September 2024 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 35510] LIGO/Virgo S240919bn: GOTO optical upper limits
by GCN Circulars 23 Sep '24

23 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37590 SUBJECT: LIGO/Virgo S240919bn: GOTO optical upper limits DATE: 24/09/23 16:54:48 GMT FROM: soheb.mandhai(a)manchester.ac.uk S. Mandhai, A. Kumar, D. O'Neill, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley; M. J. Dyer; J. Lyman; K. Ulaczyk; F. Jimenez-Ibarra; D. Steeghs; D. K. Galloway; V. Dhillon; P. O'Brien; K. Noysena; R. Kotak; R. P. Breton; L. K. Nuttall; E. Palle and D. Pollacco report on behalf of the GOTO collaboration: The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022; Dyer et al 2024) serendipitously covered a part of the localisation region of the GW trigger S240919bn (LIGO Scientific Collaboration, GCN 37552, GCN 37559) in survey mode on 2024-09-20 from 02:03:57 UT. The observations covered the location of 6 out of the 10 X-ray sources detected by the Swift XRT (Page et al. GCN 37589). Each observation consisted of 4x45s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. No new candidate optical counterparts are identified in the difference images at the locations of the below-mentioned X-ray sources detected by the Swift-XRT (Page et al. GCN 37589). The upper limits are as follows: Event Date UT t-t0 (hours) 3-sigma UL (mag) ======================================================================================== Rank 3 sources ------------------- S240919bn_X10 2024-09-20 02:06:52 19.85 >19.26 S240919bn_X11 2024-09-20 02:03:57 19.80 >19.23 Rank 4 sources ------------------- S240919bn_X5 2024-09-20 02:03:57 19.80 >19.24 S240919bn_X6 2024-09-20 02:03:57 19.80 >19.24 S240919bn_X7 2024-09-20 02:06:52 19.85 >19.20 S240919bn_X2 2024-09-20 02:06:52 19.85 A source in the difference images but pre-gw event detections. Not related to S240919bn. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and were 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 and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/37590. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35509] LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources
by GCN Circulars 23 Sep '24

23 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37589 SUBJECT: LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources DATE: 24/09/23 12:41:39 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> K.L. Page (U. Leicester), P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J. Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page (UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team: Swift has carried out 217 observations of the LVC error region for the GW trigger S240919bn convolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9), using 139 fields from the 'BAYESTAR' GW localisation map and 78 fields from the 'ligo-skymap-from-samples' GW localisation map. As these are 3D skymaps, galaxy distances were taken into account in selecting which ones to observe. The observations span from 3.2 ks to 92 ks after the LVC trigger, and the XRT has covered 6.6 deg^2 on the sky (corrected for overlaps). This covers 55% of the probability in the 'ligo-skymap-from-samples' (version ligo-skymap-from-samples.fits.gz) skymap, and 55% after convolving with the 2MPZ galaxy catalogue, as described by Evans et al. (2016, MNRAS, 462, 1591). Using the earlier 'BAYESTAR' (version BAYESTAR.fits.gz) skymap our observations cover 46% of the probability (45% when convolved). We have detected 10 X-ray sources. Each source is assigned a rank of 1-4 which describes how likely it is to be related to the GW trigger, with 1 being the most likely and 4 being the least likely. The ranks are described at https://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 * 6 sources of rank 3 * 4 sources of rank 4 RANK 3 sources ============== These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger. | Source ID | RA | Dec | Err90 | | S240919bn_X1 | 10h 26m 54.08s | -79d 50' 18.5" | 5.3" | | S240919bn_X3 | 10h 25m 18.06s | -79d 58' 45.0" | 43.1" | | S240919bn_X4 | 10h 37m 19.30s | -79d 30' 10.3" | 6.9" | | S240919bn_X9 | 10h 24m 36.66s | -79d 58' 08.5" | 7.3" | | S240919bn_X10 | 03h 33m 11.93s | +37d 44' 32.6" | 8.3" | | S240919bn_X11 | 03h 35m 10.00s | +36d 46' 56.8" | 41.6" | RANK 4 sources ============== These are catalogued X-ray sources, showing no signs of outburst compared to previous observations, so they are not likely to be related to the GW trigger. | Source ID | RA | Dec | Err90 | | S240919bn_X2 | 03h 33m 18.93s | +37d 18' 10.8" | 4.5" | | S240919bn_X5 | 03h 34m 17.94s | +35d 46' 04.0" | 8.2" | | S240919bn_X6 | 03h 33m 10.29s | +36d 33' 47.7" | 7.9" | | S240919bn_X7 | 03h 34m 29.02s | +37d 14' 55.3" | 6.4" | For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2, and photon index (Gamma)=1.7, unless otherwise stated. The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S240919bn This circular is an official product of the Swift XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/37589. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35508] GRB 240918B: AstroSat CZTI detection
by GCN Circulars 23 Sep '24

23 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37588 SUBJECT: GRB 240918B: AstroSat CZTI detection DATE: 24/09/23 00:21:43 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> J. Joshi (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240918B which was also detected by Fermi/GBM (Fermi-GBM Team, GCN Circ. 37558) and INTEGRAL SPI-ACS (Pawar et al., GCN Circ. 37560). The source was detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2024-09-18 20:57:00.50 UTC. The measured peak count rate associated with the burst is 123 (+35, -30) counts/s above the background in the combined data of all quadrants, with a total of 339 (+116, -102) counts. The local mean background count rate was 316 (+3, -5) counts/s. Using cumulative rates, we measure a T90 of 4 (+2, -1) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2024-09-18 20:57:01.32 UTC. The measured peak count rate associated with the burst is 295 (+60, -56) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1092 (+181, -204) counts. The local mean background count rate was 1049 (+6, -6) counts/s. We measure a T90 of 6 (+1, -2) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/37588. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35507] LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
by GCN Circulars 22 Sep '24

22 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37587 SUBJECT: LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate DATE: 24/09/22 14:59:56 GMT FROM: Laura Silenzi <laura.silenzi(a)unicam.it> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S240922df during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2024-09-22 14:21:06.388 UTC (GPS time: 1411050084.388). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S240922df is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.4e-24 Hz, or about one in 1e16 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S240922df The classification of the GW signal, in order of descending probability, is BBH (>99%), NSBH (<1%), BNS (<1%), or Terrestrial (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 4%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 31 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 487 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1169 +/- 306 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/37587. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35506] LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
by GCN Circulars 21 Sep '24

21 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37586 SUBJECT: LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate DATE: 24/09/21 21:17:59 GMT FROM: Dripta Bhattacharjee <dripta.bhattacharjee(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S240921cw during real-time processing of data from LIGO Livingston Observatory (L1) and Virgo Observatory (V1) at 2024-09-21 20:18:35.792 UTC (GPS time: 1410985133.792). The candidate was found by the GstLAL [1] analysis pipeline. S240921cw is an event of interest because its false alarm rate, as estimated by the online analysis, is 8e-10 Hz, or about one in 39 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S240921cw The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [3], distributed via GCN notice about 26 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 5012 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1149 +/- 439 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/37586. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35505] EP240919a: EP-FXT follow-up observation update
by GCN Circulars 21 Sep '24

21 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37585 SUBJECT: EP240919a: EP-FXT follow-up observation update DATE: 24/09/21 12:26:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang (PMO, CAS), M. J. Liu, H. Q. Cheng, X. Pan, X. P. Xu, H. N. Yang(NAOC, CAS), Z. J. Zhang (HKU), C. Y. Dai (NJU), C. X. Zhang (HUST), C. C. Jin, H. W. Pan, Z. X. Ling, W. M. Yuan, Y. Liu, C. Zhang, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. Sun, W. X. Wang, Y. L. Wang, Y. F. Xu, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F. Zhao, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team We have reported the detection of the fast X-ray transient EP240919a by the Einstein Probe (EP) mission (Liang et al. GCN 37561). An automonous follow-up observation with the EP-FXT was triggered by the onboard processing and triggering system of EP, starting at 2024-09-19T14:57:50 (UTC), 4 minutes after the onboard triggering. An uncatalogued X-ray source is clearly detected, at R.A. = 334.2790 deg, DEC = -9.7361 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The source position is consistent with that of the WXT transient within the uncertainties. The EP-FXT light curve shows a fast decline and the flux decreased to around 1.0 x 10^(-12) erg/s/cm^2 within about 400 s. The average 0.5-10 keV spectrum can be fitted with an absorbed power-law with a photon index of 2.0(+0.4/-0.4) (with the column density fixed at the Galactic value of 5.4 x 10^20 cm^-2). The absorbed average flux in 0.5-10 keV is 5.8(+2.2/-1.4) x 10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Further follow-up observations are encouraged to identify the nature of this X-ray transient. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard 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/37585. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35504] EP240913A/GRB 240913C: AbAO optical upper limit
by GCN Circulars 21 Sep '24

21 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37584 SUBJECT: EP240913A/GRB 240913C: AbAO optical upper limit DATE: 24/09/21 10:33:25 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> S. Belkin (HSE, IKI), R. Ya. Inasaridze (AbAO), A. Pozanenko (IKI), N. Pankov (HSE, IKI) report on behalf of GRB-IKI-FuN: We observed the field of EP240913A/GRB 240913C (Li et al., GCN 37492; Yin et al., GCN 37493; Dasgupta et al., GCN 37505; Bissaldi et al., GCN 37509; Pawar et al., GCN 37510) using the 70-cm AS-32 telescope at the Abastumani Observatory (AbAO) in the R-filter, starting on 2024-09-14 at 23:44:17 (UT). We did not detect the optical counterpart in the stacked image within the Swift-XRT error circle (Jiang et al., GCN 37497), consistent with reports from Asquini et al., GCN 37499; Zhu et al., GCNs 37500, 37501; Zheng et al., GCN 37511; Schneider et al., GCN 37515; Lipunov et al., GCN 37521. Preliminary photometry is as follows: Date UT Start t-T0 (days) Filter Exposure (s) OT Err UL (3σ) 2024-09-14 23:44:17 1.53211 R 113×60 n/d n/d 22.2 The magnitudes were calibrated using nearby USNO-B1.0 stars: RA: 01:06:52.7994912, DEC: +16:43:24.121128, R2: 15.96 RA: 01:07:11.4427176, DEC: +16:49:54.951564, R2: 17.09 View this GCN Circular online at https://gcn.nasa.gov/circulars/37584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35503] EP240919a / GRB 240919A: Mondy optical upper limit
by GCN Circulars 21 Sep '24

21 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37583 SUBJECT: EP240919a / GRB 240919A: Mondy optical upper limit DATE: 24/09/21 10:30:10 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> S. Belkin (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI), N. Pankov (HSE, IKI) report on behalf of GRB-IKI-FuN: We observed the field of EP240919a (Liang et al., GCN 37561) which is also confirmed as GRB 240919A (Liang et al., GCN 37563; Rodi et al., GCN 37572; Wang et al., GCN 37574) using the AZT-33IK telescope of Mondy Observatory in R-filter, starting on 2024-09-20 (UT) 14:33:23. We did not detect the optical counterpart. Preliminary photometry is the following: Date UT Start t-T0 (days) Filter Exposure (s) OT Err UL (3σ) 2024-09-20 14:33:23 1.01091 R 30*120 n/d n/d 22.5 The magnitudes were calibrated using nearby USNO-B1.0 stars: RA DEC R2 22:16:57.1780584 -09:42:25.963092 15.91 22:17:14.9879832 -09:45:26.931528 17.1 View this GCN Circular online at https://gcn.nasa.gov/circulars/37583. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35502] EP240913a/GRB 240913C: 1.6m Mephisto observations
by GCN Circulars 21 Sep '24

21 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37582 SUBJECT: EP240913a/GRB 240913C: 1.6m Mephisto observations DATE: 24/09/21 03:16:25 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Xingzhu Zou, Xiangkun Liu, Yangwei Zhang, Xin Chang, Yaosong Yu, Jinghua Zhang, Yuan Fang, Guowang Du, Yu Pan, Xinlei Chen, Brajesh Kumar, Yuanpei Yang, Xinzhong Er and Xiaowei Liu (SWIFAR, YNU) report on behalf of Mephisto Team: We observed the fast X-ray transient EP240913a (Li et al., GCN 37492, which has been proposed to be a GRB event by Yin et al., GCN 37493) with 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Multiple frames in ugi and vrz bands were simultaneously acquired on 2024-09-14 starting from 14:35:17 (~26.9 hrs after EP T0). In the co-added frames, no evidence of any new uncataloged optical source was detected within the WXT error circle of 2.5 arcmin reported by Li et al. (GCN 37492). Existing sources within this error circle exhibited no significant optical enhancement. The table below provides details of the observations and the measured 3-sigma upper limits on co-added frames (in the AB magnitude system) taken with Mephisto. This non-detection result of the transient is in agreement with the previous circulars (Asquini et al., GCN 37499, Zhu et al., GCN 37500, 37501, Zheng et al., 37511, Schneider et al., GCN 37515, Lipunov et al., GCN 37521). Time-start Time-end Filter Exposure U.L.(AB) 14:35:17 14:44:46 u 180s*3 21.29 14:46:15 14:52:29 v 180s*2 20.87 14:35:18 14:44:45 g 50s*9 21.90 14:46:16 14:52:26 r 50s*6 21.42 14:35:17 14:44:48 i 79s*6 21.25 14:49:30 14:52:28 z 79s*4 19.52 ------------------------------------------------------------------------------------------------------ Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------------ View this GCN Circular online at https://gcn.nasa.gov/circulars/37582. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 35501] EP240918a: SVOM/VT upper limit
by GCN Circulars 20 Sep '24

20 Sep '24

TITLE: GCN CIRCULAR NUMBER: 37581 SUBJECT: EP240918a: SVOM/VT upper limit DATE: 24/09/20 22:22:03 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> SVOM/VT commissioning team: Y. L.Qiu, L. P. Xin, H. L. Li, C. Wu, X. H. Han, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM) and Palmerio, J. (CEA). SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Jean-Luc Atteia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV) report on behalf of the SVOM team: During the commissioning phase of SVOM mission, we observed the field of EP240918a (Zhang et al., GCN 37541；GCN 37554) with SVOM/VT telescope in ToO mode. The observation started at 2024-09-19T14:11:29 UT, about 26.9 hours after the burst, and the total exposure time was 3820 seconds. VT made the observations with two channels simultaneously, VT_B (400nm-650nm) and VT_R (650nm-1000nm). No any new optical source was detected within the error circle of EP/FXT (Zhang et al., GCN 37541) down to the 3 sigma upper limit of VT_B=24.0 mag and VT_R=23.6 mag in AB magnitude. The non-detection is consistent with the reports (Wang et al., GCN 37544, Kong et al., GCN 37545, Sun et al., GCN 37546, Fu et al., GCN 37547, Lipunov et al., GCN 37548, Zhang et al., GCN 37568). Second follow-up was performed started at 2024-09-20T11:14:05 UT, about 48 hours after the trigger. No any new optical source was detected with the similar upper limit. 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 is an optical telescope on board SVOM with an aperture of 44 cm, designed to automatically follow the Eclairs triggers. It has two channels: VT_B and VT_R, covering wavelengths from 400 nm to 650 nm and 650 nm to 1000 nm, respectively. The two bands are observed simultaneously. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/37581. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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