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

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