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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"

11538 results found.

  1. GRB 260421B: Fermi GBM Observation
  2. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  3. GRB 260421A: AstroSat CZTI detection
  4. GRB 260412A: SVOM/ECLAIRs refined analysis
  5. GRB 260421B: SVOM/VT optical observations
  6. GRB 260310A: Late-time Chandra X-ray Detection
  7. GRB 260418A: Insight-HXMT/HE detection
  8. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  9. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  10. Fermi GRB 260421C: Global MASTER-Net observations report
  11. GRB 260421C: Fermi GBM Final Real-time Localization
  12. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  13. Fermi GRB 260421B: Global MASTER-Net observations report
  14. GRB 260421B: BOOTES-7 early optical afterglow detection
  15. GRB 260421B: LCO optical afterglow confirmation
  16. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  17. GRB 260421B: TRT optical counterpart detection
  18. GRB 260421B: SVOM detection of a long burst
  19. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  20. GRB 260421B: Fermi GBM Final Real-time Localization
  21. Fermi GRB 260421A: Global MASTER-Net observations report
  22. GRB 260421A: Fermi GBM Final Real-time Localization
  23. GRB 260412A: LCOGT Optical Upper Limits
  24. GRB 260417A: SVOM/GRM observation
  25. GRB 260419B: Fermi GBM Final Real-time Localization
  26. GRB 260419A: Fermi GBM Final Real-time Localization
  27. Fermi trigger No 798275385: Global MASTER-Net observations report
  28. Fermi GRB 260417B: Global MASTER-Net observations report
  29. GRB 260418B: Fermi GBM Final Real-time Localization
  30. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  31. GRB 260418A: Fermi GBM Final Real-time Localization
  32. Fermi GRB 260417A: Global MASTER-Net observations report
  33. Konus-Wind detection of GRB 260411B
  34. GRB 260417B: Fermi GBM Final Real-time Localization
  35. GRB 260417A: AstroSat CZTI detection
  36. IPN triangulation of GRB 260411B
  37. GRB 260414A: Insight-HXMT/HE detection
  38. GRB 260417A: Fermi GBM Final Real-time Localization
  39. GRB 260415B: Glowbug gamma-ray detection
  40. GRB 260411B: Glowbug gamma-ray detection
  41. GRB 260415A: Insight-HXMT/HE detection
  42. GRB 260415B: NuSTAR detection of long prompt emission
  43. GRB 260415B: Fermi GBM Final Localization
  44. GRB 260415A: Fermi GBM Final Real-time Localization
  45. Fermi trigger No 797912738: Global MASTER-Net observations report
  46. GRB 260414A: Glowbug gamma-ray detection
  47. GRB 260412A: Insight-HXMT/HE detection
  48. GRB 260414A: Fermi GBM Final Real-time Localization
  49. Fermi GRB 260413A: Global MASTER-Net observations report
  50. GRB 260410A: Glowbug gamma-ray detection of a short burst
  51. GRB 260413A: Fermi GBM Final Real-time Localization
  52. GRB 260410B: Insight-HXMT/HE detection
  53. GRB 260410A: Insight-HXMT/HE detection
  54. Konus-Wind detection of GRB 260410A (short/hard)
  55. GRB 260411B: GECAM-B observation of a long burst
  56. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260412A: GECAM-B observation of a long burst
  58. Fermi GRB 260412A: Global MASTER-Net observations report
  59. GRB 260412A: Fermi GBM Observation
  60. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  61. GRB 260411B: Fermi-LAT detection
  62. GRB 260412A: SVOM detection of a long burst
  63. GRB 260412A: Fermi GBM Final Real-time Localization
  64. GRB 260411B: COLIBRÍ optical observations
  65. GRB 260410B: Fermi GBM Observation
  66. GRB 260411B: Ondrejov D50 optical afterglow detection
  67. GRB260411B: 3.6m DOT optical observation
  68. GRB 260411A: SVOM/GRM observation
  69. GRB 260411B: SVOM/GRM observation of a long burst
  70. GRB 260409A: Insight-HXMT/HE detection
  71. GRB 260411B: Fermi GBM Detection
  72. GRB 260411B: GOTO optical counterpart candidate
  73. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  74. GRB 260411B: Fermi GBM Final Real-time Localization
  75. GRB 260411A: Fermi GBM Final Real-time Localization
  76. GRB 260410A: COLIBRÍ optical upper limit
  77. GRB 260410A: Fermi GBM Observation
  78. GRB 260410B: SVOM/GRM detection of a short faint burst
  79. GRB 260410B: Fermi GBM Final Real-time Localization
  80. GRB 260410A: Fermi-LAT detection
  81. GRB 260410A: Fermi GBM Final Real-time Localization
  82. GRB 260409A: Fermi GBM Final Real-time Localization
  83. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  84. GRB 260407A: GECAM-A detection
  85. GRB 260407A: Insight-HXMT/HE detection
  86. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  87. GRB 260404A: Fermi GBM Final Localization
  88. GRB 260407A: Glowbug gamma-ray detection
  89. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  90. GRB 260310A / AT2026fgk: X-ray rebrightening
  91. GRID detection of GRB 260401A
  92. GRB 260407A: Fermi GBM Final Real-time Localization
  93. Fermi trigger No 797039833: Global MASTER-Net observations report
  94. GRB 260403A: GECAM-B observation of a long burst
  95. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  96. GRB 260330B: SVOM/VT further optical observation
  97. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  98. GRB 260330B: SVOM/ECLAIRs refined analysis
  99. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  100. GRB 260330B: SVOM/VT optical candidate

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