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

[vsnet-grb-info 37888] EP250321a: Mondy AZT-33IK Continued Optical Observations
by GCN Circulars 25 Mar '25

25 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39870 SUBJECT: EP250321a: Mondy AZT-33IK Continued Optical Observations DATE: 25/03/25 17:27:37 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We continued optical observations of the field of EP250321a (Hu et. al, GCN 39800; Page et. al, GCN 39811, Hu et. al, GCN 39833) at the redshift of z = 4.368 (Zhu et. al, GCN 39769) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations started on (UT) 2025-03-22 15:35:42, i.e. about 1.4 days since trigger. The optical afterglow (Fu et. al, GCN 39804; Perez-Garcia et. al, GCN 39805; Brivio et. al, GCN 39807; Zhu et. al, GCN 39809; Becerra et. al, GCN 39810; Pérez-Fournon et. al, GCN 39812; Lee et. al, GCN 39815; Han et. al, GCN 39817; Jin et. al, GCN 39822; Zhu et. al, GCN 39827; Gill et. al, GCN 39831; Zheng et. al, GCN 39832; Bochenek & Perley, GCN 39837; Zhu et. al, GCN 39854) is not detected in the stacked images. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err UL(3sigma) (mid, days) (s) 2025-03-22 15:35:42 1.40467 17*120 R n/d n/d 22.3 2025-03-23 16:02:48 2.45336 60*120 R n/d n/d 23.6 The photometry is based on nearby stars of SDSS-DR12 and has not been corrected for the Galactic extinction. SDSS-DR12 RA Dec R(Lupton transformations, 2005) 179.2552 +17.3825 18.123 +/- 0.049 179.2436 +17.3713 18.846 +/- 0.012 View this GCN Circular online at https://gcn.nasa.gov/circulars/39870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37887] Swift follow-up observations of FRB250316A and EP J120944.2+585060
by GCN Circulars 25 Mar '25

25 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39869 SUBJECT: Swift follow-up observations of FRB250316A and EP J120944.2+585060 DATE: 25/03/25 17:26:37 GMT FROM: Eleonora <nora.gsfc(a)gmail.com> E. Troja ( U Rome), Y.-H. Yang ( U Rome), S. Dichiara (PSU), M. E. Kabir (U Rome) and H. Sun (NAO, CAS) report: We reobserved the field of FRB 20250316A (ATel #17081) with Swift starting on 2025-03-23 (~7 days after the FRB) for a total exposure of 10 ks. A blind search does not identify any X-ray source consistent with the CHIME localization (ATel #17086). However, a targeted search at the position of EP J120944.2+585060 (Sun et al., ATel #17100) finds a weak X-ray source at RA, Dec (J2000) = 182.4369, 58.8471 deg with a 90% error radius of 6 arcsec (stat+sys), as derived by xrtcentroid. The detection is significant at the >99.7% confidence level (Kraft, Nousek, and Burrows, 1991). A finder chart can be found at: https://nora.users.roma2.infn.it/FRB250316A.png Based on a preliminary analysis, we infer a count rate of (7 +/- 3)E-4 cts/s which corresponds to an observed flux of (2.4 +/- 1.0)E-14 erg/cm2/s (0.3-10 keV) assuming an absorbed power-law spectrum with a photon index of 2 and NH = 1.4E+20 cm^-2. Our observations are consistent with the reported flux for EP J120944.2+585060 (Sun et al., ATel #17100) and do not show substantial variability. We performed an independent analysis of the first epoch of Swift observations, taken at 12 hrs after the burst (Yang et al., ATel #17101). Using the above XRT position, we derive a 90% upper limit of 7E-4 cts/s, consistent with our reported value. Within the XRT localization, no optical counterpart is visible in the Swift UVOT White images down to >22.3 AB mag We thank the Swift team for scheduling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37886] GRB 250322A: third epoch of NOT optical observations
by GCN Circulars 25 Mar '25

25 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39868 SUBJECT: GRB 250322A: third epoch of NOT optical observations DATE: 25/03/25 17:11:56 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> D. B. Malesani (DAWN/NBI and Radboud), B. Schneider (LAM), A. Martin-Carrillo (UCD), A. M. Kadela (NOT and NBI) report on behalf of a larger collaboration: We secured a third observation of the field of GRB 250322A (Gupta et al., GCN 39835; Tembhurnikar et al., GCN 39849) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. Our observation consisted of 5x600 s in the r-band, with mean time 2025 Mar 24.86 UT (2.19 days after the GRB). This observation reaches a depth comparable to our first epoch (Martin-Carrillo et al., GCN 39842), taken at 4.65 hr after the GRB, unlike our second epoch (Schneider et al., GCN 39863), which suffered from worse seeing. Image subtraction of our third epoch from the first was carried out using HOTPANTS. No residuals are detected in the difference image, down to a limiting magnitude r > 23.8 AB (calibrated against Pan-STARRS). This limit is consistent with, but strengthens, our earlier determination r > 23.2 (Schneider et al., GCN 39863). View this GCN Circular online at https://gcn.nasa.gov/circulars/39868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37885] EP250321a: Xinglong 216 decaying optical observations
by GCN Circulars 25 Mar '25

25 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39822 SUBJECT: EP250321a: Xinglong 216 decaying optical observations DATE: 25/03/21 19:24:45 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Jinlei-Zhang (NAOC), Pengliang-Du (NAOC), Feng-Xiao(NAOC),Zhou-Fan (NAOC), Hong-Wu (NAOC) We performed optical observations of the field of a fast X-Ray transient EP250321a (Hu et al., GCN 39800) in the Free filter using 2.16-m telescope located at Xinglong, Hebei, China. In the band a 600 s exposures were taken , with a median observation time of 2025-03-02T20:32:28. No uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (Li et al., GCN 36405), down to 3-sigma limiting magnitudes of g ~ 20.5, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/39822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37884] GRB 250322A: Swift-BAT refined analysis
by GCN Circulars 25 Mar '25

25 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39867 SUBJECT: GRB 250322A: Swift-BAT refined analysis DATE: 25/03/25 14:56:16 GMT FROM: Rahul Gupta at NASA GSFC <rahulbhu.c157(a)gmail.com> D. Sadaula (GSFC/UMBC), 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), D. M. Palmer (LANL), T. Parsotan (GSFC), 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 250322A (trigger #1297832) (Gupta, et al., GCN Circ. 39835). The BAT ground-calculated position is RA, Dec = 106.775, 7.197 deg which is RA(J2000) = 07h 07m 06.1s Dec(J2000) = +07d 11' 47.8" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted BAT light curve shows multi-peak emission. T90 (15-350 keV) is 0.62 +- 0.05 sec (estimated error including systematics). The time-averaged spectrum from T+0.00 to T+0.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.65 +- 0.19. The fluence in the 15-150 keV band is 1.5 +- 0.2 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.16 sec in the 15-150 keV band is 1.4 +- 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/1297832 View this GCN Circular online at https://gcn.nasa.gov/circulars/39867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37883] The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
by GCN Circulars 25 Mar '25

25 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39866 SUBJECT: The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source DATE: 25/03/25 04:12:20 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Y. Lian (NAO, CAS), J. Q. Peng (IHEP,CAS), X. Fan, S. E. Xu (WHU), C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: Based on the telemetry data analysis, the EP-WXT trigger 01709133021 (designated as EP250324a) at the time of 2025-03-24T09:38:23(UTC), is not a real source. View this GCN Circular online at https://gcn.nasa.gov/circulars/39866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37882] GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39865 SUBJECT: GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit DATE: 25/03/24 17:11:05 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Schmalz (KIAM), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 250321B (Schanne et. al, GCN 39818; Capalbi et. al, GCN 39856) in the Clear light with the 0.36-meter RC-36 telescope of the ISON-Kitab observatory. The observations started on (UT) 2025-03-21 17:31:49, i.e. about 0.59 days since trigger. We do not detect an optical afterglow candidate in the stacked image. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err UL(3sigma) (mid, days) (s) 2025-03-21 17:31:49 0.59330 38*60 Clear n/d n/d 17.0 Ref. stars RA Dec r 169.5809 +39.4176 13.063 169.7213 +39.4809 13.341 The photometry is based on nearby stars of SDSS-DR12 (r-magnitudes) and has not been corrected for the Galactic extinction. Our result is consistent with non-detections of an optical (Ducoin et. al, GCN 39840) and an X-Ray (Capalbi et. al, GCN 39856) counterpart. View this GCN Circular online at https://gcn.nasa.gov/circulars/39865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37881] FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39864 SUBJECT: FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060 DATE: 25/03/24 17:09:34 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> S.Q. Jiang, Z.P. Zhu, X. Liu, J. An (NAOC), S.Y. Fu (HUST), D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), A. M. Kadela, A. A. Djupvik (NOT) report on behalf of a large collaboration: We observed the field of the X-ray candidate EP J120944.2+585060 (Sun et al., GCN 39834; ATel #17100) possibly associated with FRB 250316A (Ng et al., ATel #17081; Leung et al., ATel #17086), using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. The mid time of the observations is 01:00:20.3 UTC on 2025-03-23, and a series of 300 s frames were obtained in the Sloan r-band. No new optical source is detected in the stacked image within the EP/FXT error region by subtracting the stacked image against the Legacy Survey template. The 5-sigma limiting magnitude of the observations is r > 24.0, calibrated with Legacy Survey DR 10 and not corrected for Galactic extinction. The non-detection of an optical counterpart is consistent with previous reports by Becerra et al. (ATel #17082; GCN 39843; GCN 39853), Niino et al. (ATel #17084), Hashimoto et al. (ATel #17095), Yang et al. (ATel #17101), Aryan et al. (GCN 39839) and Pereyra et al. (GCN 39858). View this GCN Circular online at https://gcn.nasa.gov/circulars/39864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37880] GRB 250322A: further NOT optical observations
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39863 SUBJECT: GRB 250322A: further NOT optical observations DATE: 25/03/24 16:33:39 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> B. Schneider (LAM), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. M. Kadela (NOT and NBI) report on behalf of a larger collaboration: We secured a second observation of the field of GRB 250322A (Gupta et al., GCN 39835; Tembhurnikar et al., GCN 39849) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. Our observation consisted of 7x360 s in the r-band, with mean time 2025 Mar 23.88 UT (29.7 hr after the GRB). Unfortunately, the delivered seeing is worse than in our first epoch (Martin-Carrillo et al., GCN 39842), taken 4.65 hr after the GRB (1.5 vs 1.0"). The galaxy noted by Martin-Carrillo et al. (GCN 39842), Becerra et al. (GCN 39844, 39845), Kilpatrick & Fong (GCN 39846), and Fong et al. (GCN 39852) is detected in our second epoch. Image subtraction was carried out using Hotpants. No residuals are detected in the difference image, corresponding to a limiting magnitude of r > 23.2 (AB). For the galaxy, we measure (in our first epoch) r = 22.04 +/- 0.12 (AB), calibrated against nearby Pan-STARRS point-like objects. Considering a 2.5”-radius XRT error circle (Goad et al., GCN 39841; Perri et al., 39855), we estimate a chance association probability of 2%, which provides moderate evidence for a physical association with the GRB. View this GCN Circular online at https://gcn.nasa.gov/circulars/39863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37879] EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39862 SUBJECT: EP-WXT trigger 01709133021: Optical upper limit through Kinder observations DATE: 25/03/24 14:56:49 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> C.-H. Lai, Y.-H. Lee, A. Aryan, T.-W. Chen, Y. J. Yang (all NCU), S. Yang (HNAS), A. K. H. Kong (NTHU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), W.-J. Hou, H.-Y. Hsiao, C.-C. Ngeow, Y.-C. Pan, A. Sankar. K, M.-H. Lee, C.-S. Lin, H.-C. Lin, J.-K. Guo (all NCU), L. L. Fan, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the Einstein Probe (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics) discovered X-ray transient with WXT trigger ID 01709133021 using the 1m LOT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2024, arXiv:2406.09270). The first LOT epoch of observations in the r band started at 11:29 UT on the 24th of March 2025 (MJD = 60758.4017), ~1.84 hr post the EP-WXT trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked frames, we do not detect any potential uncataloged optical afterglow counterpart candidate within EP-WXT localization circle with a radius of ~3 arcminutes. Moreover, we used the Kinder pipeline (Yang et al. 2021, A&A, 646, 22) to subtract the stacked images using the templates from Pan-STARRS1 (Chambers et al. 2016 arXiv:1612.05560). We also utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, 62) to perform template subtraction using the "sfft" (Hu, 2022, ApJ, 936, 157) and "hotpants" (Becker A., 2015, ascl.soft. ascl:1504.004) algorithms. We found no evidence of any prominent optical counterpart candidate in the difference images as well. We further employed AutoPhOT to perform PSF photometry on the combined frames. The details of the observation and 3-sigma upper limits (in the AB system) were as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | tmid-t0 (hr)| Exposure (s) | Magnitude | Average Seeing | Median Airmass LOT | r | 60758.4017 | 1.84 | 2.65 | 300 * 12 | >22.77 | 1".15 | 1.56 The non-detection of any optical afterglow counterpart candidate is consistent with the previous report by Ducoin et al. (GCN 39860). The presented upper limit was calibrated using the field stars from the SDSS catalog and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_r = 0.05 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). We are grateful to the EP team for providing useful communications through GCN Notices. View this GCN Circular online at https://gcn.nasa.gov/circulars/39862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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