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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"

43659 results found.

  1. GRB 260611B: Fermi GBM Final Real-time Localization
  2. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  3. EP260610b: GTC likely spectroscopic redshift z = 1.10
  4. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  5. The EP-WXT trigger 01709269176 is likely a flaring star
  6. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  7. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  8. GRB 260610B / AT2026owq: Early ATLAS observations
  9. GRB 260610B: TRT optical observation
  10. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  11. GRB 260611A: Fermi GBM Final Real-time Localization
  12. EP260610b: COLIBRÍ optical observations
  13. GRB 260610B: DDOTI optical observations
  14. EP260610b: MAO/AZT-22 optical observations
  15. GRB 260610B: GOTO optical counterpart candidate
  16. EP260610b: NOT optical observation
  17. GRB 260610B: Fermi GBM Final Localization
  18. EP260610b: SVOM/VT optical confirmation with blue color
  19. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 260515A: SOAR optical observations
  21. EP260610b: Gemini North optical counterpart candidate
  22. EP260610a: SVOM/VT optical upper limits
  23. EP260610b: Einstein Probe detection of an X-ray transient
  24. Konus-Wind detection of GRB 260601A
  25. IPN triangulation of GRB 260601A (short/hard)
  26. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  27. GRB 260610A: Fermi GBM Final Real-time Localization
  28. EP260610a: COLIBRÍ optical upper limits
  29. EP260610a: Einstein Probe detection of a fast X-ray transient
  30. GRB 260609A: Fermi GBM Final Localization
  31. Konus-Wind detection of GRB 260604C
  32. GRB 260608A: Fermi GRB Observation
  33. GRB 260604C: AstroSat CZTI detection
  34. IPN triangulation of GRB 260601B / EP260601a
  35. GRB 260604C: SVOM/ECLAIRs refined analysis
  36. GRB 260608A: SVOM/ECLAIRs refined analysis
  37. Konus-Wind detection of GRB 260607B
  38. GRB 260607B: GECAM-B observation
  39. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  40. GRB 260608C: Fermi GBM Final Real-time Localization
  41. GRB 260604C: further SAO RAS optical observations
  42. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  43. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  44. GRB 260608B: Fermi GBM Final Localization
  45. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  46. GRB 260604C: SVOM/C-GFT upper limit
  47. GRB 260607B: AstroSat CZTI detection
  48. GRB 260608A: SVOM detection of a burst
  49. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  50. GRB 260608A: Fermi GBM Final Real-time Localization
  51. EP260605a: EP-FXT follow-up observation
  52. GRB 260607A: TRT optical observations
  53. GRB 260604C: GRANDMA further observations
  54. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  55. GRB 260604A: SVOM/GRM detection
  56. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  57. GRB 260607B: Fermi GBM Observation
  58. GRB 260607B: Fermi-LAT detection
  59. GRB 260607B: Fermi GBM Final Localization Correction
  60. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  61. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  62. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  63. GRB 260607A: Fermi GBM Final Real-time Localization
  64. GRB 260604C: GECAM-B observation
  65. GRB 260604C: 6 GHz VLA observations
  66. GRB 260604C: SAO RAS optical observations
  67. GRB 260604C: GRANDMA observations
  68. GRB 260604B: SVOM/GRM detection
  69. GRB 260605A: Insight-HXMT/HE detection
  70. GRB260603A: SVOM/ECLAIRs refined analysis
  71. EP260605a: Einstein Probe detection of a fast X-ray transient
  72. EP260603a: COLIBRÍ optical upper limit
  73. GRB 260604A: Glowbug gamma-ray detection
  74. GRB 260604C: LCO optical upper limit
  75. GRB 260604C: Liverpool Telescope optical detection
  76. The EP-WXT trigger 01709267001 is likely a flaring star
  77. EP260602d: EP-FXT follow-up observation
  78. EP260602c: EP-FXT follow-up observation
  79. GRB 260601B / EP260601a: AstroSat CZTI detection
  80. GRB 260527A/EP260527a: 6 GHz VLA observations
  81. GRB 260604C: GOTO detections of the optical afterglow
  82. GRB 260604C: Correction to GCN 44828
  83. GRB 260604C: Kilonova-Catcher optical afterglow detection
  84. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  85. The EP-WXT trigger 01709266798 is likely a flaring star
  86. GRB 260604C: Jinshan optical observations
  87. GRB 260604C: Fermi GBM Observation
  88. EP260602d: J-band upper limit with WINTER
  89. EP260602b: J-band upper limit with WINTER
  90. GRB 260604C: LAST detection of optical counterpart candidate
  91. Fermi GRB 260604C: Global MASTER-Net observations report
  92. Fermi GRB 260604C: Global MASTER-Net observations report
  93. SVOM GRB260604.85: Global MASTER-Net observations report
  94. GRB 260604C: SVOM detection of a long burst
  95. GRB 260604C: Fermi GBM Final Real-time Localization
  96. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  97. GRB 260603A: NOT optical observations
  98. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  99. GRB 260604B: Fermi GBM Final Real-time Localization
  100. GRB 260601A: CALET Gamma-Ray Burst Monitor detection

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