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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. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  2. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  3. GRB 260415B: NuSTAR detection of long prompt emission
  4. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  5. GRB 260415B: Fermi GBM Final Localization
  6. GRB 260415A: Fermi GBM Final Real-time Localization
  7. Fermi trigger No 797912738: Global MASTER-Net observations report
  8. GRB 260414A: Glowbug gamma-ray detection
  9. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  10. EP260321a: CMO SAI J,K observations
  11. GRB 260412A: Insight-HXMT/HE detection
  12. GRB 260414A: Fermi GBM Final Real-time Localization
  13. The EP-WXT trigger 01709260122 is likely a flaring star
  14. Fermi GRB 260413A: Global MASTER-Net observations report
  15. GRB 260410A: Glowbug gamma-ray detection of a short burst
  16. GRB 260413A: Fermi GBM Final Real-time Localization
  17. GRB 260410B: Insight-HXMT/HE detection
  18. GRB 260410A: Insight-HXMT/HE detection
  19. Konus-Wind detection of GRB 260410A (short/hard)
  20. GRB 260411B: GECAM-B observation of a long burst
  21. EP260321a: SVOM/VT optical observations and color changes around peak
  22. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  23. The EP-WXT trigger 01709260010 is likely a flaring star
  24. GRB 260412A: GECAM-B observation of a long burst
  25. Fermi GRB 260412A: Global MASTER-Net observations report
  26. GRB 260412A: Fermi GBM Observation
  27. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  28. GRB 260411B: Fermi-LAT detection
  29. GRB 260412A: SVOM detection of a long burst
  30. GRB 260412A: Fermi GBM Final Real-time Localization
  31. GRB 260411B: COLIBRÍ optical observations
  32. GRB 260410B: Fermi GBM Observation
  33. GRB 260411B: Ondrejov D50 optical afterglow detection
  34. GRB260411B: 3.6m DOT optical observation
  35. GRB 260411A: SVOM/GRM observation
  36. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  37. GRB 260411B: SVOM/GRM observation of a long burst
  38. GRB 260409A: Insight-HXMT/HE detection
  39. GRB 260411B: Fermi GBM Detection
  40. GRB 260411B: GOTO optical counterpart candidate
  41. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  42. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  43. GRB 260411B: Fermi GBM Final Real-time Localization
  44. GRB 260411A: Fermi GBM Final Real-time Localization
  45. GRB 260410A: COLIBRÍ optical upper limit
  46. EP-WXT01709259790: Optical Upper limits with kinder observations
  47. GRB 260410A: Fermi GBM Observation
  48. GRB 260410B: SVOM/GRM detection of a short faint burst
  49. The EP-WXT trigger 01709259790 is likely a flaring star
  50. GRB 260410B: Fermi GBM Final Real-time Localization
  51. EP-WXT01709259790: Xinglong optical upper limit
  52. GRB 260410A: Fermi-LAT detection
  53. GRB 260410A: Fermi GBM Final Real-time Localization
  54. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  55. EP260321a: Chandra X-ray Non-detection
  56. GRB 260409A: Fermi GBM Final Real-time Localization
  57. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  58. The EP-WXT trigger 01709259773 is likely a flaring star
  59. GRB 260407A: GECAM-A detection
  60. GRB 260407A: Insight-HXMT/HE detection
  61. EP260409a: SVOM/VT optical upper limits
  62. EP260409a: COLIBRÍ optical upper limits
  63. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  64. EP260409a: Global MASTER-Net observations report
  65. EP260409a: Einstein Probe detection of an X-ray transient
  66. EP260321a: VLA radio detection
  67. GRB 260404A: Fermi GBM Final Localization
  68. GRB 260407A: Glowbug gamma-ray detection
  69. GRB 260402A: SVOM/ECLAIRs refined analysis
  70. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  71. GRB 260310A / AT2026fgk: X-ray rebrightening
  72. EP260402a / GRB 260402A: Mephisto optical upper limits
  73. EP-WXT01709259586: Xinglong optical upper limit
  74. EP260403a: Mephisto optical upper limits
  75. EP260402a/GRB 260402A: Xinglong optical upper limit
  76. EP260321a: Upper limits from VLA radio observations
  77. GRID detection of GRB 260401A
  78. EP260321a: uGMRT observations
  79. GRB 260407A: Fermi GBM Final Real-time Localization
  80. EP260405a: GMOS-N optical upper limits
  81. EP260405a: SVOM/VT optical upper limits
  82. EP260405a: Global MASTER-Net observations report
  83. EP260405a: Einstein Probe detection of a fast X-ray transient
  84. The EP-WXT trigger 01709259621 is likely a flaring star
  85. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  86. The EP-WXT trigger 01709259615 is likely a flaring star
  87. Fermi trigger No 797039833: Global MASTER-Net observations report
  88. GRB 260403A: GECAM-B observation of a long burst
  89. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  90. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  91. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  92. The EP-WXT trigger 01709259586 is likely a flaring star
  93. GRB 260330B: SVOM/VT further optical observation
  94. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  95. GRB 260330B: SVOM/ECLAIRs refined analysis
  96. EP260403a: LCO optical observations of the counterpart
  97. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  98. EP260403a: LCO optical counterpart detection
  99. EP260403a: COLIBRÍ optical counterpart candidate
  100. GRB 260330B: SVOM/VT optical candidate

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