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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').
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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"

32490 results found.

  1. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  2. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  3. GRB 260614A: AstroSat CZTI detection
  4. EP260616a: EP-WXT detection of a fast X-ray transient
  5. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  6. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  7. GRB 260614B: SVOM/ECLAIRs refined analysis
  8. GRB 260610B: Terskol optical observations
  9. GRB 260614B: GECAM-B observation
  10. GRB 260610B: SVOM/GRM observation
  11. GRB 260614B: SVOM/VT optical afterglow confirmation
  12. GRB 260614B: Fermi GBM Observation
  13. GRB 260610B: ALMA detection
  14. GRB 260614A: GECAM-B observation
  15. GRB 260614B: SVOM/VT optical candidate from VHF data
  16. GRB 260614B: SVOM detection of a burst
  17. GRB 260611B: SVOM/GRM detection
  18. GRB 260610B: further Liverpool Telescope optical observations
  19. GRB 260610B: Fermi GBM Observation
  20. GRB 260610B / AT2026owq: GRANDMA optical observations
  21. GRB 260610B / AT2026owq: further SAO RAS optical observations
  22. EP260605a: COLIBRÍ optical upper limits
  23. GRB 260610b: Liverpool Telescope optical observations
  24. EP260610b: Liverpool Telescope optical upper limits
  25. IceCube-260610A: No candidates from the Zwicky Transient Facility
  26. IceCube-260610A: EP-FXT follow-up observation
  27. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  28. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  29. GRB 260610B / AT2026owq: SVOM/VT optical observations
  30. GRB 260610B / AT2026owq: OASDG optical observations
  31. GRB 260610B: IAC-80 Optical observations
  32. GRB 260610B / AT2026owq: SAO RAS optical observations
  33. EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
  34. EP260610b: GTC likely spectroscopic redshift z = 1.10
  35. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  36. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  37. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  38. GRB 260610B / AT2026owq: Early ATLAS observations
  39. GRB 260610B: TRT optical observation
  40. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  41. EP260610b: COLIBRÍ optical observations
  42. GRB 260610B: DDOTI optical observations
  43. EP260610b: MAO/AZT-22 optical observations
  44. GRB 260610B: GOTO optical counterpart candidate
  45. EP260610b: NOT optical observation
  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. Konus-Wind detection of GRB 260601A
  52. IPN triangulation of GRB 260601A (short/hard)
  53. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  54. EP260610a: COLIBRÍ optical upper limits
  55. Konus-Wind detection of GRB 260604C
  56. GRB 260608A: Fermi GRB Observation
  57. GRB 260604C: AstroSat CZTI detection
  58. IPN triangulation of GRB 260601B / EP260601a
  59. GRB 260604C: SVOM/ECLAIRs refined analysis
  60. GRB 260608A: SVOM/ECLAIRs refined analysis
  61. Konus-Wind detection of GRB 260607B
  62. GRB 260607B: GECAM-B observation
  63. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  64. GRB 260604C: further SAO RAS optical observations
  65. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  66. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  67. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  68. GRB 260604C: SVOM/C-GFT upper limit
  69. GRB 260607B: AstroSat CZTI detection
  70. GRB 260608A: SVOM detection of a burst
  71. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  72. EP260605a: EP-FXT follow-up observation
  73. GRB 260607A: TRT optical observations
  74. GRB 260604C: GRANDMA further observations
  75. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  76. GRB 260604A: SVOM/GRM detection
  77. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  78. GRB 260607B: Fermi GBM Observation
  79. GRB 260607B: Fermi-LAT detection
  80. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  81. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  82. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  83. GRB 260604C: GECAM-B observation
  84. GRB 260604C: 6 GHz VLA observations
  85. GRB 260604C: SAO RAS optical observations
  86. GRB 260604C: GRANDMA observations
  87. GRB 260604B: SVOM/GRM detection
  88. GRB260603A: SVOM/ECLAIRs refined analysis
  89. EP260603a: COLIBRÍ optical upper limit
  90. GRB 260604A: Glowbug gamma-ray detection
  91. GRB 260604C: LCO optical upper limit
  92. GRB 260604C: Liverpool Telescope optical detection
  93. EP260602d: EP-FXT follow-up observation
  94. EP260602c: EP-FXT follow-up observation
  95. GRB 260601B / EP260601a: AstroSat CZTI detection
  96. GRB 260527A/EP260527a: 6 GHz VLA observations
  97. GRB 260604C: GOTO detections of the optical afterglow
  98. GRB 260604C: Correction to GCN 44828
  99. GRB 260604C: Kilonova-Catcher optical afterglow detection
  100. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations

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