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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 220107A: Swift-XRT afterglow detection
  2. GRB 220107B: Fermi-LAT detection
  3. GRB 220107A: AstroSat CZTI detection
  4. GRB 220107B: Tiled Swift observations
  5. GRB 220107A: Fermi GBM observations
  6. Fermi trigger No 663274898: Global MASTER-Net observations report
  7. GRB 220107A: Swift ToO observations
  8. Fermi GRB 220107A: Global MASTER-Net observations report
  9. GRB 220107A: Swift/BAT-GUANO arcminute localization
  10. GRB 220101A: Tautenburg observations
  11. GRB 220107A: BALROG localization (Fermi Trigger 663259536 / GRB 220107615)
  12. GRB 220107A: Fermi GBM Final Real-time Localization
  13. GRB 220101A: Continued Mondy optical observations
  14. GECAM observation of a burst from SGR J1555.2-5402
  15. GECAM detection of a short burst from SGR 1935+2154
  16. GRB 220101A: further TNG NIR observations
  17. GRB 220101A: continued 1.3m DFOT Optical Observations
  18. Fermi trigger No 663129379: Global MASTER-Net observations report
  19. GRB 220104A: Fermi GBM Observation
  20. GECAM observations of a series of bursts from SGR J1935+2154
  21. GRB 220101A: Mondy optical observations
  22. GRB 220101A: 3rd LCO Optical Observation
  23. GRB 220101A: 2.2m CAHA (+CAFOS) first day optical detection
  24. GRB 220101A: iTelescope optical observations
  25. GRB 211227A: Lijiang 2.4m Telescope Optical Observations
  26. GRB 220101A: VLA detection
  27. GRB 220101A: 1.3m DFOT observations
  28. GRB 220101A: LCO Continued Optical Observations
  29. GRB 220104A：GECAM detection
  30. Fermi GRB 220104A: Global MASTER-Net observations report
  31. GRB 220104A: Fermi GBM Final Real-time Localization
  32. GRB 211229B: Fermi GBM observation
  33. Fermi GRB 220103A: Global MASTER-Net observations report
  34. GRB 220103A: Fermi GBM Final Real-time Localization
  35. GRB 211227A: Gemini South Optical Observations
  36. GRB 211229B: Swift/BAT-GUANO detection outside the coded FOV
  37. Alert from the HAWC Burst Monitor HAWC-220103A
  38. GRB 220101A: TNG NIR afterglow detection
  39. GRB 220101A: ALMA detection
  40. GRB 220101A: LCO Optical Observations
  41. GRB 220101A: Tautenburg observations
  42. GRB 220101A: Swift-BAT refined analysis
  43. GRB 220101A: GMG observation (2nd epoch)
  44. GRB 211231A: AstroSat CZTI detection
  45. GRB 220101A: OASDG optical observations
  46. GRB 220101A : Eiso equals the maximum isotropic GRB energy
  47. GRB 220101A: GMG observation
  48. GRB 220101A: Asiago spectroscopic and photometric detection
  49. Fermi trigger No 662768315: Global MASTER-Net observations report
  50. GRB220101A: optical afterglow detection from Konkoly Observatory
  51. GRB 220101A: Fermi GBM Detection
  52. GRB 220101A: NOT redshift confirmation
  53. GRB 220101A: CAHA 2.2m/CAFOS detection
  54. GRB 220101A: Liverpool telescope imaging of a high-redshift afterglow
  55. GRB 220101A: THO optical observations
  56. GRB 220101A: Swift-XRT refined Analysis
  57. GRB 220101A: AGILE detection
  58. GRB 220101A: Xinglong-2.16m photometry and spectroscopy
  59. Swift GRB220101.22: Global MASTER-Net observations report
  60. GRB 220101: Swift/UVOT Detection
  61. GRB 220101A: Fermi-LAT detection
  62. GRB 220101A: Enhanced Swift-XRT position
  63. GRB 220101A: Correction to GCN 31347
  64. GRB 220101A: Swift detection of a burst with a bright optical counterpart
  65. IPN triangulation of GRB 211219A
  66. GRB 211231A: GECAM detection
  67. GRB 211229B: AGILE detection
  68. GRB 211231A: Fermi GBM Final Real-time Localization
  69. GRB 211229A: Swift-XRT and UVOT observations
  70. GRB 211227A: Deep early CAHA 2.2m/CAFOS observation
  71. GRB 211229A: Fermi GBM observation
  72. GRB 211229B: GECAM detection
  73. GRB 211229C: Swift/BAT-GUANO detection likely outside the coded FOV
  74. Fermi GRB 211229B: Global MASTER-Net observations report
  75. GRB 211229B: Fermi GBM Final Real-time Localization
  76. GRB 211229A: Swift ToO observations
  77. GRB 211229A: Swift/BAT-GUANO arcminute localization
  78. GRB 211227A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 211225B: CALET Gamma-Ray Burst Monitor detection
  80. GRB 211229A: GECAM detection
  81. Fermi GRB 211229A: Global MASTER-Net observations report
  82. GRB 211229A: Fermi GBM Final Real-time Localization
  83. GRB 211227A: Swift/UVOT Upper Limits
  84. GRB 211227A: Swift-XRT refined Analysis
  85. GRB 211227A: Swift-BAT refined analysis
  86. Konus-Wind detection of the intermediate flare from SGR 1935+2154
  87. GRB 211227A: A possible short GRB with extended emission at z = 0.228?
  88. GRB 211227A: Liverpool Telescope upper limits
  89. GRB 211227A: Enhanced Swift-XRT position
  90. GRB 211227A: LCO Optical Observations
  91. GRB 211227A: Nanshan/NEXT optical observations and host galaxy candidate
  92. GRB 211227A: MAXI/GSC detection
  93. GRB 211227A: BOOTES-2/TELMA optical upper limit
  94. GRB 211221A: Swift/UVOT Upper Limits
  95. GRB 211227A: Swift detection of a burst
  96. Swift GRB211227.98: Global MASTER-Net observations report
  97. IceCube-20211216B: observations of SN2021gpw in the errorbox of the neutrino trigger
  98. GRB 211226A: Swift/BAT-GUANO detection outside the coded FOV
  99. GRB 211225B: Swift-BAT refined analysis
  100. Fermi trigger No 662216114: Global MASTER-Net observations report

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