TITLE: GCN CIRCULAR
NUMBER: 40790
SUBJECT: EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
DATE: 25/06/20 05:30:21 GMT
FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn>
H. Sun (NAO, CAS), J. Yang (NJU), H. Z. Wu (HUST), X. L. Chen (YNU), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of a new X-ray outburst from the black hole low-mass X-ray
binary GRS 1739-278, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The source exhibited a rapid rise in its 0.5-4 keV flux since June 15th, 2025 and triggered EP-WXT (ID: 01709179036) at 2025-06-19T14:54:11 (UTC, ATel #17238).
A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP was performed automatically around 2 minutes after the trigger, with an exposure time of 1.2 ks. A bright X-ray source, whose position is consistent with GRS 1739-278, was detected by FXT, thus confirming the new outburst of GRS 1739-278. The FXT spectrum can be fitted by an absorbed power-law with a photon index of 2.1 (+/-0.1) and a neutral hydrogen column density of 2.3 (+/-0.1) x 10^22 cm^-2. The derived unabsorbed flux in 0.5-10 keV is 1.8 (+/-0.1) x 10^-9 erg/s/cm^2.
Multi-wavelength follow-up observations are strongly encouraged.
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).
View this GCN Circular online at https://gcn.nasa.gov/circulars/40790.
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TITLE: GCN CIRCULAR
NUMBER: 40789
SUBJECT: GRB 250617B: Nickel telescope optical observations
DATE: 25/06/20 00:49:40 GMT
FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu>
Eli Gendreau-Distler, Gracelynn Jost, William Wu, WeiKang Zheng and
Alex Filippenko (UC Berkeley) report on behalf of the KAIT GRB team:
We observed the field of GRB 250617B (Page et. al, GCN 40760; The
Fermi GBM team, GCN 40763) with the 1-m Nickel telescope located at
Lick observatory, California. Observations were performed in R band
with 600s x 5 exposure time started at 09:46 UT on June 18. We
clearly detected the optical afterglow (Page et. al, GCN 40760,
Moskvitin et. al, GCN 40761, Jelinek et. al, GCN 40762; Kumar et. al,
GCN 40768; Lipunov et. al, GCN 40769; Grossan et. al, GCN 40771;
Ma et. al, GCN 40772; Schneider et. al, GCN 40774; Antier et. al,
GCN 40775; Corcoran et. al, GCN 40776; Turpin et. al, GCN 40777;
Siegel & Page, GCN 40778; Pankov et al., GCN 40783) in our coadd image
with 21.4 +/- 0.1 mag at a mid time of 13.10 hours after the burst.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40789.
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TITLE: GCN CIRCULAR
NUMBER: 40786
SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
DATE: 25/06/19 21:58:33 GMT
FROM: eliza.neights(a)gmail.com
E. Neights (GWU, NASA GSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"The Fermi Gamma-ray Burst Monitor (GBM) trigger 772058337/250619860 at 20:38:52.44 UT
on 19 June 2025, tentatively classified as a GRB, is in fact not due
to a GRB. This trigger is likely due to local particles."
View this GCN Circular online at https://gcn.nasa.gov/circulars/40786.
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TITLE: GCN CIRCULAR
NUMBER: 40785
SUBJECT: GRB 250615A: Kilonova-Catcher optical upper limits
DATE: 25/06/19 21:45:50 GMT
FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com>
D. Turpin (CEA-Saclay/Irfu), R. Hellot, M. Freeberg (KNC), C. Andrade(UMN), M. Pillas (ULiege), M. Tanasan (NARIT), S. Antier (OCA/IJCLAB) on behalf of the GRANDMA/Kilonova-Catcher collaboration:
We observed the field of GRB 250615A (Dichiara et al., GCN 40736) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the TEC160FL telescope operated by M. Freeberg and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+7.6hr.
In our stacked frames, subtracted from the PanSTARRS DR2 template image, we do not detect any optical counterpart inside the Swift/XRT refined position (Goad et al., GCN 40739).
We report our follow-up results in the table below:
+---------------+-------------+---------+---------------------+--------------+
| Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument |
+===============+=============+=========+=====================+==============+
| 7.9 | 6 x 300s | r (AB) | 20.1 (U.L., 5sigma) | TEC160FL |
| 8.1 | 11 x 300s | g (AB) | 20.8 (U.L., 5sigma) | CDK17-AITP |
| 8.5 | 6 x 300s | g (AB) | 20.4 (U.L., 5sigma) | TEC160FL |
| 9.0 | 6 x 300s | i (AB) | 19.2 (U.L., 5sigma) | TEC160FL |
| 9.6 | 11 x 300s | r (AB) | 20.2 (U.L., 5sigma) | CDK17-AITP |
+---------------+-------------+---------+---------------------+--------------+
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan images were calibrated using the PanSTARRS DR1 catalog.
We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
View this GCN Circular online at https://gcn.nasa.gov/circulars/40785.
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TITLE: GCN CIRCULAR
NUMBER: 40783
SUBJECT: GRB 250617B: Assy AZT-20 Optical Observations
DATE: 25/06/19 14:26:12 GMT
FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com>
N. Pankov (HSE, IKI), V. Kim (FAI), A. Pozanenko (IKI), M. Krugov (FAI) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of GRB 250617B (Page et. al, GCN 40760; The Fermi GBM team, GCN 40763) using the 1.5-meter AZT-20 of the Assy-Turgen Observatory. The observations were conducted starting on 2025-06-18 at 18:02:27 UT, i.e. ~0.87 days since the Swift trigger. The series of 53*60 sec images was taken in the r'-filter. We detect the optical afterglow (Page et. al, GCN 40760, Moskvitin et. al, GCN 40761, Jelinek et. al, GCN 40762; Kumar et. al, GCN 40768; Lipunov et. al, GCN 40769; Grossan et. al, GCN 40771; Ma et. al, GCN 40772; Schneider et. al, GCN 40774; Antier et. al, GCN 40775; Corcoran et. al, GCN 40776; Turpin et. al, GCN 40777; Siegel & Page, GCN 40778). The preliminary photometry is given below:
Date UT start t-T0 Exp. Filter OT Err. UL
(mid, days) (n*s) (3sigma)
2025-06-18 18:02:27 0.87577 53*60 r' 21.58 0.04 22.5
The photometry has calibrated using nearby stars from PS1 (at the same coordinates as USNO-B1.0 stars given in Moskvitin et. al, GCN 40761) and has not corrected for the Galactic extinction.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40783.
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TITLE: GCN CIRCULAR
NUMBER: 40782
SUBJECT: GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
DATE: 25/06/18 22:43:10 GMT
FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov>
H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
R. Gupta (GSFC), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC),
T. Sakamoto (AGU), M. H. Siegel (PSU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250612A (trigger #1323295) (Siegel, et al., GCN Circ. 40694).
The BAT ground-calculated position is
RA, Dec = 250.873, -38.948 deg which is
RA(J2000) = 16h 43m 29.6s
Dec(J2000) = -38d 56' 53.9"
with an uncertainty of 4.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 64%.
The BAT mask-weighted light curve showed a complex structure with a duration of about 300 sec.
T90 (15-350 keV) is 274.17 +- 66.54 sec (estimated error including systematics).
The time-averaged spectrum from T-0.58 to T+291.52 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.55 +- 0.43. The fluence in the 15-150 keV band is 1.0 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+0.62 sec in the 15-150 keV band
is 0.9 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
Given the BAT detection at a Galactic latitude of 4.6 deg and the absence of a detected X-ray afterglow in XRT observations ~ 17 hours post-trigger, a Galactic origin of this source remains plausible. If confirmed as a new Galactic transient, it would be designated Swift J1643.6−3854.
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1323295
View this GCN Circular online at https://gcn.nasa.gov/circulars/40782.
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TITLE: GCN CIRCULAR
NUMBER: 40781
SUBJECT: Fermi GRB 250617A: Global MASTER-Net observations report
DATE: 25/06/18 22:15:43 GMT
FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru>
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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250617A ( Fermi GBM team, GCN 40758) errorbox 1 days 17814 sec after notice time and 1 days 17823 sec after trigger time at 2025-06-18 21:06:16 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 66 deg. The sun altitude is -23.6 deg.
The galactic latitude b = -25 deg., longitude l = 107 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2905762
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
104253 | 2025-06-18 21:06:16 | MASTER-Kislovodsk | (23h 40m 51.75s , +35d 31m 02.8s) | C | 60 | 17.7 |
104540 | 2025-06-18 21:11:02 | MASTER-Kislovodsk | (23h 27m 52.38s , +37d 23m 28.9s) | C | 60 | 16.0 |
104624 | 2025-06-18 21:12:26 | MASTER-Kislovodsk | (23h 37m 52.75s , +37d 24m 33.4s) | C | 60 | 16.3 |
104845 | 2025-06-18 21:16:08 | MASTER-Kislovodsk | (23h 46m 54.05s , +37d 24m 18.0s) | C | 60 | 17.3 |
104928 | 2025-06-18 21:17:31 | MASTER-Kislovodsk | (23h 57m 02.84s , +37d 22m 47.1s) | C | 60 | 16.6 |
105010 | 2025-06-18 21:18:53 | MASTER-Kislovodsk | (23h 40m 51.77s , +35d 28m 47.9s) | C | 60 | 17.1 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40781.
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