Gamma-ray Burst 240627A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #36776
  J. Joshi (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/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., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240627A. Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst. We also note that this trigger is ~13 min after a solar flare in NASA/GOES X-ray flux data. While we cannot accurately localize this GRB because of low counts in our detectors, the relative intensities in different quadrants of CZT and Veto detectors indicate a different source direction.
  The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-06-27 23:59:01.50 UTC. The measured peak count rate associated with the burst is 502 (+47, -44) counts/s above the background in the combined data of all quadrants, with a total of 2665 (+211, -223) counts. We caution that there is a 0.3 s readout dead time in CZT data during the burst which affects the calculated total counts. The local mean background count rate was 320 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 11 (+1, -2) s.
  The source 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 2024-06-27 23:59:00.62 UTC. The measured peak count rate associated with the burst is 1745 (+92, -99) counts/s above the background in the combined data of all quadrants, with a total of 9056 (+393, -439) counts. The local mean background count rate was 1452 (+7, -8) counts/s. We measure a T90 of 12 (+1, -1) s from the cumulative Veto light curve.
  CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
  CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb
• GCN Circular #36778
  B. Grefenstette (Caltech) reports on behalf of the NuSTAR Search for INtere= sting Gamma-ray Signals (SINGS) working group:
  The NuSTAR SINGS working group reports the detection of prompt emission fro= m the Long GRB 240627A in both the NuSTAR CsI anti-coincidence shields. The= NuSTAR CsI shield data are recorded at 1 Hz. This GRB was identified throu= gh a blind search using the CsI shield rates. Details of the search algorit= hm will be described in a future paper.
  The NuSTAR SINGS algorithm triggered at 2024-06-27 23:58:55 (with a resolut= ion ~5-seconds). This is consistent with the Astrosat CTZI detection (Warat= kar et al, GCN circ. 36776). The GRB appears to be composed of main peak (= at 2024-06-27 23:58:59) along with several additional (potentially unresolv= ed) peaks. The duration of the event is roughly 15-s, which is consistent w= ith the T90 from Astrosat. Peak rates are around 3,500 cps (typical backgro= und rates are 1,000 cps).
  There is a simultaneous marginal detection in the CdZnTe detectors, resulti= ng in a net of a <20 excess counts.
  Lightcurves and analysis for this GRB can be found here:
  https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2024/240627A/
  Information on NuSTAR SINGS can be found here:
  https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/
  NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA=E2=80=99s Science Mission Directorate in Washington.
• GCN Circular #36798
  K. Kobayashi (Waseda U) A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike (Waseda U), Y. Shimizu, T. Tamura (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 GRB 240627A (AstroSat CZTI detection: Joshi et al., GCN Circ. 36776; NuSTAR Detection: Grefenstette et al., GCN Circ. 36778) was detected in the ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data around 23:59:01.50 on 27 June 2024 (referenced to the AstroSat detection: GCN Circ. 36776). (https://cgbm.calet.jp/cgbm_trigger/flight/1403567463/index.html) The burst signal was seen by only the SGM detector.
  The burst light curve shows a multi-peaked structure that starts at T-7.5 sec and ends at T+8.0 sec. The T90 and T50 durations measured by the SGM data are 12.1 +/- 0.5 sec and 4.6 +/- 0.2 sec (40-1000 keV), respectively.
  The ground-processed light curve is available at
  https://cgbm.calet.jp/cgbm_trigger/ground/1403567463/index.html
  The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University.
• GCN Circular #36814
  A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team,
  D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
  A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team,
  E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team,
  G. Waratkar, V. Jethwani, J.Joshi, V. Bhalerao, D. Bhattacharya, and S. Vadawale, on behalf of the Astrosat-CZTI team,
  and
  W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report:
  The bright, long-duration GRB 240627A (AstroSat-CZTI detection: Joshi et al., GCN 36776; NuSTAR anti-coincidence shields detection: Grefenstette, GCN 36778; CALET-CGBM detection: Kobayashi et al., GCN 36798) was detected by Astrosat (CZTI), Konus-Wind, INTEGRAL (SPI-ACS), NuSTAR (ACS), CALET (CGBM), and Mars-Odyssey (HEND) at about 86341 s UT (23:59:01).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

   ---------------------------------------------
    RA(2000), deg                 Dec(2000), deg
   ---------------------------------------------
   Center:
    164.155 (10h 56m 37s) +72.806 (+72d 48' 23")
   Corners:
    166.270 (11h 05m 05s) +73.674 (+73d 40' 25")
    166.346 (11h 05m 23s) +73.611 (+73d 36' 38")
    162.228 (10h 48m 55s) +71.917 (+71d 55' 02")
    162.147 (10h 48m 35s) +71.979 (+71d 58' 45")
   ---------------------------------------------
  

  The error box area is 416 sq. arcmin, and its maximum dimension is 2.1 deg (the minimum one is 3.4 arcmin). The Sun distance was 60 deg.
  This localization may be improved.
  A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB240627_T86332/IPN The HEALPix triangulation map is the multi-order HEALPix in units of probability density.
  The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #36830
  A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
  The long-duration GRB 240627A (AstroSat-CZTI detection: Joshi et al., GCN 36776; NuSTAR anti-coincidence shields detection: Grefenstette, GCN 36778; CALET-CGBM detection: Kobayashi et al., GCN 36798; IPN triangulation: Kozyrev et al., GCN 36814;) triggered Konus-Wind at T0=86332.21 s UT (23:58:52.210).
  The burst light curve shows a multipeaked structure which starts at ~T0-45.2 s and has a total duration of ~91.0 s. The emission is seen up to ~4 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240627_T86332/
  As observed by Konus-Wind, the burst had a fluence of 5.22(-0.54,+0.57)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+6.016 s, of 1.27(-0.23,+0.23)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+47.616 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.31(-0.07,+0.09), the high energy photon index beta = -2.47(-0.39,+0.20), the peak energy Ep = 191(-23,+25) keV (chi2 = 110/87 dof).
  The spectrum near the maximum count rate (measured from T0+5.376 to T0+7.168 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.06(-0.10,+0.11), the high energy photon index beta = -2.49(-0.63,+0.26), the peak energy Ep = 314(-54,+61) keV (chi2 = 49/55 dof).
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
• GCN Circular #36952
  M. Dafcikova, J. Ripa, M. Kolar (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Dur= iskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M.= Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (= Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Ha= nak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Cen= ter/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (IS= AS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hirosh= ima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos= U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakaz= awa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torig= oe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Morit= aki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.
  The long-duration GRB 240627A (AstroSat/CZTI detection: GCN 36776; NuSTAR d= etection: GCN 36778; CALET/CGBM detection: GCN 36798; Konus/Wind detection:= GCN 36830; INTEGRAL/SPI-ACS peak detection at 2024-06-27 ~23:59:03 UT) was= observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https:= //ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).
  The detection was confirmed at the peak time 2024-06-27 23:59:07.2 UTC. The T90 duration measured by GRBAlpha is 13.5 s and the overall significance during T90 reaches 29 sigma.
  The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240627A_GCN.pdf
  All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a futur= e CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GR= BAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM ar= ray, covering the energy range from ~50 keV to ~1000 keV. To increase the d= uty cycle and the downlink rate, the upgrade of the on-board data acquisiti= on software stack is in progress. The ground segment is also supported by t= he radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume.