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

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