//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28702 SUBJECT: GRB 201020B: Fermi GBM Final Real-time Localization DATE: 20/10/20 17:41:58 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 17:33:54 UT on 20 Oct 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 201020B (trigger 624908039.329288 / 201020732). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 71.6, Dec = 76.6 (J2000 degrees, equivalent to J2000 04h 46m, 76d 35'), with a statistical uncertainty of 1.6 degrees. The angle from the Fermi LAT boresight is 69.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201020732/quicklook/glg_skymap_all_bn201020732.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201020732/quicklook/glg_healpix_all_bn201020732.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201020732/quicklook/glg_lc_medres34_bn201020732.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28704 SUBJECT: Fermi GRB 201020B: Global MASTER-Net observations report DATE: 20/10/20 19:30:28 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), 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 201020B ( Fermi GBM team, GCN 28702) errorbox 116 sec after notice time and 145 sec after trigger time at 2020-10-20 17:36:19 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 51 deg. The sun altitude is -30.3 deg. The galactic latitude b = 20 deg., longitude l = 135 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1465475 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 160 | 2020-10-20 17:36:19 | MASTER-Tavrida | (05h 02m 15.44s , +77d 01m 50.6s) | C | 30 | 18.1 | 205 | 2020-10-20 17:36:19 | MASTER-Tavrida | (05h 02m 15.47s , +77d 01m 50.6s) | C | 120 | 19.0 | Coadd 216 | 2020-10-20 17:37:09 | MASTER-Tavrida | (05h 02m 09.73s , +77d 00m 53.6s) | C | 40 | 18.4 | 281 | 2020-10-20 17:38:10 | MASTER-Tavrida | (05h 02m 16.10s , +77d 01m 14.1s) | C | 50 | 18.4 | 356 | 2020-10-20 17:39:20 | MASTER-Tavrida | (05h 02m 11.94s , +77d 02m 41.5s) | C | 60 | 18.5 | 447 | 2020-10-20 17:40:41 | MASTER-Tavrida | (05h 02m 11.08s , +77d 01m 36.7s) | C | 80 | 18.7 | 557 | 2020-10-20 17:42:21 | MASTER-Tavrida | (04h 48m 10.21s , +76d 33m 54.4s) | C | 100 | 18.8 | 688 | 2020-10-20 17:44:21 | MASTER-Tavrida | (04h 48m 02.35s , +76d 33m 21.4s) | C | 120 | 18.9 | 843 | 2020-10-20 17:46:42 | MASTER-Tavrida | (04h 48m 00.81s , +76d 34m 32.4s) | C | 150 | 18.6 | 1029 | 2020-10-20 17:49:33 | MASTER-Tavrida | (04h 48m 05.91s , +76d 33m 45.8s) | C | 180 | 18.6 | 1230 | 2020-10-20 17:52:54 | MASTER-Tavrida | (04h 47m 57.59s , +76d 33m 01.0s) | C | 180 | 18.6 | 1431 | 2020-10-20 17:56:14 | MASTER-Tavrida | (04h 48m 03.67s , +76d 33m 39.0s) | C | 180 | 18.6 | 1631 | 2020-10-20 17:59:35 | MASTER-Tavrida | (04h 47m 58.81s , +76d 35m 03.2s) | C | 180 | 18.6 | 1772 | 2020-10-20 18:02:56 | MASTER-Tavrida | (04h 50m 47.49s , +78d 02m 09.0s) | C | 60 | 18.6 | 1852 | 2020-10-20 18:04:16 | MASTER-Tavrida | (04h 09m 27.94s , +76d 03m 59.8s) | C | 60 | 18.8 | 2013 | 2020-10-20 18:06:57 | MASTER-Tavrida | (05h 15m 54.03s , +76d 01m 47.7s) | C | 60 | 18.6 | 4831 | 2020-10-20 18:53:55 | MASTER-Tavrida | (04h 50m 27.27s , +78d 03m 32.9s) | C | 60 | 18.3 | 4912 | 2020-10-20 18:55:16 | MASTER-Tavrida | (05h 29m 10.28s , +78d 03m 58.0s) | C | 60 | 18.6 | 4992 | 2020-10-20 18:56:36 | MASTER-Tavrida | (04h 09m 07.67s , +76d 04m 40.5s) | C | 60 | 18.7 | 5073 | 2020-10-20 18:57:56 | MASTER-Tavrida | (04h 42m 20.94s , +76d 05m 39.8s) | C | 60 | 18.7 | 5233 | 2020-10-20 19:00:37 | MASTER-Tavrida | (05h 01m 52.50s , +80d 03m 12.9s) | C | 60 | 18.9 | 5315 | 2020-10-20 19:01:58 | MASTER-Tavrida | (05h 15m 37.60s , +76d 03m 36.6s) | C | 60 | 18.7 | 5814 | 2020-10-20 19:10:18 | MASTER-Tavrida | (05h 29m 01.57s , +78d 05m 11.8s) | C | 60 | 18.4 | 5895 | 2020-10-20 19:11:38 | MASTER-Tavrida | (04h 42m 17.73s , +76d 04m 03.6s) | C | 60 | 18.6 | 6260 | 2020-10-20 19:17:44 | MASTER-Tavrida | (04h 36m 28.16s , +74d 04m 22.2s) | C | 60 | 18.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28710 SUBJECT: GRB 201020B: Fermi GBM detection DATE: 20/10/21 01:14:36 GMT FROM: Christian Malacaria at NASA-MSFC/USRA C. Malacaria (NASA-MSFC/USRA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 17:33:54.33 UT on 20 October 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 201020B (trigger 624908039 / 201020732). The Fermi GBM Final Real-time Localization was reported in GCN 28702. The angle from the Fermi LAT boresight at the GBM trigger time is 69 degrees. The GBM light curve shows multiple peaks around the bright, main peak. The duration (T90) is about 16 s (50-300 keV). The time-averaged spectrum from T0-5.1 s to T0+23.5 s is best fit by a Band function with Epeak = 136.9 +/- 3.4 keV, alpha = -0.71 +/- 0.02, and beta = -2.20 +/- 0.03 The event fluence (10-1000 keV) in this time interval is (3.929 +/- 0.040)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+9.4 s in the 10-1000 keV band is 43.7 +/- 0.4 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: 28714 SUBJECT: GRB 201020B: AGILE detection DATE: 20/10/21 08:43:31 GMT FROM: Alessandro Ursi at INAF/IAPS A. Ursi (INAF/IAPS), M. Pilia (INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team: The AGILE Mini-CALorimeter (MCAL) detected GRB 201020B at T0 = 2020-10-20 17:34:03.78 +/- 0.01 s (UTC), reported by Fermi/GBM (GCNs #28702 and #28710). The event lasted about 5 s and released a total number of 3250 counts in the detector (in the 0.4-100 MeV energy range), above an average background rate of 550 Hz. The MCAL light curve can be found at http://www.agilescienceapp.it/notices/GRB_069336_525794310.907011.png . The time-integrated spectrum of the burst can be fitted in the energy range 0.4-20 MeV with a single power-law with ph.ind. = -2.78 -0.03/+0.04, resulting in a reduced chi-squared of 1.05 (89 d.o.f.) and a fluence of 4.56e-06 ergs/cm^2 (90% confidence level), in the same energy range. The burst is clearly visible in the AGILE scientific ratemeters of the SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and AntiCoincidence (AC; 50-200 keV) detectors. The event lasted ~27 s and released a total number of 5856 counts in the SA detector (above a background rate of 80 Hz); it lasted ~17.5 s and released a total number of 66750 counts in the AC detector (above a background rate of 3670 Hz); it lasted ~5 s and released a total number of 7506 counts in the MCAL detector (above a background rate of 1260 Hz). The AGILE ratemeter light curves can be found at http://www.agilescienceapp.it/notices/GRB_201020B_AGILE_RM.png . The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28716 SUBJECT: GRB 201020B: Fermi-LAT detection DATE: 20/10/21 09:28:52 GMT FROM: Magnus Axelsson at Stockholm U. M. Arimoto (Kanazawa Univ.), M. Axelsson (KTH and Stockholm Univ.), F. Longo (University and INFN, Trieste) and E. Bissaldi (INFN and Politecnico Bari) report on behalf of the Fermi-LAT Collaboration: On October 20, 2020, Fermi-LAT detected high-energy emission from GRB 201020B, which was also detected by Fermi-GBM (trigger 624908039.329288 / 201020732; GCN 28702). The best LAT on-ground location is found to be RA, Dec = 74.9, 77.0 (degrees, J2000) with an error radius of 0.21 deg (90% containment, statistical error only). This was 67 deg from the LAT boresight at the time of the GBM trigger: T0 = 17:33:54.33 UT. At the time of the trigger, the source was outside the field of view of the LAT. Observations began at T0+2300s and the data from the Fermi-LAT show a significant increase in the event rate in the interval T0+2300 to T0+4600s that is spatially correlated with the GBM emission with high significance. The photon flux above 100 MeV in this time interval is 6.5e-7 +/- 3.3e-7 ph/cm2/s. The estimated photon index above 100 MeV is -1.6+/-0.3. The highest-energy photon is a 6 GeV event which is observed ~2700 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (Elisabetta.Bissaldi@ba.infn.it). 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: 28718 SUBJECT: GRB 201020B: MASTER bright optical afterglow detection DATE: 20/10/21 12:19:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, A.Kuznetsov, K.Zhirkov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-Tavrida wide field robotic-telescope (Lipunov et al. GCN 28704) and very wide field cameras observed in alert mode Fermi GRB201020B (GBM GCN 28703, LAT GCN 28716 https://gcn.gsfc.nasa.gov/other/201020B.gcn3 ) MASTER auto-detection system (Lipunov et al. 2010, Advances in Astronomy, vol. 2010, 30L) discovered MASTER OT J050152.74+770406.3 with afterglow light curve at (RA, Dec2000) = 05h 01m 52.74s +77d 04m 06.3s with m_OT=13.7 at 2020-10-20.73413 UT. The OT is seen in 35 images with afterglow behaviour. We have reference image on 2020-01-02.78682 UT with unfiltered mlim=19.5m. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28719 SUBJECT: GRB 201020B: Nanshan/NEXT optical afterglow confirmation DATE: 20/10/21 13:20:48 GMT FROM: Dong Xu at NAOC/CAS D. Xu (NAOC), Z.P. Zhu (NAOC, HUST), S.Y. Fu, X. Liu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of GRB 201020B detected by Fermi/GBM, Fermi/LAT, and AGILE (Fermi GBM team, GCN 28702; Malacaria et al., GCN 28710; Arimoto et al., GCN 28716; Ursi et al., GCN 28714), starting at 12:35:28 UT on 2020-10-21, i.e., 0.7927 day after the Fermi trigger. Photometry has been done in Sloan r-filter with 60s for each exposure, and observations are ongoing. The optical transient reported by MASTER (Lipunov et al., GCN 28718) is clearly detected in our single image at improved coordinates R.A. (J2000) = 5:01:52.80 Dec. (J2000) = +77:04:06.23 with a positional uncertainty of ~0.5 arcsec. It has decayed to m_r = 19.0 +/- 0.1 at T_mid = 0.7944 day post-trigger, calibrated with nearby PS1 stars. Based on the quick decay behaviour, we confirm that the source is very likely the afterglow of the burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28720 SUBJECT: GRB 201020B: Swift ToO observations DATE: 20/10/21 13:32:38 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 201020B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021035 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: 28723 SUBJECT: Konus-Wind detection of GRB 201020B DATE: 20/10/21 16:18:09 GMT FROM: Anna Ridnaia at Ioffe Institute A. Ridnaia, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 201020B (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 28702, Malacaria & Meegan, GCN Circ. 28710; AGILE detection: Ursi et al., GCN Circ. 28714; Fermi-LAT detection: Arimoto et al., GCN Circ. 28716) triggered Konus-Wind at T0=63237.477 s UT (17:33:57.477). The burst light curve shows a multipeaked structure started at ~T0-5.6 s with a total duration of ~53.7 s. The emission is seen up to ~6 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB201020_T63237/ As observed by Konus-Wind, the burst had a fluence of 4.72(-0.61,+0.70)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+8.016 s, of 1.38(-0.25,+0.25)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+50.432 s) is best fit in the 20 keV - 6 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.12(-0.09,+0.10), the high energy photon index beta = -2.55(-0.56,+0.26), the peak energy Ep = 193(-23,+23) keV (chi2 = 72/97 dof). The spectrum near the maximum count rate (measured from T0+7.424 to T0+8.448 s) is best fit in the 20 keV - 6 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.85(-0.13,+0.14), the high energy photon index beta = -2.78(-3.16,+0.36), the peak energy Ep = 259(-35,+44) keV (chi2 = 41/52 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28725 SUBJECT: GRB 201020B: Mondy optical observations DATE: 20/10/21 17:09:41 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE), A. Volnova (IKI) report on behalf of IKI GRB FuN: We observed the field of GRB 201020B (Fermi GBM team, GCN 28702; Malacaria et al., GCN 28710; Arimoto et al., GCN 28716; Ursi et al., GCN 28714; Ridnaia et al., GCN 28723) with AZT-33IK telescope of Sayan observatory (Mondy) starting on Oct. 21 (UT) 14:20:10. The optical transient (Lipunov et al. GCN 28718; Xu et al. GCN 28719) is well detected in our images in R-filter. Preliminary photometry of the optical transient in a combined image is following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2020-10-21 14:20:10 0.88629 R 60*60 18.99 0.03 22.7 The photometry is based on the nearby USNO-B1.0 stars USNO-B1.0_id R2 1670-0037414 16.74 1670-0037586 16.16 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28740 SUBJECT: GRB 201020B: Swift-XRT afterglow detection DATE: 20/10/22 09:04:39 GMT FROM: Paolo D'Avanzo at INAF - OAB B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), J. D. Gropp (PSU) 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 201020B (Arimoto et al. GCN Circ. 28716), collecting 1.7 ks of Photon Counting (PC) mode data between T0+72.1 ks and T0+74.3 ks. An uncatalogued X-ray source is detected and is above the RASS limit, and is therefore likely the GRB afterglow. Using 1015 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 75.46680, +77.06830 which is equivalent to: RA (J2000): 05h 01m 52.03s Dec(J2000): +77d 04' 05.9" with an uncertainty of 2.0 arcsec (radius, 90% confidence). This position is 9.6 arcmin from the Fermi/LAT position and consistent with the optical counterpart detected by MASTER (Lipunov et al. GCN Circ. 28718). The light curve is consistent with a constant source of mean count rate 1.5e-01 ct/sec. With the currently available dataset we cannot constrain the temporal evolution. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+0.4, -0.3). The best-fitting absorption column is 4.0 (+1.7, -1.4) x 10^21 cm^-2, in excess of the Galactic value of 1.4 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.0 (+1.7, -1.4) x 10^21 cm^-2 Galactic foreground: 1.4 x 10^21 cm^-2 Excess significance: 3.0 sigma Photon index: 2.2 (+0.4, -0.3) The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021035/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021035. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28743 SUBJECT: GRB 201020B: Swift/UVOT Detection DATE: 20/10/22 12:34:19 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 201020B 72102 s after the Fermi GMB/LAT trigger (Fermi GBM team, GCN Circ. 28702; Malacaria and Meegan, GCN Circ. 28710; Arimoto et al., GCN Circ. 28716). A source consistent with the Master position (Lipunov et al., GCN Circ. 28718), also detected by Xu et al., (GCN Circ. 28719), Ridnaia et al. (GCN Circ. 28723), Belkin et al. (GCN Circ. 28723) and Sbarufatti et al. (GCN Circ. 28740), is detected in the initial UVOT exposures. We note there is a faint USNO-B1.0 source (1670-0037526, Bmag ~21.7) 5.2" away from this position. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 73636 73973 332 19.54 ± 0.09 v 73979 74316 331 19.30 ± 0.28 u 72102 72821 708 19.12 ± 0.11 u 73293 73631 332 19.41 ± 0.19 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.15 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28750 SUBJECT: GRB 201020B: Konkoly Obs. optical detection DATE: 20/10/22 18:48:16 GMT FROM: Jozsef Vinko at Konkoly Observatory J. Vinko (Konkoly/ELTE/U Szeged), A. Pal, L. Kriskovics, R. Szakats, A. Ordasi and K. Vida (Konkoly) report on behalf of the "Transient Astrophysical Objects" project: We observed the field of GRB 201020B (Fermi team, GCN 28702; Lipunov et al. GCN 28704; Malacaria and Meegan, GCN 28710; Ursi et al. 28714; Arimoto et al., GCN 28716; Lipunov et al., GCN 28718; Xu et al., GCN 28719; Ridnaia et al., GCN 28723; Belkin et al., GCN 28725; Sbarufatti et al., GCN 28740; Breeveld et al., GCN 28743) with the 0.8m RC80 robotic telescope at Piszkesteto Mountain Station of Konkoly Observatory through SDSS r' and i' filters (exposure time 3 x 300 sec per filter) on 2020 Oct 21.807 UT (MJD 59143.807; 25.8 hours = 92880 s after the trigger). The frames were tied to PS1-photometry of local stellar sources. An optical afterglow of the GRB has been detected with the following AB-magnitudes: r' = 20.869 +/- 2.311 AB mag i' = 19.368 +/- 0.696 AB mag which are consistent with previous detections of the fading afterglow. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28753 SUBJECT: GRB 201020B: GROWTH-India Telescope optical observations DATE: 20/10/22 20:37:16 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar(IITB), K. Sharma(IITB), J. Stanzin(IAO), V. Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA), report on behalf of the GROWTH-India collaboration: We followed-up GRB 201020B reported by Fermi GBM Team (GCN #28702, also see: V. Lipunov et. al., GCN #28718; D. Xu et. al., GCN #28719) with 0.7m GROWTH-India telescope. We obtained 300-sec exposures in the SDSS r’ filter starting at 2020-10-21T14:53:24.42 UT (~ 21.4 hrs after the burst detection by Fermi-GBM). We clearly detected uncataloged sources at a position consistent with V. Lipunov et. al., GCN #28718; D. Xu et. al., GCN #28719. Here are the photometric results from GIT observations:- ------------------------------------------------------------------ JD (mid) | T_mid-T0(hrs) | Filter | Mag | ------------------------------------------------------------------ 2459144.12392 | 21.45 | r | 19.36 +/- 0.07 2459144.12752 | 21.53 | r | 19.49 +/- 0.08 2459144.13110 | 21.62 | r | 19.37 +/- 0.07 2459144.27999 | 25.15 | r | 19.64 +/- 0.02 2459144.30582 | 25.77 | r | 19.79 +/- 0.02 2459144.35140 | 26.86 | r | 19.83 +/- 0.03 2459144.39582 | 27.91 | r | 19.83 +/- 0.03 2459144.42656 | 28.67 | r | 19.89 +/- 0.02 ----------------------------------------------------------------- Combining our photometric results with r band measurements of D. Xu et. al., GCN #28719, we conclude that the source is fading with a power-law index of 1.65 +/- 0.21. The magnitudes are calibrated against PanSTARRs PS1 data release, (Flewelling et al., 2018) and not corrected for galactic extinction. Extrapolating backwards to the epoch of MASTER observations (t0 + 3.2 min), the expected r magnitude is approximately 8.6, significantly higher than the measured clear band magnitude of 13.7. This may be indicative of a break in the afterglow. Further observations are strongly encouraged. 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: 28765 SUBJECT: GRB 201020B: Redshift from GTC/OSIRIS DATE: 20/10/24 06:29:31 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), M. Blazek, J. F. Agui Fernandez, C. C. Thoene (all HETH/IAA-CSIC), S. Geier, and M. Rivero (both GRANTECAN) report: We observed the afterglow (Lipunov et al., GCN#28718; Xu et al., GCN#28719; Belkin et al., GCN#28725; Breeveld & Lien, GCN#28743; Vinko et al., GCN#28750; Kumar et al., GCN#28753) of GRB 201020B (Fermi GBM Team, GCN#28702; Fermi GBM detection: Malacaria & Meegan, GCN#28710; Fermi LAT detection: Arimoto et al., GCN#28716; AGILE detection: Ursi et al., GCN#28714; Konus-Wind detection: Ridnaia et al., GCN#28723) with the 10.4m GTC telescope, at Roque de los Muchachos Observatory (La Palma, Spain) equipped with OSIRIS. The observation started on 24 October 2020 at 04:05:16 UT (3.438 days after the GRB trigger, following a period of inclement weather) and consisted of 4 x 1200 s with the R1000B grism, covering the wavelength range between 3700 and 7800 AA. Observations were taken under good conditions. At the afterglow position, a source is clearly detected. We measure i' ~ 21.45 mag (AB) vs. a nearby PanSTARRS field star. This represents a significant decay compared to the value reported by Vinko et al. (GCN#28750). The afterglow is seen to decay with a slope of 1.68, in full agreement with Kumar et al. (GCN#28753). A preliminary reduction of the spectrum shows a clear but featureless continuum. There is an emission feature, which we identify as due to the [OII]3727 doublet at z = 0.804. Other interpretations (as Hbeta, [OIII] or Halpha) would imply other emission lines should be visible, which they are not. At the same redshift there could be marginal, weak features consistent with FeII, MgII, and MgI. Therefore, we suggest z = 0.804 as the redshift of the GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28768 SUBJECT: GRB 201020B: continued Mondy optical observations DATE: 20/10/24 09:51:25 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) report on behalf of IKI GRB FuN: We continued observations of the GRB 201020B (Fermi GBM team, GCN 28702; Malacaria et al., GCN 28710; Arimoto et al., GCN 28716; Ursi et al., GCN 28714; Ridnaia et al., GCN 28723) with AZT-33IK telescope of Sayan observatory (Mondy) on Oct. 22, 23. The optical afterglow (Lipunov et al., GCN 28718; Xu et al., GCN 28719; Belkin et al., GCN 28725; Breeveld & Lien, GCN 28743; Vinko et al., GCN 28750; Kumar et al., GCN 28753) with redshift of z= 0.804 (Kann et al., GCN 28765) is detected in our stacked images in R-filter. Preliminary photometry of the optical transient in a combined image is following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2020-10-22 17:35:31 2.02195 R 60*60 20.40 0.05 23.0 2020-10-23 14:33:52 2.89719 R 32*120 20.99 0.26 21.1 The photometry is based on the nearby USNO-B1.0 stars USNO-B1.0_id R2 1670-0037414 16.74 1670-0037586 16.16 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28769 SUBJECT: GRB 201020B: follow-up observations at Konkoly DATE: 20/10/24 11:11:02 GMT FROM: Jozsef Vinko at Konkoly Observatory J. Vinko (Konkoly/ELTE/U Szeged), A. Pal, L. Kriskovics, R. Szakats, A. Ordasi and K. Vida (Konkoly) report on behalf of the "Transient Astrophysical Objects" project: Follow-up observations of the optical afterglow of GRB 201020B (Fermi team, GCN 28702; Lipunov et al. GCN 28704; Malacaria and Meegan, GCN 28710; Ursi et al. 28714; Arimoto et al., GCN 28716; Lipunov et al., GCN 28718; Xu et al., GCN 28719; Ridnaia et al., GCN 28723; Belkin et al., GCN 28725; Sbarufatti et al., GCN 28740; Breeveld et al., GCN 28743; Vinko et al. GCN 28750; Kumar et al. GCN 28753; Kann et al. GCN 28765; Belkin et al. GCN 28768) with the 0.8m RC80 telescope at Konkoly Observatory yielded the following magnitudes for the transient: Date UT-mid t-T0(hr) Exp(s) Filter AB mag Err 2020-10-22 19:31:01 49.94 6 x 300 SDSS-r 20.592 0.172 2020-10-22 19:36:07 50.04 6 x 300 SDSS-i 20.566 0.264 tied to local PS1 stars. Our data are consistent with the magnitudes reported by Belkin et al. (GCN 28768). At the redshift of z=0.8 (Kann et al. GCN 28765) these correspond to M ~ -22.9 absolute mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28772 SUBJECT: GRB 201020B: 1.3m DFOT optical observations DATE: 20/10/24 18:24:59 GMT FROM: Dimple Panchal at ARIES, India Dimple (ARIES), A. Ghosh (ARIES), Bhavya (ARIES) , R. Gupta (ARIES) , A. Kumar (ARIES), B. Kumar (ARIES), K. Misra (ARIES), and S. B. Pandey (ARIES) report: We carried out the follow-up observations of GRB 201020B ( Fermi team, GCN 28702; Lipunov et al. GCN 28704; Malacaria and Meegan, GCN 28710; Ursi et al. 28714; Arimoto et al., GCN 28716; Lipunov et al., GCN 28718; Xu et al., GCN 28719; Ridnaia et al., GCN 28723; Belkin et al., GCN 28725; Sbarufatti et al., GCN 28740; Breeveld et al., GCN 28743; Vinko et al. GCN 28750; Kumar et al. GCN 28753; Kann et al. GCN 28765; Belkin et al. GCN 28768; Vinko et al. GCN 28769 ) using 1.3m Devasthal Fast Optical Telescope (DFOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. The observation was started on 2020-10-21 at 21:41:37 UT. We observed a series of images with the exposure time of 60 seconds in both R and I filters (Johnson-Cousins) covering Swift UVOT position RA, Dec = 05h 01m 52.03s, +77d 04' 05.9" ( Sbarufatti et al. GCN 28740). An uncataloged source is clearly visible in the stacked images in both the bands at the position consistent with V. Lipunov et. al. GCN 28718; D. Xu et. al. GCN 28719. Preliminary photometry of the optical transient in the combined images is following Date Start_UT T_start-T0 (hrs) Filter Exp time (s) Magnitude Mag_error ---------------------------------------------------------------------------------------------------------------------------- 2020-10-21 21:41:37 28.280 R 15*60 19.741 0.0262 2020-10-21 22:00:04 28.588 I 15*60 19.298 0.0468 ---------------------------------------------------------------------------------------------------------------------------- Photometry is done based on the USNO-B1.0 catalog. This magnitude is not corrected for Galactic extinction in the direction of the GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28773 SUBJECT: GRB 201020B: follow-up observations with Savelli Telescope DATE: 20/10/24 19:34:16 GMT FROM: Luciano Nicastro at INAF-OAS L. Nicastro (INAF-OAS), A. Brosio (Osservatorio Astronomico Lilio), S. Savaglio (UNICAL) We observed the afterglow (Lipunov et al., GCN 28718; Xu et al., GCN 28719; Belkin et al., GCN 28725; Breeveld & Lien, GCN 28743; Vinko et al., GCN 28750; Kumar et al., GCN 28753; Kann et al., GCN 28765; Belkin et al., GCN 28768; Dimple et al., GCN 28772) of GRB 201020B (Fermi GBM Team, GCN 28702; Fermi GBM detection: Malacaria & Meegan, GCN 28710; Fermi LAT detection: Arimoto et al., GCN 28716; AGILE detection: Ursi et al., GCN 28714; Konus-Wind detection: Ridnaia et al., GCN 28723) with the 0.5m telescope of the Osservatorio Astronomico Lilio, located in Savelli (South Italy). Date / UT-mid JD T-T0(hr) Exp(s) Filter Mag (AB) 2020-10-21T18:47:48.85 | 2459144.28320 | 25.23 | 5 x 300 | Sloan-r | 19.60 +/- 0.12 2020-10-21T19:35:28.72 | 2459144.31630 | 26.03 | 5 x 300 | Sloan-g | 20.02 +/- 0.15 Magnitudes, calibrated wrt nearby PanSTARRS field stars, are not corrected for galactic extinction. Fog prevented us from performing further observations in the following nights. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28776 SUBJECT: GRB 201020B: HCT and GIT continued optical follow-up observations DATE: 20/10/25 09:04:20 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar(IITB), S. Kiran (IIA), J.Stanzin (IAO), V. Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the HCT team: We followed-up GRB 201020B reported by Fermi GBM Team (GCN #28702, also see: V. Lipunov et. al., GCN #28718; D. Xu et. al., GCN #28719) with 2.0m Himalayan Chandra Telescope (HCT) and 0.7m GROWTH-India Telescope (GIT). We obtained a series of 300-sec exposures in the Rc, r filters. Afterglow was clearly detected at a position consistent with V. Lipunov et. al., GCN #28718; D. Xu et. al., GCN #28719. Here are the photometric results from HCT & GIT observations:- ------------------------------------------------------- JD (mid) | T_mid-T0(hrs) | Filter | Mag | Telescope | ------------------------------------------------------- 2459145.40625 | 52.22 | r | 21.01 +/- 0.04 | GIT | 2459146.32699 | 74.80 | Rc | 21.28 +/- 0.04 | HCT | ------------------------------------------------------- Our results are consistent with the power-law decay of 1.67 reported in S. Belkin et al. GCN #28768; H. Kumar et al. GCN #28753. These observations were carried out under the ToO program HCT-2020-C3-P6. We thank HCT and GIT staff for undertaking the observations. 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: 28781 SUBJECT: GRB 201020B: 1.3m DFOT continued optical follow-up observations DATE: 20/10/26 12:23:26 GMT FROM: Amit Kumar at ARIES, India Amit Kumar (ARIES), Rahul Gupta (ARIES), Dimple (ARIES), Ankur Ghosh (ARIES), Kaushal Sharma (ARIES), Amar Aryan (ARIES), Brajesh Kumar (ARIES), Kuntal Misra (ARIES), and Shashi B. Pandey (ARIES) report: We followed-up Fermi GBM triggered GRB 201020B (Fermi team, GCN 28702; Lipunov et al. GCN 28704; Malacaria and Meegan, GCN 28710; Ursi et al. GCN 28714; Arimoto et al., GCN 28716; Lipunov et al., GCN 28718; Xu et al., GCN 28719; Kann et al. GCN 28765) using the 1.3m Devasthal Fast Optical Telescope (DFOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. The observations were carried out on 2020-10-23 (from 19:14:51 to 19:26:16 UT) and 2020-10-24 (from 18:18:43 to 19:24:14 UT) in multiple bands. We took a series of images with the exposure time of 120 seconds in multiple Bessel filters, covering Swift UVOT position (Sbarufatti et al. GCN 28740). The optical transient reported by V. Lipunov et. al. GCN 28718; D. Xu et. al. GCN 28719 is clearly visible in the stacked images. The R-band magnitudes of the GRB afterglow estimated from the photometry of stacked images are as follows: Date Start_UT T_start-T0 (hrs) Filter Exp time (s) Magnitude Mag_error ---------------------------------------------------------------------------------------------------------------------------- 2020-10-23 19:14:51 73.683 R 15*120 21.34 0.05 2020-10-24 19:24:14 97.839 R 30*120 21.83 0.05 ---------------------------------------------------------------------------------------------------------------------------- The estimated magnitudes have not been corrected for the Galactic extinction in the direction of the GRB. Photometric calibration is performed using the following standard stars from the USNO-B1.0 catalog: 1670-0037558 1670-0037526 1670-0037460 1670-0037451 1670-0037450 1670-0037447 Our estimated magnitudes in the R-band, along with the measurements reported by Belkin et al., GCN 28725; Vinko et al. GCN 28750; Belkin et al. GCN 28768; Vinko et al. GCN 28769; Dimple et al. GCN 28772; Nicastro et al. GCN 28773, and Kumar et al. GCN 28776, suggest that the afterglow of GRB 201020B is fading with a power-law index of 1.66 +/- 0.12. The magnitudes reported by Vinko et al. GCN 28750, Vinko et al. GCN 28769, and Nicastro et al. GCN 28773 are convetred to R-band magnitudes using the tranformation equations provided by Lupton et al. (2005). This power-law index is well consistent with those reported by Kumar et al. GCN 28753 and Belkin et al. GCN 28768. This circular may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29191 SUBJECT: GRB 201020B: Assy, Koshka, Mondy and Maidanak optical observations DATE: 20/12/28 21:53:13 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), A. Pozanenko (IKI), V. Kim (FAI, Pulkovo Observatory), M. Krugov (FAI), A. Novichonok (Petrozavodsk State University, KIAM), A. Zhornichenko (KIAM), E. Klunko (ISTP), O. Burhonov (UBAI), Sh. Ehgamberdiev (UBAI) report on behalf of IKI GRB FuN: We additionally observed the GRB 201020B (Fermi GBM team, GCN 28702; Malacaria et al., GCN 28710; Arimoto et al., GCN 28716; Ursi et al., GCN 28714; Ridnaia et al., GCN 28723) with AZT-20 telescope of Assy observatory, Zeiss-1000 of Koshka observatory, AZT-33IK telescope of Sayan observatory (Mondy), and AZT-22 telescope of Maidanak observatory. The optical afterglow (Lipunov et al., GCN 28718; Xu et al., GCN 28719; Belkin et al., GCN 28725; Breeveld & Lien, GCN 28743; Vinko et al., GCN 28750; Kumar et al., GCN 28753; Belkin et al., GCN 28768; Vinko et al., GCN 28769; Vinko et al., GCN 28769; Panchal et al., GCN 28772; Nicastro et al., GCN 28773; Kumar et al., GCN 28776; Kumar et al., GCN 28781) with redshift of z= 0.804 (Kann et al., GCN 28765) is detected in most of stacked images of our observations in R-filter. Preliminary light curve of the afterglow based on our observations including reported earlier (Belkin et al., GCNs 28725, 28768) can be found in http://grb.rssi.ru/GRB201020B/GRB201020B_R_LC.png The photometry is based on the nearby USNO-B1.0 stars USNO-B1.0_id R2 1670-0037414 16.74 1670-0037586 16.16