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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. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  2. GRB 260604C: SVOM/C-GFT upper limit
  3. GRB 260607B: AstroSat CZTI detection
  4. GRB 260608A: SVOM detection of a burst
  5. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  6. GRB 260608A: Fermi GBM Final Real-time Localization
  7. EP260605a: EP-FXT follow-up observation
  8. GRB 260607A: TRT optical observations
  9. GRB 260604C: GRANDMA further observations
  10. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  11. GRB 260604A: SVOM/GRM detection
  12. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  13. GRB 260607B: Fermi GBM Observation
  14. GRB 260607B: Fermi-LAT detection
  15. GRB 260607B: Fermi GBM Final Localization Correction
  16. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  17. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  18. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  19. GRB 260607A: Fermi GBM Final Real-time Localization
  20. GRB 260604C: GECAM-B observation
  21. GRB 260604C: 6 GHz VLA observations
  22. GRB 260604C: SAO RAS optical observations
  23. GRB 260604C: GRANDMA observations
  24. GRB 260604B: SVOM/GRM detection
  25. GRB 260605A: Insight-HXMT/HE detection
  26. GRB260603A: SVOM/ECLAIRs refined analysis
  27. EP260605a: Einstein Probe detection of a fast X-ray transient
  28. EP260603a: COLIBRÍ optical upper limit
  29. GRB 260604A: Glowbug gamma-ray detection
  30. GRB 260604C: LCO optical upper limit
  31. GRB 260604C: Liverpool Telescope optical detection
  32. The EP-WXT trigger 01709267001 is likely a flaring star
  33. EP260602d: EP-FXT follow-up observation
  34. EP260602c: EP-FXT follow-up observation
  35. GRB 260601B / EP260601a: AstroSat CZTI detection
  36. GRB 260527A/EP260527a: 6 GHz VLA observations
  37. GRB 260604C: GOTO detections of the optical afterglow
  38. GRB 260604C: Correction to GCN 44828
  39. GRB 260604C: Kilonova-Catcher optical afterglow detection
  40. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. The EP-WXT trigger 01709266798 is likely a flaring star
  42. GRB 260604C: Jinshan optical observations
  43. GRB 260604C: Fermi GBM Observation
  44. EP260602d: J-band upper limit with WINTER
  45. EP260602b: J-band upper limit with WINTER
  46. GRB 260604C: LAST detection of optical counterpart candidate
  47. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  48. Fermi GRB 260604C: Global MASTER-Net observations report
  49. Fermi GRB 260604C: Global MASTER-Net observations report
  50. SVOM GRB260604.85: Global MASTER-Net observations report
  51. GRB 260604C: SVOM detection of a long burst
  52. GRB 260604C: Fermi GBM Final Real-time Localization
  53. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  54. GRB 260603A: NOT optical observations
  55. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  56. GRB 260604B: Fermi GBM Final Real-time Localization
  57. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  58. EP260602a: EP-FXT follow-up observation
  59. EP260603a: Global MASTER-Net observations report
  60. EP260603a: Einstein Probe detection of a fast X-ray transient
  61. EP260602d: Optical Upper limits with kinder observations
  62. GRB 260604A: Fermi GBM Final Real-time Localization
  63. EP260602b: Liverpool Telescope observations
  64. EP260602a: Liverpool Telescope optical upper limits
  65. EP260602b: Liverpool Telescope and LCO observations
  66. GRB 260603B: Fermi GBM Final Localization
  67. EP260602a: GTC and Liverpool Telescope optical observations
  68. Konus-Wind detection of GRB 260601B/EP260601a
  69. GRB 260603A: EP-FXT follow-up observation
  70. EP260601a/GRB 260601B: EP-FXT follow-up observation
  71. GRB 260601B / EP260601a: Mondy optical upper limit
  72. EP260602b: EP-FXT follow-up observation
  73. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  74. GRB 260603A: Kilonova-Catcher optical upper limit
  75. GRB 260603A: SVOM/VT optical observations
  76. EP260602a: NOT NIR J-band observations
  77. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  78. EP260602d: Einstein Probe detection of a fast X-ray transient
  79. Fermi trigger No 802141998: Global MASTER-Net observations report
  80. EP260602a: SVOM/VT optical magnitudes correction
  81. GRB 260601A: SVOM/GRM observation of a short burst
  82. EP260602c: Einstein Probe detection of a fast X-ray transient
  83. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  84. EP260602a: COLIBRÍ optical observations
  85. GRB260601B/EP260601a: NOT near-infrared observations
  86. SVOM GRB260603.23: Global MASTER-Net observations report
  87. GRB 260603A: SVOM detection of a burst
  88. EP260602b: Einstein Probe detection of a fast X-ray transient
  89. GRB 260601B/EP260601a: Insight-HXMT detection
  90. Fermi GRB 260602B: Global MASTER-Net observations report
  91. Fermi GRB 260602B: Global MASTER-Net observations report
  92. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  93. EP260602a: SVOM/VT optical candidate
  94. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  95. GRB 260602B: Fermi GBM Final Localization
  96. GRB 260601A: GECAM-B observation of a short burst
  97. GRB 260601B/EP260601a: J-band upper limit with WINTER
  98. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  99. EP260530a/AT 2026nwl: KAIT optical observations
  100. GRB 260602A: Fermi GBM Final Real-time Localization

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