuznetsov, E.Gorbovskoy, I.Panchenko, P.Balanutsa, G.Antipov, N.Tiurina, V.Senik, A.Chasovnikov, Ya.Kechin, V.Topolev, D.Vlasenko, A.Sankovich, I.Gorbunov (Lomonosov MSU),
M.J. Segura, C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
N.Budnev, O.Gress (ISU),
D.Buckley (SAAO),
A. Gabovich (Blagoveschensk Educational StateUniversity)
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella,
J.Tanori, L. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Tavrida robotic telescope of MASTER Global Robotic Net [1-4]
started GOTO26djh/AT2026jpw
(discovered by GOTO O'Neill et al., GCN 44301, also observed by NOT (Corcoran et al., GCN 44303) and Zeiss-1000 at SAO RAS (Moskvitin et al. GCN 44304)
observations at 2026-04-15 23:10:27UT.
There is optical transient at summary MASTER image (2520s exposition, mlim=22.2m)
with unfiltered m_OT~21.5+-0.6m , calibrated by Pan-STARRs stars in our field.
MASTER images are available on request.
Observation and reduction will continue.
[1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L
[2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271
[3] Lipunov et a. 2019, ARep, vol.63, 293
[4] Lipunov et al. 2023, Astronomical Robotic Networks and Operative Multichanel
Astrophysics,Lomonosov MSU PRESS, 591pp.
http://www.pereplet.ru/lipunov/625.html#625
GCN Circular 44305
Subject
GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
Date
2026-04-16T01:54:19Z (11 days ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
D. Xu (NAOC), B. P. Gompertz (U. Birmingham), S.Q. Jiang (NAOC) report on behalf of a large group:
We performed a ToO observation at the location of GOTO26djh/AT2026jpw, a candidate orphan GRB afterglow (O'Neill et al., GCN 44301) with the Follow-up X-ray Telescope (FXT) onboard the Einstein Probe (EP) mission. The observation started at 18:49:01 on 2026-04-15 UT with a total exposure time of ~3000 s.
An uncatalogued X-ray source, with a flux of ~ 1.7 x 10^-13 erg/cm^2/s (0.5-10 keV; observed), is detected at coordinates
R.A.(J2000) = 13:22:13.34
Dec.(J2000) = +37:02:26.88
with an uncertainty of 15 arcsec, being consistent with the location of GOTO26djh/AT2026jpw, confirming it's the soft X-ray counterpart of GOTO26djh/AT2026jpw. The X-ray counterpart detection at ~ 3 days since the event happening favors its nature of an afterglow of a high-energy burst.
Further EP-FXT observations are scheduled.
GCN Circular 44304
Subject
GOTO26djh/AT2026jpw transient: SAO RAS optical observations
Date
2026-04-16T00:39:58Z (11 days ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. S. Moskvitin and O. I. Spiridonova (SAO RAS)
report on behalf of GRB follow-up team.
We observed the field of the fast-fading transient GOTO26djh/AT2026jpw
(O'Neill et al., GCN 44301) with the Zeiss-1000 1m telescope
of the SAO RAS on April 15/16 night. We obtained two series of images
in Rc band.
The OT (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303) is clearly
detected in the stacked images with the following brightness.
Date UT start t-T0 Exp. Filter OT Err. UL
(mid,days) (n*s) (3sigma)
2026-04-15T19:30:44 1.87945 8*300 Rc 21.6 +/- 0.1 23.3
2026-04-15T22:01:13 1.97747 13*300 Rc 22.0 +/- 0.1 23.8
This preliminary photometry is based on nearby stars from the USNO-B1
catalogue (R2 magnitudes) and is not corrected for the Galactic
extinction.
GCN Circular 44303
Subject
NOT r-band observations of the transient GOTO26djh/AT2026jpw
Date
2026-04-15T23:26:03Z (11 days ago)
From
Laura Cotter at University College Dublin <laura.cotter@ucdconnect.ie>
Via
Web form
G. Corcoran (UCD), A. de Ugarte Postigo (LAM), L. Cotter (UCD), A. Martin-Carrillo (UCD), B. P. Gompertz (Birmingham), D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), N. Pyykkinen (NOT and UTU), report on behalf of a larger collaboration:
We observed the field of the transient GOTO26djh/AT2026jpw (O'Neill et al., GCN 44301) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. Observations consisted of 3x500 s in the SDSS-r band starting at 21:01:12 UT on the 15th of April 2026 (45.73 hr after the GOTO discovery).
In our stacked image, the transient is well detected. The calculated AB magnitude was found to be r = 21.85 +/- 0.05 (AB), calculated against the Pan-STARRS catalog, and is not corrected for Galactic extinction.
GCN Circular 44301
Subject
GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
Date
2026-04-15T18:38:37Z (11 days ago)
From
d.s.oneill@bham.ac.uk
Via
Web form
D. O'Neill, M. Wortley, M. Pursiainen, B. P. Gompertz, J. Lyman, R. Starling, G. Ramsay, K. Ackley, M. Dyer, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar, on behalf of GOTO collaboration,
A. Aryan, T.-W. Chen, Y.-H. Lee, T. K. Ho Ngo, and H.-Y. Hsiao (all NCU), report:
We report on the discovery of the rapidly-evolving transient GOTO26djh/AT2026jpw with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) during survey operations.
The object was discovered at 2026-04-13 23:17:32 UT at co-ordinates:
RA,DEC (J2000): = 13:22:13.21, +37:02:15.16,
200.555049, 37.03754
Observations consisted of 4 x 45s exposures taken in the L band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations.
The source was initially detected with L = 19.00 ± 0.08 AB mag at t0=2026-04-13 23:17:32 UT before fading to L = 19.61 ± 0.18 AB mag at 2026-04-14 03:21:27 UT (t0 +4.06h), suggesting a decay rate of ~3.5 mag/d.
No underlying source is detected in either the Pan-STARRS or SDSS surveys that would suggest the presence of a host galaxy or stellar counterpart. Additionally, the high Galactic latitude (b = +78.15 deg) would be unusual for a local stellar origin.
We performed follow-up observations with the 1 m Lulin One-meter Telescope (LOT) at Lulin Observatory, Taiwan, as part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86). The first epoch of LOT observations began at 2026-04-15 14:41 UT (MJD 61145.612, t0 +39.40h). The transient was detected with an r-band magnitude r=21.55 ± 0.07 AB mag.
Using this combined dataset, the estimated decay index ranges from -1.6 < alpha < -1.1, assuming explosion times of 12h to 6h pre-discovery, consistent with the decay indices seen in GRB afterglows. GOTO26djh/AT2026jpw is not detected in the most recent pre-discovery GOTO observations taken at 2026-04-12 00:00 UT (t0 -47.29h) to a 3-sigma limiting magnitude of L > 20.5. This constrains its onset to a window of < 2 days before discovery.
Despite the apparent lack of an underlying star and an evolution consistent with GRB afterglows, a local stellar origin cannot be definitively excluded with the current data. We encourage further follow-up to determine the nature of this transient. EP/FXT ToO observations have been scheduled.
GOTO magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018). LOT magnitudes were calibrated using SDSS stars. Observations are not corrected for Galactic extinction.
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).