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

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