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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"

32508 results found.

  1. GRB 260618B: Fermi-LAT detection
  2. IPN triangulation of GRB 260617A (short)
  3. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  4. GRB 260616A: Insight-HXMT detection
  5. EP260618a: EP-WXT detection of an X-ray transient
  6. GRB 260610B: AbAO optical observations
  7. EP260616a/GRB 260616B: EP-FXT follow-up observation
  8. GRB 260506B: cubesat Avion detection
  9. GRB 260616C: GECAM-B observation of a burst
  10. GRB 260616A: Fermi GBM Observation
  11. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  12. Konus-Wind detection of GRB 260616B/EP260616a
  13. Konus-Wind detection of GRB 260616A
  14. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  15. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  16. GRB 260616A: GECAM-B observation
  17. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  18. GRB 260429A: cubesat Avion detection
  19. GRB 260616A: Fermi-LAT detection
  20. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  21. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  22. GRB 260614A: AstroSat CZTI detection
  23. EP260616a: EP-WXT detection of a fast X-ray transient
  24. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  25. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  26. GRB 260614B: SVOM/ECLAIRs refined analysis
  27. GRB 260610B: Terskol optical observations
  28. GRB 260614B: GECAM-B observation
  29. GRB 260610B: SVOM/GRM observation
  30. GRB 260614B: SVOM/VT optical afterglow confirmation
  31. GRB 260614B: Fermi GBM Observation
  32. GRB 260610B: ALMA detection
  33. GRB 260614A: GECAM-B observation
  34. GRB 260614B: SVOM/VT optical candidate from VHF data
  35. GRB 260614B: SVOM detection of a burst
  36. GRB 260611B: SVOM/GRM detection
  37. GRB 260610B: further Liverpool Telescope optical observations
  38. GRB 260610B: Fermi GBM Observation
  39. GRB 260610B / AT2026owq: GRANDMA optical observations
  40. GRB 260610B / AT2026owq: further SAO RAS optical observations
  41. EP260605a: COLIBRÍ optical upper limits
  42. GRB 260610b: Liverpool Telescope optical observations
  43. EP260610b: Liverpool Telescope optical upper limits
  44. IceCube-260610A: No candidates from the Zwicky Transient Facility
  45. IceCube-260610A: EP-FXT follow-up observation
  46. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  47. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  48. GRB 260610B / AT2026owq: SVOM/VT optical observations
  49. GRB 260610B / AT2026owq: OASDG optical observations
  50. GRB 260610B: IAC-80 Optical observations
  51. GRB 260610B / AT2026owq: SAO RAS optical observations
  52. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  53. EP260610b: GTC likely spectroscopic redshift z = 1.10
  54. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  55. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  56. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  57. GRB 260610B / AT2026owq: Early ATLAS observations
  58. GRB 260610B: TRT optical observation
  59. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  60. EP260610b: COLIBRÍ optical observations
  61. GRB 260610B: DDOTI optical observations
  62. EP260610b: MAO/AZT-22 optical observations
  63. GRB 260610B: GOTO optical counterpart candidate
  64. EP260610b: NOT optical observation
  65. EP260610b: SVOM/VT optical confirmation with blue color
  66. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  67. GRB 260515A: SOAR optical observations
  68. EP260610b: Gemini North optical counterpart candidate
  69. EP260610a: SVOM/VT optical upper limits
  70. Konus-Wind detection of GRB 260601A
  71. IPN triangulation of GRB 260601A (short/hard)
  72. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  73. EP260610a: COLIBRÍ optical upper limits
  74. Konus-Wind detection of GRB 260604C
  75. GRB 260608A: Fermi GRB Observation
  76. GRB 260604C: AstroSat CZTI detection
  77. IPN triangulation of GRB 260601B / EP260601a
  78. GRB 260604C: SVOM/ECLAIRs refined analysis
  79. GRB 260608A: SVOM/ECLAIRs refined analysis
  80. Konus-Wind detection of GRB 260607B
  81. GRB 260607B: GECAM-B observation
  82. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  83. GRB 260604C: further SAO RAS optical observations
  84. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  85. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  86. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  87. GRB 260604C: SVOM/C-GFT upper limit
  88. GRB 260607B: AstroSat CZTI detection
  89. GRB 260608A: SVOM detection of a burst
  90. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  91. EP260605a: EP-FXT follow-up observation
  92. GRB 260607A: TRT optical observations
  93. GRB 260604C: GRANDMA further observations
  94. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  95. GRB 260604A: SVOM/GRM detection
  96. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  97. GRB 260607B: Fermi GBM Observation
  98. GRB 260607B: Fermi-LAT detection
  99. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  100. GRB 260604C: OPD1.6m - GRANDMA observations - detection

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