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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"

32497 results found.

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