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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
  1. GRB 210702A: iTelescope optical afterglow observations
  2. GRB 210702A: AGILE detection
  3. GRB 210702A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 210619B: JCMT SCUBA-2 sub-mm observations
  5. GRB 210610B: JCMT SCUBA-2 sub-mm observations
  6. GRB 210610A: JCMT SCUBA-2 sub-mm observations
  7. GRB 210702A: Swift-XRT refined Analysis
  8. GRB 210702A: VLT/X-shooter redshift
  9. GRB 210702A: preliminary Swift/UVOT photometry
  10. GRB 210702A: Swift/UVOT redshift
  11. GRB210702A: MeerLICHT multi-colour photometry
  12. Swift GRB 210702A: Global MASTER-Net observations report
  13. Swift GRB210702.80: Global MASTER-Net OT detection
  14. GRB 210702A: Swift detection of a burst with a bright optical counterpart
  15. IceCube-210629A: Upper limits from a search for additional neutrino events in IceCube
  16. IceCube-210629A: One Candidate Counterpart from the Zwicky Transient Facility
  17. IceCube-210629A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  18. Fermi-LAT Gamma-ray Observations of IceCube-210629A
  19. IceCube-210629A: Upper limits from Fermi-GBM Observations
  20. GRB 210627B: GECAM detection
  21. IceCube Alert 210629.76: Global MASTER-Net observations report
  22. GRB 210619B: Sayan observatory 1.6-m telescope observations
  23. IceCube-210629A - IceCube observation of a high-energy neutrino candidate track-like event
  24. GRB 210626A: Swift/XRT afterglow confirmation
  25. GRB 210626A: Fermi GBM observation
  26. GRB 210626A: CAHA 2.2m telescope optical limit
  27. GRB 210619B: Deep CAHA 2.2m detection and late-time light curve behavior
  28. GRB 210626A: Ondrejov D50 optical limit
  29. GRB 210626A: GIT optical upper limit
  30. Fermi trigger No 646443989: Global MASTER-Net observations report
  31. Fermi GRB 210627B: Global MASTER-Net observations report
  32. GRB 210627B: BALROG localization (Fermi Trigger 646509445/ GRB 210627748)
  33. GRB 210627B: Fermi GBM Final Real-time Localization
  34. Fermi GRB 210627A: Global MASTER-Net observations report
  35. GRB 210627A: Fermi GBM Final Real-time Localization
  36. GRB 210626A: Swift-XRT afterglow detection
  37. Fermi trigger No 646322348: Global MASTER-Net observations report
  38. Fermi GRB 210626A: Global MASTER-Net observations report
  39. GRB 210626A: Swift ToO observations
  40. GRB 210626A: Swift/BAT-GUANO detection and arcminute localization
  41. GRB 150428A: late-time radio observations
  42. GRB 210626A: Fermi GBM Final Real-time Localization
  43. GRB 210618A: 1.5m OSN optical upper limit
  44. Fermi GRB 210625A: Global MASTER-Net observations report
  45. GRB210619B: optical afterglow detection from Konkoly Observatory
  46. GRB 210625A: Fermi GBM Final Real-time Localization
  47. IPN triangulation of GRB 210624A (short)
  48. GRB 210622A: Swift-XRT observations
  49. GRB 210610B: T-CAT optical observations
  50. GRB 210619B: ASIM observation
  51. Fermi trigger No 646189108: Global MASTER-Net observations report
  52. Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
  53. GRB 210618A: Swift-XRT afterglow detection
  54. Fermi trigger No 646194855: Global MASTER-Net observations report
  55. GRB 210622A: Swift ToO observations
  56. GRB 210619B: Even further SAO RAS optical observations
  57. GRB 210619B: Mini-MegaTORTORA early optical observations
  58. Fermi GRB 210622B: Global MASTER-Net observations report
  59. GRB 210622A: Fermi GBM detection
  60. GRB 210619B: Abbey Ridge Observatory optical afterglow observation
  61. GRB 210619B: SPI-ACS/INTEGRAL observations
  62. GRB 210619B: Further SAO RAS optical observations
  63. GRB 210622A: Swift/BAT-GUANO detection and arcminute localization of a long burst
  64. GRB 210619B: possibility of lensed visible afterglow?
  65. GECAM detection of GRB 210622B
  66. GRB 210619B: AbAO optical observations
  67. GRB 210622B: Fermi GBM Final Real-time Localization
  68. GRB 210622A: Fermi GBM Final Real-time Localization
  69. Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
  70. Swift GRB210621.71: Global MASTER-Net observations report
  71. GRB 210619B: NOT optical observations
  72. GRB 210619B: 1.5m OSN optical observation
  73. GRB 210619B: iTelescope optical afterglow observation
  74. GRB 210619B: SAO RAS optical observations
  75. GRB 210619B: SEDM Optical Observations
  76. GRB 210619B: TNG NIR observations of the afterglow
  77. GRB 210619B: REM optical/NIR afterglow detection
  78. Fermi GRB 210621A: Global MASTER-Net observations report
  79. GRB 210619B: GIT optical follow-up and confirmation of jet-break
  80. GRB 210621A: Fermi GBM Final Real-time Localization
  81. GRB 210619B: CALET Gamma-Ray Burst Monitor detection
  82. GRB 210619B: SRG/ART-XC detection
  83. GRB 210619B: Swift-BAT refined analysis
  84. GRB 210619B: steepening of the decay observed at the D50
  85. GRB 210619B: Liverpool Telescope First Hour Observations
  86. GRB 210619B: Fermi GBM detection
  87. GRB 210619B: Swift/UVOT Detection
  88. GRB 210619B: Xinglong TNT optical observations
  89. Konus-Wind detection of GRB 210619B
  90. GRB 210619B: CAHA 2.2m photometric monitoring
  91. GRB 210619B: Liverpool Telescope r'-band observations
  92. GRB 210619B: KAIT Optical Detection
  93. GRB 210619B: Redshift from OSIRIS/GTC
  94. GRB 210619B: Liverpool telescope imaging of a red afterglow
  95. GRB 210619B: Fermi-LAT detection
  96. GRB 210619B: Swift-XRT refined Analysis
  97. GRB 210619B: SARA-KP 0.9m Optical Afterglow Detection
  98. GRB 210619B: Enhanced Swift-XRT position
  99. Fermi trigger No 645857659: Global MASTER-Net observations report
  100. GRB 210619B: iTelescope T18 detection

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