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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"

36130 results found.

  1. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  2. GRB 260510A: Fermi GBM Final Real-time Localization
  3. GRB 260509A: SVOM/VT optical candidate with VHF data
  4. GRB 260509A: LCO optical counterpart detection
  5. GRB 260509A: GOTO optical counterpart candidate
  6. GRB 260509A: SVOM detection of a burst
  7. GRB 260506B: AstroSat CZTI detection
  8. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  10. GRB 260507A: Fermi GBM Final Real-time Localization
  11. GRB 260504B: AstroSat CZTI detection
  12. GRB 260504B: SVOM/ECLAIRs refined analysis
  13. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  14. GRB 260506B: Fermi GBM Final Real-time Localization
  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. GRB 260430B: Glowbug gamma-ray detection
  19. GRB 260504B: SVOM/VT optical upper limits
  20. GRB 260421B: radio observation with the VLA
  21. Konus-Wind detection of GRB 260504B (short/hard)
  22. GRB 260504B: GECAM-B detection
  23. GRB 260504C: SVOM/GRM observation of short GRB
  24. GRB 260504B: SVOM/GRM spectral analysis
  25. GRB 260430B: AstroSat CZTI detection of a long burst
  26. GRB 260504B: SVOM/MXT refined analysis and potential detection
  27. GRB 260504B: EP-FXT upper limit
  28. GRB 260502A: SVOM/GRM observation of a short GRB
  29. GRB 260503A: SVOM/GRM observation of a GRB
  30. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  31. Konus-Wind detection of GRB 260415C
  32. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  33. Konus-Wind detection of GRB 260411C
  34. GRB 260504B: REM optical/NIR observations
  35. IPN triangulation of GRB 260429A
  36. IPN triangulation of GRB 260428A
  37. GRB 260504B: AST3-2 i-band upper limit
  38. GRB 260504B: LCO z-band upper limit
  39. SVOM GRB 260504B: MASTER-OAFA optical observations
  40. GRB 260504B: SVOM detection of a short burst
  41. Fermi GRB 260504A: Global MASTER-Net observations report
  42. GRB 260504A: Fermi GBM Final Real-time Localization
  43. GRB 260503A: Fermi GBM Final Real-time Localization
  44. GRB 260502A: GECAM-B observation of a short burst
  45. IPN triangulation of a bright burst from SGR 1E1841-045
  46. GRB 260502A: Fermi GBM Final Localization
  47. GRB 260429B / EP260429a: EP-FXT follow-up observation
  48. GRB 260429B / EP260429a: AstroSat CZTI detection
  49. GRB 260429A: SVOM/GRM observation of a short burst
  50. GRB 260424B: AstroSat CZTI detection
  51. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  52. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  53. GRB 260429A: Fermi GBM Detection
  54. Fermi GRB 260429A: Global MASTER-Net observations report
  55. GRB 260429A: Fermi GBM Final Real-time Localization
  56. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  57. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  58. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 260428A: AstroSat CZTI detection
  60. Fermi GRB 260428A: Global MASTER-Net observations report
  61. EP260416a: Mondy and Terskol optical upper limits
  62. GRB 260424B: Glowbug gamma-ray detection of a short burst
  63. GRB 260424B: COLIBRÍ optical upper limit
  64. Konus-Wind detection of GRB 260424B
  65. GRB 260428A: Fermi GBM Final Real-time Localization
  66. GRB 260424C: Fermi GBM Final Localization
  67. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  68. IPN triangulation of GRB 260424B (short)
  69. GRB 260424B: SVOM/GRM detection of a short burst
  70. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  71. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  72. GRB 260401A: cubesat Avion detection
  73. GRB 260424A: AstroSat CZTI detection of a long burst
  74. GRB 260421B: Kilonova-Catcher optical afterglow detection
  75. GRB 260421B: Insight-HXMT/HE detection
  76. The EP-WXT trigger 01709258652: Mondy optical observations
  77. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  78. EP260416a: Mondy optical observations
  79. GRB 260421B: SVOM/ECLAIRs refined analysis
  80. GRB 260421B: 3.6m DOT optical observation
  81. EP260416a: ZTSh R band observations
  82. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  83. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  84. GRB 260419A: AstroSat CZTI detection
  85. GRB 260421B: SVOM/GRM observation
  86. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  87. GRB 260421B: EP-FXT follow-up observation
  88. GRB 260421B: J-band upper limit with WINTER
  89. GRB 260421B: LCO optical counterpart detection
  90. GRB 260421B: Fermi GBM Observation
  91. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  92. GRB 260421A: AstroSat CZTI detection
  93. GRB 260412A: SVOM/ECLAIRs refined analysis
  94. GRB 260421B: SVOM/VT optical observations
  95. GRB 260310A: Late-time Chandra X-ray Detection
  96. GRB 260418A: Insight-HXMT/HE detection
  97. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  98. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  99. Fermi GRB 260421C: Global MASTER-Net observations report
  100. GRB 260421C: Fermi GBM Final Real-time Localization

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