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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"

11519 results found.

  1. Fermi GRB 260421C: Global MASTER-Net observations report
  2. GRB 260421C: Fermi GBM Final Real-time Localization
  3. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  4. Fermi GRB 260421B: Global MASTER-Net observations report
  5. GRB 260421B: BOOTES-7 early optical afterglow detection
  6. GRB 260421B: LCO optical afterglow confirmation
  7. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  8. GRB 260421B: TRT optical counterpart detection
  9. GRB 260421B: SVOM detection of a long burst
  10. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  11. GRB 260421B: Fermi GBM Final Real-time Localization
  12. Fermi GRB 260421A: Global MASTER-Net observations report
  13. GRB 260421A: Fermi GBM Final Real-time Localization
  14. GRB 260412A: LCOGT Optical Upper Limits
  15. GRB 260417A: SVOM/GRM observation
  16. GRB 260419B: Fermi GBM Final Real-time Localization
  17. GRB 260419A: Fermi GBM Final Real-time Localization
  18. Fermi trigger No 798275385: Global MASTER-Net observations report
  19. Fermi GRB 260417B: Global MASTER-Net observations report
  20. GRB 260418B: Fermi GBM Final Real-time Localization
  21. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  22. GRB 260418A: Fermi GBM Final Real-time Localization
  23. Fermi GRB 260417A: Global MASTER-Net observations report
  24. Konus-Wind detection of GRB 260411B
  25. GRB 260417B: Fermi GBM Final Real-time Localization
  26. GRB 260417A: AstroSat CZTI detection
  27. IPN triangulation of GRB 260411B
  28. GRB 260414A: Insight-HXMT/HE detection
  29. GRB 260417A: Fermi GBM Final Real-time Localization
  30. GRB 260415B: Glowbug gamma-ray detection
  31. GRB 260411B: Glowbug gamma-ray detection
  32. GRB 260415A: Insight-HXMT/HE detection
  33. GRB 260415B: NuSTAR detection of long prompt emission
  34. GRB 260415B: Fermi GBM Final Localization
  35. GRB 260415A: Fermi GBM Final Real-time Localization
  36. Fermi trigger No 797912738: Global MASTER-Net observations report
  37. GRB 260414A: Glowbug gamma-ray detection
  38. GRB 260412A: Insight-HXMT/HE detection
  39. GRB 260414A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 260413A: Global MASTER-Net observations report
  41. GRB 260410A: Glowbug gamma-ray detection of a short burst
  42. GRB 260413A: Fermi GBM Final Real-time Localization
  43. GRB 260410B: Insight-HXMT/HE detection
  44. GRB 260410A: Insight-HXMT/HE detection
  45. Konus-Wind detection of GRB 260410A (short/hard)
  46. GRB 260411B: GECAM-B observation of a long burst
  47. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  48. GRB 260412A: GECAM-B observation of a long burst
  49. Fermi GRB 260412A: Global MASTER-Net observations report
  50. GRB 260412A: Fermi GBM Observation
  51. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  52. GRB 260411B: Fermi-LAT detection
  53. GRB 260412A: SVOM detection of a long burst
  54. GRB 260412A: Fermi GBM Final Real-time Localization
  55. GRB 260411B: COLIBRÍ optical observations
  56. GRB 260410B: Fermi GBM Observation
  57. GRB 260411B: Ondrejov D50 optical afterglow detection
  58. GRB260411B: 3.6m DOT optical observation
  59. GRB 260411A: SVOM/GRM observation
  60. GRB 260411B: SVOM/GRM observation of a long burst
  61. GRB 260409A: Insight-HXMT/HE detection
  62. GRB 260411B: Fermi GBM Detection
  63. GRB 260411B: GOTO optical counterpart candidate
  64. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  65. GRB 260411B: Fermi GBM Final Real-time Localization
  66. GRB 260411A: Fermi GBM Final Real-time Localization
  67. GRB 260410A: COLIBRÍ optical upper limit
  68. GRB 260410A: Fermi GBM Observation
  69. GRB 260410B: SVOM/GRM detection of a short faint burst
  70. GRB 260410B: Fermi GBM Final Real-time Localization
  71. GRB 260410A: Fermi-LAT detection
  72. GRB 260410A: Fermi GBM Final Real-time Localization
  73. GRB 260409A: Fermi GBM Final Real-time Localization
  74. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  75. GRB 260407A: GECAM-A detection
  76. GRB 260407A: Insight-HXMT/HE detection
  77. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260404A: Fermi GBM Final Localization
  79. GRB 260407A: Glowbug gamma-ray detection
  80. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  81. GRB 260310A / AT2026fgk: X-ray rebrightening
  82. GRID detection of GRB 260401A
  83. GRB 260407A: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 797039833: Global MASTER-Net observations report
  85. GRB 260403A: GECAM-B observation of a long burst
  86. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  87. GRB 260330B: SVOM/VT further optical observation
  88. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  89. GRB 260330B: SVOM/ECLAIRs refined analysis
  90. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  91. GRB 260330B: SVOM/VT optical candidate
  92. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  93. GRB 260403A: AstroSat CZTI detection
  94. GRB 260402B: GECAM-B observation
  95. GRB 260403A: Fermi GBM Final Real-time Localization
  96. GRB 260402B: Fermi GBM Final Real-time Localization
  97. GRB 260401A: SVOM/GRM observation
  98. GRB 260401A: GECAM-B observation
  99. Fermi GRB 260401A: Global MASTER-Net observations report
  100. GRB 260401A: Fermi GBM Observation

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