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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"

27398 results found.

  1. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  2. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  3. GRB 260616A: Fermi-LAT detection
  4. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  5. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  6. The EP-WXT trigger 01709270148 is likely a flaring star
  7. GRB 260616B: Fermi GBM Detection
  8. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  9. The EP-WXT trigger 01709269893 is likely a flaring star
  10. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  11. GRB 260616A: Fermi GBM Final Real-time Localization
  12. GRB 260614B: SVOM/ECLAIRs refined analysis
  13. GRB 260614B: SVOM/VT optical afterglow confirmation
  14. GRB 260614B: Fermi GBM Observation
  15. GRB 260614B: SVOM/VT optical candidate from VHF data
  16. GRB 260614B: SVOM detection of a burst
  17. GRB 260614B: Fermi GBM Final Real-time Localization
  18. GRB 260614A: Fermi GBM Final Localization
  19. The EP-WXT trigger 01709269488 is likely a flaring star
  20. GRB 260610B: further Liverpool Telescope optical observations
  21. GRB 260610B: Fermi GBM Observation
  22. GRB 260610B / AT2026owq: GRANDMA optical observations
  23. EP260605a: COLIBRÍ optical upper limits
  24. GRB 260610b: Liverpool Telescope optical observations
  25. EP260610b: Liverpool Telescope optical upper limits
  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 / AT2026owq: SAO RAS optical observations
  32. GRB 260611B: Fermi GBM Final Real-time Localization
  33. EP260610b: GTC likely spectroscopic redshift z = 1.10
  34. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  35. The EP-WXT trigger 01709269176 is likely a flaring star
  36. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  37. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  38. GRB 260611A: Fermi GBM Final Real-time Localization
  39. EP260610b: COLIBRÍ optical observations
  40. GRB 260610B: DDOTI optical observations
  41. GRB 260610B: GOTO optical counterpart candidate
  42. GRB 260610B: Fermi GBM Final Localization
  43. EP260610b: SVOM/VT optical confirmation with blue color
  44. GRB 260515A: SOAR optical observations
  45. EP260610a: SVOM/VT optical upper limits
  46. IPN triangulation of GRB 260601A (short/hard)
  47. GRB 260610A: Fermi GBM Final Real-time Localization
  48. EP260610a: COLIBRÍ optical upper limits
  49. GRB 260609A: Fermi GBM Final Localization
  50. GRB 260608A: Fermi GRB Observation
  51. IPN triangulation of GRB 260601B / EP260601a
  52. GRB 260604C: SVOM/ECLAIRs refined analysis
  53. GRB 260608A: SVOM/ECLAIRs refined analysis
  54. GRB 260608C: Fermi GBM Final Real-time Localization
  55. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  56. GRB 260608B: Fermi GBM Final Localization
  57. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  58. GRB 260604C: SVOM/C-GFT upper limit
  59. GRB 260608A: SVOM detection of a burst
  60. GRB 260608A: Fermi GBM Final Real-time Localization
  61. GRB 260607A: TRT optical observations
  62. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  63. GRB 260607B: Fermi GBM Observation
  64. GRB 260607B: Fermi-LAT detection
  65. GRB 260607B: Fermi GBM Final Localization Correction
  66. GRB 260607A: Fermi GBM Final Real-time Localization
  67. GRB 260604C: 6 GHz VLA observations
  68. GRB260603A: SVOM/ECLAIRs refined analysis
  69. EP260603a: COLIBRÍ optical upper limit
  70. GRB 260604C: LCO optical upper limit
  71. The EP-WXT trigger 01709267001 is likely a flaring star
  72. GRB 260527A/EP260527a: 6 GHz VLA observations
  73. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. The EP-WXT trigger 01709266798 is likely a flaring star
  75. GRB 260604C: Fermi GBM Observation
  76. EP260602d: J-band upper limit with WINTER
  77. EP260602b: J-band upper limit with WINTER
  78. Fermi GRB 260604C: Global MASTER-Net observations report
  79. Fermi GRB 260604C: Global MASTER-Net observations report
  80. SVOM GRB260604.85: Global MASTER-Net observations report
  81. GRB 260604C: SVOM detection of a long burst
  82. GRB 260604C: Fermi GBM Final Real-time Localization
  83. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  84. GRB 260603A: NOT optical observations
  85. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  86. GRB 260604B: Fermi GBM Final Real-time Localization
  87. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  88. EP260603a: Global MASTER-Net observations report
  89. GRB 260604A: Fermi GBM Final Real-time Localization
  90. EP260602b: Liverpool Telescope observations
  91. EP260602a: Liverpool Telescope optical upper limits
  92. GRB 260603B: Fermi GBM Final Localization
  93. GRB 260603A: EP-FXT follow-up observation
  94. EP260601a/GRB 260601B: EP-FXT follow-up observation
  95. GRB 260603A: SVOM/VT optical observations
  96. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  97. EP260602d: Einstein Probe detection of a fast X-ray transient
  98. Fermi trigger No 802141998: Global MASTER-Net observations report
  99. EP260602c: Einstein Probe detection of a fast X-ray transient
  100. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate

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