September 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 39803] EP250905a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 06 Sep '25

06 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41737 SUBJECT: EP250905a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/09/06 11:24:15 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO), Y.H.Cheng (SWIFAR,YNU), R. D. Liang, W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team: The X-ray transient EP250905a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (GCN 41725), with several multi-wavelength follow-up observations (GCN 41727, GCN 41732, GCN 41734). The refined WXT data shows that the flare started at about 2025-09-05 11:07:08 UTC (T0). WXT detected the source from T0 to before the slew with a peak flux of 1.4 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 Galactic hydrogen column density of 7.0 x 10^20 cm^-2 and a photon index of 1.7 (+/-0.4). The derived average unabsorbed 0.5-4 keV flux is around 5.7 (-1.3/+1.6) x 10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 405 s after T0. On-ground analysis of the FXT data found an fading source at R.A. = 4.4504 deg, DEC = 37.4697 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), within the WXT error circle. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 7.0 x 10^20 cm^-2 and a photon index of 2.3(+/-0.4). The derived average unabsorbed 0.5-10 keV flux is around 4.5(-1.0/+1.5) x 10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 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/41737. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39802] EP250905b: Global MASTER-Net observations report
by GCN Circulars 06 Sep '25

06 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41736 SUBJECT: EP250905b: Global MASTER-Net observations report DATE: 25/09/06 08:27:35 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250905b ( EP Team et al., GCN 41735) errorbox 2238 sec after notice time and 46512 sec after trigger time at 2025-09-06 08:13:40 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 43 deg. The sun altitude is -33.0 deg. The galactic latitude b = -28 deg., longitude l = 262 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2985909 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 46542 | 2025-09-06 08:13:40 | MASTER-OAFA | (06h 03m 11.78s , -54d 19m 04.9s) | C | 60 | 19.5 | 46618 | 2025-09-06 08:14:56 | MASTER-OAFA | (06h 03m 19.42s , -54d 18m 45.3s) | C | 60 | 19.5 | 46697 | 2025-09-06 08:16:14 | MASTER-OAFA | (06h 03m 15.86s , -54d 17m 05.6s) | C | 60 | 19.5 | 46771 | 2025-09-06 08:17:29 | MASTER-OAFA | (06h 03m 15.93s , -54d 18m 30.1s) | C | 60 | 19.5 | 46837 | 2025-09-06 08:18:35 | MASTER-OAFA | (06h 03m 15.94s , -54d 18m 27.8s) | C | 60 | 19.5 | 46903 | 2025-09-06 08:19:41 | MASTER-OAFA | (06h 03m 15.97s , -54d 18m 25.3s) | C | 60 | 19.5 | 46981 | 2025-09-06 08:20:59 | MASTER-OAFA | (06h 03m 19.09s , -54d 17m 19.1s) | C | 60 | 19.5 | 47047 | 2025-09-06 08:22:05 | MASTER-OAFA | (06h 03m 19.11s , -54d 17m 16.9s) | C | 60 | 19.5 | 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/41736. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39801] EP250905b: EP-WXT detection of a fast X-ray transient
by GCN Circulars 06 Sep '25

06 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41735 SUBJECT: EP250905b: EP-WXT detection of a fast X-ray transient DATE: 25/09/06 07:35:38 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Liu (THU), Y. H. Cheng (SWIFAR,YNU), X. Mao, G. J. Yang, Y. Liu (NAO,CAS) on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient, designated EP250905b, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2025-09-05T19:18:28 (UTC). The position of the source is R.A. = 90.724 deg, DEC = -54.167 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for nearly 200 seconds. No automated X-ray follow-up observation was performed due to the solar angle constraint. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.4 (+0.6/-0.6). The column density is fixed at the Galactic value of 7.64 x 10^20 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 7 (+4/-2) x 10^-10 erg/s/cm^2. The peak flux is around 2.9 x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations with the Follow-up X-ray Telescope (FXT) on board EP have been scheduled, and further information will be updated when the telemetry data received. 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/41735. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39800] EP250905a: FTW one optical and multiple NIR counterpart candidates
by GCN Circulars 06 Sep '25

06 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41734 SUBJECT: EP250905a: FTW one optical and multiple NIR counterpart candidates DATE: 25/09/06 02:50:51 GMT FROM: xjh(a)andrew.cmu.edu We observed the localization of the x-ray flare EP250905a (GCN 41725), with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands starting at 2025-09-05T20:12:28 UTC (0.38 days after the X-ray flare) for 52 x 180s. In the difference imaging with templates from PS1, we detect no new sources down to r ~ 23.2 and i ~ 23.1. However, our image depth is far deeper (r ~ 24.5, i ~ 24.3, J ~ 23.2). By eye, we compare to PS1 and 2MASS catalogs and present 5 potential new sources within the 20” error circle: | id | ra | dec | mag_J | mag_J_err | mag_r | mag_r_err | | ----------- | ------------- | ------------- | ---- | --- | ----- | ---- | | EP250905a_2 | 00:17:47.9940 | +37:28:19.306 | 21.3 | 0.1 | 22.14 | 0.04 | EP250905a_2 was reported by He et al. (GCN 41732), however in our difference imaging we see no source. In our science image, we note a distinct point source there below the galaxy. We report a noticeably brighter r ~ 22.14 than reported by He et al. (GCN 41732), but there is significant bleed from the nearby galaxy. There also appears to be a faint source at that position in the PS1 template. We note that these following four sources are not detected above our three sigma limit in r or i band photometry, but have clear sources in J. | id | ra | dec | mag_J | mag_J_err | | ----------- | ------------- | ------------- | ---- | ----| | EP250905a_1 | 00:17:47.4836 | +37:28:25.975 | 22.1 | 0.1 | | EP250905a_3 | 00:17:46.8641 | +37:28:16.316 | 21.40 | 0.06 | | EP250905a_4 | 00:17:47.4834 | +37:28:07.901 | 21.9 | 0.1 | | EP250905a_5 | 00:17:47.4630 | +37:28:05.478 | 21.9 | 0.1 | We encourage continued follow-up to determine the variable nature of these sources. The magnitudes are reported in AB and calibrated against the PS1 and 2MASS catalog and not corrected for Galactic extinction. We thank Michael Schmidt from the Wendelstein Observatory staff for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41734. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39799] GRB 250905A: Swift-XRT refined Analysis
by GCN Circulars 06 Sep '25

06 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41733 SUBJECT: GRB 250905A: Swift-XRT refined Analysis DATE: 25/09/06 02:25:05 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 4.7 ks of XRT data for GRB 250905A, from 140 s to 27.9 ks after the trigger. The data comprise 26 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=5.2 (+0.4, -0.3). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.8, -0.6). The best-fitting absorption column is 1.8 (+3.2, -1.2) x 10^21 cm^-2, consistent with the Galactic value of 5.5 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 4.1 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.8 (+3.2, -1.2) x 10^21 cm^-2 Galactic foreground: 5.5 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.9 (+0.8, -0.6) If the light curve continues to decay with a power-law decay index of 5.2, the count rate at T+24 hours will be 2.5 x 10^-14 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-24 (1.3 x 10^-24) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01347265. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41733. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39798] EP250905a: JinShan likely optical counterpart detection
by GCN Circulars 06 Sep '25

06 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41732 SUBJECT: EP250905a: JinShan likely optical counterpart detection DATE: 25/09/06 01:19:57 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> L.B. He, X. Liu, J. An, D. Xu, S.Q. Jiang, Z.P. Zhu (NAOC), S.Y. Fu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of EP250905a detected by Einstein Probe (Cheng et al., GCN 41725), using the 100C telescope of the JinShan project, located at Altay, Xinjiang, China. We obtained 40 x 180 s Sloan i-band frames, starting from 2025-09-05 13:56:23 UT, i.e., 2.74 hrs since the EP trigger. A new source is detected positionally in a known GLADE galaxy (GLADE+ #2980788) via image subtraction, which is within the EP-FXT 20-arcsec error circle , at coordinates R.A. (J2000) = 0:17:48.01 Dec. (J2000) = +37:28:19.44 with an uncertainty of ~ 0.6 arcsec. The source has r ~ 22.9 mag, calibrated with PanSTARRS. We think the source is very likely the counterpart of EP250905a. In this case, the galaxy is the host with a redshfit of z ~ 0.28 from GLADE. Further observations are planned and encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/41732. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39797] IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41731 SUBJECT: IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/09/05 22:22:56 GMT FROM: Erik Blaufuss at University of Maryland, College Park <blaufuss(a)umd.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-09-05 20:08:36.01 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 0.41 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141315_25569816.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-09-05 Time: 20:08:36.01 UT RA: 348.31 (+0.93, -1.09 deg 90% PSF containment) J2000 Dec: 38.87 (+0.78, -0.86 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/41731. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39796] GRB 250904A: Swift-BAT refined analysis
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41730 SUBJECT: GRB 250904A: Swift-BAT refined analysis DATE: 25/09/05 21:28:22 GMT FROM: D. R. Sadaula at NASA GSFC <dev.r.sadaula(a)nasa.gov> D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250904 A (trigger #1347179) (Salvaggio, et al., GCN Circ. 41704). The BAT ground-calculated position is RA, Dec = 84.377, 3.575 deg which is RA(J2000) = 05h 37m 30.5s Dec(J2000) = +03d 34' 29.9" with an uncertainty of 1.0 arcmin (radius, sys+stat, 90% containment). The partial coding was 100%. The BAT light curve showed a complex structure with a duration of about 50 sec. T90 (15-350 keV) is 37.11 +- 13.89 sec (estimated error including systematics). The time-averaged spectrum from T-19.68 to T+54.44 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.40 +- 0.11. The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+5.11 sec in the 15-150 keV band is 1.1 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1347179 View this GCN Circular online at https://gcn.nasa.gov/circulars/41730. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39795] IceCube Alert 250905.84: Global MASTER-Net observations report
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41729 SUBJECT: IceCube Alert 250905.84: Global MASTER-Net observations report DATE: 25/09/05 20:39:22 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the IceCube Alert 250905.84 (trigger No 25569816,23h 15m 48.96s , +38d 16m 19.2s, R=0.51) errorbox 34 sec after notice time and 87 sec after trigger time at 2025-09-05 20:10:03 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 80 deg. The sun altitude is -47.4 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the IceCube Alert 250905.84 errorbox 48 sec after notice time and 101 sec after trigger time at 2025-09-05 20:10:17 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 15 deg. The sun altitude is -38.6 deg. The galactic latitude b = -21 deg., longitude l = 104 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2985645 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 97 | 2025-09-05 20:10:03 | MASTER-SAAO | (23h 13m 56.30s , +37d 51m 11.7s) | C | 20 | 16.2 | 97 | 2025-09-05 20:10:03 | MASTER-SAAO | (23h 11m 44.72s , +38d 07m 09.5s) | C | 20 | 16.4 | 111 | 2025-09-05 20:10:17 | MASTER-Kislovodsk | (23h 14m 08.98s , +38d 35m 46.0s) | P- | 20 | 15.4 | 136 | 2025-09-05 20:10:17 | MASTER-Kislovodsk | (23h 14m 08.98s , +38d 35m 46.1s) | P- | 70 | 16.2 | Coadd 141 | 2025-09-05 20:10:42 | MASTER-SAAO | (23h 13m 56.43s , +37d 51m 17.0s) | C | 30 | 16.4 | 141 | 2025-09-05 20:10:42 | MASTER-SAAO | (23h 11m 44.83s , +38d 07m 15.6s) | C | 30 | 16.7 | 151 | 2025-09-05 20:10:57 | MASTER-Kislovodsk | (23h 14m 08.82s , +38d 35m 44.8s) | P- | 20 | 15.4 | 195 | 2025-09-05 20:11:31 | MASTER-SAAO | (23h 13m 56.59s , +37d 51m 22.5s) | C | 40 | 16.6 | 195 | 2025-09-05 20:11:31 | MASTER-SAAO | (23h 11m 44.98s , +38d 07m 20.6s) | C | 40 | 16.9 | 196 | 2025-09-05 20:11:37 | MASTER-Kislovodsk | (23h 14m 08.65s , +38d 35m 44.0s) | P- | 30 | 15.8 | 252 | 2025-09-05 20:12:27 | MASTER-Kislovodsk | (23h 14m 08.46s , +38d 35m 43.3s) | P- | 40 | 15.8 | 312 | 2025-09-05 20:12:27 | MASTER-Kislovodsk | (23h 14m 08.45s , +38d 35m 43.5s) | P- | 160 | 16.6 | Coadd 259 | 2025-09-05 20:12:30 | MASTER-SAAO | (23h 13m 56.76s , +37d 51m 27.4s) | C | 50 | 16.7 | 259 | 2025-09-05 20:12:30 | MASTER-SAAO | (23h 11m 45.14s , +38d 07m 24.6s) | C | 50 | 17.0 | 317 | 2025-09-05 20:13:27 | MASTER-Kislovodsk | (23h 14m 08.26s , +38d 35m 43.2s) | P- | 50 | 15.8 | 333 | 2025-09-05 20:13:39 | MASTER-SAAO | (23h 13m 56.93s , +37d 51m 32.0s) | C | 60 | 16.8 | 333 | 2025-09-05 20:13:39 | MASTER-SAAO | (23h 11m 45.32s , +38d 07m 27.8s) | C | 60 | 17.1 | 397 | 2025-09-05 20:14:37 | MASTER-Kislovodsk | (23h 14m 08.05s , +38d 35m 43.6s) | P- | 70 | 16.0 | 412 | 2025-09-05 20:14:58 | MASTER-SAAO | (23h 13m 57.13s , +37d 51m 36.8s) | C | 60 | 16.8 | 412 | 2025-09-05 20:14:58 | MASTER-SAAO | (23h 11m 45.54s , +38d 07m 31.7s) | C | 60 | 17.1 | 497 | 2025-09-05 20:16:07 | MASTER-Kislovodsk | (23h 14m 07.75s , +38d 35m 44.0s) | P- | 90 | 16.2 | 612 | 2025-09-05 20:16:07 | MASTER-Kislovodsk | (23h 14m 07.76s , +38d 35m 44.0s) | P- | 320 | 17.0 | Coadd 617 | 2025-09-05 20:17:58 | MASTER-Kislovodsk | (23h 14m 07.43s , +38d 35m 44.9s) | P- | 110 | 16.4 | 753 | 2025-09-05 20:20:09 | MASTER-Kislovodsk | (23h 14m 07.06s , +38d 35m 46.5s) | P- | 120 | 16.4 | 893 | 2025-09-05 20:22:28 | MASTER-Kislovodsk | (23h 14m 06.67s , +38d 35m 47.7s) | P- | 120 | 16.3 | 1013 | 2025-09-05 20:22:28 | MASTER-Kislovodsk | (23h 14m 06.67s , +38d 35m 47.7s) | P- | 360 | 17.0 | Coadd 1035 | 2025-09-05 20:24:51 | MASTER-Kislovodsk | (23h 14m 06.26s , +38d 35m 49.4s) | P- | 120 | 16.4 | 1175 | 2025-09-05 20:27:11 | MASTER-Kislovodsk | (23h 14m 05.86s , +38d 35m 51.3s) | P- | 120 | 16.4 | 1315 | 2025-09-05 20:29:31 | MASTER-Kislovodsk | (23h 14m 05.49s , +38d 35m 53.3s) | P- | 120 | 16.4 | 1456 | 2025-09-05 20:31:52 | MASTER-Kislovodsk | (23h 14m 05.12s , +38d 35m 55.7s) | P- | 120 | 16.4 | 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/41729. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39794] GRB 250905A: Swift/UVOT Upper Limits
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41728 SUBJECT: GRB 250905A: Swift/UVOT Upper Limits DATE: 25/09/05 20:04:34 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates(a)alumni.ucl.ac.uk> S. R. Oates (Lancaster Uni.) and R. Brivio (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250905A 140 s after the BAT trigger (Brivio et al., GCN Circ. 41714). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 41722) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag/3sigUL white (FC) 140 290 147 >21.0 u (FC) 300 405 103 >19.8 v 4973 16058 1082 >20.3 b 5794 5978 181 >20.3 u 5588 27905 1036 >21.1 uvw1 5383 27038 1082 >20.4 uvm2 5178 16867 989 >20.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.054 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41728. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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