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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"

11529 results found.

  1. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  2. GRB 260614A: AstroSat CZTI detection
  3. EP260616a: EP-WXT detection of a fast X-ray transient
  4. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  5. GRB 260616B: Fermi GBM Detection
  6. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  7. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  8. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  9. GRB 260616A: Fermi GBM Final Real-time Localization
  10. GRB 260614B: SVOM/ECLAIRs refined analysis
  11. GRB 260610B: Terskol optical observations
  12. GRB 260614B: GECAM-B observation
  13. GRB 260610B: SVOM/GRM observation
  14. GRB 260614B: SVOM/VT optical afterglow confirmation
  15. GRB 260614B: Fermi GBM Observation
  16. GRB 260610B: ALMA detection
  17. GRB 260614A: GECAM-B observation
  18. GRB 260614B: SVOM detection of a burst
  19. GRB 260614B: Fermi GBM Final Real-time Localization
  20. GRB 260611B: SVOM/GRM detection
  21. GRB 260614A: Fermi GBM Final Localization
  22. GRB 260610B: further Liverpool Telescope optical observations
  23. GRB 260610B: Fermi GBM Observation
  24. GRB 260610B / AT2026owq: GRANDMA optical observations
  25. GRB 260610B / AT2026owq: further SAO RAS optical observations
  26. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  27. GRB 260610B / AT2026owq: SVOM/VT optical observations
  28. GRB 260610B / AT2026owq: OASDG optical observations
  29. GRB 260610B: IAC-80 Optical observations
  30. GRB 260610B / AT2026owq: SAO RAS optical observations
  31. GRB 260611B: Fermi GBM Final Real-time Localization
  32. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  33. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  34. GRB 260610B / AT2026owq: Early ATLAS observations
  35. GRB 260610B: TRT optical observation
  36. GRB 260611A: Fermi GBM Final Real-time Localization
  37. GRB 260610B: DDOTI optical observations
  38. GRB 260610B: GOTO optical counterpart candidate
  39. GRB 260610B: Fermi GBM Final Localization
  40. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  41. Konus-Wind detection of GRB 260601A
  42. IPN triangulation of GRB 260601A (short/hard)
  43. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  44. GRB 260610A: Fermi GBM Final Real-time Localization
  45. GRB 260609A: Fermi GBM Final Localization
  46. Konus-Wind detection of GRB 260604C
  47. GRB 260608A: Fermi GRB Observation
  48. GRB 260604C: AstroSat CZTI detection
  49. IPN triangulation of GRB 260601B / EP260601a
  50. GRB 260604C: SVOM/ECLAIRs refined analysis
  51. GRB 260608A: SVOM/ECLAIRs refined analysis
  52. Konus-Wind detection of GRB 260607B
  53. GRB 260607B: GECAM-B observation
  54. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  55. GRB 260608C: Fermi GBM Final Real-time Localization
  56. GRB 260604C: further SAO RAS optical observations
  57. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  58. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  59. GRB 260608B: Fermi GBM Final Localization
  60. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  61. GRB 260607B: AstroSat CZTI detection
  62. GRB 260608A: SVOM detection of a burst
  63. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  64. GRB 260608A: Fermi GBM Final Real-time Localization
  65. GRB 260607A: TRT optical observations
  66. GRB 260604C: GRANDMA further observations
  67. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  68. GRB 260604A: SVOM/GRM detection
  69. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  70. GRB 260607B: Fermi GBM Observation
  71. GRB 260607B: Fermi-LAT detection
  72. GRB 260607B: Fermi GBM Final Localization Correction
  73. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  74. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  75. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  76. GRB 260607A: Fermi GBM Final Real-time Localization
  77. GRB 260604C: GECAM-B observation
  78. GRB 260604C: 6 GHz VLA observations
  79. GRB 260604C: SAO RAS optical observations
  80. GRB 260604C: GRANDMA observations
  81. GRB 260604B: SVOM/GRM detection
  82. GRB 260604A: Glowbug gamma-ray detection
  83. GRB 260604C: LCO optical upper limit
  84. GRB 260604C: Liverpool Telescope optical detection
  85. GRB 260604C: GOTO detections of the optical afterglow
  86. GRB 260604C: Kilonova-Catcher optical afterglow detection
  87. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  88. GRB 260604C: Jinshan optical observations
  89. GRB 260604C: Fermi GBM Observation
  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. GRB 260604C: SVOM detection of a long burst
  94. GRB 260604C: Fermi GBM Final Real-time Localization
  95. GRB 260604B: Fermi GBM Final Real-time Localization
  96. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  97. GRB 260604A: Fermi GBM Final Real-time Localization
  98. GRB 260603B: Fermi GBM Final Localization
  99. Konus-Wind detection of GRB 260601B/EP260601a
  100. Fermi trigger No 802141998: Global MASTER-Net observations report

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