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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"

42752 results found.

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

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