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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"

42755 results found.

  1. GRB 260610B: Terskol optical observations
  2. GRB 260614B: GECAM-B observation
  3. GRB 260610B: SVOM/GRM observation
  4. GRB 260614B: SVOM/VT optical afterglow confirmation
  5. GRB 260614B: Fermi GBM Observation
  6. GRB 260610B: ALMA detection
  7. GRB 260614A: GECAM-B observation
  8. GRB 260614B: SVOM/VT optical candidate from VHF data
  9. GRB 260614B: SVOM detection of a burst
  10. GRB 260614B: Fermi GBM Final Real-time Localization
  11. GRB 260611B: SVOM/GRM detection
  12. GRB 260614A: Fermi GBM Final Localization
  13. The EP-WXT trigger 01709269488 is likely a flaring star
  14. GRB 260603C: AstroSat CZTI detection
  15. GRB 260610B: further Liverpool Telescope optical observations
  16. GRB 260610B: Fermi GBM Observation
  17. GRB 260610B / AT2026owq: GRANDMA optical observations
  18. GRB 260610B / AT2026owq: further SAO RAS optical observations
  19. EP260605a: COLIBRÍ optical upper limits
  20. GRB 260610b: Liverpool Telescope optical observations
  21. EP260610b: Liverpool Telescope optical upper limits
  22. IceCube-260610A: No candidates from the Zwicky Transient Facility
  23. IceCube-260610A: EP-FXT follow-up observation
  24. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  25. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  26. GRB 260610B / AT2026owq: SVOM/VT optical observations
  27. GRB 260610B / AT2026owq: OASDG optical observations
  28. GRB 260610B: IAC-80 Optical observations
  29. GRB 260610B / AT2026owq: SAO RAS optical observations
  30. GRB 260611B: Fermi GBM Final Real-time Localization
  31. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  32. EP260610b: GTC likely spectroscopic redshift z = 1.10
  33. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  34. The EP-WXT trigger 01709269176 is likely a flaring star
  35. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  36. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  37. GRB 260610B / AT2026owq: Early ATLAS observations
  38. GRB 260610B: TRT optical observation
  39. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  40. GRB 260611A: Fermi GBM Final Real-time Localization
  41. EP260610b: COLIBRÍ optical observations
  42. GRB 260610B: DDOTI optical observations
  43. GRB 260610B: GOTO optical counterpart candidate
  44. EP260610b: NOT optical observation
  45. GRB 260610B: Fermi GBM Final Localization
  46. EP260610b: SVOM/VT optical confirmation with blue color
  47. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 260515A: SOAR optical observations
  49. EP260610b: Gemini North optical counterpart candidate
  50. EP260610a: SVOM/VT optical upper limits
  51. EP260610b: Einstein Probe detection of an X-ray transient
  52. Konus-Wind detection of GRB 260601A
  53. IPN triangulation of GRB 260601A (short/hard)
  54. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  55. GRB 260610A: Fermi GBM Final Real-time Localization
  56. EP260610a: COLIBRÍ optical upper limits
  57. EP260610a: Einstein Probe detection of a fast X-ray transient
  58. GRB 260609A: Fermi GBM Final Localization
  59. Konus-Wind detection of GRB 260604C
  60. GRB 260608A: Fermi GRB Observation
  61. GRB 260604C: AstroSat CZTI detection
  62. IPN triangulation of GRB 260601B / EP260601a
  63. GRB 260604C: SVOM/ECLAIRs refined analysis
  64. GRB 260608A: SVOM/ECLAIRs refined analysis
  65. Konus-Wind detection of GRB 260607B
  66. GRB 260607B: GECAM-B observation
  67. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  68. GRB 260608C: Fermi GBM Final Real-time Localization
  69. GRB 260604C: further SAO RAS optical observations
  70. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  71. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  72. GRB 260608B: Fermi GBM Final Localization
  73. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  74. GRB 260604C: SVOM/C-GFT upper limit
  75. GRB 260607B: AstroSat CZTI detection
  76. GRB 260608A: SVOM detection of a burst
  77. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  78. GRB 260608A: Fermi GBM Final Real-time Localization
  79. EP260605a: EP-FXT follow-up observation
  80. GRB 260607A: TRT optical observations
  81. GRB 260604C: GRANDMA further observations
  82. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  83. GRB 260604A: SVOM/GRM detection
  84. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  85. GRB 260607B: Fermi GBM Observation
  86. GRB 260607B: Fermi-LAT detection
  87. GRB 260607B: Fermi GBM Final Localization Correction
  88. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  89. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  90. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  91. GRB 260607A: Fermi GBM Final Real-time Localization
  92. GRB 260604C: GECAM-B observation
  93. GRB 260604C: 6 GHz VLA observations
  94. GRB 260604C: SAO RAS optical observations
  95. GRB 260604C: GRANDMA observations
  96. GRB 260604B: SVOM/GRM detection
  97. GRB 260605A: Insight-HXMT/HE detection
  98. GRB260603A: SVOM/ECLAIRs refined analysis
  99. EP260605a: Einstein Probe detection of a fast X-ray transient
  100. EP260603a: COLIBRÍ optical upper limit

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