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

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