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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 260601A (short/hard)
  2. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  3. GRB 260610A: Fermi GBM Final Real-time Localization
  4. EP260610a: COLIBRÍ optical upper limits
  5. EP260610a: Einstein Probe detection of a fast X-ray transient
  6. GRB 260609A: Fermi GBM Final Localization
  7. Konus-Wind detection of GRB 260604C
  8. GRB 260608A: Fermi GRB Observation
  9. GRB 260604C: AstroSat CZTI detection
  10. IPN triangulation of GRB 260601B / EP260601a
  11. GRB 260604C: SVOM/ECLAIRs refined analysis
  12. GRB 260608A: SVOM/ECLAIRs refined analysis
  13. Konus-Wind detection of GRB 260607B
  14. GRB 260607B: GECAM-B observation
  15. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  16. GRB 260608C: Fermi GBM Final Real-time Localization
  17. GRB 260604C: further SAO RAS optical observations
  18. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  19. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  20. GRB 260608B: Fermi GBM Final Localization
  21. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  22. GRB 260604C: SVOM/C-GFT upper limit
  23. GRB 260607B: AstroSat CZTI detection
  24. GRB 260608A: SVOM detection of a burst
  25. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  26. GRB 260608A: Fermi GBM Final Real-time Localization
  27. EP260605a: EP-FXT follow-up observation
  28. GRB 260607A: TRT optical observations
  29. GRB 260604C: GRANDMA further observations
  30. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  31. GRB 260604A: SVOM/GRM detection
  32. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  33. GRB 260607B: Fermi GBM Observation
  34. GRB 260607B: Fermi-LAT detection
  35. GRB 260607B: Fermi GBM Final Localization Correction
  36. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  37. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  38. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  39. GRB 260607A: Fermi GBM Final Real-time Localization
  40. GRB 260604C: GECAM-B observation
  41. GRB 260604C: 6 GHz VLA observations
  42. GRB 260604C: SAO RAS optical observations
  43. GRB 260604C: GRANDMA observations
  44. GRB 260604B: SVOM/GRM detection
  45. GRB 260605A: Insight-HXMT/HE detection
  46. GRB260603A: SVOM/ECLAIRs refined analysis
  47. EP260605a: Einstein Probe detection of a fast X-ray transient
  48. EP260603a: COLIBRÍ optical upper limit
  49. GRB 260604A: Glowbug gamma-ray detection
  50. GRB 260604C: LCO optical upper limit
  51. GRB 260604C: Liverpool Telescope optical detection
  52. The EP-WXT trigger 01709267001 is likely a flaring star
  53. EP260602d: EP-FXT follow-up observation
  54. EP260602c: EP-FXT follow-up observation
  55. GRB 260601B / EP260601a: AstroSat CZTI detection
  56. GRB 260527A/EP260527a: 6 GHz VLA observations
  57. GRB 260604C: GOTO detections of the optical afterglow
  58. GRB 260604C: Correction to GCN 44828
  59. GRB 260604C: Kilonova-Catcher optical afterglow detection
  60. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. The EP-WXT trigger 01709266798 is likely a flaring star
  62. GRB 260604C: Jinshan optical observations
  63. GRB 260604C: Fermi GBM Observation
  64. EP260602d: J-band upper limit with WINTER
  65. EP260602b: J-band upper limit with WINTER
  66. GRB 260604C: LAST detection of optical counterpart candidate
  67. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  68. Fermi GRB 260604C: Global MASTER-Net observations report
  69. Fermi GRB 260604C: Global MASTER-Net observations report
  70. SVOM GRB260604.85: Global MASTER-Net observations report
  71. GRB 260604C: SVOM detection of a long burst
  72. GRB 260604C: Fermi GBM Final Real-time Localization
  73. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  74. GRB 260603A: NOT optical observations
  75. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  76. GRB 260604B: Fermi GBM Final Real-time Localization
  77. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  78. EP260602a: EP-FXT follow-up observation
  79. EP260603a: Global MASTER-Net observations report
  80. EP260603a: Einstein Probe detection of a fast X-ray transient
  81. EP260602d: Optical Upper limits with kinder observations
  82. GRB 260604A: Fermi GBM Final Real-time Localization
  83. EP260602b: Liverpool Telescope observations
  84. EP260602a: Liverpool Telescope optical upper limits
  85. EP260602b: Liverpool Telescope and LCO observations
  86. GRB 260603B: Fermi GBM Final Localization
  87. EP260602a: GTC and Liverpool Telescope optical observations
  88. Konus-Wind detection of GRB 260601B/EP260601a
  89. GRB 260603A: EP-FXT follow-up observation
  90. EP260601a/GRB 260601B: EP-FXT follow-up observation
  91. GRB 260601B / EP260601a: Mondy optical upper limit
  92. EP260602b: EP-FXT follow-up observation
  93. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  94. GRB 260603A: Kilonova-Catcher optical upper limit
  95. GRB 260603A: SVOM/VT optical observations
  96. EP260602a: NOT NIR J-band observations
  97. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  98. EP260602d: Einstein Probe detection of a fast X-ray transient
  99. Fermi trigger No 802141998: Global MASTER-Net observations report
  100. EP260602a: SVOM/VT optical magnitudes correction

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