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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"

35423 results found.

  1. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  2. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  3. GRB 260507A: Fermi GBM Final Real-time Localization
  4. GRB 260504B: AstroSat CZTI detection
  5. GRB 260504B: SVOM/ECLAIRs refined analysis
  6. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  7. GRB 260506B: Fermi GBM Final Real-time Localization
  8. Fermi GRB 260506A: Global MASTER-Net observations report
  9. GRB 260506A: Fermi GBM Final Real-time Localization
  10. GRB 260503A: GECAM-B observation of a burst
  11. GRB 260430B: Glowbug gamma-ray detection
  12. GRB 260504B: SVOM/VT optical upper limits
  13. GRB 260421B: radio observation with the VLA
  14. Konus-Wind detection of GRB 260504B (short/hard)
  15. GRB 260504B: GECAM-B detection
  16. GRB 260504C: SVOM/GRM observation of short GRB
  17. GRB 260504B: SVOM/GRM spectral analysis
  18. GRB 260430B: AstroSat CZTI detection of a long burst
  19. GRB 260504B: SVOM/MXT refined analysis and potential detection
  20. GRB 260504B: EP-FXT upper limit
  21. GRB 260502A: SVOM/GRM observation of a short GRB
  22. GRB 260503A: SVOM/GRM observation of a GRB
  23. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  24. Konus-Wind detection of GRB 260415C
  25. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  26. Konus-Wind detection of GRB 260411C
  27. GRB 260504B: REM optical/NIR observations
  28. IPN triangulation of GRB 260429A
  29. IPN triangulation of GRB 260428A
  30. GRB 260504B: AST3-2 i-band upper limit
  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. IPN triangulation of a bright burst from SGR 1E1841-045
  39. GRB 260502A: Fermi GBM Final Localization
  40. GRB 260429B / EP260429a: EP-FXT follow-up observation
  41. GRB 260429B / EP260429a: AstroSat CZTI detection
  42. GRB 260429A: SVOM/GRM observation of a short burst
  43. GRB 260424B: AstroSat CZTI detection
  44. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  45. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  46. GRB 260429A: Fermi GBM Detection
  47. Fermi GRB 260429A: Global MASTER-Net observations report
  48. GRB 260429A: Fermi GBM Final Real-time Localization
  49. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  50. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  51. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 260428A: AstroSat CZTI detection
  53. Fermi GRB 260428A: Global MASTER-Net observations report
  54. EP260416a: Mondy and Terskol optical upper limits
  55. GRB 260424B: Glowbug gamma-ray detection of a short burst
  56. GRB 260424B: COLIBRÍ optical upper limit
  57. Konus-Wind detection of GRB 260424B
  58. GRB 260428A: Fermi GBM Final Real-time Localization
  59. GRB 260424C: Fermi GBM Final Localization
  60. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  61. IPN triangulation of GRB 260424B (short)
  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. GRB 260401A: cubesat Avion detection
  66. GRB 260424A: AstroSat CZTI detection of a long burst
  67. GRB 260421B: Kilonova-Catcher optical afterglow detection
  68. GRB 260421B: Insight-HXMT/HE detection
  69. The EP-WXT trigger 01709258652: Mondy optical observations
  70. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  71. EP260416a: Mondy optical observations
  72. GRB 260421B: SVOM/ECLAIRs refined analysis
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP260416a: ZTSh R band observations
  75. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  76. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  77. GRB 260419A: AstroSat CZTI detection
  78. GRB 260421B: SVOM/GRM observation
  79. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  80. GRB 260421B: EP-FXT follow-up observation
  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. GRB 260310A: Late-time Chandra X-ray Detection
  89. GRB 260418A: Insight-HXMT/HE detection
  90. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  91. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  92. Fermi GRB 260421C: Global MASTER-Net observations report
  93. GRB 260421C: Fermi GBM Final Real-time Localization
  94. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  95. Fermi GRB 260421B: Global MASTER-Net observations report
  96. GRB 260421B: BOOTES-7 early optical afterglow detection
  97. GRB 260421B: LCO optical afterglow confirmation
  98. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  99. GRB 260421B: TRT optical counterpart detection
  100. GRB 260421B: SVOM detection of a long burst

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