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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. EP260507a: LCO optical counterpart
  2. EP260507a: Einstein Probe detection of an X-ray transient
  3. GRB 260504B: AstroSat CZTI detection
  4. GRB 260504B: SVOM/ECLAIRs refined analysis
  5. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  6. GRB 260506B: Fermi GBM Final Real-time Localization
  7. EP260502a is likely a flaring star
  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. IceCube Alert 260505A: Global MASTER-Net observations report
  12. GRB 260430B: Glowbug gamma-ray detection
  13. GRB 260504B: SVOM/VT optical upper limits
  14. GRB 260421B: radio observation with the VLA
  15. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  16. Konus-Wind detection of GRB 260504B (short/hard)
  17. GRB 260504B: GECAM-B detection
  18. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  19. GRB 260504C: SVOM/GRM observation of short GRB
  20. GRB 260504B: SVOM/GRM spectral analysis
  21. GRB 260430B: AstroSat CZTI detection of a long burst
  22. GRB 260504B: SVOM/MXT refined analysis and potential detection
  23. GRB 260504B: EP-FXT upper limit
  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. Konus-Wind detection of GRB 260415C
  28. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  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. GRB 260502A: GECAM-B observation of a short burst
  42. IPN triangulation of a bright burst from SGR 1E1841-045
  43. GRB 260502A: Fermi GBM Final Localization
  44. The EP-WXT trigger 01709261576 is likely a flaring star
  45. GRB 260429B / EP260429a: EP-FXT follow-up observation
  46. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  47. GRB 260429B / EP260429a: AstroSat CZTI detection
  48. EP260502a: BOOTES-7: early optical upper limit
  49. EP260502a: Las Cumbres upper limit
  50. EP260502a: Einstein Probe detection of an X-ray transient
  51. GRB 260429A: SVOM/GRM observation of a short burst
  52. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  53. EP260429a: Global MASTER-Net observations report
  54. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  55. GRB 260424B: AstroSat CZTI detection
  56. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  57. EP260429a: LCO optical upper limits
  58. EP260430a: LCO optical upper limits
  59. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  60. GRB 260429A: Fermi GBM Detection
  61. Fermi GRB 260429A: Global MASTER-Net observations report
  62. EP260430a: Global MASTER-Net observations report
  63. EP260430a: Einstein Probe detection of an X-ray transient
  64. EP260429a: EP-WXT detection of a fast X-ray transient
  65. GRB 260429A: Fermi GBM Final Real-time Localization
  66. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  67. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  68. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 260428A: AstroSat CZTI detection
  70. Fermi GRB 260428A: Global MASTER-Net observations report
  71. EP260416a: Mondy and Terskol optical upper limits
  72. GRB 260424B: Glowbug gamma-ray detection of a short burst
  73. GRB 260424B: COLIBRÍ optical upper limit
  74. Konus-Wind detection of GRB 260424B
  75. GRB 260428A: Fermi GBM Final Real-time Localization
  76. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  77. GRB 260424C: Fermi GBM Final Localization
  78. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  79. IPN triangulation of GRB 260424B (short)
  80. GRB 260424B: SVOM/GRM detection of a short burst
  81. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  83. IceCube Alert 260425A: Global MASTER-Net observations report
  84. Fermi trigger No 798737427: Global MASTER-Net observations report
  85. GRB 260401A: cubesat Avion detection
  86. GRB 260424A: AstroSat CZTI detection of a long burst
  87. EP260321a: Upper limits from ATCA radio observations
  88. GRB 260421B: Kilonova-Catcher optical afterglow detection
  89. GRB 260421B: Insight-HXMT/HE detection
  90. The EP-WXT trigger 01709258652: Mondy optical observations
  91. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  92. EP260416a: Mondy optical observations
  93. GRB 260421B: SVOM/ECLAIRs refined analysis
  94. GRB 260421B: 3.6m DOT optical observation
  95. EP260416a: ZTSh R band observations
  96. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  97. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  98. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  99. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  100. GRB 260419A: AstroSat CZTI detection

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