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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"

31539 results found.

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

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