EP251214b
GCN Circular 43138
Subject
EP251214b: KAIT optical upper limit
Date
2025-12-16T08:38:39Z (2 days ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) 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 EP251214b (Jiang et al.,
GCN 43125) starting at 08:17, Dec 14 UT, about 0.95 hours after
the trigger. A set of 29x60s and again 40x60s clear (roughly R)
filter images were obtained. In our coadd images, we did not detect
any new source within the EP-WXT error circle (Jiang et al., GCN
43125) down to limiting mag of 20.8 and 21.5 mag (Vega) at a
mid-time of 1.23 and 3.12 hours after the trigger. Our result is
consistent with the upper limit reported by other groups
(Eyles-Ferris et al., GCN 43117; Lipunov et al., GCN 43127).
GCN Circular 43127
Subject
EP251214b: Global MASTER-Net observations report
Date
2025-12-15T16:09:37Z (2 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP251214b ( EP Team et al., GCN 43125) errorbox 1777 sec after trigger time at 2025-12-14 07:49:59 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 14 deg. The sun altitude is -17.5 deg.
The galactic latitude b = 22 deg., longitude l = 256 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3071744
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
1807 | 2025-12-14 07:49:59 | MASTER-OAFA | (09h 37m 50.45s , -22d 35m 38.5s) | C | 60 | 20.5 |
1873 | 2025-12-14 07:51:04 | MASTER-OAFA | (09h 37m 50.56s , -22d 35m 35.8s) | C | 60 | 20.5 |
1939 | 2025-12-14 07:52:10 | MASTER-OAFA | (09h 37m 50.68s , -22d 35m 33.3s) | C | 60 | 20.5 |
2004 | 2025-12-14 07:53:16 | MASTER-OAFA | (09h 37m 50.79s , -22d 35m 30.8s) | C | 60 | 20.4 |
2070 | 2025-12-14 07:54:22 | MASTER-OAFA | (09h 37m 50.91s , -22d 35m 28.4s) | C | 60 | 20.4 |
2137 | 2025-12-14 07:55:28 | MASTER-OAFA | (09h 37m 51.00s , -22d 35m 26.1s) | C | 60 | 20.5 |
2202 | 2025-12-14 07:56:34 | MASTER-OAFA | (09h 37m 51.12s , -22d 35m 23.9s) | C | 60 | 20.4 |
2268 | 2025-12-14 07:57:39 | MASTER-OAFA | (09h 37m 51.21s , -22d 35m 21.8s) | C | 60 | 20.5 |
2334 | 2025-12-14 07:58:45 | MASTER-OAFA | (09h 37m 51.29s , -22d 35m 19.7s) | C | 60 | 20.5 |
2399 | 2025-12-14 07:59:51 | MASTER-OAFA | (09h 37m 51.36s , -22d 35m 17.2s) | C | 60 | 20.4 |
2465 | 2025-12-14 08:00:57 | MASTER-OAFA | (09h 37m 51.42s , -22d 35m 15.1s) | C | 60 | 20.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.
http : // www.pereplet.ru/lipunov/625.html
GCN Circular 43126
Subject
EP251214b : Einstein Probe detection of a fast X-ray transient
Date
2025-12-15T15:57:54Z (2 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on 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 EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2.
The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2.
We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing.
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 Circular 43125
Subject
EP251214b : Einstein Probe detection of a fast X-ray transient
Date
2025-12-15T15:56:40Z (2 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on 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 EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2.
The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2.
We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing.
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 Circular 43117
Subject
EP251214b (EP trigger 01709250023): LCO optical limits
Date
2025-12-15T12:43:14Z (2 days ago)
Edited On
2025-12-15T16:18:03Z (2 days ago)
From
Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
Web form
R. A. J. Eyles-Ferris (Leicester), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud) report on behalf of a larger collaboration:
We observed the field of EP251214b (EP/EXT trigger 01709250023; trigger time 2025-12-14T07:20:22.899 UT), using the Sinistro instrument at the 1m telescope in Siding Springs, Australia, part of the LCO network. Observations were carried out in the r (3x300 s) and z (6x300 s) bands, at mean epochs of 2025 Dec 14.658 and 14.687 UT, respectively (8.395 and 9.076 hr after trigger).
After subtracting from our stacks archival templates from the Pan-STARRS survey, we detect no new sources in either bands within the EP/WXT error circle, down to 3-sigma limiting AB magnitudes r > 22.4 and z > 21.6 (photometry calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction).
The two sources detected by Swift/XRT outside the EP/WXT error circle (https://www.swift.ac.uk/EP/EP_FIELD00087/) have stellar counterparts in Pan-STARRS. This further confirms that they are unlikely to be related to the EP transient. Furthermore, XRT source #1 matches an AGN from the C75 WISE AGN catalog (Assef et al. 2018; doi:10.3847/1538-4365/aaa00a), and is thus possibly an AGN.
The lack of detection is consistent with the results by COLIBRÍ (Basa et al., GCN 43090) and Swift/XRT.