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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"

27394 results found.

  1. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  2. The EP-WXT trigger 01709270148 is likely a flaring star
  3. GRB 260616B: Fermi GBM Detection
  4. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  5. The EP-WXT trigger 01709269893 is likely a flaring star
  6. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  7. GRB 260616A: Fermi GBM Final Real-time Localization
  8. GRB 260614B: SVOM/ECLAIRs refined analysis
  9. GRB 260614B: SVOM/VT optical afterglow confirmation
  10. GRB 260614B: Fermi GBM Observation
  11. GRB 260614B: SVOM/VT optical candidate from VHF data
  12. GRB 260614B: SVOM detection of a burst
  13. GRB 260614B: Fermi GBM Final Real-time Localization
  14. GRB 260614A: Fermi GBM Final Localization
  15. The EP-WXT trigger 01709269488 is likely a flaring star
  16. GRB 260610B: further Liverpool Telescope optical observations
  17. GRB 260610B: Fermi GBM Observation
  18. GRB 260610B / AT2026owq: GRANDMA optical observations
  19. EP260605a: COLIBRÍ optical upper limits
  20. GRB 260610b: Liverpool Telescope optical observations
  21. EP260610b: Liverpool Telescope optical upper limits
  22. IceCube-260610A: EP-FXT follow-up observation
  23. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  24. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  25. GRB 260610B / AT2026owq: SVOM/VT optical observations
  26. GRB 260610B / AT2026owq: OASDG optical observations
  27. GRB 260610B / AT2026owq: SAO RAS optical observations
  28. GRB 260611B: Fermi GBM Final Real-time Localization
  29. EP260610b: GTC likely spectroscopic redshift z = 1.10
  30. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  31. The EP-WXT trigger 01709269176 is likely a flaring star
  32. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  33. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  34. GRB 260611A: Fermi GBM Final Real-time Localization
  35. EP260610b: COLIBRÍ optical observations
  36. GRB 260610B: DDOTI optical observations
  37. GRB 260610B: GOTO optical counterpart candidate
  38. GRB 260610B: Fermi GBM Final Localization
  39. EP260610b: SVOM/VT optical confirmation with blue color
  40. GRB 260515A: SOAR optical observations
  41. EP260610a: SVOM/VT optical upper limits
  42. IPN triangulation of GRB 260601A (short/hard)
  43. GRB 260610A: Fermi GBM Final Real-time Localization
  44. EP260610a: COLIBRÍ optical upper limits
  45. GRB 260609A: Fermi GBM Final Localization
  46. GRB 260608A: Fermi GRB Observation
  47. IPN triangulation of GRB 260601B / EP260601a
  48. GRB 260604C: SVOM/ECLAIRs refined analysis
  49. GRB 260608A: SVOM/ECLAIRs refined analysis
  50. GRB 260608C: Fermi GBM Final Real-time Localization
  51. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  52. GRB 260608B: Fermi GBM Final Localization
  53. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  54. GRB 260604C: SVOM/C-GFT upper limit
  55. GRB 260608A: SVOM detection of a burst
  56. GRB 260608A: Fermi GBM Final Real-time Localization
  57. GRB 260607A: TRT optical observations
  58. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  59. GRB 260607B: Fermi GBM Observation
  60. GRB 260607B: Fermi-LAT detection
  61. GRB 260607B: Fermi GBM Final Localization Correction
  62. GRB 260607A: Fermi GBM Final Real-time Localization
  63. GRB 260604C: 6 GHz VLA observations
  64. GRB260603A: SVOM/ECLAIRs refined analysis
  65. EP260603a: COLIBRÍ optical upper limit
  66. GRB 260604C: LCO optical upper limit
  67. The EP-WXT trigger 01709267001 is likely a flaring star
  68. GRB 260527A/EP260527a: 6 GHz VLA observations
  69. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  70. The EP-WXT trigger 01709266798 is likely a flaring star
  71. GRB 260604C: Fermi GBM Observation
  72. EP260602d: J-band upper limit with WINTER
  73. EP260602b: J-band upper limit with WINTER
  74. Fermi GRB 260604C: Global MASTER-Net observations report
  75. Fermi GRB 260604C: Global MASTER-Net observations report
  76. SVOM GRB260604.85: Global MASTER-Net observations report
  77. GRB 260604C: SVOM detection of a long burst
  78. GRB 260604C: Fermi GBM Final Real-time Localization
  79. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  80. GRB 260603A: NOT optical observations
  81. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  82. GRB 260604B: Fermi GBM Final Real-time Localization
  83. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  84. EP260603a: Global MASTER-Net observations report
  85. GRB 260604A: Fermi GBM Final Real-time Localization
  86. EP260602b: Liverpool Telescope observations
  87. EP260602a: Liverpool Telescope optical upper limits
  88. GRB 260603B: Fermi GBM Final Localization
  89. GRB 260603A: EP-FXT follow-up observation
  90. EP260601a/GRB 260601B: EP-FXT follow-up observation
  91. GRB 260603A: SVOM/VT optical observations
  92. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  93. EP260602d: Einstein Probe detection of a fast X-ray transient
  94. Fermi trigger No 802141998: Global MASTER-Net observations report
  95. EP260602c: Einstein Probe detection of a fast X-ray transient
  96. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  97. EP260602a: COLIBRÍ optical observations
  98. GRB260601B/EP260601a: NOT near-infrared observations
  99. SVOM GRB260603.23: Global MASTER-Net observations report
  100. GRB 260603A: SVOM detection of a burst

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