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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"

27032 results found.

  1. GRB 260617A: Fermi GBM Final Real-time Localization
  2. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  3. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  4. GRB 260616A: GECAM-B observation
  5. GRB 260616A: Fermi-LAT detection
  6. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  7. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  8. EP260616a: EP-WXT detection of a fast X-ray transient
  9. The EP-WXT trigger 01709270148 is likely a flaring star
  10. GRB 260616B: Fermi GBM Detection
  11. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  12. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  13. The EP-WXT trigger 01709269893 is likely a flaring star
  14. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  15. GRB 260616A: Fermi GBM Final Real-time Localization
  16. GRB 260614B: SVOM/ECLAIRs refined analysis
  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 260614A: GECAM-B observation
  22. GRB 260614B: SVOM/VT optical candidate from VHF data
  23. GRB 260614B: SVOM detection of a burst
  24. GRB 260614B: Fermi GBM Final Real-time Localization
  25. GRB 260611B: SVOM/GRM detection
  26. GRB 260614A: Fermi GBM Final Localization
  27. The EP-WXT trigger 01709269488 is likely a flaring star
  28. GRB 260610B: further Liverpool Telescope optical observations
  29. GRB 260610B: Fermi GBM Observation
  30. GRB 260610B / AT2026owq: GRANDMA optical observations
  31. EP260605a: COLIBRÍ optical upper limits
  32. GRB 260610b: Liverpool Telescope optical observations
  33. EP260610b: Liverpool Telescope optical upper limits
  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 / AT2026owq: SAO RAS optical observations
  40. GRB 260611B: Fermi GBM Final Real-time Localization
  41. EP260610b: GTC likely spectroscopic redshift z = 1.10
  42. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  43. The EP-WXT trigger 01709269176 is likely a flaring star
  44. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  45. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  46. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  47. GRB 260611A: Fermi GBM Final Real-time Localization
  48. EP260610b: COLIBRÍ optical observations
  49. GRB 260610B: DDOTI optical observations
  50. GRB 260610B: GOTO optical counterpart candidate
  51. GRB 260610B: Fermi GBM Final Localization
  52. EP260610b: SVOM/VT optical confirmation with blue color
  53. GRB 260515A: SOAR optical observations
  54. EP260610a: SVOM/VT optical upper limits
  55. EP260610b: Einstein Probe detection of an X-ray transient
  56. IPN triangulation of GRB 260601A (short/hard)
  57. GRB 260610A: Fermi GBM Final Real-time Localization
  58. EP260610a: COLIBRÍ optical upper limits
  59. EP260610a: Einstein Probe detection of a fast X-ray transient
  60. GRB 260609A: Fermi GBM Final Localization
  61. GRB 260608A: Fermi GRB Observation
  62. IPN triangulation of GRB 260601B / EP260601a
  63. GRB 260604C: SVOM/ECLAIRs refined analysis
  64. GRB 260608A: SVOM/ECLAIRs refined analysis
  65. GRB 260607B: GECAM-B observation
  66. GRB 260608C: Fermi GBM Final Real-time Localization
  67. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  68. GRB 260608B: Fermi GBM Final Localization
  69. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  70. GRB 260604C: SVOM/C-GFT upper limit
  71. GRB 260608A: SVOM detection of a burst
  72. GRB 260608A: Fermi GBM Final Real-time Localization
  73. EP260605a: EP-FXT follow-up observation
  74. GRB 260607A: TRT optical observations
  75. GRB 260604C: GRANDMA further observations
  76. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  77. GRB 260604A: SVOM/GRM detection
  78. GRB 260607B: Fermi GBM Observation
  79. GRB 260607B: Fermi-LAT detection
  80. GRB 260607B: Fermi GBM Final Localization Correction
  81. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  82. GRB 260607A: Fermi GBM Final Real-time Localization
  83. GRB 260604C: GECAM-B observation
  84. GRB 260604C: 6 GHz VLA observations
  85. GRB 260604C: GRANDMA observations
  86. GRB 260604B: SVOM/GRM detection
  87. GRB260603A: SVOM/ECLAIRs refined analysis
  88. EP260605a: Einstein Probe detection of a fast X-ray transient
  89. EP260603a: COLIBRÍ optical upper limit
  90. GRB 260604C: LCO optical upper limit
  91. The EP-WXT trigger 01709267001 is likely a flaring star
  92. EP260602d: EP-FXT follow-up observation
  93. EP260602c: EP-FXT follow-up observation
  94. GRB 260527A/EP260527a: 6 GHz VLA observations
  95. GRB 260604C: Kilonova-Catcher optical afterglow detection
  96. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  97. The EP-WXT trigger 01709266798 is likely a flaring star
  98. GRB 260604C: Fermi GBM Observation
  99. EP260602d: J-band upper limit with WINTER
  100. EP260602b: J-band upper limit with WINTER

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