//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27797 SUBJECT: GRB 200524A: Fermi-LAT detection DATE: 20/05/24 14:49:12 GMT FROM: Masanori Ohno at Hiroshima University F. Fana Dirirsa (Univ. of Johannesburg), M. Axelsson (KTH & Stockholm Univ.), M. Ohno (Hiroshima Univ.), F. Piron (CNRS/IN2P3/LUPM) and F. Longo (University and INFN, Trieste) report on behalf of the Fermi-LAT Collaboration: On May 24, 2020, Fermi-LAT detected high-energy emission from GRB 200524A, which was also detected by Fermi-GBM (trigger 611989445). At the time of the trigger (T0 = 05:04:00.36 UT) Fermi-LAT was passing through the SAA, and observations started at roughly T0+110 seconds. The GRB is detected at high energy (>100 MeV) by Fermi-LAT at a location of: RA, Dec = 212.8, 61.0 (degrees, J2000) with an error radius of 0.2 deg (90% containment, statistical error only). This was ~25 deg from the LAT boresight when observations started (T0+110s), and is ~3 deg from the GBM final ground position. The photon flux above 100 MeV in the time interval 110-900 s after the GBM trigger is 2.2e-06 +/- 0.8e-06 ph/cm2/s. The estimated photon index above 100 MeV is -1.7 +/ - 0.2. The highest-energy photon is a 9.2 GeV event which is observed 748 seconds after the GBM trigger. After ~T0+900s, the GRB location moved outside the LAT FoV. A Swift ToO has been approved for this burst. The Fermi-LAT point of contact for this burst is Feraol Fana Dirirsa (fdirirsa@uj.ac.za ). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27798 SUBJECT: GRB 200524A: Swift ToO observations DATE: 20/05/24 15:15:41 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/LAT GRB 200524A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021001 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/LAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27799 SUBJECT: ZTF Discovery of ZTF20abbiixp: The Likely Optical Afterglow to GRB 200524A DATE: 20/05/24 18:47:58 GMT FROM: Anna Ho at Caltech Anna Y. Q. Ho, Yuhan Yao (Caltech), Daniel A. Perley (LJMU) report on behalf of the Zwicky Transient Facility collaboration: The Zwicky Transient Facility (ZTF, Bellm et al. 2019, Graham et al. 2019) discovered ZTF20abbiixp, a fast transient at 14h12m10.33s +60d54m19.0s (J2000) 213.043037 +60.905288 (J2000) as part of the ZTF Uniform Depth Survey (Goldstein et al. in prep). ZTF20abbiixp was first detected at r~17.4 mag on UT 2020-05-24T06:52:07 and faded by 0.3 mag over the next 30 minutes, with a total of four observations showing continuous fading. The last non-detection was 24 hours prior (2020-05-23T06:43:03) with a limiting magnitude of r>20.4 mag. There is no counterpart in ZTF reference images down to a limiting magnitude of r>22.90. We searched the GCN archive and determined that ZTF20abbiixp is in the error circle of GRB 200524A, which was detected by Fermi-GBM and Fermi-LAT (GCN 27797). The position of ZTF20abbiixp is 0.151 degrees offset from the LAT position, within the 0.2 degree error radius (90% containment). The time of GRB 200524A was 1.802 hours prior to the first detection of ZTF20abbiixp. We conclude that ZTF20abbiixp is very likely to be the GRB afterglow. Follow-up observations are highly encouraged. ZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL #11266), and includes IPAC; WIS, Israel; OKC, Sweden; JSI/UMd, USA; UW,USA; DESY, Germany; NRC, Taiwan; UW Milwaukee, USA and LANL USA. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. Alert distribution service provided by DIRAC@UW. Alert filtering is being undertaken by the GROWTH marshal system, supported by NSF PIRE grant 1545949. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27800 SUBJECT: GRB 200524A: GROWTH-India confirmation of optical afterglow DATE: 20/05/24 19:58:19 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar, V. Bhalerao(IITB), G. C. Anupama, S. Barway, U. Stanzin (IIA) report on behalf of the GROWTH-India collaboration: We followed up GRB 200524A (F. F. Dirirsa et al., GCN 27797, A. Ho et al., GCN 27799) with 0.7m GROWTH-India telescope. We obtained 600-sec exposures in SDSS g, r, i filters starting at UT 2020-05-24T10:41:57 (~5.6 hrs after the burst). We detect a faint transient with magnitudes r = 20.56 +- 0.14 and i = 20.59 +- 0.28 (calibrated against PanSTARRs PS1 data release, Flewelling et al., 2018). The source position matches with the likely afterglow candidate by A. Ho et al. (GCN 27799). The fading rate is approximately 3 magnitudes in four hours, consistent with the fading rate reported in the ZTF GCN. We hereby, confirm ZTF20abbiixp as the afterglow of GRB 200524A. We obtained the following photometric results:- ------------------------------------------------------------------ JD(Start) | T-T0(hrs) | Filter | Mag | ------------------------------------------------------------------ 2458993.946 | 5.64 | g | > 21.01 (5-sigma) 2458993.954 | 5.83 | r | 20.56 +/- 0.14 2458993.962 | 6.02 | i | 20.59 +/- 0.28 ------------------------------------------------------------------ Given the fast fading, we encourage the followup of the source. The magnitudes are not corrected for galactic extinction. The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). [GCN OPS NOTE(24may20): Please see Circular 27804 for a correction to this Circular.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27801 SUBJECT: Fermi GRB 200524A: Global MASTER-Net observations report DATE: 20/05/24 20:45:10 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 200524A ( F. Fana Dirirsa et al., GCN 27797) errorbox 74 sec after notice time and 111 sec after trigger time at 2020-05-24 05:05:51 UT, with upper limit up to 17.9 mag. Observations started at twilight. The observations began at zenith distance = 67 deg. The sun altitude is -13.1 deg. MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 200524A errorbox 47446 sec after notice time and 47483 sec after trigger time at 2020-05-24 18:15:23 UT, with upper limit up to 18.9 mag. Observations started at twilight. The observations began at zenith distance = 22 deg. The sun altitude is -10.0 deg. The galactic latitude b = 53 deg., longitude l = 110 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1364553 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 121 | 2020-05-24 05:05:51 | MASTER-IAC | (13h 54m 44.48s , +64d 23m 18.5s) | P| | 20 | 16.4 | 121 | 2020-05-24 05:05:51 | MASTER-IAC | (13h 52m 51.72s , +64d 28m 46.4s) | P- | 20 | 16.2 | 202 | 2020-05-24 05:07:06 | MASTER-IAC | (14h 05m 35.11s , +64d 25m 10.2s) | P| | 30 | 16.5 | 262 | 2020-05-24 05:07:06 | MASTER-IAC | (14h 05m 35.11s , +64d 25m 10.3s) | P| | 150 | 17.4 | Coadd 447 | 2020-05-24 05:07:06 | MASTER-IAC | (14h 05m 35.11s , +64d 25m 10.2s) | P| | 520 | 17.5 | Coadd 202 | 2020-05-24 05:07:06 | MASTER-IAC | (14h 03m 42.26s , +64d 30m 39.9s) | P- | 30 | 16.6 | 262 | 2020-05-24 05:07:06 | MASTER-IAC | (14h 03m 42.26s , +64d 30m 39.9s) | P- | 150 | 17.7 | Coadd 447 | 2020-05-24 05:07:06 | MASTER-IAC | (14h 03m 42.26s , +64d 30m 39.9s) | P- | 520 | 17.9 | Coadd 298 | 2020-05-24 05:08:33 | MASTER-IAC | (14h 05m 41.22s , +64d 25m 34.8s) | P| | 50 | 16.8 | 298 | 2020-05-24 05:08:33 | MASTER-IAC | (14h 03m 48.47s , +64d 31m 05.3s) | P- | 50 | 17.0 | 417 | 2020-05-24 05:10:22 | MASTER-IAC | (14h 05m 37.30s , +64d 26m 44.3s) | P| | 70 | 16.7 | 417 | 2020-05-24 05:10:22 | MASTER-IAC | (14h 03m 44.58s , +64d 32m 15.1s) | P- | 70 | 17.0 | 555 | 2020-05-24 05:12:30 | MASTER-IAC | (14h 05m 37.10s , +64d 25m 14.7s) | P| | 90 | 16.7 | 695 | 2020-05-24 05:12:30 | MASTER-IAC | (14h 05m 37.10s , +64d 25m 14.7s) | P| | 370 | 17.2 | Coadd 555 | 2020-05-24 05:12:30 | MASTER-IAC | (14h 03m 44.50s , +64d 30m 45.6s) | P- | 90 | 17.0 | 695 | 2020-05-24 05:12:30 | MASTER-IAC | (14h 03m 44.49s , +64d 30m 45.6s) | P- | 370 | 17.7 | Coadd 720 | 2020-05-24 05:15:00 | MASTER-IAC | (14h 05m 40.33s , +64d 26m 43.7s) | P| | 120 | 16.6 | 720 | 2020-05-24 05:15:00 | MASTER-IAC | (14h 03m 47.66s , +64d 32m 14.6s) | P- | 120 | 17.0 | 922 | 2020-05-24 05:18:02 | MASTER-IAC | (14h 05m 33.40s , +64d 26m 06.3s) | P| | 160 | 16.4 | 922 | 2020-05-24 05:18:02 | MASTER-IAC | (14h 03m 40.77s , +64d 31m 37.6s) | P- | 160 | 16.6 | 1151 | 2020-05-24 05:21:41 | MASTER-IAC | (14h 05m 33.93s , +64d 27m 05.4s) | P| | 180 | 15.8 | 1151 | 2020-05-24 05:21:41 | MASTER-IAC | (14h 03m 41.21s , +64d 32m 36.9s) | P- | 180 | 16.4 | 1331 | 2020-05-24 05:21:41 | MASTER-IAC | (14h 03m 41.17s , +64d 32m 36.9s) | P- | 540 | 16.5 | Coadd 1391 | 2020-05-24 05:25:41 | MASTER-IAC | (14h 05m 40.44s , +64d 26m 04.0s) | P| | 180 | 15.3 | 1391 | 2020-05-24 05:25:41 | MASTER-IAC | (14h 03m 47.80s , +64d 31m 35.5s) | P- | 180 | 15.8 | 1629 | 2020-05-24 05:29:39 | MASTER-IAC | (14h 03m 42.61s , +64d 30m 34.8s) | P- | 180 | 15.5 | 47513 | 2020-05-24 18:15:23 | MASTER-Tavrida | (14h 04m 04.92s , +62d 01m 07.4s) | C | 60 | 17.4 | 47594 | 2020-05-24 18:16:44 | MASTER-Tavrida | (13h 50m 59.78s , +64d 00m 37.7s) | C | 60 | 17.6 | 47675 | 2020-05-24 18:18:05 | MASTER-Tavrida | (13h 29m 49.44s , +62d 00m 37.3s) | C | 60 | 17.6 | 47756 | 2020-05-24 18:19:25 | MASTER-Tavrida | (13h 44m 19.15s , +60d 01m 24.6s) | C | 60 | 17.8 | 47836 | 2020-05-24 18:20:46 | MASTER-Tavrida | (14h 03m 58.14s , +62d 02m 08.5s) | C | 60 | 17.8 | 48129 | 2020-05-24 18:25:38 | MASTER-Tavrida | (14h 18m 44.20s , +62d 08m 50.8s) | C | 60 | 18.1 | 48209 | 2020-05-24 18:26:59 | MASTER-Tavrida | (13h 48m 27.80s , +64d 10m 01.2s) | C | 60 | 18.3 | 48290 | 2020-05-24 18:28:19 | MASTER-Tavrida | (14h 06m 45.51s , +64d 11m 10.3s) | C | 60 | 18.2 | 48451 | 2020-05-24 18:31:01 | MASTER-Tavrida | (13h 44m 38.52s , +62d 11m 16.6s) | C | 60 | 18.4 | 48531 | 2020-05-24 18:32:21 | MASTER-Tavrida | (13h 42m 06.69s , +60d 10m 42.5s) | C | 60 | 18.5 | 48612 | 2020-05-24 18:33:41 | MASTER-Tavrida | (13h 58m 09.72s , +60d 11m 28.6s) | C | 60 | 18.8 | 48693 | 2020-05-24 18:35:03 | MASTER-Tavrida | (14h 18m 50.75s , +62d 10m 04.4s) | C | 60 | 18.6 | 48773 | 2020-05-24 18:36:23 | MASTER-Tavrida | (14h 06m 42.74s , +64d 09m 24.8s) | C | 60 | 18.7 | 48854 | 2020-05-24 18:37:44 | MASTER-Tavrida | (13h 44m 37.74s , +62d 10m 11.8s) | C | 60 | 18.9 | 48935 | 2020-05-24 18:39:04 | MASTER-Tavrida | (13h 58m 12.40s , +60d 11m 28.7s) | C | 60 | 18.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27802 SUBJECT: GRB 200524A: CrAO observations of ZTF20abbiixp DATE: 20/05/24 20:53:20 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev (CrAO), A. Pozanenko (IKI), S. Belkin (IKI), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed Fermi-LAT detected GRB 200524A (Dirirsa et al., GCN 27797) with ZTSh 2.6m telescope of CrAO starting on 2020-05-24 (UT) 19:35:16. We clearly detected the OT discovered by ZTF (Ho et al., GCN 27799); see also Kumar et al. (GCN 27800). The R magnitude of the OT is 20.1 +/- 0.2 at the time of the first exposure. Observations and data reduction is ongoing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27803 SUBJECT: GRB 200524A: 3.6m DOT observations of the afterglow candidate ZTF20abbiixp DATE: 20/05/24 21:50:57 GMT FROM: Kuntal Misra at ARIES,India Pankaj Sanwal, Kuntal Misra, Ankur Ghosh, Dimple, Amit Kumar, Amar Aryan, Rahul Gupta, S. B. Pandey, Brijesh Kumar, T. S. Kumar and Amitesh Omar (ARIES) report on behalf of the GRB collaboration: We observed the field of GRB 200524A (Fana Dirirsa et al., GCN 27797) with the 3.6m Devasthal Optical Telescope (DOT) located in Devasthal, India on 2020-05-24T19:18:00 (UT) using the recently commissioned ADFOSC instrument. We observed a sequence of 300 sec images in g, r and i bands. We clearly detect the optical transient discovered by ZTF (Ho et al., GCN 27799) and also reported by Kumar et al. (GCN 27800) and Rumyantsev et al. (GCN 27802). In the first r band image the afterglow has a r band magnitude of 21.1+/-0.03. Further processing of the data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27804 SUBJECT: GRB 200524A: Correction to the GCN 27800 DATE: 20/05/24 21:53:38 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar, V. Bhalerao(IITB), G. C. Anupama, S. Barway, U. Stanzin (IIA) report on behalf of the GROWTH-India collaboration: We mistakenly reported the wrong observation time in our previous GCN 27800. We deeply apologize for the confusion caused. Here is the corrected GCN:- ----------------------------------------------------------------- We followed up GRB 200524A (F. F. Dirirsa et al., GCN 27797, A. Ho et al., GCN 27799) with 0.7m GROWTH-India telescope. We obtained 600-sec exposures in SDSS g, r, i filters starting at UT 2020-05-24T16:11:57 (~11.11 hrs after the burst). We detect a faint transient with magnitudes r = 20.56 +/- 0.14 and i = 20.59 +/- 0.28 (calibrated against PanSTARRs PS1 data release, Flewelling et al., 2018). The source position matches with the likely afterglow candidate by A. Ho et al. (GCN 27799). The fading rate is approximately 3 magnitudes in ~9.4 hours, consistent with the fading rate reported in the ZTF GCN. We hereby, confirm ZTF20abbiixp as the afterglow of GRB 200524A. We obtained the following photometric results:- ------------------------------------------------------------------ JD(Start) | T-T0(hrs) | Filter | Mag | ------------------------------------------------------------------ 2458994.174 | 11.11 | g | > 21.01 2458994.183 | 11.33 | r | 20.56 +/- 0.14 2458994.191 | 11.52 | i | 20.59 +/- 0.28 ------------------------------------------------------------------ Given the fast fading of the source, we encourage the followup of the source. The magnitudes are not corrected for galactic extinction. The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27805 SUBJECT: GRB 200524A: Liverpool Telescope observations DATE: 20/05/24 22:28:15 GMT FROM: Daniel Perley at Liverpool JMU D. A. Perley (LJMU) and Anna Ho (Caltech) report: We observed the location of ZTF20abbiixp/AT2020krl (Ho et al., GCN 27799), the presumed optical afterglow of GRB 200524A (Fana Dirirsa et al., GCN 27797), with the 2m robotic Liverpool Telescope between UT 2020-05-24 21:39 and 21:53. We acquired 120s of exposure time in each of the u, g, r, i, and z filters. Photometry is as follows (all times relative to the LAT trigger as reported in GCN 27797): t_mid(d) filter magnitude -------- ------ ---------- 0.6921 z 20.49 +/- 0.15 0.6941 i 20.86 +/- 0.09 0.6961 r 21.03 +/- 0.07 0.6981 g 21.32 +/- 0.06 0.7000 u 21.64 +/- 0.24 DisclaimerNone //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27806 SUBJECT: GRB 200524A: 1.3m DFOT Optical Observation of ZTF20abbiixp DATE: 20/05/24 22:32:48 GMT FROM: Amit Kumar at ARIES, India A. Kumar (ARIES), S. B. Pandey (ARIES), A. Ghosh (ARIES), Dimple (ARIES), K. Misra (ARIES), R. Gupta (ARIES), K. Chand (ARIES) and A. Aryan (ARIES) report: We observed the optical afterglow of GRB 200524A (F. F. Dirirsa et al., GCN 27797, Evans et al., GCN 27798) with the 1.3m Devasthal Fast Optical Telescope (DFOT) at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital (India), from 2020-05-24T19:50:12 UTC (corresponding to ~14.770 hours after the burst). We observed 5 frames each of 300 seconds in Bessell I filter. In the stacked image, we clearly detected the optical afterglow of GRB 200524A (detected by Ho et al., GCN 27799, see also Kumar et al., GCN 27800, Rumyantsev et al., GCN 27802 and Sanwal et al., GCN 27803). The observed magnitude is as follows: T_start-T0 (hours) Start Date (UTC) End Date (UTC) Filter Magnitudes (mag) --------------------------------------------------------------------------------------------------------------- 14.770 2020-05-24T19:50:12 2020-05-24T20:32:37 I 20.33 +- 0.07 Photometry is done based on the USNO-B1.0 catalog. The quoted magnitude is not corrected for Galactic extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27807 SUBJECT: GRB 200524A: CAHA multicolor afterglow detection DATE: 20/05/24 23:38:09 GMT FROM: Alexander Kann at IAA-CSIC A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann, M. Blazek, C. Thoene, J. F. Agui Fernandez (all HETH/IAA-CSIC), R. Pedro Hedrosa, and A. Guijarro (both CAHA) report: We observed the field of GRB 200524A (Fermi-LAT detection: Dirirsa et al. GCN #27797) with CAFOS, on the 2.2 m telescope, at Calar Alto observatory (Almeria, Spain). Observations consisted of 3 x 500 s in BVRc each, and 8 x 180 s in Ic-band. The afterglow (Ho et al., GCN #27799, Kumar et al., GCN #27800, Rumyantsev et al., GCN #27802, Sanwal et al., GCN #27803, Perley et al., GCN #27805, Kumar et al., GCN #27806) is well-detected in each image. In an Rc image starting at 21:49:33 UT (mid-time 0.701188 days after the Fermi GBM trigger), we measure Rc = 20.86 +/- 0.12 mag (Vega mags) against five nearby SDSS stars transformed to the Rc band. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27808 SUBJECT: GRB 200524: Swift/UVOT observations missed the ZTF20abbiixp position DATE: 20/05/24 23:43:57 GMT FROM: Paul Kuin at MSSL Paul Kuin (MSSL/UCL) and Kim Page (Leicester University) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200524 36366 s after the LAT trigger (Evans et al., GCN Circ. 27798). The initial Swift UVOT follow up missed the likely afterglow of 200524A as reported by Ho et al, GCN Circ. 27799, and confirmed by Kumar et al. GCN Circ. 27800/27804/27806, Rumyantsev et al. GCN Circ. 27802, Sanwal et al. GCN Circ. 27803, Perley et al., GCN Circ. 27805 and de Ugarte Postigo et al, GCN.Circ. 27807. The UVOT field of view is smaller than the XRT field of view and XRT source 6 (Evans et al., GCN Circ. 27798), which is consistent with the PTF source, falls outside the field observed by Swift UVOT. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27809 SUBJECT: GRB 200524A: Fermi GBM detection DATE: 20/05/25 00:03:51 GMT FROM: Stephen Lesage at Fermi-GBM Team S. Pookalil (UAH), B. Mailyan (Institute for Basic Science, South Korea), and R. Hamburg (UAH) report on behalf of the Fermi GBM Team: "At 05:04:00.36 UT on 24 May 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200524A (trigger 611989445 / GBM200524211), which was also detected by the Fermi/LAT (Dirirsa et al. 2020, GCN 27797) The Fermi GBM Final Real-time Localization is consistent with the LAT position. Swift has initiated a ToO observation of this burst (GCN 27798). The angle from the Fermi LAT boresight at the GBM trigger time is 23 degrees. The GBM light curve shows a multi-peaked structure with a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-1.5 s to T0+25.1 s is best fit by a Band function with Epeak = 192 +/- 16 keV, alpha = -0.66 +/- 0.06, and beta = -1.77 +/- 0.03 The event fluence (10-1000 keV) in this time interval is (2.08 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+5.3 s in the 10-1000 keV band is 13.3 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27810 SUBJECT: GRB 200524A: OAJ multicolor afterglow detection DATE: 20/05/25 00:52:33 GMT FROM: Alexander Kann at IAA-CSIC M. Blazek, D. A. Kann (both HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. Thoene, J. F. Agui Fernandez (both HETH/IAA-CSIC), and N. Maicas (CEFCA) report: We observed the field of GRB 200524A (Fermi-LAT detection: Dirirsa et al. GCN #27797, Fermi GBM detection: Pookalil et al., GCN #27809) with the T80 0.8m telescope at the Observatorio de Javalambre (Teruel, Spain). Observations consisted of 3 x 300 s in g', 2 x 300 s in r', and 5 x 180 s in i' and z' each. The afterglow (Ho et al., GCN #27799, Kumar et al., GCN #27800, Rumyantsev et al., GCN #27802, Sanwal et al., GCN #27803, Perley et al., GCN #27805, Kumar et al., GCN #27806, de Ugarte Postigo et al., GCN #27807) is well-detected in each image. In the stacked r' image centered at 21:59:24 UT (mid-time 0.705135 days after the Fermi GBM trigger), we measure r' = 21.08 +/- 0.04 mag (AB mags) against PanSTARRS stars in the field. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27811 SUBJECT: GRB 200524A: Swift-XRT afterglow detection DATE: 20/05/25 04:14:56 GMT FROM: Kim Page at U.of Leicester M. Capalbi (INAF-IASFPA), M. Perri (ASDC), V. D'Elia (ASDC), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 200524A (Fana Dirirsa et al. GCN Circ. 27797), collecting 5.0 ks of Photon Counting (PC) mode data between T0+36.4 ks and T0+55.7 ks. Four uncatalogued X-ray sources are detected, of which one ("Source 6") is believed to be the afterglow. Using 1644 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 213.04474, +60.90538 which is equivalent to: RA (J2000): 14h 12m 10.74s Dec(J2000): +60d 54' 19.4" with an uncertainty of 4.4 arcsec (radius, 90% confidence). This position is 9.2 arcmin from the Fermi/LAT position, and 3 arcsec from ZTF20abbiixp (Ho et al., GCN 27799). The light curve can be modelled with a power-law decay with a decay index of alpha=3.42 (+0.06, -2.83). The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021001. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021001. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27813 SUBJECT: GRB 200524A: MITSuME Akeno optical observation DATE: 20/05/25 07:18:07 GMT FROM: Ogawa Futa at Tokyo Institute of Technology F. Ogawa, R. Hosokawa, R. Adachi, K. L. Murata, M. Niwano, N. Nakamura, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 200524A (Fermi-LAT detection: Dirirsa et al., GCN #27797, Fermi-GBM detection: Pookalil et al., GCN #27809, Swift-XRT afterglow detection: Capalbi et al. GCN #27811, and others) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 13:07:01.89 UT. We detected a point source clearly in g' and Rc band, and marginally in Ic band at the position consistent with the afterglow reported previously (Ho et al., GCN #27799, Kumar et al., GCN #27800, Rumyantsev et al., GCN #27802, Sanwal et al., GCN #27803, Perley et al., GCN #27805, Kumar et al., GCN #27806, de Ugarte Postigo et al., GCN #27807, Blazek et al., GCN #27810). We measured the magnitudes as follows. T0+[hour] MID-UT T-EXP[sec] measured magnitudes ------------------------------------------------------------------------------------------------ 8.03 13:10:54 420 g'=19.6+/-0.3, Rc=19.5+/-0.3, Ic=19.4+/-0.5 ------------------------------------------------------------------------------------------------ T0+: Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration. The magnitudes are expressed in the Vega system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. ,in prep; https://github.com/MNiwano/Eclair) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27814 SUBJECT: GRB 200524A: KAIT Optical Observations DATE: 20/05/25 08:57:28 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) 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 GRB 200524A (Fermi-LAT detection: Dirirsa et al., GCN 27797; Fermi GBM detection: Pookalil et al., GCN 27809), starting at ~1.08 days after the burst. We obtained 24x60s images in the clear (roughly R) filter. We detect the optical afterglow at the location of ZTF20abbiixp/AT2020krl (Ho et al., GCN 27799) in our co-added image. We estimate the afterglow, which was also reported by other groups (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813), to be 21.2 +/- 0.2 magnitude in clear filter, calibrated to PS1 catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27817 SUBJECT: GRB 200524A: Further Liverpool Telescope observations DATE: 20/05/25 11:26:47 GMT FROM: Luca Izzo at DARK/NBI L. Izzo (DARK/NBI) reports: We observed the field of GRB 200524A (Fermi-LAT detection: Dirirsa et al. GCN #27797, Fermi GBM detection: Pookalil et al., GCN #27809) with the IO:O camera mounted on the 2-m Liverpool Telescope located in La Palma, Spain. Observations started on May 25th at 01:08:27 UT (0.837 days after the GRB trigger) and we obtained a series of 5x60s images in the gri filters. The afterglow (Ho et al., GCN #27799, Kumar et al., GCN #27800, Rumyantsev et al., GCN #27802, Sanwal et al., GCN #27803, Perley et al., GCN #27805, Kumar et al., GCN #27806, de Ugarte Postigo et al., GCN #27807, Blazek et al., GCN #27810, Ogawa et al., GCN #27813, Zheng et al., GCN #27814) is detected in all the stacked images. We measure a preliminary AB magnitude for the afterglow of g = 21.67 +- 0.35 mag (t_mid = 0.839 d), r = 21.37 +- 0.20 mag (t_mid = 0.844 d), i = 21.34 +- 0.25 mag(t_mid = 0.849 d) calibrated against Pan-STARRS catalogue stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27818 SUBJECT: GRB 200524A: AstroSat CZTI detection DATE: 20/05/25 14:44:59 GMT FROM: Soumya Gupta at IUCAA/ASTROSAT S. Gupta, V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (IUCAA/TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of a long GRB 200524A, which was also detected by Fermi-LAT (Dirirsa F. et al., GCN #27797), Swift (Evans P.et al., GCN # 27798), ZTF (Ho A. et al., GCN # 27799), GROWTH-India (Kumar H. et al., GCN # 27800), Global MASTER-Net (Lipunov V. et al., GCN # 27801), CrAO (Rumyantsev V. et al., GCN # 27802), 3.6m DOT (Sanwal P. et al., GCN # 27803), Liverpool (Perley D. et al., GCN # 27805), CAHA (Postigo A. et al., GCN # 27807), Fermi GBM (Pookalil S. et al., GCN # 27809), OAJ (Blazek M. et al., GCN # 27810) and Swift-XRT (Capalbi M. et al., GCN # 27811). The source was clearly detected in the 40-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-05-24 05:04:05.494 UT. The measured peak count rate associated with the burst is 303 +/- 22 cts/s above the background in the combined data of four quadrants, with a total of 2111 +/- 37 cts. The local mean background count rate was 537 +/- 1 cts/s. Using cumulative rates, we measure a T90 of 15.38 +/- 0.27 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-05-24 05:04:04.236 UT. The measured peak count rate is 430 +/- 40 cts/s above the background in the combined Veto data of four quadrants, with a total of 2951 +/- 79 cts. The local mean background count rate was 1623 +/- 3 cts/s. We measure a T90 of 16.89 +/- 0.67 s from the cumulative Veto light curve. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27820 SUBJECT: GRB 200524A: Kitab observatory afterglow observations DATE: 20/05/25 15:37:06 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI), I. Molotov (KIAM), Sh. Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN: We observed Fermi-LAT detected localization area of GRB 200524A (Dirirsa et al., GCN 27797; see also Pookalil et al., GCN 27809; Capalbi et al., GCN 27811; Gupta et al., GCN 27818) with Kitab-ISON RC-36 telescope starting on 2020-05-24 (UT) 19:07:41. In a stacked image in Clear filter (CR) we marginally detected optical afterglow discovered by ZTF (Ho et al., GCN 27799) and confirmed by several observations (Kumar et al. GCN 27800; (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813; Izzo, GCN 27817). Preliminary photometry is following Date, UT start, t-T0, Exp., Filter, OT, Err., UL (mid, days) 2020-05-24 19:07:41 0.60673 60*60 CR 20.48 0.25 21.0 The photometry is based on nearby USNO-B1.0 stars USNO-B1.0_id R2 1508-0206198 15.78 1509-0204466 16.48 1509-0204434 16.53 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27821 SUBJECT: GRB 200524A: CrAO optical observations DATE: 20/05/25 16:02:51 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), A. Volnova (IKI), E. Mazaeva (IKI) report on behalf of larger GRB follow-up collaboration: We observed Fermi-LAT GRB 200524A (Dirirsa et al., GCN 27797; see also Pookalil et al., GCN 27809; Capalbi et al., GCN 27811; Gupta et al., GCN 27818) with ZTSH 2.6m telescope of CrAO observatory starting on 2020-05-24 (UT) 19:35:16 (Rumyantsev et al., GCN 27802). Optical afterglow discovered by ZTF (Ho et al., GCN 27799) and confirmed by several observations (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813; Izzo, GCN 27817). Preliminary photometry of the afterglow is following Date, UT start, t-T0, Exp., Filter, OT, Err., UL (mid, days) 2020-05-24 19:35:16 0.60644 240 R 20.43 0.05 22.6 2020-05-24 19:39:28 0.60935 240 R 20.48 0.05 22.7 2020-05-24 19:43:39 0.61226 240 R 20.52 0.05 22.7 2020-05-24 19:47:52 0.61519 240 R 20.55 0.05 22.6 2020-05-24 19:52:03 0.61809 240 R 20.60 0.08 22.5 2020-05-24 19:56:15 0.62101 240 R 20.59 0.09 22.5 2020-05-24 20:00:27 0.62392 240 R 20.60 0.09 22.3 The photometry is based on nearby USNO-B1.0 stars USNO-B1.0_id R2 1508-0206198 15.78 1509-0204466 16.48 1509-0204434 16.53 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27824 SUBJECT: GRB 200524A: optical upper limits from further MITSuME Akeno observation DATE: 20/05/26 07:22:56 GMT FROM: Ryohei Hosokawa at Tokyo Institute of Technology R. Hosokawa, N. Nakamura, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We performed further observation of the field of GRB 200524A (Fermi-LAT detection: Dirirsa et al., GCN #27797, Fermi-GBM detection: Pookalil et al., GCN #27809, Swift-XRT afterglow detection: Capalbi et al. GCN #27811, and others) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2020-05-25 11:27:25.65 UT. We did not detect the optical afterglow (Ho et al., GCN #27799, Kumar et al., GCN #27800, Rumyantsev et al., GCN #27802, Sanwal et al., GCN #27803, Perley et al., GCN #27805, Kumar et al., GCN #27806, de Ugarte Postigo et al., GCN #27807, Blazek et al., GCN #27810, Ogawa et al., GCN #27813, Zheng et al., GCN #27814, Izzo et al., GCN #27817, Belkin et al., GCN #27820, Belkin et al., GCN #27821) in the stacked images. We obtained the 5-sigma limits as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 30.5 2020-05-25 11:34:26 660 g'>18.7, Rc>18.7, Ic>18.0 ------------------------------------------------------------------------------------------------ T0+: Elapsed time after the burst T-EXP: Total Exposure time We used the GSC2.3 catalog for flux calibration. The magnitudes are expressed in the Vega system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. ,in prep; https://github.com/MNiwano/Eclair) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27825 SUBJECT: GRB200524A: UVOT detection DATE: 20/05/26 13:49:24 GMT FROM: Paul Kuin at MSSL N.P.M. Kuin (MSSL/UCL) and K.L. Page (U. Leicester) report on behalf of the Swift UVOT team Swift UVOT did a further follow up of the Fermi-LAT detected GRB200524A (Dirirsa et al. GCN Circ. 27797). We detect the afterglow discovered by Ho et al. (GCN Circ. 27799), ZTF20abbiixp, in the UVOT white filter in 5.4ks exposure taken between To+1.15d and To+1.57d, with white = 22.06 +/- 0.12 magnitudes (on the UVOT photometric system, Breeveld et al. 2011, AIP Conf. Proc. 1358, 373 ). The source does not vary significantly during these observations. No correction has been made for the Galactic reddening E(B-V)=0.02 (Schlafy et al., ApJ 737, 10, 2011) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27830 SUBJECT: GRB 200524A: Assy optical observations DATE: 20/05/27 15:13:26 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), V. Kim (AFIF, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (AFIF), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of larger GRB IKI FuN collaboration: We observed Fermi-LAT GRB 200524A (Dirirsa et al., GCN 27797; see also Pookalil et al., GCN 27809; Capalbi et al., GCN 27811; Gupta et al., GCN 27818) with AZT-20 1.5 m telescope of Assy-Turgen observatory starting on May. 26 (UT) 15:34:49 in r'-filter. Optical afterglow discovered by ZTF (Ho et al., GCN 27799) and observed by several observations (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813; Izzo, GCN 27817; Belkin et al., GCN 27820; Kuin et al., GCN 27825). Preliminary photometry of the afterglow is following Photometry of the field is following. Date UT start t-T0 Filter Exp. OT Err. UL (3sigma) (mid, days) (s) 2020-05-26 15:34:49 2.4721 r'(AB) 98*60 22.57 0.10 24.4 The photometry is based on the nearby stars of PS1 catalog. PanSTARRS-PS1_id r 181072130294808209 20.4066 181072130171186332 20.9877 181082129951473104 20.1196 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27850 SUBJECT: GRB 200524A: Assy continued optical observations DATE: 20/05/29 08:45:32 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), V. Kim (AFIF, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (AFIF), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of larger GRB IKI FuN collaboration: We observed GRB 200524A (Dirirsa et al., GCN 27797; Pookalil et al., GCN 27809; Capalbi et al., GCN 27811; Gupta et al., GCN 27818) with AZT-20 1.5 m telescope of Assy-Turgen observatory starting on May. 27 (UT) 17:29:53 in r'-filter. Optical afterglow discovered by ZTF (Ho et al., GCN 27799) and observed by several observations (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813; Izzo, GCN 27817; Belkin et al., GCN 27820; Kuin et al., GCN 27825). Preliminary photometry of the afterglow is following Date UT start t-T0 Filter Exp. OT Err. UL (3sigma) (mid, days) (s) 2020-05-27 17:29:53 3.55617 r'(AB) 110*60 22.80 0.17 24.4 The photometry is based on the nearby stars of PS1 catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27851 SUBJECT: GRB 200524A: SAO RAS optical observations DATE: 20/05/29 09:29:23 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Moskvitin (SAO RAS), A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of larger GRB IKI FuN collaboration: We observed GRB 200524A (Dirirsa et al., GCN 27797; Pookalil et al., GCN 27809; Capalbi et al., GCN 27811; Gupta et al., GCN 27818) with Zeiss-1.0 m telescope of SAO RAS observatory in Rc-filter. Optical afterglow discovered by ZTF (Ho et al., GCN 27799) and observed by several observations (Kumar et al., GCN 27800; Rumyantsev et al., GCN 27802; Sanwal et al., GCN 27803; Perley et al., GCN 27805; Kumar et al., GCN 27806; de Ugarte Postigo et al., GCN 27807; Blazek et al., GCN 27810; Ogawa et al., GCN 27813; Izzo, GCN 27817; Belkin et al., GCN 27820; Kuin et al., GCN 27825). Preliminary photometry is following Date UT start t-T0 Filter Exp. OT Err. UL (3sigma) (mid, days) (s) 2020-05-27 21:48:28 3.71143 Rc 2400 22.54 0.20 23.6 2020-05-28 22:17:40 4.73171 Rc 2400 n/d n/d 22.6 The photometry is based on the nearby stars of SDSS DR12 catalog and Lupton' transformation gri -> R. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27867 SUBJECT: Konus-Wind observation of GRB 200524A DATE: 20/05/30 14:10:03 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 200524A (Fermi-LAT detection: Fana Dirirsa et al., GCN Circ. 27797; Fermi-GBM detection: Pookalil et al., GCN Circ. 27809; AstroSat-CZTI detection: Gupta et al., GCN Circ. 27818) triggered Konus-Wind at T0=18243.246 s UT (05:04:03.246). The burst light curve shows a multipeaked structure which starts at ~T0-4.8 s, peaks at ~T0-3.3 s, and to background level at ~T0+84 s. The total burst duration is ~89 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB200524_T18243/ As observed by Konus-Wind, the burst had a fluence of 3.48(-0.62,+0.74)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+3.280 s, of 6.33(-1.64,+1.75)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+40.704 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.75(-0.18,+0.25), the high energy photon index beta = -2.13(-0.31,+0.20), the peak energy Ep = 215(-46,+48) keV (chi2 = 105/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+7.936 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.55(-0.18,+0.26), the high energy photon index beta = -2.14(-0.21,+0.16), the peak energy Ep = 203(-36,+36) keV (chi2 = 130/97 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29673 SUBJECT: GRB 200524A: Redshift from Gemini-North DATE: 21/03/19 18:16:33 GMT FROM: Yuhan Yao at Caltech Yuhan Yao (Caltech), Adam Miller (Northwestern), Anna Ho (UCB), Daniel Perley (LJMU) We observed ZTF20abbiixp/AT2020kym (Ho et al., GCN #27799), the afterglow of the long-duration GRB 200524A (Pookalil et al., GCN #27809; Fana Dirirsa et al., GCN #27797; Gupta et al., GCN #27818; Svinkin et al., GCN #27867), with GMOS-N under our ToO program GN-2020A-Q-117 (PI: Miller). The observation, conducted in the Nod-and-Shuffle mode with a 1 arcsec slit, started at 2020-05-25 07:39:14.9 UT, corresponding to 26.6 hours after the Fermi-GBM trigger (Pookalil et al., GCN #27809). A power-law fit to the afterglow light curve (Ho et al., GCN #27799; Kumar et al., GCN #27800, #27804; Perley & Ho, GCN #27805) suggests that ZTF20abbiixp was at r=21.5 and g=21.8 at the time of Gemini observation. We obtained 3 x 550 s spectroscopic exposures with the B600 grating and 3 x 550 s exposures with the R400 grating, providing coverage over the range 3620-9600 AA. No flux calibration was performed. The spectrum was reduced using the IRAF package for GMOS. A trace was detected redwards of 4900 AA. Bluewards of 4900 AA, the source was not significantly detected, probably because of the faintness of the object, the intrinsic red color of the afterglow (g-r ~ 0.3 mag) and low sensitivity at the blue end. We clearly identified absorption lines of Mg II 2796 and Mg II 2803 at the redshift of z = 1.256 in the three individual exposures. Absorption from Mg I 2852 is marginally detected in the combined spectrum at consistent redshift. We therefore identify z=1.256 as the most probable redshift for the GRB, although in practice this is only a lower limit. The lack of a DLA or Lyman break places an upper limit of z < 3.