//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30587 SUBJECT: GRB 210802A: Tiled Swift observations DATE: 21/08/03 07:42:50 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the Fermi/LAT GRB 210802A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00100 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the Fermi/LAT event is high: 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: 30589 SUBJECT: GRB 210802A: Fermi-LAT detection DATE: 21/08/03 13:12:38 GMT FROM: Magnus Axelsson at Stockholm U. F. Longo (University and INFN, Trieste), M. Arimoto (Kanazawa Univ.), E. Bissaldi (Politecnico and INFN, Bari), M. Axelsson (KTH & Stockholm Univ.) and M. Ohno (Hiroshima Univ. & Eötvös Univ.) report on behalf of the Fermi-LAT Collaboration: On 2 August 2021, Fermi-LAT detected high-energy emission from GRB 210802A which was also detected by Fermi-GBM (trigger 649627691/210802839). The best LAT on-ground location is found to be RA, Dec = 230.9, 29.8 (degrees, J2000) with an error radius of 0.35 deg (90% containment, statistical error only). This was 51 deg from the LAT boresight at the time of the GBM trigger: T0 = 20:08:06.49 UT. The data from the Fermi-LAT show a significant increase in the event rate after the GBM trigger that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0-1000 s after the GBM trigger is (1.0 +/- 0.3) E-5 ph/cm2/s. The estimated photon index above 100 MeV is -2.3 +/- 0.3. The highest-energy photon is a 1.4 GeV event which is observed 3 seconds after the GBM trigger. A Swift ToO has been approved for this burst. 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: 30590 SUBJECT: GRB 210802A: Fermi GBM detection DATE: 21/08/03 14:58:46 GMT FROM: Oliver J Roberts at USRA/NASA O.J. Roberts (USRA/NASA-MSFC) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 20:08:06.49 UT on 02 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210802A (trigger 649627691 / 210802839), which was also detected by Fermi-LAT (F. Longo et al. 2021, GCN 30589). The Fermi GBM on-ground location is consistent with the LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 51 degrees. The GBM light curve consists of multiple bright pulses with a duration (T90) of about 11 s (50-300 keV). The time-averaged spectrum from T0-0.3 s to T0+12.8 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.66 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 372 +/- 12 keV. The event fluence (10-1000 keV) in this time interval is (2.10 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.6 s in the 10-1000 keV band is 16.4 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 365 +/- 15 keV, alpha = -0.65 +/- 0.03 and beta = -3.22 +/- 0.75. 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: 30591 SUBJECT: GRB 210802A: Swift-XRT afterglow detection DATE: 21/08/03 19:23:02 GMT FROM: Valerio D'Elia at ASDC B. Sbarufatti (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , D.N. Burrows (PSU), 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 210802A (Longo et al. GCN Circ. 30589) in a series of observations tiled on the sky. The total exposure time is 5.2 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 2.3 ks. The data were collected between T0+41.7 ks and T0+43.0 ks, and are entirely in Photon Counting (PC) mode. Twenty-eight uncatalogued X-ray sources are detected. Many of these sources are in the bottom tile (likely a high background effect), and in the left tile (possibly an extended emission related to a nearby cluster of galaxies). One of the most significant sources ("Source 7") is above the 2SXPS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 1246 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 = 230.72285, +29.90180 which is equivalent to: RA (J2000): 15h 22m 53.48s Dec(J2000): +29d 54' 06.5" with an uncertainty of 3.5 arcsec (radius, 90% confidence). This position is 9.8 arcmin from the Fermi/LAT position. While we cannot determine at the present time whether the source is fading, we note that a previous 1 ks Swift-XRT visit of the field showed no sign of Source 7 (https://www.swift.ac.uk/2SXPS/Fields/10000004351). The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/xrt_products/TILED_GRB00100/Source7.php. The results of the full analysis of the tiled XRT observations are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00100. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30592 SUBJECT: GRB 210802A: BOOTES-2/TELMA optical upper limit DATE: 21/08/03 22:25:19 GMT FROM: Youdong HU at IAA-CSIC Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report: Following the Fermi trigger of GRB 210802A (Longo GCNC 30589, Roberts et al. GCNC 30590), we triggered the 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) after the twilight as soon as it was possible. Useful images were taken only after 20:12 UT on 03 Aug (~1 day after trigger). In the co-added 12 x 60 s exposure image (clear filter), no optical afterglow is detected within the X-ary afterglow position reported by XRT/Swift (Sbarufatti et al. GCNC 30591) down to 20.3 mag. We thank the staff at La Mayora for its excellent support. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30593 SUBJECT: GRB 210802A: DDOTI Upper Limits DATE: 21/08/04 00:14:44 GMT FROM: Alan M Watson at UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC/UMD), Rosa L. Becerra (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Diego Gonzalez (UNAM), Océlotl Lopez (UNAM), Margarita Pereyra (UNAM), and Srihari Ravi (ASU) report: We observed the field of the Fermi GBM/LAT event GRB 210802A (Longo et al., GCN Circ., 30589; Roberts et al., GCN Circ., 30590) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Martir ( http://ddoti.astroscu.unam.mx) from 2021-08-03 03:35 to 07:37 UTC (7.45 to 11.48 hours after the trigger). We observed a region of about 14 degrees in RA by 10 degrees in declination, with a 1 x 2 grid of pointings centered on the Fermi GBM Final Position 15:19:40.80 +30:18:00.0 (J2000) and including the entire LAT uncertainty region (Longo et al., GCN Circ., 30589). We obtained about 105 minutes exposure on the LAT uncertainty region. We obtained AB photometry by calibration against the APASS catalog. Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point sources in the LAT uncertainty region to a 10-sigma limiting magnitude of w = 21.0. At the position of the candidate X-ray afterglow (Sbarufatti et al., GCN Circ., 30591), we detect no point source to a 5-sigma limiting magnitude of w = 21.8. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30596 SUBJECT: GRB 210802A: MITSuME Okayama optical upper limits DATE: 21/08/04 12:26:45 GMT FROM: Ryohei Hosokawa at Tokyo Institute of Technology R. Hosokawa, N. Ito, Y. Imai, K. L. Murata, M. Niwano, H. Takamatsu, R. Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 210802A (V. Lipunov et al. GCN Circular #30586, P. A. Evans et al. GCN Circular #30587, F. Longo et al. GCN Circular #30589, O.J. Roberts et al. GCN Circular #30590, B. Sbarufatti et al. GCN Circular #30591, Y.-D. Hu et al. GCN Circular #30592, Alan M. Watson et al. GCN Circular #30593) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Okayama. The observation with a series of 60 sec exposures started at 2021-08-03 10:34:24 UT (14.4 hours after Fermi trigger). We stacked the images with good conditions. We did not detect any uncatalogued sources within the XRT error region (B. Sbarufatti et al. GCN Circular #30591). We obtained the 5-sigma limits of the stacked images as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 15.8 2021-08-03 11:54:24 1080 Rc>17.2, Ic>16.9 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used PS1 catalog for flux calibration. 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: 30622 SUBJECT: GRB 210802A: Further Swift/XRT observation and afterglow confirmation DATE: 21/08/09 13:55:33 GMT FROM: Valerio D'Elia at ASDC V. D'Elia (ASI-SSDC & INAF-OAR) and S.B. Cenko (GSFC) report on behalf of the Swift-XRT team: Swift-XRT has performed further follow-up observations of the Fermi burst (Longo et al., GCN Circ. 30589; Roberts et al., GCN Circ. 30590). The possible afterglow reported in Sbarufatti et al. (GCN Circ. 30591, "source 7") is no longer detected in a 4 ks observation, down to a three sigma upper limit of 4.8E-3 cts/s (corresponding to 1.28E-13 erg/cm^2/s) at the position of the transient. This value is significantly below the previously reported flux value for the candidate, thus confirming “source 7” as the afterglow of GRB 210802A. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/xrt_curves/00021456/. This circular is an official product of the Swift-XRT team.