//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29777 SUBJECT: GRB 210410A: Fermi GBM Final Real-time Localization DATE: 21/04/10 01:03:49 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 00:53:16 UT on 10 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210410A (trigger 639708801.519268 / 210410037). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 268.1, Dec = 47.2 (J2000 degrees, equivalent to J2000 17h 52m, 47d 12'), with a statistical uncertainty of 1.6 degrees. The angle from the Fermi LAT boresight is 50.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210410037/quicklook/glg_skymap_all_bn210410037.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/bn210410037/quicklook/glg_healpix_all_bn210410037.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210410037/quicklook/glg_lc_medres34_bn210410037.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29778 SUBJECT: GRB 210410A: Swift XRT localization DATE: 21/04/10 01:28:44 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT A. Melandri (INAF-OAB), J. A. Kennea (PSU) and N. J. Klingler (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: Swift BAT triggered on GRB 210410A, previously reported by Fermi/GBM (GCN #29777). Due to a telemetry drop-out, no prompt BAT data are available, however XRT has localized the source. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 269.75417, 45.36339 which is equivalent to: RA(J2000) = 17h 59m 01.00s Dec(J2000) = +45d 21' 48.2" with an uncertainty of 6.1 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. No spectrum from the promptly downlinked event data is yet available to determine the column density. Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.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: 29779 SUBJECT: Fermi GRB 210410A: Global MASTER-Net observations report DATE: 21/04/10 01:30:12 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210410A ( Fermi GBM team, GCN 29777) errorbox 42 sec after notice time and 69 sec after trigger time at 2021-04-10 00:54:26 UT, with upper limit up to 16.8 mag. The observations began at zenith distance = 85 deg. The sun altitude is -50.6 deg. MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210410A errorbox 112 sec after notice time and 139 sec after trigger time at 2021-04-10 00:55:36 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 15 deg. The sun altitude is -22.5 deg. The galactic latitude b = 29 deg., longitude l = 74 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1588428 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 75 | 2021-04-10 00:54:26 | MASTER-SAAO | (17h 48m 53.00s , +47d 14m 34.0s) | C | 10 | 16.4 | 110 | 2021-04-10 00:54:56 | MASTER-SAAO | (17h 48m 58.82s , +47d 13m 30.3s) | C | 20 | 16.8 | 155 | 2021-04-10 00:55:36 | MASTER-Tavrida | (17h 47m 38.38s , +48d 29m 25.0s) | C | 30 | 18.4 | 209 | 2021-04-10 00:56:25 | MASTER-Tavrida | (17h 47m 31.30s , +48d 28m 35.5s) | C | 40 | 18.5 | 666 | 2021-04-10 01:03:22 | MASTER-Tavrida | (17h 54m 11.52s , +47d 16m 38.2s) | C | 120 | 19.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29780 SUBJECT: GRB210410A: Candidate optical afterglow by Ondrejov D50 DATE: 21/04/10 03:36:29 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report: We observed the position of the Fermi/GBM GRB 210410A (Fermi, GCNC 29777) with the D50 robotic telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We performed a series of 120 s unfiltered exposures starting 56 min after the trigger. Within the Swift/XRT error box (Melandri et al. GCNC 29778) we detect a fading object at (269.7542, 45.3629) (17:59:01.00 +45:21:46.6 J2000 +/-0.3"). The preliminary magnitude 103 min after the trigger was r'(AB) = 21.5 +/- 0.2 and the object seems to fade with alpha ~ 0.95 +/- 0.27. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29781 SUBJECT: GRB 210410A: Fermi-LAT detection DATE: 21/04/10 08:25:22 GMT FROM: Makoto Arimoto at Tokyo Inst of Tech M. Arimoto (Kanazawa Univ.), M. Ohno (Hiroshima Univ. & Eotvos Univ.), F. Longo (University and INFN, Trieste) and M. Axelsson (KTH & Stockholm Univ.) report on behalf of the Fermi-LAT team: On April 10, 2021, Fermi-LAT detected high-energy emission from GRB 210410A, which was also detected by Fermi-GBM (trigger 639708801 / 210410037, Fermi GBM team, GCN 29777) and Swift/BAT&XRT (Kennea et al. 2021, GCN 29778). The best LAT on-ground location is found to be RA, Dec = 268.9, 45.2 (J2000) with an error radius of 0.5 deg (90 % containment, statistical error only). This position is consistent with the Swift/XRT localization. This was 51 deg from the LAT boresight at the time of the GBM trigger: T0 = 00:53:16.5 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 (2 degrees from the GBM location) with high significance. The photon flux above 100 MeV in the time interval 0-300s after the GBM trigger is (4.0 +/- 0.7)e-05 ph/cm2/s, while the flux above 1 GeV is (1.3 +/- 0.7)e-06 ph/cm2/s. The estimated photon index above 100 MeV is -2.5 +/- 0.2. The highest-energy photon is a 4.2 GeV event which is observed 30 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Masanori Ohno (ohno@astro.hiroshima-u.ac.jp). 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: 29782 SUBJECT: GRB 210410A: AGILE detection of a burst DATE: 21/04/10 10:48:53 GMT FROM: Alessandro Ursi at INAF/IAPS A. Ursi (INAF/IAPS), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, 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 satellite detected the long GRB 210410A at T0 = 2021-04-10 00:53:16.64 +/- 0.01 s (UTC), reported by Fermi/GBM (GCN #29777), Swift/XRT (GCN #29778), and Fermi/LAT (GCN #29781). The burst is 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 ~15 s and released a total number of 1050 counts in the SA detector (above a background rate of 60 Hz), 29400 counts in the MCAL detector (above a background rate of 1200 Hz), and 72250 counts in the AC detector (above a background rate of 3320 Hz). The AGILE ratemeter light curves can be found at http://www.agilescienceapp.it/notices/GRB210410_AGILE_RM.png . The event also triggered a partial high time resolution MCAL data acquisition, whose light curve can be found at: http://www.agilescienceapp.it/notices/072541_GRB_545100796.643050.png . 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: 29784 SUBJECT: GRB 210410A: RATIR Optical and NIR Observations DATE: 21/04/10 13:41:41 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 210410A (Fermi GBM team, et al., GCN 29777) with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2021/04 10.30 to 2021/04 10.51 UTC (6.26 to 11.25 hours after the BAT trigger), obtaining a total of 2.16 hours exposure in the r and i bands and 0.87 hours exposure in the Z, Y, J, and H bands. We detect one source within the Swift-XRT error circle (Melandri, et al., GCN 29778). In comparison with the USNO-B1 and 2MASS catalogs, we find these magnitudes (in the AB system and not corrected for Galactic extinction in the direction of the GRB): r = 23.79 +/- 0.30 i = 22.49 +/- 0.14 Z = 22.07 +/- 0.27 Y = 21.14 +/- 0.18 J = 20.24 +/- 0.11 H = 20.17 +/- 0.15 The source is located at RA, Dec = 17:59:1.00, +45:21:44.6 (J2000, +/-0.5"), which is 2 arcsec away from the candidate optical afterglow position reported by Jelinek et al. (GCN 29780). It is possible that an astrometric cross-comparison could reveal our sources to be the same, in which case the optical afterglow continues to fade strongly. It is also possible that we are detecting the GRB host galaxy. A photo-z analysis suggests the redshift is z<3.6 (90% confidence). We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29786 SUBJECT: GRB210410A: Joint inspection of RATIR and D50 data DATE: 21/04/10 15:36:33 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov Nat Butler (ASU) and Martin Jelinek (ASU AV CR Ondrejov) report: We performed a joint inspection of the D50 (Jelinek et al., GCNC29780) and RATIR (Butler et al., GCNC29784) images and agreed that the object reported in both circulars is identical. Joint photometric fit of the data provides a decay rate of 1.18 ± 0.24 (chisq=1.68). Seeing this, we conclude that this object is indeed the optical afterglow of GRB 210410A (cf. Fermi team, GCN 29777, Melandri et al., GCN 29778, Arimoto at al., GCN 29781, Ursi et al., GCNC 29782). The preliminary coordinates reported by the D50 team are flawed and the RATIR value, i.e. RA, Dec = 17:59:1.00, +45:21:44.6 (J2000, +/-0.5") should be used. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29787 SUBJECT: GRB 210410A: Swift/UVOT Upper Limits DATE: 21/04/10 21:16:09 GMT FROM: Paul Kuin at MSSL Paul Kuin (MSSL/UCL) and A. Melandri(INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210410A (trigger 01042113; previously reported by Fermi/GBM in GCN #29777) 1113 s after the Fermi trigger at 2021-04-10 00:53:16 UT. No optical afterglow consistent with the XRT position (Melandri et al. GCN Circ. 29778) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) mag 3-sigma UL v 1129 1149 19 >17.0 b 5021 5109 85 >19.7 u 4817 5014 197 >19.9 w1 4610 4809 197 >19.3 m2 4403 4602 197 >19.4 w2 1113 1125 12 >17.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29788 SUBJECT: GRB 210410A: Fermi GBM detection DATE: 21/04/11 01:42:52 GMT FROM: Joshua Wood at MSFC/Fermi-GBM J. Wood (NASA/MSFC) and C.Meegan (UAH) report on behalf of the Fermi GBM Team: "At 00:53:16.52 UT on 10 April 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210410A (trigger 639708801 / 210410037). which was also detected by the Swift/XRT (A. Melandri et al. 2021, GCN 29778), the Fermi/LAT (M. Arimoto et al. 2021, GCN 29781), and AGILE (A. Ursi et al. 2021, GCN 29782). The Fermi GBM Final Real-time Localization (GCN 29777) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 51.0 degrees. The GBM light curve consists of a single peak with a duration (T90) of about 48 s (50-300 keV). The time-averaged spectrum from T0-0 s to T0+50 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.70 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 1300 +/- 100 keV The event fluence (10-1000 keV) in this time interval is (4.5 +/- 0.5)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0 s in the 10-1000 keV band is 12.6 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 1300 +/- 100 keV, alpha = -0.70 +/- 0.03 and beta = 4.0 +/- 1.6. 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: 29790 SUBJECT: GRB 210410A: Swift-XRT refined Analysis DATE: 21/04/11 04:35:55 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team: We have analysed 4.4 ks of XRT data for GRB 210410A, from 61 s to 52.6 ks after the BAT trigger. The data comprise 115 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 702 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 = 269.75437, +45.36192 which is equivalent to: RA (J2000): 17h 59m 01.05s Dec(J2000): +45d 21' 42.9" with an uncertainty of 2.4 arcsec (radius, 90% confidence). The late-time light curve (from T0+4.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.5 (+0.5, -0.4). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.33 (+/-0.11). The best-fitting absorption column is 1.4 (+0.5, -0.4) x 10^21 cm^-2, in excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.47 (+0.18, -0.16) and a best-fitting absorption column of 7.2 (+6.0, -3.2) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.5 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.2 (+6.0, -3.2) x 10^20 cm^-2 Galactic foreground: 4.0 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.47 (+0.18, -0.16) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01042113. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29793 SUBJECT: GRB 210410A: Swift-BAT refined analysis DATE: 21/04/11 14:53:46 GMT FROM: Amy Lien at GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210410A (trigger #1042113) (Melandri et al., GCN Circ. 29778). The BAT ground-calculated position is RA, Dec = 269.741, 45.359 deg which is RA(J2000) = 17h 58m 57.8s Dec(J2000) = +45d 21' 31.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 55%. The mask-weighted light curve shows a FRED pulse that starts at ~T0, peaks at ~T0, peaks at ~T+2 s, and ends at ~T+100 s. T90 (15-350 keV) is 52.88 +- 4.15 sec (estimated error including systematics). The time-averaged spectrum from T-0.00 to T+66.06 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.04 +- 0.06. The fluence in the 15-150 keV band is 5.6 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.74 sec in the 15-150 keV band is 4.0 +- 0.3 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/1042113/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29797 SUBJECT: Konus-Wind detection of GRB 210410A DATE: 21/04/11 18:02:54 GMT FROM: Anna Ridnaia at Ioffe Institute A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, report: The long-duration GRB 210410A (Fermi-GBM detection: Fermi GBM team, GCN 29777, Wood and Meegan, GCN 29788; Fermi-LAT detection: Arimoto et al., GCN 29781; AGILE detection: Ursi et al., GCN 29782; Swift-BAT observation: Lien et al., GCN 29793) triggered Konus-Wind at T0=3196.651 s UT (00:53:16.651). The burst light curve starts at ~T0 with a narrow (~128 ms) pulse followed by a gradually decaying emission until ~T0+85s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210410_T03196/ As observed by Konus-Wind, the burst had a fluence of 7.29(-0.44,+0.47)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.002 s, of 2.95(-0.69,+0.76)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+47.104 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.74(-0.07,+0.08) and Ep = 1081(-126,+150) keV (chi2 = 72/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.7 (chi2 = 72/97 dof). The spectrum of the initial pulse (measured from T0 to T0+0.128 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model with alpha = 0.11(-0.29,+0.38) and Ep = 1210(-250,+326) keV (chi2 = 38/32 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -1.9 (chi2 = 36/31 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29798 SUBJECT: GRB 210410A: AGILE/MCAL analysis DATE: 21/04/11 19:51:25 GMT FROM: Alessandro Ursi at INAF/IAPS A. Ursi (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, 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: We carried out further analysis of the AGILE/MCAL data of GRB 210410A (GCNs #29777, #29778, #29779, #29780, #29781, #29782, #29786, #29787, #29788, #29790, #29793, #29797). The first 4 s of the burst released 5700 counts in the detector, above a background rate of 560 Hz. The spectral analysis shows a clear component up to 100 MeV. The time-integrated spectrum of the first ~4 s of the burst can be fitted in the energy range 0.4-100 MeV with a CPL model with alpha = -0.6 -0.25/+0.14 and cutoff energy Ec = 500 keV, plus an extra PL component with ph.ind. -1.31 -0.04/+0.04. The fit results in a reduced chi-squared of 1.48 (81 d.o.f.) and a fluence of 1.3e-04 ergs/cm^2 (90% confidence level), in the same energy range. We divided the data acquisition into three time intervals: interval a [T0-0.16s - T0+0.70s], interval b [T0+0.70s - T0+2.85s], and interval c [T0+2.85s - T0+4.00s]. The spectral analysis in the energy range 0.4-100 MeV shows an evolution of the PL high-energy spectral component, evolving from alpha = -1.91 to alpha = -0.92. Details are reported below: | model | CPL alpha | Ec | PL ph.ind. | redX^2 (dof) a | CPL+PL | -0.57 -1.46/+3.84 | 438 keV | -1.91 -0.96/+0.78 | 0.97 (81) b | CPL+PL | -0.57 -1.68/+0.67 | 365 keV | -0.98 -0.61/+0.39 | 1.38 (81) c | PL | ----- | --- | -0.92 -0.98/+0.40 | 1.05 (84) MCAL light curve and spectra in the different time intervals can be found at: http://www.agilescienceapp.it/notices/GRB210410A_AGILE-MCAL_intervals.png . 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: 29805 SUBJECT: GRB 210410A: MITSuME Akeno optical upper limits DATE: 21/04/12 10:29:30 GMT FROM: Katsuhiro L. Murata at Nagoya U K. L. Murata, R. Hosokawa, M. Niwano, N. Ito, H. Takamatsu, Y. Yatsu, and N.Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 210410A (The Fermi GBM team et al. GCN Circular #29777, A. Melandri et al. GCN Circular #29778, V. Lipunov et al. GCN Circular #29779, M. Jelinek et al. GCN Circular #29780, M. Arimoto et al. GCN Circular #29781, A. Ursi et al. GCN Circular #29782, Nat Butler et al. GCN Circular #29784, Nat Butler et al. GCN Circular #29786, Paul Kuin et al. GCN Circular #29787, J. Wood et al. GCN Circular #29788, A. D'Ai et al. GCN Circular #29790, A. Y. Lien et al. GCN Circular #29793, A. Ridnaia et al. GCN Circular #29797, A. Ursi et al. GCN Circular #29798) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation with a series of 60 sec exposures started at 2021-04-10 13:35 (9.7 hours after the Fermi/GBM trigger). We stacked the images with good conditions. We did not detect the optical afterglow reported previously (Jelinek et al. GCN Circular #29780, Butler et al. GCN Circular #29784) in all three bands. We obtained the 5-sigma limits of the stacked images as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 10.0 14:00:15 1740 g'>19.3, Rc>19.6, Ic>19.0 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used the 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: 29812 SUBJECT: GRB 210410A: Swift/UVOT Upper Limits (revision) DATE: 21/04/13 12:29:44 GMT FROM: Paul Kuin at MSSL Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team: In our previous report (Kuin & Melandri, GCN Circ 29787) we made an error computing T0, which affected our T_start and T_stop times. Below are the corrected values. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) mag 3-sigma UL v 1070 1095 19 >17.0 b 4967 5055 85 >19.7 u 4763 4960 197 >19.9 w1 4556 4755 197 >19.3 m2 4349 4548 197 >19.4 w2 1059 1071 12 >17.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29816 SUBJECT: GRB 210410A: A twin of short GRB 090510 with complementary observations DATE: 21/04/15 08:43:33 GMT FROM: Remo Rufinni at ICRA Y. Aimuratov, C.L. Bianco, L. Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N. Sahakyan, Y. Wang, S.S. Xue on behalf of the ICRANet team, report: GRB 210410A has been announced as a likely long GRB (Fermi GBM Team 2021, GCN 29777), it has been also observed by Swift-XRT (A. Melandri et al 2021, GCN 29778, and A. D’Ai et al, 2021, GCN 29790), by Fermi-LAT (M. Arimoto et al 2021, GCN 29781), by AGILE (A. Ursi et al. 2021, GCN 29782), by Swift BAT (A. Y. Lien et al, 2021 GCN 29793) as well as by Konus-Wind (A. Ridnaia et al 2021, GCN 29797). The Fermi-GBM has determined T90=48 s in 50-300 keV (J. Wood et al 2021, GCN 29788). A possible detection of the host galaxy at redshift z<3.6 was indicated by Butler et al 2021 (GCN 29784). We here propose that GRB 210410A is a twin and covers the complementary observation to the short GRB 090510, with T90=0.3 s. (R. Ruffini et al 2016 ApJ 831 178). We infer that GRB 210410A is a short GRB originating from a black hole formation in view of its observed GeV emission (M. Arimoto et al GCN29781) that and no supernova will be detected. We evidence for the first time an angle dependence of the emission of short GRB: in the polar observation for GRB 090510, with T90=0.3 s and in the equatorial observation for GRB 210410A, with T90=48 s. The spectroscopic determination of the redshift of the host galaxy is essential for the determination of the GeV luminosity and consequently the BH mass (R. Ruffini et al 2019 ApJ 886 82). We indicate the relevance of the redshift determinations in the two enclosed figures. "http://www.icranet.org/documents/GRB210410A-z=0.6-and-GRB090510-z=0.903.pdf" "http://www.icranet.org/documents/GRB210410A-z=3.6-and-GRB090510-z=0.903.pdf" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29817 SUBJECT: GRB 210410A: AstroSat CZTI detection DATE: 21/04/15 14:44:22 GMT FROM: Gaurav Waratkar at IIT Bombay P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed detection of a long GRB 210410A, which was also detected by Fermi-GBM (GCN #29777, #29788), Swift-XRT (GCN #29778, #29790), Fermi-LAT (GCN #29781), Swift-BAT (GCN #29793), Konus-Wind (GCN #29797) and AGILE-MCAL (GCN #29798). The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-10 00:53:16.50 UT. Quadrant D was noisy, and we exclude it from further analysis. The measured peak count rate associated with the burst is 225 (+45, -16) cts/s above the background in the combined data of four quadrants, with a total of 1808 (+239, -299) cts. The local mean background count rate was 373 (+2, -2) cts/s. Using cumulative rates, we measure a T90 of 20 (+6, -7) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-10 00:53:15.867 UT. The measured peak count rate is 1149 (+91, -57) cts/s above the background in the combined Veto data of four quadrants, with a total of 8483 (+515, -574) cts. The local mean background count rate was 1580 (+4, -4) cts/s. We measure a T90 of 18 (+6, -4) s from the cumulative Veto light curve. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.