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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"

45461 results found.

  1. EP260502a is likely a flaring star
  2. Fermi GRB 260506A: Global MASTER-Net observations report
  3. GRB 260506A: Fermi GBM Final Real-time Localization
  4. GRB 260503A: GECAM-B observation of a burst
  5. IceCube Alert 260505A: Global MASTER-Net observations report
  6. GRB 260430B: Glowbug gamma-ray detection
  7. GRB 260504B: SVOM/VT optical upper limits
  8. GRB 260421B: radio observation with the VLA
  9. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  10. Konus-Wind detection of GRB 260504B (short/hard)
  11. GRB 260504B: GECAM-B detection
  12. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  13. GRB 260504C: SVOM/GRM observation of short GRB
  14. GRB 260504B: SVOM/GRM spectral analysis
  15. GRB 260430B: AstroSat CZTI detection of a long burst
  16. GRB 260504B: SVOM/MXT refined analysis and potential detection
  17. GRB 260504B: EP-FXT upper limit
  18. GRB 260502A: SVOM/GRM observation of a short GRB
  19. GRB 260503A: SVOM/GRM observation of a GRB
  20. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  21. Konus-Wind detection of GRB 260415C
  22. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  23. Konus-Wind detection of GRB 260411C
  24. GRB 260504B: REM optical/NIR observations
  25. IPN triangulation of GRB 260429A
  26. IPN triangulation of GRB 260428A
  27. GRB 260504B: AST3-2 i-band upper limit
  28. GRB 260504B: LCO z-band upper limit
  29. SVOM GRB 260504B: MASTER-OAFA optical observations
  30. GRB 260504B: SVOM detection of a short burst
  31. Fermi GRB 260504A: Global MASTER-Net observations report
  32. GRB 260504A: Fermi GBM Final Real-time Localization
  33. GRB 260503A: Fermi GBM Final Real-time Localization
  34. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  35. GRB 260502A: GECAM-B observation of a short burst
  36. IPN triangulation of a bright burst from SGR 1E1841-045
  37. GRB 260502A: Fermi GBM Final Localization
  38. The EP-WXT trigger 01709261576 is likely a flaring star
  39. GRB 260429B / EP260429a: EP-FXT follow-up observation
  40. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  41. GRB 260429B / EP260429a: AstroSat CZTI detection
  42. EP260502a: BOOTES-7: early optical upper limit
  43. EP260502a: Las Cumbres upper limit
  44. EP260502a: Einstein Probe detection of an X-ray transient
  45. GRB 260429A: SVOM/GRM observation of a short burst
  46. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  47. EP260429a: Global MASTER-Net observations report
  48. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  49. GRB 260424B: AstroSat CZTI detection
  50. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  51. EP260429a: LCO optical upper limits
  52. EP260430a: LCO optical upper limits
  53. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  54. GRB 260429A: Fermi GBM Detection
  55. Fermi GRB 260429A: Global MASTER-Net observations report
  56. EP260430a: Global MASTER-Net observations report
  57. EP260430a: Einstein Probe detection of an X-ray transient
  58. EP260429a: EP-WXT detection of a fast X-ray transient
  59. GRB 260429A: Fermi GBM Final Real-time Localization
  60. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  61. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  62. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 260428A: AstroSat CZTI detection
  64. Fermi GRB 260428A: Global MASTER-Net observations report
  65. EP260416a: Mondy and Terskol optical upper limits
  66. GRB 260424B: Glowbug gamma-ray detection of a short burst
  67. GRB 260424B: COLIBRÍ optical upper limit
  68. Konus-Wind detection of GRB 260424B
  69. GRB 260428A: Fermi GBM Final Real-time Localization
  70. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  71. GRB 260424C: Fermi GBM Final Localization
  72. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  73. IPN triangulation of GRB 260424B (short)
  74. GRB 260424B: SVOM/GRM detection of a short burst
  75. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  77. IceCube Alert 260425A: Global MASTER-Net observations report
  78. Fermi trigger No 798737427: Global MASTER-Net observations report
  79. GRB 260401A: cubesat Avion detection
  80. GRB 260424A: AstroSat CZTI detection of a long burst
  81. EP260321a: Upper limits from ATCA radio observations
  82. GRB 260421B: Kilonova-Catcher optical afterglow detection
  83. GRB 260421B: Insight-HXMT/HE detection
  84. The EP-WXT trigger 01709258652: Mondy optical observations
  85. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  86. EP260416a: Mondy optical observations
  87. GRB 260421B: SVOM/ECLAIRs refined analysis
  88. GRB 260421B: 3.6m DOT optical observation
  89. EP260416a: ZTSh R band observations
  90. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  91. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  92. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  93. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  94. GRB 260419A: AstroSat CZTI detection
  95. GRB 260421B: SVOM/GRM observation
  96. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  97. GRB 260421B: EP-FXT follow-up observation
  98. The EP-WXT trigger 01709260362 is likely a flaring star
  99. GOTO26djh/AT2026jpw: ATCA radio detection
  100. GRB 260421B: J-band upper limit with WINTER

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