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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"

31636 results found.

  1. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  3. EP260507a: COLIBRÍ optical observations
  4. EP260507a: SVOM/VT optical observations
  5. EP260507a: NOT optical observations
  6. EP260507a: further Liverpool Telescope observations
  7. EP260507a: Liverpool Telescope optical upper limits
  8. EP260507a: GOTO optical counterpart detection
  9. EP260507a: TRT optical counterpart detection
  10. EP260507a: Kinder optical counterpart candidate
  11. EP260507a: LCO optical counterpart
  12. GRB 260504B: AstroSat CZTI detection
  13. GRB 260504B: SVOM/ECLAIRs refined analysis
  14. EP260502a is likely a flaring star
  15. Fermi GRB 260506A: Global MASTER-Net observations report
  16. GRB 260503A: GECAM-B observation of a burst
  17. GRB 260430B: Glowbug gamma-ray detection
  18. GRB 260504B: SVOM/VT optical upper limits
  19. GRB 260421B: radio observation with the VLA
  20. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  21. Konus-Wind detection of GRB 260504B (short/hard)
  22. GRB 260504B: GECAM-B detection
  23. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  24. GRB 260504B: SVOM/GRM spectral analysis
  25. GRB 260504B: SVOM/MXT refined analysis and potential detection
  26. GRB 260504B: EP-FXT upper limit
  27. GRB 260502A: SVOM/GRM observation of a short GRB
  28. GRB 260503A: SVOM/GRM observation of a GRB
  29. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  31. GRB 260504B: REM optical/NIR observations
  32. IPN triangulation of GRB 260429A
  33. IPN triangulation of GRB 260428A
  34. GRB 260504B: AST3-2 i-band upper limit
  35. GRB 260504B: LCO z-band upper limit
  36. SVOM GRB 260504B: MASTER-OAFA optical observations
  37. Fermi GRB 260504A: Global MASTER-Net observations report
  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 260429B / EP260429a: EP-FXT follow-up observation
  42. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  43. GRB 260429B / EP260429a: AstroSat CZTI detection
  44. EP260502a: BOOTES-7: early optical upper limit
  45. EP260502a: Las Cumbres upper limit
  46. GRB 260429A: SVOM/GRM observation of a short burst
  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. Fermi GRB 260429A: Global MASTER-Net observations report
  55. EP260430a: Global MASTER-Net observations report
  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. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  66. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  67. IPN triangulation of GRB 260424B (short)
  68. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  70. GRB 260401A: cubesat Avion detection
  71. EP260321a: Upper limits from ATCA radio observations
  72. GRB 260421B: Kilonova-Catcher optical afterglow detection
  73. GRB 260421B: Insight-HXMT/HE detection
  74. The EP-WXT trigger 01709258652: Mondy optical observations
  75. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  76. EP260416a: Mondy optical observations
  77. GRB 260421B: SVOM/ECLAIRs refined analysis
  78. GRB 260421B: 3.6m DOT optical observation
  79. EP260416a: ZTSh R band observations
  80. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  81. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  82. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  83. GRB 260419A: AstroSat CZTI detection
  84. GRB 260421B: SVOM/GRM observation
  85. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  86. GRB 260421B: EP-FXT follow-up observation
  87. GOTO26djh/AT2026jpw: ATCA radio detection
  88. GRB 260421B: J-band upper limit with WINTER
  89. GRB 260421B: LCO optical counterpart detection
  90. GRB 260421B: Fermi GBM Observation
  91. GRB 260421A: AstroSat CZTI detection
  92. GOTO26djh/AT2026jpw: radio detection at 15GHz
  93. GRB 260412A: SVOM/ECLAIRs refined analysis
  94. GRB 260421B: SVOM/VT optical observations
  95. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  96. GRB 260310A: Late-time Chandra X-ray Detection
  97. GRB 260418A: Insight-HXMT/HE detection
  98. EP260416a: 1.3m DFOT optical observation
  99. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  100. GRB 260415B: CALET Gamma-Ray Burst Monitor detection

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