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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"

24278 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: LCO optical afterglow confirmation
  6. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  7. GRB 260421B: TRT optical counterpart detection
  8. GRB 260421B: SVOM detection of a long burst
  9. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  10. GRB 260421B: Fermi GBM Final Real-time Localization
  11. Fermi GRB 260421A: Global MASTER-Net observations report
  12. GRB 260421A: Fermi GBM Final Real-time Localization
  13. GRB 260412A: LCOGT Optical Upper Limits
  14. The EP-WXT trigger 01709260314 is likely a flaring star
  15. The EP-WXT trigger 01709260303 is likely a flaring star
  16. GRB 260417A: SVOM/GRM observation
  17. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  18. GRB 260419B: Fermi GBM Final Real-time Localization
  19. GRB 260419A: Fermi GBM Final Real-time Localization
  20. Fermi trigger No 798275385: Global MASTER-Net observations report
  21. EP260417a: GROWTH-India Telescope optical upper limit
  22. Fermi GRB 260417B: Global MASTER-Net observations report
  23. EP260417b: GROWTH-India Telescope optical upper limit
  24. EP260416a: Ondrejov D50 optical detection
  25. GRB 260418B: Fermi GBM Final Real-time Localization
  26. EP260417a: Global MASTER-Net observations report
  27. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  28. GRB 260418A: Fermi GBM Final Real-time Localization
  29. Fermi GRB 260417A: Global MASTER-Net observations report
  30. Konus-Wind detection of GRB 260411B
  31. GRB 260417B: Fermi GBM Final Real-time Localization
  32. IPN triangulation of GRB 260411B
  33. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  34. EP260417a: TRT optical counterpart detection
  35. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260416a: KAIT optical upper limit
  37. GRB 260417A: Fermi GBM Final Real-time Localization
  38. EP260416a: SVOM/VT optical observation
  39. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  40. GRB 260411B: Glowbug gamma-ray detection
  41. EP260416a: Global MASTER-Net observations report
  42. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  43. GRB 260415B: NuSTAR detection of long prompt emission
  44. GRB 260415B: Fermi GBM Final Localization
  45. GRB 260415A: Fermi GBM Final Real-time Localization
  46. Fermi trigger No 797912738: Global MASTER-Net observations report
  47. GRB 260414A: Glowbug gamma-ray detection
  48. GRB 260414A: Fermi GBM Final Real-time Localization
  49. The EP-WXT trigger 01709260122 is likely a flaring star
  50. Fermi GRB 260413A: Global MASTER-Net observations report
  51. GRB 260413A: Fermi GBM Final Real-time Localization
  52. Konus-Wind detection of GRB 260410A (short/hard)
  53. EP260321a: SVOM/VT optical observations and color changes around peak
  54. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  55. The EP-WXT trigger 01709260010 is likely a flaring star
  56. Fermi GRB 260412A: Global MASTER-Net observations report
  57. GRB 260412A: Fermi GBM Observation
  58. GRB 260411B: Fermi-LAT detection
  59. GRB 260412A: SVOM detection of a long burst
  60. GRB 260412A: Fermi GBM Final Real-time Localization
  61. GRB 260410B: Fermi GBM Observation
  62. GRB 260411B: Ondrejov D50 optical afterglow detection
  63. GRB260411B: 3.6m DOT optical observation
  64. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  65. GRB 260411B: SVOM/GRM observation of a long burst
  66. GRB 260411B: Fermi GBM Detection
  67. GRB 260411B: GOTO optical counterpart candidate
  68. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  69. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  70. GRB 260411B: Fermi GBM Final Real-time Localization
  71. GRB 260411A: Fermi GBM Final Real-time Localization
  72. GRB 260410A: Fermi GBM Observation
  73. GRB 260410B: SVOM/GRM detection of a short faint burst
  74. The EP-WXT trigger 01709259790 is likely a flaring star
  75. GRB 260410B: Fermi GBM Final Real-time Localization
  76. EP-WXT01709259790: Xinglong optical upper limit
  77. GRB 260410A: Fermi-LAT detection
  78. GRB 260410A: Fermi GBM Final Real-time Localization
  79. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  80. EP260321a: Chandra X-ray Non-detection
  81. GRB 260409A: Fermi GBM Final Real-time Localization
  82. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  83. The EP-WXT trigger 01709259773 is likely a flaring star
  84. EP260409a: SVOM/VT optical upper limits
  85. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  86. EP260409a: Global MASTER-Net observations report
  87. GRB 260404A: Fermi GBM Final Localization
  88. GRB 260402A: SVOM/ECLAIRs refined analysis
  89. EP260402a / GRB 260402A: Mephisto optical upper limits
  90. EP-WXT01709259586: Xinglong optical upper limit
  91. EP260403a: Mephisto optical upper limits
  92. EP260402a/GRB 260402A: Xinglong optical upper limit
  93. GRB 260407A: Fermi GBM Final Real-time Localization
  94. EP260405a: SVOM/VT optical upper limits
  95. EP260405a: Global MASTER-Net observations report
  96. EP260405a: Einstein Probe detection of a fast X-ray transient
  97. The EP-WXT trigger 01709259621 is likely a flaring star
  98. The EP-WXT trigger 01709259615 is likely a flaring star
  99. Fermi trigger No 797039833: Global MASTER-Net observations report
  100. EP260324A / AT 2026hir: COLIBRÍ further optical observations

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