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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"

28863 results found.

  1. EP260507a: REM optical/NIR observations
  2. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  3. EP260507a: COLIBRÍ optical observations
  4. EP260507a: SVOM/VT optical observations
  5. EP260507a: Liverpool Telescope optical upper limits
  6. GRB 260507A: Fermi GBM Final Real-time Localization
  7. EP260507a: GOTO optical counterpart detection
  8. EP260507a: TRT optical counterpart detection
  9. EP260507a: Kinder optical counterpart candidate
  10. EP260507a: LCO optical counterpart
  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. GRB 260503A: GECAM-B observation of a burst
  18. IceCube Alert 260505A: Global MASTER-Net observations report
  19. GRB 260504B: SVOM/VT optical upper limits
  20. GRB 260421B: radio observation with the VLA
  21. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  22. GRB 260504C: SVOM/GRM observation of short GRB
  23. GRB 260504B: SVOM/MXT refined analysis and potential detection
  24. GRB 260502A: SVOM/GRM observation of a short GRB
  25. GRB 260503A: SVOM/GRM observation of a GRB
  26. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  28. GRB 260504B: REM optical/NIR observations
  29. IPN triangulation of GRB 260429A
  30. IPN triangulation of GRB 260428A
  31. GRB 260504B: LCO z-band upper limit
  32. SVOM GRB 260504B: MASTER-OAFA optical observations
  33. GRB 260504B: SVOM detection of a short burst
  34. Fermi GRB 260504A: Global MASTER-Net observations report
  35. GRB 260504A: Fermi GBM Final Real-time Localization
  36. GRB 260503A: Fermi GBM Final Real-time Localization
  37. GRB 260502A: GECAM-B observation of a short burst
  38. GRB 260502A: Fermi GBM Final Localization
  39. The EP-WXT trigger 01709261576 is likely a flaring star
  40. GRB 260429B / EP260429a: EP-FXT follow-up observation
  41. EP260502a: BOOTES-7: early optical upper limit
  42. EP260502a: Las Cumbres upper limit
  43. GRB 260429A: SVOM/GRM observation of a short burst
  44. EP260429a: Global MASTER-Net observations report
  45. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  46. EP260429a: LCO optical upper limits
  47. EP260430a: LCO optical upper limits
  48. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  49. GRB 260429A: Fermi GBM Detection
  50. Fermi GRB 260429A: Global MASTER-Net observations report
  51. EP260430a: Global MASTER-Net observations report
  52. EP260430a: Einstein Probe detection of an X-ray transient
  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. GRB 260428A: AstroSat CZTI detection
  57. Fermi GRB 260428A: Global MASTER-Net observations report
  58. GRB 260424B: COLIBRÍ optical upper limit
  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. GRB 260424B: SVOM/GRM detection of a short burst
  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 260421B: Kilonova-Catcher optical afterglow detection
  69. GRB 260421B: Insight-HXMT/HE detection
  70. The EP-WXT trigger 01709258652: Mondy optical observations
  71. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  72. GRB 260421B: SVOM/ECLAIRs refined analysis
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  75. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  76. GRB 260419A: AstroSat CZTI detection
  77. GRB 260421B: SVOM/GRM observation
  78. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  79. GRB 260421B: EP-FXT follow-up observation
  80. The EP-WXT trigger 01709260362 is likely a flaring star
  81. GRB 260421B: J-band upper limit with WINTER
  82. GRB 260421B: LCO optical counterpart detection
  83. GRB 260421B: Fermi GBM Observation
  84. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  85. GRB 260421A: AstroSat CZTI detection
  86. GRB 260412A: SVOM/ECLAIRs refined analysis
  87. GRB 260421B: SVOM/VT optical observations
  88. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  89. GRB 260310A: Late-time Chandra X-ray Detection
  90. GRB 260418A: Insight-HXMT/HE detection
  91. EP260416a: 1.3m DFOT optical observation
  92. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  93. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  94. Fermi GRB 260421C: Global MASTER-Net observations report
  95. GRB 260421C: Fermi GBM Final Real-time Localization
  96. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  97. Fermi GRB 260421B: Global MASTER-Net observations report
  98. GRB 260421B: BOOTES-7 early optical afterglow detection
  99. GRB 260421B: LCO optical afterglow confirmation
  100. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart

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