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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"

37550 results found.

  1. GRB 260415B: Fermi GBM Final Localization
  2. GRB 260415A: Fermi GBM Final Real-time Localization
  3. Fermi trigger No 797912738: Global MASTER-Net observations report
  4. GRB 260414A: Glowbug gamma-ray detection
  5. EP260321a: CMO SAI J,K observations
  6. GRB 260412A: Insight-HXMT/HE detection
  7. GRB 260414A: Fermi GBM Final Real-time Localization
  8. Fermi GRB 260413A: Global MASTER-Net observations report
  9. GRB 260410A: Glowbug gamma-ray detection of a short burst
  10. GRB 260413A: Fermi GBM Final Real-time Localization
  11. GRB 260410B: Insight-HXMT/HE detection
  12. GRB 260410A: Insight-HXMT/HE detection
  13. Konus-Wind detection of GRB 260410A (short/hard)
  14. GRB 260411B: GECAM-B observation of a long burst
  15. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  16. GRB 260412A: GECAM-B observation of a long burst
  17. Fermi GRB 260412A: Global MASTER-Net observations report
  18. GRB 260412A: Fermi GBM Observation
  19. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  20. GRB 260411B: Fermi-LAT detection
  21. GRB 260412A: SVOM detection of a long burst
  22. GRB 260412A: Fermi GBM Final Real-time Localization
  23. GRB 260411B: COLIBRÍ optical observations
  24. GRB 260410B: Fermi GBM Observation
  25. GRB 260411B: Ondrejov D50 optical afterglow detection
  26. GRB260411B: 3.6m DOT optical observation
  27. GRB 260411A: SVOM/GRM observation
  28. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  29. GRB 260411B: SVOM/GRM observation of a long burst
  30. GRB 260409A: Insight-HXMT/HE detection
  31. GRB 260411B: Fermi GBM Detection
  32. GRB 260411B: GOTO optical counterpart candidate
  33. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  34. GRB 260411B: Fermi GBM Final Real-time Localization
  35. GRB 260411A: Fermi GBM Final Real-time Localization
  36. GRB 260410A: COLIBRÍ optical upper limit
  37. GRB 260410A: Fermi GBM Observation
  38. GRB 260410B: SVOM/GRM detection of a short faint burst
  39. GRB 260410B: Fermi GBM Final Real-time Localization
  40. GRB 260410A: Fermi-LAT detection
  41. GRB 260410A: Fermi GBM Final Real-time Localization
  42. EP260321a: Chandra X-ray Non-detection
  43. GRB 260409A: Fermi GBM Final Real-time Localization
  44. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  45. GRB 260407A: GECAM-A detection
  46. GRB 260407A: Insight-HXMT/HE detection
  47. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  48. GRB 260404A: Fermi GBM Final Localization
  49. GRB 260407A: Glowbug gamma-ray detection
  50. GRB 260402A: SVOM/ECLAIRs refined analysis
  51. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  52. GRB 260310A / AT2026fgk: X-ray rebrightening
  53. EP260402a / GRB 260402A: Mephisto optical upper limits
  54. EP260402a/GRB 260402A: Xinglong optical upper limit
  55. GRID detection of GRB 260401A
  56. GRB 260407A: Fermi GBM Final Real-time Localization
  57. Fermi trigger No 797039833: Global MASTER-Net observations report
  58. GRB 260403A: GECAM-B observation of a long burst
  59. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  60. GRB 260330B: SVOM/VT further optical observation
  61. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  62. GRB 260330B: SVOM/ECLAIRs refined analysis
  63. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  64. GRB 260330B: SVOM/VT optical candidate
  65. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  66. GRB 260403A: AstroSat CZTI detection
  67. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 260402B: GECAM-B observation
  69. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  70. GRB 260402C: NuSTAR detection of prompt emission
  71. GRB 260402C: AstroSat CZTI detection of a long burst
  72. GRB 260403A: Fermi GBM Final Real-time Localization
  73. GRB 260402B: Fermi GBM Final Real-time Localization
  74. GRB 260402A: WINTER J-band upper limit
  75. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  76. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  77. GRB 260401A: SVOM/GRM observation
  78. GRB 260401A: GECAM-B observation
  79. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  80. GRB 260402A: Kilonova-Catcher optical upper limit
  81. GRB 260402A: MASTER optical observations
  82. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  83. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  84. GRB 260402A: SVOM detection of a burst
  85. Fermi GRB 260401A: Global MASTER-Net observations report
  86. GRB 260401A: Fermi GBM Observation
  87. GRB 260401A: NuSTAR detection of prompt emission
  88. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  89. GRB 260401A: MAXI/GSC detection
  90. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  91. GRB 260401A: Fermi GBM Final Real-time Localization
  92. EP260329b: Mondy and Assy-Turgen optical upper limits
  93. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  94. EP260329b: GOTO detection of optical counterpart
  95. GRB 260330B: SVOM/VT optical upper limits
  96. Konus-Wind detection of GRB 260320A
  97. Konus-Wind detection of GRB 260316B (duplicate submission)
  98. Konus-Wind detection of GRB 260316B
  99. GRB 260321A: SVOM/ECLAIRs refined analysis
  100. EP260329b: J-band upper limits with WINTER

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