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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"

24361 results found.

  1. GRB 260509A: GOTO optical counterpart candidate
  2. GRB 260509A: SVOM detection of a burst
  3. GRB 260506B: AstroSat CZTI detection
  4. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  5. EP260507a: REM optical/NIR observations
  6. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  8. EP260507a: SVOM/VT optical observations
  9. GRB 260507A: Fermi GBM Final Real-time Localization
  10. EP260507a: TRT optical counterpart detection
  11. GRB 260504B: SVOM/ECLAIRs refined analysis
  12. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  13. GRB 260506B: Fermi GBM Final Real-time Localization
  14. EP260502a is likely a flaring star
  15. Fermi GRB 260506A: Global MASTER-Net observations report
  16. GRB 260506A: Fermi GBM Final Real-time Localization
  17. IceCube Alert 260505A: Global MASTER-Net observations report
  18. GRB 260504B: SVOM/VT optical upper limits
  19. Konus-Wind detection of GRB 260504B (short/hard)
  20. GRB 260504B: GECAM-B detection
  21. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  22. GRB 260504B: SVOM/GRM spectral analysis
  23. GRB 260504B: SVOM/MXT refined analysis and potential detection
  24. GRB 260504B: EP-FXT upper limit
  25. GRB 260502A: SVOM/GRM observation of a short GRB
  26. GRB 260503A: SVOM/GRM observation of a GRB
  27. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  28. Konus-Wind detection of GRB 260415C
  29. Konus-Wind detection of GRB 260411C
  30. GRB 260504B: REM optical/NIR observations
  31. IPN triangulation of GRB 260429A
  32. IPN triangulation of GRB 260428A
  33. GRB 260504B: AST3-2 i-band upper limit
  34. GRB 260504B: LCO z-band upper limit
  35. SVOM GRB 260504B: MASTER-OAFA optical observations
  36. GRB 260504B: SVOM detection of a short burst
  37. Fermi GRB 260504A: Global MASTER-Net observations report
  38. GRB 260504A: Fermi GBM Final Real-time Localization
  39. GRB 260503A: Fermi GBM Final Real-time Localization
  40. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  41. IPN triangulation of a bright burst from SGR 1E1841-045
  42. GRB 260502A: Fermi GBM Final Localization
  43. The EP-WXT trigger 01709261576 is likely a flaring star
  44. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  45. EP260502a: BOOTES-7: early optical upper limit
  46. GRB 260429A: SVOM/GRM observation of a short burst
  47. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  48. EP260429a: Global MASTER-Net observations report
  49. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  50. GRB 260429A: Fermi GBM Detection
  51. Fermi GRB 260429A: Global MASTER-Net observations report
  52. EP260430a: Global MASTER-Net observations report
  53. GRB 260429A: Fermi GBM Final Real-time Localization
  54. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  55. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  56. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  57. Fermi GRB 260428A: Global MASTER-Net observations report
  58. Konus-Wind detection of GRB 260424B
  59. GRB 260428A: Fermi GBM Final Real-time Localization
  60. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  61. GRB 260424C: Fermi GBM Final Localization
  62. IPN triangulation of GRB 260424B (short)
  63. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  65. IceCube Alert 260425A: Global MASTER-Net observations report
  66. Fermi trigger No 798737427: Global MASTER-Net observations report
  67. GRB 260401A: cubesat Avion detection
  68. GRB 260424A: AstroSat CZTI detection of a long burst
  69. GRB 260421B: SVOM/ECLAIRs refined analysis
  70. GRB 260421B: 3.6m DOT optical observation
  71. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  72. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  73. GRB 260421B: SVOM/GRM observation
  74. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  75. GRB 260421B: EP-FXT follow-up observation
  76. The EP-WXT trigger 01709260362 is likely a flaring star
  77. GRB 260421B: Fermi GBM Observation
  78. GRB 260412A: SVOM/ECLAIRs refined analysis
  79. GRB 260421B: SVOM/VT optical observations
  80. GRB 260310A: Late-time Chandra X-ray Detection
  81. EP260416a: 1.3m DFOT optical observation
  82. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  83. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  84. Fermi GRB 260421C: Global MASTER-Net observations report
  85. GRB 260421C: Fermi GBM Final Real-time Localization
  86. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  87. Fermi GRB 260421B: Global MASTER-Net observations report
  88. GRB 260421B: LCO optical afterglow confirmation
  89. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  90. GRB 260421B: TRT optical counterpart detection
  91. GRB 260421B: SVOM detection of a long burst
  92. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  93. GRB 260421B: Fermi GBM Final Real-time Localization
  94. Fermi GRB 260421A: Global MASTER-Net observations report
  95. GRB 260421A: Fermi GBM Final Real-time Localization
  96. GRB 260412A: LCOGT Optical Upper Limits
  97. The EP-WXT trigger 01709260314 is likely a flaring star
  98. The EP-WXT trigger 01709260303 is likely a flaring star
  99. GRB 260417A: SVOM/GRM observation
  100. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT

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