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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"
  1. GRB 260504B: AstroSat CZTI detection
  2. GRB 260504B: SVOM/ECLAIRs refined analysis
  3. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  4. GRB 260506B: Fermi GBM Final Real-time Localization
  5. EP260502a is likely a flaring star
  6. Fermi GRB 260506A: Global MASTER-Net observations report
  7. GRB 260506A: Fermi GBM Final Real-time Localization
  8. GRB 260503A: GECAM-B observation of a burst
  9. IceCube Alert 260505A: Global MASTER-Net observations report
  10. GRB 260430B: Glowbug gamma-ray detection
  11. GRB 260504B: SVOM/VT optical upper limits
  12. GRB 260421B: radio observation with the VLA
  13. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  14. Konus-Wind detection of GRB 260504B (short/hard)
  15. GRB 260504B: GECAM-B detection
  16. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  17. GRB 260504C: SVOM/GRM observation of short GRB
  18. GRB 260504B: SVOM/GRM spectral analysis
  19. GRB 260430B: AstroSat CZTI detection of a long burst
  20. GRB 260504B: SVOM/MXT refined analysis and potential detection
  21. GRB 260504B: EP-FXT upper limit
  22. GRB 260502A: SVOM/GRM observation of a short GRB
  23. GRB 260503A: SVOM/GRM observation of a GRB
  24. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  25. Konus-Wind detection of GRB 260415C
  26. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  27. Konus-Wind detection of GRB 260411C
  28. GRB 260504B: REM optical/NIR observations
  29. IPN triangulation of GRB 260429A
  30. IPN triangulation of GRB 260428A
  31. GRB 260504B: AST3-2 i-band upper limit
  32. GRB 260504B: LCO z-band upper limit
  33. SVOM GRB 260504B: MASTER-OAFA optical observations
  34. GRB 260504B: SVOM detection of a short burst
  35. Fermi GRB 260504A: Global MASTER-Net observations report
  36. GRB 260504A: Fermi GBM Final Real-time Localization
  37. GRB 260503A: Fermi GBM Final Real-time Localization
  38. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  39. GRB 260502A: GECAM-B observation of a short burst
  40. IPN triangulation of a bright burst from SGR 1E1841-045
  41. GRB 260502A: Fermi GBM Final Localization
  42. The EP-WXT trigger 01709261576 is likely a flaring star
  43. GRB 260429B / EP260429a: EP-FXT follow-up observation
  44. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  45. GRB 260429B / EP260429a: AstroSat CZTI detection
  46. EP260502a: BOOTES-7: early optical upper limit
  47. EP260502a: Las Cumbres upper limit
  48. EP260502a: Einstein Probe detection of an X-ray transient
  49. GRB 260429A: SVOM/GRM observation of a short burst
  50. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  51. EP260429a: Global MASTER-Net observations report
  52. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  53. GRB 260424B: AstroSat CZTI detection
  54. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  55. EP260429a: LCO optical upper limits
  56. EP260430a: LCO optical upper limits
  57. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  58. GRB 260429A: Fermi GBM Detection
  59. Fermi GRB 260429A: Global MASTER-Net observations report
  60. EP260430a: Global MASTER-Net observations report
  61. EP260430a: Einstein Probe detection of an X-ray transient
  62. EP260429a: EP-WXT detection of a fast X-ray transient
  63. GRB 260429A: Fermi GBM Final Real-time Localization
  64. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  65. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  66. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 260428A: AstroSat CZTI detection
  68. Fermi GRB 260428A: Global MASTER-Net observations report
  69. EP260416a: Mondy and Terskol optical upper limits
  70. GRB 260424B: Glowbug gamma-ray detection of a short burst
  71. GRB 260424B: COLIBRÍ optical upper limit
  72. Konus-Wind detection of GRB 260424B
  73. GRB 260428A: Fermi GBM Final Real-time Localization
  74. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  75. GRB 260424C: Fermi GBM Final Localization
  76. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  77. IPN triangulation of GRB 260424B (short)
  78. GRB 260424B: SVOM/GRM detection of a short burst
  79. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  80. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  81. IceCube Alert 260425A: Global MASTER-Net observations report
  82. Fermi trigger No 798737427: Global MASTER-Net observations report
  83. GRB 260401A: cubesat Avion detection
  84. GRB 260424A: AstroSat CZTI detection of a long burst
  85. EP260321a: Upper limits from ATCA radio observations
  86. GRB 260421B: Kilonova-Catcher optical afterglow detection
  87. GRB 260421B: Insight-HXMT/HE detection
  88. The EP-WXT trigger 01709258652: Mondy optical observations
  89. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  90. EP260416a: Mondy optical observations
  91. GRB 260421B: SVOM/ECLAIRs refined analysis
  92. GRB 260421B: 3.6m DOT optical observation
  93. EP260416a: ZTSh R band observations
  94. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  95. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  96. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  97. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  98. GRB 260419A: AstroSat CZTI detection
  99. GRB 260421B: SVOM/GRM observation
  100. GRB260421B: J band upper limit by SYSU 80cm infrared telescope

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