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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"

32499 results found.

  1. GRB 260616A: Fermi GBM Observation
  2. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  3. Konus-Wind detection of GRB 260616B/EP260616a
  4. Konus-Wind detection of GRB 260616A
  5. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  6. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  7. GRB 260616A: GECAM-B observation
  8. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  9. GRB 260429A: cubesat Avion detection
  10. GRB 260616A: Fermi-LAT detection
  11. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  12. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  13. GRB 260614A: AstroSat CZTI detection
  14. EP260616a: EP-WXT detection of a fast X-ray transient
  15. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  16. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  17. GRB 260614B: SVOM/ECLAIRs refined analysis
  18. GRB 260610B: Terskol optical observations
  19. GRB 260614B: GECAM-B observation
  20. GRB 260610B: SVOM/GRM observation
  21. GRB 260614B: SVOM/VT optical afterglow confirmation
  22. GRB 260614B: Fermi GBM Observation
  23. GRB 260610B: ALMA detection
  24. GRB 260614A: GECAM-B observation
  25. GRB 260614B: SVOM/VT optical candidate from VHF data
  26. GRB 260614B: SVOM detection of a burst
  27. GRB 260611B: SVOM/GRM detection
  28. GRB 260610B: further Liverpool Telescope optical observations
  29. GRB 260610B: Fermi GBM Observation
  30. GRB 260610B / AT2026owq: GRANDMA optical observations
  31. GRB 260610B / AT2026owq: further SAO RAS optical observations
  32. EP260605a: COLIBRÍ optical upper limits
  33. GRB 260610b: Liverpool Telescope optical observations
  34. EP260610b: Liverpool Telescope optical upper limits
  35. IceCube-260610A: No candidates from the Zwicky Transient Facility
  36. IceCube-260610A: EP-FXT follow-up observation
  37. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  38. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  39. GRB 260610B / AT2026owq: SVOM/VT optical observations
  40. GRB 260610B / AT2026owq: OASDG optical observations
  41. GRB 260610B: IAC-80 Optical observations
  42. GRB 260610B / AT2026owq: SAO RAS optical observations
  43. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  44. EP260610b: GTC likely spectroscopic redshift z = 1.10
  45. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  46. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  47. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  48. GRB 260610B / AT2026owq: Early ATLAS observations
  49. GRB 260610B: TRT optical observation
  50. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  51. EP260610b: COLIBRÍ optical observations
  52. GRB 260610B: DDOTI optical observations
  53. EP260610b: MAO/AZT-22 optical observations
  54. GRB 260610B: GOTO optical counterpart candidate
  55. EP260610b: NOT optical observation
  56. EP260610b: SVOM/VT optical confirmation with blue color
  57. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 260515A: SOAR optical observations
  59. EP260610b: Gemini North optical counterpart candidate
  60. EP260610a: SVOM/VT optical upper limits
  61. Konus-Wind detection of GRB 260601A
  62. IPN triangulation of GRB 260601A (short/hard)
  63. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  64. EP260610a: COLIBRÍ optical upper limits
  65. Konus-Wind detection of GRB 260604C
  66. GRB 260608A: Fermi GRB Observation
  67. GRB 260604C: AstroSat CZTI detection
  68. IPN triangulation of GRB 260601B / EP260601a
  69. GRB 260604C: SVOM/ECLAIRs refined analysis
  70. GRB 260608A: SVOM/ECLAIRs refined analysis
  71. Konus-Wind detection of GRB 260607B
  72. GRB 260607B: GECAM-B observation
  73. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  74. GRB 260604C: further SAO RAS optical observations
  75. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  76. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  77. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  78. GRB 260604C: SVOM/C-GFT upper limit
  79. GRB 260607B: AstroSat CZTI detection
  80. GRB 260608A: SVOM detection of a burst
  81. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  82. EP260605a: EP-FXT follow-up observation
  83. GRB 260607A: TRT optical observations
  84. GRB 260604C: GRANDMA further observations
  85. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  86. GRB 260604A: SVOM/GRM detection
  87. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  88. GRB 260607B: Fermi GBM Observation
  89. GRB 260607B: Fermi-LAT detection
  90. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  91. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  92. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  93. GRB 260604C: GECAM-B observation
  94. GRB 260604C: 6 GHz VLA observations
  95. GRB 260604C: SAO RAS optical observations
  96. GRB 260604C: GRANDMA observations
  97. GRB 260604B: SVOM/GRM detection
  98. GRB260603A: SVOM/ECLAIRs refined analysis
  99. EP260603a: COLIBRÍ optical upper limit
  100. GRB 260604A: Glowbug gamma-ray detection

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