//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31201 SUBJECT: GRB 211211A: Fermi GBM Final Real-time Localization DATE: 21/12/11 13:20:10 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 13:09:59 UT on 11 Dec 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 211211A (trigger 660921004.65092 / 211211549). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 211.3, Dec = 27.1 (J2000 degrees, equivalent to J2000 14h 05m, 27d 06'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 111.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211211549/quicklook/glg_skymap_all_bn211211549.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211211549/quicklook/glg_healpix_all_bn211211549.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn211211549/quicklook/glg_lc_medres34_bn211211549.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31202 SUBJECT: GRB 211211A: Swift detection of a bright burst DATE: 21/12/11 13:32:57 GMT FROM: David Palmer at LANL A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 13:09:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 211211A (trigger=1088940). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 212.272, +27.884d which is RA(J2000) = 14h 09m 05s Dec(J2000) = +27d 53' 01" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to a telemetry dropout, the immediately available BAT lightcurve starts at T+8s, and shows a bright complex burst that extends at least to T+100s. At T+8s the count rate is 300k counts/sec (15-350 keV), but the earlier peak may be significantly higher. The XRT began observing the field at 13:11:18.7 UT, 79.2 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 212.2912, 27.8899 which is equivalent to: RA(J2000) = 14h 09m 9.89s Dec(J2000) = +27d 53' 23.6" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 64 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of nominal 150.000 seconds with the White filter starting 87 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Data from the 2.7'x2.7' sub-image are not available at this time. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.018. Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31203 SUBJECT: GRB 211211A: KAIT Optical Afterglow Candidate DATE: 21/12/11 14:37:08 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, responded to Swift GRB 211211A (Trigger 1088940) starting at Dec. 11, 13:46:25 UT. We detected an uncataloged optical afterglow candidate at position (error ~0.5"): RA: 14:09:10.09 (J2000) Dec: +27:53:18.23 (J2000) We estimate the clear band magnitude ~20.3 in out clear band image at ~0.63 hours after burst. We can not estimate the variability at this time, further observations are encouraged. We also notice the afterglow candidate location is very close to a SDSS galaxy (SDSS ID: 1237665429707096375, with r = 19.53 mag), it is unclear if the galaxy is related to the GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31205 SUBJECT: GRB 211211A: Enhanced Swift-XRT position DATE: 21/12/11 19:41:53 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1514 s of XRT Photon Counting mode data and 3 UVOT images for GRB 211211A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 212.29202, +27.88857 which is equivalent to: RA (J2000): 14h 09m 10.09s Dec (J2000): +27d 53' 18.8" with an uncertainty of 2.1 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31206 SUBJECT: Fermi GRB 211211A: Global MASTER-Net observations report DATE: 21/12/11 21:45:07 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, T.Pogrosheva, E.Minkina, A.Chasovnikov, V.Topolev, V.Grinshpun, 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 (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University) MASTER-Amur robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Blagoveshchensk State Pedagogical University) started inspect of the Fermi GRB 211211A ( Fermi GBM team, GCN 31201) errorbox 29692 sec after notice time and 29701 sec after trigger time at 2021-12-11 21:25:00 UT, with upper limit up to 13.5 mag. The observations began at zenith distance = 39 deg. The sun altitude is -17.3 deg. The galactic latitude b = 73 deg., longitude l = 37 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1810719 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 29791 | 2021-12-11 21:25:00 | MASTER-Amur | (14h 05m 02.43s , +27d 44m 17.7s) | C | 180 | 13.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31209 SUBJECT: GRB 211211A: Swift-BAT refined analysis DATE: 21/12/12 03:14:09 GMT FROM: Amy Lien at GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+360 sec from the recent telemetry downlink, we report further analysis of BAT GRB 211211A (trigger #1088940) (D'Ai et al., GCN Circ. 31202). The BAT ground-calculated position is RA, Dec = 212.272, 27.884 deg which is RA(J2000) = 14h 09m 05.2s Dec(J2000) = +27d 53' 03.8" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 21%. The mask-weighted light curve shows a multi-peaked structure that starts at ~T0 and ends at ~T+140 s. The main peak occurs at ~T+7 s. T90 (15-350 keV) is 51.37 +- 0.80 sec (estimated error including systematics). The time-averaged spectrum from T0 to T+142.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.56 +- 0.02. The fluence in the 15-150 keV band is 1.5 +- 0.02 x 10^-04 erg/cm2. The 1-sec peak photon flux measured from T+6.86 sec in the 15-150 keV band is 155.0 +- 3.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1088940/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31210 SUBJECT: GRB 211211A: Fermi GBM observation DATE: 21/12/12 07:31:36 GMT FROM: Joe Mangan at UCD J.Mangan (UCD), R.Dunwoody (UCD) and C.Meegan (UAH) report on behalf of the Fermi GBM Team: At 13:09:59.651 UT on 11 December 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 211211A (trigger 660921004 / 211211549) which was also detected by the Swift/BAT (D'Ai et al., GCN 31202). The Fermi GBM Final Real-time Localization (GCN 31201) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 106.5 degrees. The GBM light curve consists of an exceptionally bright emission made up of three separate pulses with a duration (T90) of about 34.3s (50-300 keV). The time-averaged spectrum from T0-1.264 s to T0+54.033 s is best fit by a Band function with Epeak = 646.8 +/- 7.8 keV, alpha = -1.3 +/- 0.00, and beta = -2.4 +/- 0.02 The event fluence (10-1000 keV) in this time interval is (5.4 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.8 s in the 10-1000 keV band is 324.9 +/- 1.5 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: 31212 SUBJECT: GRB 211211A: Swift-XRT refined Analysis DATE: 21/12/12 11:39:52 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester) and A. D'Ai report on behalf of the Swift-XRT team: We have analysed 8.1 ks of XRT data for GRB 211211A (D'Ai et al. GCN Circ. 31202), from 69 s to 74.2 ks after the BAT trigger. The data comprise 214 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 31205). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.99 (+0.13, -0.10). At T+171 s the decay steepens to an alpha of 4.19 (+0.31, -0.21). The light curve breaks again at T+704 s to a decay with alpha=-0.4 (+0.7, -0.6), before a final break at T+5861 s s after which the decay index is 1.63 (+0.15, -0.13). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.80 (+/-0.03). The best-fitting absorption column is 4.5 (+/-0.8) x 10^20 cm^-2, in excess of the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.50 (+0.12, -0.06) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.2 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.8 (+2.5, -0.0) x 10^20 cm^-2 Galactic foreground: 1.8 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.50 (+0.12, -0.06) If the light curve continues to decay with a power-law decay index of 1.63, the count rate at T+24 hours will be 0.020 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x 10^-13 (8.9 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01088940. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31213 SUBJECT: GRB 211211A: Nanshan/NEXT optical observations DATE: 21/12/12 11:42:12 GMT FROM: Dong Xu at NAOC/CAS S.Q. Jiang (NAOC), Z.P. Zhu (NAOC, HUST), S.Y. Fu, X. Liu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of GRB 211211A detected by Fermi (Fermi GBM team, GCN 31201) and Swift (D'Ai et al., GCN 31202) using the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. Observations started at 23:01:09 UT on 2021-12-11, i.e., 9.85 hr after the BAT trigger, and 10x200 s frames in the Sloan r-filter as well as 12x200 s frames in the Sloan z-filter were obtained. The optical afterglow candidate of the GRB reported by KAIT (Zheng & Filippenko, GCN 31203), consistent with the enhanced Swift-XRT position (Beardmore et al., GCN 31205), is detected in our stacked r- and z-band images. Preliminary photometry is as follows: T_mid-T0 (hr) Mag MagErr Filter 10.34 20.29 0.07 r 10.68 19.9 0.3 z both calibrated with nearby PS1 stars. We note that the NEXT's r-band magnitude is comparable to that of KAIT in the clear band, although the time interval of the two observations is ~10 hr. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31214 SUBJECT: GRB 211211A: LCO Optical Observations DATE: 21/12/12 12:50:00 GMT FROM: Robert Strausbaugh at U. of the Virgin Islands R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (College of Marin) report on behalf of a larger collaboration: We observed Swift GRB 211211A (D'Ai et al., GCN 31202) with the LCO 1-m Sinistro instrument at the Teide Observatory, Tenerife site, on December 12, from 05:57 to 06:33 UT (corresponding to 16.8 to 17.4 hours from the GRB trigger time) with the Bessel R and I filters. We performed a series of 3x400s exposures in R and I bands. We detect a source in both R-band and I-band that is consistent with the Swift Enhanced XRT coordinates (Osborne, et al., GCN 31212) and the optical observations by KAIT (Zheng et al., GCN 31203) and Nanshan/NEXT (Jiang et al., GCN 31213); there appears to be fading in the R band compared to those earlier observations. The following magnitudes are calculated using the USNO-B.1 catalog as reference: R=20.83+/-0.09 I=21.49+/-0.25 These magnitudes are not corrected for galactic extinction. R.S. is funded by NSF AST grant #1831682 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31216 SUBJECT: Swift GRB 211211A: Global MASTER-Net observations report DATE: 21/12/12 13:10:09 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, T.Pogrosheva, E.Minkina, A.Chasovnikov, V.Topolev, V.Grinshpun, 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 (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University) MASTER-Amur robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Blagoveshchensk State Pedagogical University) was pointed to the Swift GRB 211211A ( A. D'Ai et al., GCN 31202) errorbox 29687 sec after notice time and 29621 sec after trigger time at 2021-12-11 21:25:00 UT, with upper limit up to 13.5 mag. The observations began at zenith distance = 39 deg. The sun altitude is -17.3 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 211211A errorbox 35200 sec after notice time and 35135 sec after trigger time at 2021-12-11 22:56:53 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 80 deg. The sun altitude is -59.4 deg. MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 211211A errorbox 37423 sec after notice time and 37358 sec after trigger time at 2021-12-11 23:33:56 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 79 deg. The sun altitude is -58.1 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 211211A errorbox 52860 sec after notice time and 52795 sec after trigger time at 2021-12-12 03:51:13 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 76 deg. The sun altitude is -50.4 deg. The galactic latitude b = 72 deg., longitude l = 39 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1810696 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 29712 | MASTER-Amur | C | 180 | 13.5 | 35165 | MASTER-Kislovodsk | C | 60 | 17.4 | 35165 | MASTER-Kislovodsk | C | 60 | 17.5 | 35706 | MASTER-Kislovodsk | C | 180 | 18.0 | 35706 | MASTER-Kislovodsk | C | 180 | 18.2 | 36851 | MASTER-Kislovodsk | C | 60 | 17.4 | 36851 | MASTER-Kislovodsk | C | 60 | 17.7 | 37448 | MASTER-Tavrida | C | 180 | 17.1 | 37472 | MASTER-Kislovodsk | C | 180 | 18.3 | 37472 | MASTER-Kislovodsk | C | 180 | 18.6 | 38013 | MASTER-Kislovodsk | C | 60 | 17.5 | 38013 | MASTER-Kislovodsk | C | 60 | 18.0 | 38452 | MASTER-Tavrida | C | 60 | 17.0 | 39166 | MASTER-Tavrida | C | 60 | 17.2 | 39404 | MASTER-Tavrida | C | 60 | 17.1 | 40330 | MASTER-Tavrida | C | 60 | 15.6 | 40488 | MASTER-Tavrida | C | 60 | 15.1 | 40697 | MASTER-Kislovodsk | C | 180 | 18.3 | 40697 | MASTER-Kislovodsk | C | 180 | 18.4 | 41906 | MASTER-Tavrida | C | 60 | 12.8 | 41960 | MASTER-Kislovodsk | C | 60 | 18.0 | 42458 | MASTER-Tavrida | C | 60 | 12.2 | 42921 | MASTER-Kislovodsk | C | 60 | 18.3 | 43375 | MASTER-Tavrida | C | 180 | 13.2 | 43594 | MASTER-Tavrida | C | 60 | 12.0 | 43883 | MASTER-Kislovodsk | C | 60 | 18.3 | 48892 | MASTER-Kislovodsk | C | 180 | 18.9 | 48892 | MASTER-Kislovodsk | C | 180 | 19.1 | 49751 | MASTER-Tavrida | C | 180 | 14.4 | 49972 | MASTER-Tavrida | C | 60 | 13.9 | 50256 | MASTER-Kislovodsk | C | 180 | 18.5 | 50256 | MASTER-Kislovodsk | C | 180 | 18.5 | 50288 | MASTER-Tavrida | C | 60 | 13.2 | 51619 | MASTER-Kislovodsk | C | 180 | 16.8 | 51619 | MASTER-Kislovodsk | C | 180 | 14.5 | 52825 | MASTER-IAC | C | 60 | 16.3 | 52905 | MASTER-IAC | C | 60 | 14.0 | 52985 | MASTER-IAC | C | 60 | 17.3 | 54066 | MASTER-Tavrida | C | 60 | 15.2 | 54626 | MASTER-IAC | C | 60 | 17.4 | 54706 | MASTER-IAC | C | 60 | 17.4 | 54786 | MASTER-IAC | C | 60 | 17.6 | 55666 | MASTER-IAC | C | 60 | 17.5 | 55746 | MASTER-IAC | C | 60 | 17.9 | 56120 | MASTER-IAC | C | 60 | 17.9 | 59363 | MASTER-IAC | C | 180 | 18.7 | 59363 | MASTER-IAC | C | 180 | 18.7 | 60352 | MASTER-IAC | C | 180 | 18.9 | 60352 | MASTER-IAC | C | 180 | 18.7 | 61693 | MASTER-IAC | C | 180 | 18.9 | 61693 | MASTER-IAC | C | 180 | 18.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31217 SUBJECT: GRB 211211A: MITSuME Akeno optical observation DATE: 21/12/12 13:18:20 GMT FROM: Naohiro Ito at Tokyo Tech N. Ito, R. Hosokawa, K. L. Murata, Y. Imai, Y. Takamatsu, M. Takaku, M. Niwano, R. Noto, S. Sato, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 211211A (The Fermi GBM team GCN Circular #31201, A. D'Ai et al. GCN Circular #31202, WeiKang Zheng and Alexei V. Filippenko GCN Circular #31203, A.P. Beardmore et al. GCN Circular #31205, V. Lipunov et al. GCN Circular #31206, M. Stamatikos et al. GCN Circular #31209, J.Mangan et al. GCN Circular #31210, J.P. Osborne et al. GCN Circular #31212, S.Q. Jiang et al. GCN Circular #31213, R. Strausbaugh and A. Cucchiara GCN Circular #32214) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation with a series of 60 sec exposures was carried out from 2021-12-11 17:32:12 UT (~4.4 hours after the Fermi trigger) to 2021-12-11 21:20:21 UT. We stacked the images with good conditions. We marginally detected the optical afterglow candidate reported by the KAIT observation (WeiKang Zheng and Alexei V. Filippenko GCN Circular #31203), Nanshan/NEXT observation (S.Q. Jiang et al. GCN Circular #31213) and LCO observation (R. Strausbaugh and A. Cucchiara GCN Circular #32214) in our g'-, Rc- and Ic- band images. The candidate in our images is blended with the nearby SDSS galaxy (SDSS ID: 1237665429707096375, reported by GCN Circular #31203). We performed forced photometry at the position of the candidate against the nearby galaxy. The magnitudes and the 5-sigma limits of the stacked images are as follows. T0+[hour] | MID-UT | T-EXP[sec] | candidate magnitude | 5-sigma limits ------------------------------------------------------------------------------------------------ 6.3 | 2021-12-11 19:25:34 | 6600 | g'=20.4 +/- 0.2, Rc=20.3 +/- 0.1, Ic=20.4 +/- 0.3 | g'>20.2, Rc>20.7, Ic>19.7 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used id 141492123232234127 of PS1 catalog for flux calibration. The conversion from PS1 r and i band to our Rc and Ic band is by the equation of Tonry et al. (2012), Table. 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31218 SUBJECT: GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA DATE: 21/12/12 13:53:45 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (Obs. Cote d’Azur), D.A. Kann, C. Thoene, J.F. Agui Fernandez, M. Blazek (HETH/IAA-CSIC) and A. Guijarro (CAHA) report: We observed the optical afterglow of GRB 211211A (Fermi team GCN31201; D’Ai et al. GCN31202; Zheng and Filipenko GCN 31203) with CAFOS, mounted on the 2.2m telescope, at the Calar Alto Observatory (Almería, Spain). The observation started at 04:54 UT (15.73 hr after the GRB) and consisted of 30x90s in i-band. The optical afterglow is well detected at a magnitude (AB) of i = 20.83+/-0.05, as compared to field stars from the SDSS catalogue. This magnitude confirms the plateau or very shallow decay phase undergone by the afterglow light curve since the early detection (Zheng and Filipenko GCN 31203) already noted by Jiang et al. (GCN 31213) and consistent with the observations of Strausbaugh & Cucchiara (GCN 31214) and Ito et al. (GCN 31217). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31221 SUBJECT: GRB 211211A: NOT optical spectroscopy DATE: 21/12/12 16:24:56 GMT FROM: Daniele B Malesani at Radboud U D. B. Malesani (Univ. Radboud and DAWN/NBI), J. P. U. Fynbo (DAWN/NBI), A. de Ugarte Postigo (Obs. Cote d'Azur), L. Izzo (DARK/NBI), S. Fu, D. Xu, Z. Zhu (NAOC/CAS), N. R. Tanvir (Univ. Leicester), A. A. Djupvik (NOT), report on behalf of a larger collaboration: We observed the optical afterglow of GRB 211211A (D'Ai et al., GCN 31202; Zheng & Filippenko, GCN 31203) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. Images were secured in the SDSS r, g and i filters. At the mean time of Dec 12.24 UT (16.6 hr after the GRB), we measure a magnitude r = 20.89 +- 0.05 AB, calibrated against nearby stars from the Pan-STARRS survey. Our measurement is in agreement with those by Strausbaugh & Cucchiara (GCN 31214) and de Ugarte Postigo et al. (GCN 31218), taken at a comparable epoch. Compared to the magnitudes reported by Zheng & Filippenko (GCN 31203), Ito et al. (GCN 31217) and Jang (GCN 31213), our data confirm the unusually slow decay, We report for the afterglow the following coordinates (0.3" uncertainty): RA = 14:09:10.12 Dec = +27:53:18.1 A bright, extended object (r ~ 19.5) is visible about 5.5" to the N-E of the afterglow (as already pointed out by Zheng & Filippenko, GCN 31203), which is also visible in the SDSS, Pan-STARRS, and Legacy surveys. A spectrum was secured covering both the afterglow and the nearby galaxy (wavelength range 3700-9400 AA). A weak emission line is detected on top of the host galaxy trace at 7063 AA, which could be due to Halpha at z = 0.076. This is marginally consistent with the SDSS photometric redshift 0.140 +- 0.0375, unlike other interpretations of the same line. No clear absorption or emission features are detected in the afterglow trace. This may be due to the modest S/N, and is also consistent with a low redshift, as is the detection of the afterglow in all the UVOT UV filters (Swift observation ID 1088940000). It is not clear at the present stage whether the afterglow is physically associated with the galaxy at z = 0.076. While the sky proximity and the low redshift are indeed suggestive, the physical offset at z = 0.076 would be about 8 kpc (in projection), an unusually large value for long GRBs. There is also no visible emission in the archival images down to r ~ 24 (AB) at the location of the afterglow, which would be unusual for a long GRB at z = 0.076. Moreover, if placed at z = 0.076, GRB 211211A would be an outlier of the the Amati relation (e.g. Nava et al. 2012, MNRAS, 421, 1256), with E_iso = 1.4*10^54 erg and E_peak ~ 700 keV (using the Fermi/GBM prompt properties from Mangan et al., GCN 31210). Overall, a moderate-redshift GRB (with z > 0.076) is consistent with the available information. The detection of an emerging supernova could clarify the situation. We encourage further photometric and spectroscopic follow-up of this potentially interesting event. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31222 SUBJECT: GRB 211211A: Swift/UVOT detection DATE: 21/12/12 18:19:57 GMT FROM: Alexander Belles at PSU/Swift A. Belles (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 211211A 92 s after the BAT trigger (D'Ai et al., GCN Circ. 31202). A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 31205) and optical position (Zheng & Filippenko, GCN Circ. 31203) is detected in the initial UVOT exposures. Preliminary detections and 3-sigma upper limits 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 wh_FC 92 242 147 18.93+/-0.22 wh 3906 4106 196 18.33+/-0.09 wh 68215 68397 179 >19.74 b 3701 3901 196 18.97+/-0.28 b 16837 17437 587 19.27+/-0.28 b 67303 68210 885 19.70+/-0.24 v 4317 4517 196 >18.33 u 3496 5012 275 18.26+/-0.16 u 15924 16831 885 18.44+/-0.11 u 57177 74247 362 >18.89 w1 4727 4927 196 17.46+/-0.16 m2 4522 4721 196 17.58+/-0.19 m2 21678 22153 467 18.18+/-0.18 w2 4112 4312 196 17.30+/-0.15 w2 61756 62656 885 18.94+/-0.24 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.018 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31223 SUBJECT: GRB 211211A: incorrect E_iso value in GCN 31221 DATE: 21/12/12 18:45:59 GMT FROM: Daniele B Malesani at Radboud U D. B. Malesani (Radboud Univ. and DAWN/NBI) reports: The GRB 211211A E_iso value reported by Malesani et al. (GCN 31221) is incorrect. Using the Fermi GBM fluence 5.4*10^-4 erg cm^-2 (Mangan et al., GCN 31210), the corresponding E_iso value is 6.9*10^51 erg, assuming the GRB is at z = 0.076. The conclusion that GRB 211211A would not be consistent with the Amati relation if at z = 0.076 was based on the correct E_iso value, and still holds. This may indicate that the GRB lies in fact at a higher redshift. I sincerely apologize for any confusion caused by this mistake, and I am grateful to those who pointed it out, including Peter Veres, D. Alexander Kann, and Lorenzo Amati. No blame should be assigned to the other co-authors of GCN 31221, who saw an earlier draft which did not contain the mistake. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31226 SUBJECT: GRB 211211A: CALET Gamma-Ray Burst Monitor detection DATE: 21/12/13 08:58:30 GMT FROM: Valentin Pal'shin at AGU T. Tamura (Kanagawa U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long bright GRB 211211A (Swift detection: Ambrosi et al., GCN Circ. 31202, Stamatikos et al., GCN Circ. 31209; Fermi GBM observation: Mangan et al., GCN Circ. 31210; https://gcn.gsfc.nasa.gov/other/211211A.gcn3) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 13:09:57.513 UTC on 11 December 2021 (http://cgbm.calet.jp/cgbm_trigger/flight/1323263412/index.html). The burst signal was seen by all CGBM detectors. The burst light curve shows several partially overlapped multi-peaked pulses which start at T+3.6 sec, peak at T+9.1 sec,and end at T+73.1 sec. The T90 and T50 durations measured by the SGM data are 33.8 +- 0.9 sec and 12.1 +- 0.4 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1323263412/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31227 SUBJECT: GRB 211211A: HCT and GIT optical follow up observations DATE: 21/12/13 11:11:53 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar(IITB), V. Bhalerao(IITB), Rahul Gupta(ARIES), Rigzin Norbu (IAO), G. C. Anupama(IIA), D. K. Sahu (IIA), S. Barway(IIA), A. Dutta (IIA), B. Kumar (ARIES), Dimple (ARIES), S.B. Pandey (ARIES), Kuntal Mishra (ARIES) report on behalf of the HCT and GIT team: We observed GRB 211211A detected by Fermi GBM (GCN #31201) and Swift-BAT (A. D'Ai et al., GCN #31202); optical counterpart first reported by W Zheng and A V. Filippenko, (GCN #31203) with 2.0m Himalayan Chandra Telescope (HCT) and 0.7m GROWTH-India Telescope (GIT). We obtained a 900-sec exposure in the Bessell R filter using HCT and multiple 300-sec r' band exposures with GIT. We obtained the following photometric results:- --------------------------------------------------------------------- JD (mid) | T_mid-T0(hrs) | Exposure | Filter | Magnitude | Tel | --------------------------------------------------------------------- 2459560.50469 | 10.94 | 900 sec | Bessell R | 20.30 +/- 0.13 | HCT | 2459561.47439 | 34.21 | 1500 sec | r' | > 21.19 | GIT | --------------------------------------------------------------------- Our results from HCT are similar to R band magnitudes reported in N. Ito et. al, (GCN #31217) which suggests that there was no significant decay in the early hours ( <~11 hrs). GIT r' band observations at ~34 hrs did not detect the afterglow, with a limiting magnitude of 21.19 - confirming the fading of the afterglow at late times reported by R. Strausbaugh et. al., (GCN #31214). The magnitudes were calibrated by querying the SDSS catalog (Alam+, 2015). We converted magnitudes to the R band using Lupton (2005) equations for HCT calibration. HCT observations were carried out under the ToO program HCT-2021-C3-P02. We thank HCT and GIT observers, 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 (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31228 SUBJECT: GRB 211211A: Further observations from CAFOS/2.2m CAHA DATE: 21/12/13 17:22:44 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (Obs. Cote d’Azur), D.A. Kann, C. Thoene, J.F. Agui Fernandez, M. Blazek (HETH/IAA-CSIC), I. Vico and A. Guijarro (CAHA) report: We obtained a second imaging observation of the optical afterglow of GRB 211211A (Fermi team GCN31201; D’Ai et al. GCN31202; Zheng and Filipenko GCN 31203) with CAFOS, mounted on the 2.2m telescope, at the Calar Alto Observatory (Almería, Spain). The observation started at 04:47 UT (39.6 hr after the GRB) and consisted of 30x90s in i-band. The optical afterglow is still detected, at a magnitude (AB) of i = 22.45+/-0.09, as compared to field stars from the SDSS catalogue. With respect to our earlier CAFOS photometry (de Ugarte Postigo et al. GCN 31218) this implies a rapid decay rate of alpha = 1.65, where F_nu ~ t^-alpha, which would indicate a post-jet break evolution. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31229 SUBJECT: GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA DATE: 21/12/14 16:25:45 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (Obs. Cote d’Azur), D.A. Kann, C. Thoene, J.F. Agui Fernandez, M. Blazek (HETH/IAA-CSIC), I. Vico and A. Guijarro (CAHA) report: We obtained further i-band imaging of the afterglow of GRB 211211A (Fermi team GCN31201; D’Ai et al. GCN31202; Zheng and Filipenko GCN 31203) from CAFOS/2.2m CAHA 2.66 days after the burst onset. The observation consisted of 20x120s exposures under good seeing and yielded a faint detection. The light curve decay, compared to our previous observation from Calar Alto (de Ugarte Postigo et al., GCN 31228) indicates an extreme decay index of alpha = 3.25+/-0.40. This is similar to what is observed from the XRT light curve, which currently decays with an index of 3.2 (-0.7,+0.8) (https://www.swift.ac.uk/xrt_live_cat/01088940/ ; Evans et al. 2007; Evans et al. 2009). We note that this is amongst the fastest post-break decays that are normally observed for GRB afterglows. Further observations with larger telescopes are encouraged. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31230 SUBJECT: GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection DATE: 21/12/14 17:35:39 GMT FROM: Alexei Pozanenko at IKI, Moscow P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN: We analyzed GRB 211211A (D'Ai et al. GCN 31202; Mangan et al. GCN 31210; Tamura et al. GCN 31226) using publicly available data of GBM/Fermi and SPI-ACS/INTEGRAL. Using GBM/Fermi we estimate a duration in 7 - 850 keV energy band T_90 = 50.6 +/- 0.1 s, while the emission is seen at least up to 130 s after the trigger. We performed spectral analysis in time interval of (-0.5, 60) s, covering the main part of GRB activity. The best fit is obtained for (Band model + thermal component) with following parameters: E_p = 758 +/- 13 keV, alpha = -1.21 +/- 0.01, beta = -2.54 +/- 0.03 and thermal spectral component with kT = 13.9 +/- 0.3 keV. The fluence of F = (5.47 +/- 0.01)E-4 erg/cm**2 is obtained in 10 - 1000 keV energy band. The parameter E_p = 758 +/- 13 keV is higher than preliminary value presented by GBM team (Mangan et al., GCN 31210) due to inclusion of the thermal component in the fit. Assuming a redshift of z = 0.076 (Malesani et al., GCN 31221) we estimated E_iso = (1.161 +/- 0.006)E52 erg in the 1 keV - 10 MeV energy band. The burst is placed very close but outside the 2 sigma correlation region at E_p,i - E_iso and T_90,i - EH diagrams [1,2], see the Figures in http://grb.rssi.ru/GRB211211A/GRB211211A_Ep-Eiso-2.png http://grb.rssi.ru/GRB211211A/GRB211211A_EHD.png Using T_90,i - EH diagram we found minimal possible redshift value of z = 0.080, very close to the redshift of z = 0.076 (Malesani et al., GCN 31221). Therefore, we consider GRB 211211A as not a significant outlier. The burst was also detected by SPI-ACS/INTEGRAL. Its duration in the SPI-ACS energy band (> 80 keV) is T_90 = 30.0 +/- 0.2 s, while the emission is seen up to 70 s. Comparing fluences of long-duration GRBs simultaneously recorded by SPI-ACS and Fermi/GBM (Chelovekov et al., in preparation) we estimated the GRB 211211A fluence to be 5.5E-4 erg/cm**2 in the 10-1000 keV energy band (the 95% confidence region 1.6-4 – 1.9E-3 erg/cm**2, incl. systematics). GRB 211211A is one of the brightest GRBs of SPI-ACS/INTEGRAL sample in terms of peak flux (about 40000 cnts/50 ms). The SPI-ACS light curve of GRB 211211A can be found in http://grb.rssi.ru/GRB211211A/GRB211211A_SPI-ACS_lc-2.png [1] - Minaev et al., MNRAS, 492, 1919, 2020 [2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31232 SUBJECT: GRB 211211A: GMG upper limit DATE: 21/12/15 02:00:51 GMT FROM: Jirong Mao at Yunnan Obs J. Mao, Y.-X. Xin, and J.-M. Bai (YNAO) report: We observed the field of GRB 211211A (D'Ai et al. GCN 31202) by the GMG telescope in Yunnan observatories. The observation began from UT 22:41:02 Dec 12, 2021, about 33.5 hours from the trigger. We could not observe the optical afterglow down to a magnitude limit of r~22.0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31233 SUBJECT: GRB 211211A: AbAO optical observations DATE: 21/12/15 15:44:10 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE, IKI), A. Pozanenko (IKI), S. Belkin (IKI), R. Ya. Inasaridze (AbAO), D. Datashvili (AbAO), V. R. Ayvazian (AbAO), G. V. Kapanadze (AbAO) report on behalf of GRB IKI FuN: We observed the field of GRB 211211A (Fermi team GCN 31201, D'Ai et al. GCN 31202; Mangan et al. GCN 31210; Tamura et al. GCN 31226) with AS-32 telescope of Abastumani observatory (AbAO) in R-filter on 2021-12-13 (UT) 02:21:44 and 2021-12-14 (UT) 01:49:33. In the first epoch we marginally detected an afterglow (Zheng and Filippenko GCN 31203; Jiang et al. GCN 31213; Strausbaugh et al. GCN 31214; Ito et al. GCN 31217; de Ugarte Postigo et al. GCN 31218,31228,31229; Malesani et al. GCN 31221; Belles et al. GCN 31222; Kumar et al. GCN 31227). In the second epoch we obtained only an upper limit. Preliminary photometry of the field is following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2021-12-13 02:21:44 1.56233 R 36*60 21.6 S/N=3 21.6 2021-12-14 01:49:33 2.52748 R 43*60 n/d n/d 21.8 The photometry is based on the nearby SDSS stars: SDSS-DR12 RA DEC R(Lupton transfoemations) 14:09:08.84448 +27:53:54.5604 15.833 14:09:04.53240 +27:54:10.4760 16.701 14:08:57.03480 +27:54:50.2632 17.677 14:08:57.87816 +27:55:06.0924 17.805 14:09:03.80928 +27:55:56.5464 17.104 14:09:07.89072 +27:55:43.9968 18.640 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31234 SUBJECT: GRB 211211A: SAO RAS optical observations DATE: 21/12/15 17:28:29 GMT FROM: Moskvitin Alexander at SAO RAS A. Moskvitin (SAO), O. Spiridonova (SAO), S. Belkin (IKI), A. Pozanenko (IKI), N. Pankov (HSE, IKI) report on behalf of GRB IKI FuN: We observed the field of GRB 211211A (Fermi team GCN 31201, D'Ai et al. GCN 31202; Mangan et al. GCN 31210; Tamura et al. GCN 31226) with Zeiss-1000 telescope of SAO RAS in Rc-filter on 2021.12.14 (UT) 02:03:33. We marginally detected an afterglow (Zheng and Filippenko GCN 31203; Jiang et al. GCN 31213; Strausbaugh et al. GCN 31214; Ito et al. GCN 31217; de Ugarte Postigo et al. GCN 31218,31228,31229; Malesani et al. GCN 31221; Belles et al. GCN 31222; Kumar et al. GCN 31227; Pankov et al. GCN 31233). Preliminary photometry of the afterglow is following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2021-12-14 02:03:33 2.55803 Rc 6*600 23.2 S/N=2.5 23.1 The photometry is based on the nearby SDSS stars: SDSS-DR12 RA DEC R(Lupton transformations) 14:09:08.84 +27:53:54.56 15.833 14:09:04.53 +27:54:10.48 16.701 14:08:57.03 +27:54:50.26 17.677 14:08:57.88 +27:55:06.09 17.805 14:09:03.81 +27:55:56.55 17.104 14:09:07.89 +27:55:44.00 18.640 The light curve based on published photometry can be found in http://grb.rssi.ru/GRB211211A/GRB211211A_LC.png Using R-photometry we found a single power law decay index of -1.5 between 0.4 and 2.6 days after the burst trigger. However the power law index between 1.6 days (Pankov et al. GCN 31233) and 2.6 days (this circ.) we may assume power law index of -3.25 which confirm very fast decay in i-filter observed by CAFOS/2.2mCAHA (de Ugarte Postigo et al. GCN 31229). Based on a typical power law decay of afterglows we may suggest a bump in the LC at ~ 2.5 days followed by a power law decay index of 1.5. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31235 SUBJECT: GRB 211211A - Gemini K-band detection DATE: 21/12/15 21:19:50 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (Radboud), J. Rastinejad (Northwestern), B. Gompertz (Birmingham), W. Fong (Northwestern), D. B. Malesani (Radboud), M. Nicholl (Birmingham) report for a larger collaboration: “We obtained K-band observations of GRB 211211A (D’Ai et al., GCN 31202) with the Gemini-North Telescope and NIRI. Observations began at 14:40 UT on 15 Dec 2021 (~4 days after the GRB). A total of 900 s of exposure were obtained. At the location of the afterglow identified by Zheng & Fillipenko (GCN 31203) we clearly detect a K-band source. Photometry is complicated by the narrow field of view, however, using the 2MASS source at RA, DEC(J2000)=14:09:08,86, 27:53:54.4 with a magnitude of K=12.8, we determine an afterglow magnitude of K = 20.5 +/- 0.1 (Vega) or 22.4 +/- 0.1 (AB). This magnitude is substantially brighter than expected for afterglow emission given the rapid decay observed in the i-band (de Ugarte Postigo et al., GCN 31229), and the relatively blue colours and spectra of the source at earlier times (Malesani et al., GCN 31221; Belles & D’Ai, GCN 31222). The rapid fading and relative faintness in the optical apparently rules out a classical long-GRB at z = 0.076, since a supernova akin to those seen in long GRBs at this epoch would have i ~ 20, 4 magnitudes brighter than observed by de Ugarte Postigo et al. (GCN 31229). Alternatively, the prompt light curve appears to show some similarities with GRB 060614, another suggested short-GRB with extended emission (Gehrels et al. 2006 Nature 444 1044). If GRB 211211A is associated with a compact object merger, its large offset relative to the putative host at z = 0.076 may be expected. The absolute magnitude of the source seen in the K-band is -15.2 (AB), comparable to that of AT2017gfo at the same epoch. Hence, while it remains possible that GRB 211211A is a higher redshift event in chance projection with a low redshift galaxy, a compact binary merger at z=0.076 provides a good explanation of the galactic location, rapid optical fading and red colour of the source. We thank the Gemini staff for the rapid execution of these observations." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31236 SUBJECT: GRB 211211A: Insight-HXMT/HE detection DATE: 21/12/16 06:44:10 GMT FROM: Y Q Zhang at IHEP Y. Q. Zhang, S. L. Xiong, X. B. Li, C. Cai, Q. Luo, S. Xiao, J. C. Liu, W. C. Xue, Q. B. Yi, C. Zheng，Y. Huang, C. K. Li, G. Li, J. Y. Liao, X. Y. Song, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: At 2021-12-11T13:09:59.500 (T0), Insight-HXMT/HE detected GRB 211211A (trigger ID: HEB211211548) in a routine search of the data, which also triggered Fermi/GBM (Fermi GBM Team, GCN #31201), Swift/BAT (D'Ai A. et al., GCN #31202), CALET (Tamura T. et al., GCN #31226) and INTEGRAL/SPI-ACS (Minaev P. et al., GCN #31230) URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB211211548_lc.jpg It should be noted that there is a significant saturation effect (data loss) during bright parts of this GRB in HXMT. All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31242 SUBJECT: GRB 211211A: TNG NIR observations DATE: 21/12/16 12:40:41 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF-OAB), A. Rossi (INAF-OAS), D. B. Malesani (Radboud), V. D'Elia (ASI-SSDC), A. Melandri (INAF-OAB), M. De Pasquale (Univ. Messina), S. Piranomonte (INAF-OAR), G. Andreuzzi, A. Garcia de Gurtubai (INAF-TNG) on behalf of the CIBO collaboration report: We observed the field of GRB 211211A (D’Ai et al., GCN Circ. 31202) with the Italian 3.6m TNG telescope equipped with the near-infrared camera NICS. A series of images were obtained with the H filter on 2021-12-16 from 05:51:36 UT to 07:00:51 UT (i.e. at a mid time of about 4.7 days after the burst). No source is detected at the optical and NIR counterpart position (Zheng & Filippenko, GCN Circ. 31203; Levan et al., GCN Circ. 31235) down to the following 3sigma upper limit: H > 20.5 (Vega) or H > 21.9 (AB) (calibrated against the 2MASS catalogue). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31264 SUBJECT: GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source DATE: 21/12/18 21:26:07 GMT FROM: Wen-fai Fong at Northwestern U J. Rastinejad, W. Fong (Northwestern), A. J. Levan, D. B. Malesani (Radboud), J. Jencson, D. Sand (U. Arizona), N. R. Tanvir (Leicester) report: We observed the location of GRB 211211A (D’Ai et al., GCN 31202) with the MMT and Magellan Infrared Spectrograph (MMIRS) instrument mounted on the MMT 6.5-meter telescope on Mount Hopkins, Arizona. At a mid-time of 2021 December 18.52 UT (~6.9 days post-burst), we obtained 126 x 30 s of K-band imaging at a median airmass of 1.5 and seeing of 0.8 arcsec. A faint K-band source is still detected at the location of the optical afterglow (first reported by Zheng & Fillipenko; GCN 31203). Based on calibration to 2MASS, we estimate a preliminary magnitude for the source of K_AB ~ 24 mag, although we caution that the faintness of the source precludes a precise measure at this time. Visual inspection relative to our Gemini K-band imaging (Levan et al. GCN 31235) is in support of clear fading of the source. Taken at face value, the K-band source has declined by ~1.5 mag between ~4 and 7 days post-burst, while AT2017gfo only faded by ~0.4 mag in the K band (Villar et al., 2017, ApJL, 851, L21) on these same timescales. Further observations are planned. We thank Joannah Hinz and ShiAnne Kattner at MMT for the rapid planning and execution of these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31299 SUBJECT: GRB 211211A: observations with the 3.6m Devasthal Optical Telescope DATE: 21/12/24 16:40:23 GMT FROM: Rahul Gupta at ARIES, India Rahul Gupta, S. B. Pandey, A. Ror, A. Kumar, A. Aryan, Dimple, A. Ghosh, B. Kumar, and K. Misra (ARIES) as a part of larger international collaboration: We performed late-time photometric observations of the optical afterglow (Zheng and Filipenko GCN 31203) of Fermi (Fermi GBM team, GCN 31201) and Swift (D'Ai et al., GCN 31202) detected GRB 211211A using the 4Kx4K CCD Imager (Pandey et al. 2017, arXiv:1711.05422v1) mounted at the axial port of the 3.6m Devasthal Optical Telescope of ARIES Nainital at multiple epochs in several filters. We report the preliminary brightness of the afterglow to be R = 21.66 +/- 0.07 mag ~ 1.41 days after the GBM trigger. At successive epochs, we obtained the limiting mag of 23.7 mag ~ 4.42 days post-burst. Our observations are consistent with the rapid decay nature of the afterglow reported by de Ugarte Postigo et al. GCN 31229 and A. Moskvitin et al. GCN 31234. The magnitude value reported is calibrated against UNSO B1 nearby stars. This circular may be cited. 3.6m Devasthal Optical Telescope (DOT) is the recently commissioned facility in the Northern Himalayan region of India (long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital ( https://www.aries.res.in). Authors of this GCN circular thankfully acknowledge consistent support from the staff members to run and maintain the 3.6m DOT.