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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45723 results found.

  1. Konus-Wind detection of GRB 260415C
  2. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  3. Konus-Wind detection of GRB 260411C
  4. GRB 260504B: REM optical/NIR observations
  5. IPN triangulation of GRB 260429A
  6. IPN triangulation of GRB 260428A
  7. GRB 260504B: AST3-2 i-band upper limit
  8. GRB 260504B: LCO z-band upper limit
  9. SVOM GRB 260504B: MASTER-OAFA optical observations
  10. GRB 260504B: SVOM detection of a short burst
  11. Fermi GRB 260504A: Global MASTER-Net observations report
  12. GRB 260504A: Fermi GBM Final Real-time Localization
  13. GRB 260503A: Fermi GBM Final Real-time Localization
  14. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  15. GRB 260502A: GECAM-B observation of a short burst
  16. IPN triangulation of a bright burst from SGR 1E1841-045
  17. GRB 260502A: Fermi GBM Final Localization
  18. The EP-WXT trigger 01709261576 is likely a flaring star
  19. GRB 260429B / EP260429a: EP-FXT follow-up observation
  20. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  21. GRB 260429B / EP260429a: AstroSat CZTI detection
  22. EP260502a: BOOTES-7: early optical upper limit
  23. EP260502a: Las Cumbres upper limit
  24. EP260502a: Einstein Probe detection of an X-ray transient
  25. GRB 260429A: SVOM/GRM observation of a short burst
  26. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  27. EP260429a: Global MASTER-Net observations report
  28. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  29. GRB 260424B: AstroSat CZTI detection
  30. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  31. EP260429a: LCO optical upper limits
  32. EP260430a: LCO optical upper limits
  33. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  34. GRB 260429A: Fermi GBM Detection
  35. Fermi GRB 260429A: Global MASTER-Net observations report
  36. EP260430a: Global MASTER-Net observations report
  37. EP260430a: Einstein Probe detection of an X-ray transient
  38. EP260429a: EP-WXT detection of a fast X-ray transient
  39. GRB 260429A: Fermi GBM Final Real-time Localization
  40. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  41. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  42. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 260428A: AstroSat CZTI detection
  44. Fermi GRB 260428A: Global MASTER-Net observations report
  45. EP260416a: Mondy and Terskol optical upper limits
  46. GRB 260424B: Glowbug gamma-ray detection of a short burst
  47. GRB 260424B: COLIBRÍ optical upper limit
  48. Konus-Wind detection of GRB 260424B
  49. GRB 260428A: Fermi GBM Final Real-time Localization
  50. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  51. GRB 260424C: Fermi GBM Final Localization
  52. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  53. IPN triangulation of GRB 260424B (short)
  54. GRB 260424B: SVOM/GRM detection of a short burst
  55. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  57. IceCube Alert 260425A: Global MASTER-Net observations report
  58. Fermi trigger No 798737427: Global MASTER-Net observations report
  59. GRB 260401A: cubesat Avion detection
  60. GRB 260424A: AstroSat CZTI detection of a long burst
  61. EP260321a: Upper limits from ATCA radio observations
  62. GRB 260421B: Kilonova-Catcher optical afterglow detection
  63. GRB 260421B: Insight-HXMT/HE detection
  64. The EP-WXT trigger 01709258652: Mondy optical observations
  65. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  66. EP260416a: Mondy optical observations
  67. GRB 260421B: SVOM/ECLAIRs refined analysis
  68. GRB 260421B: 3.6m DOT optical observation
  69. EP260416a: ZTSh R band observations
  70. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  71. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  72. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  73. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  74. GRB 260419A: AstroSat CZTI detection
  75. GRB 260421B: SVOM/GRM observation
  76. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  77. GRB 260421B: EP-FXT follow-up observation
  78. The EP-WXT trigger 01709260362 is likely a flaring star
  79. GOTO26djh/AT2026jpw: ATCA radio detection
  80. GRB 260421B: J-band upper limit with WINTER
  81. GRB 260421B: LCO optical counterpart detection
  82. GRB 260421B: Fermi GBM Observation
  83. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  84. GRB 260421A: AstroSat CZTI detection
  85. GOTO26djh/AT2026jpw: radio detection at 15GHz
  86. GRB 260412A: SVOM/ECLAIRs refined analysis
  87. GRB 260421B: SVOM/VT optical observations
  88. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  89. GRB 260310A: Late-time Chandra X-ray Detection
  90. GRB 260418A: Insight-HXMT/HE detection
  91. EP260416a: 1.3m DFOT optical observation
  92. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  93. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  94. Fermi GRB 260421C: Global MASTER-Net observations report
  95. GRB 260421C: Fermi GBM Final Real-time Localization
  96. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  97. Fermi GRB 260421B: Global MASTER-Net observations report
  98. GRB 260421B: BOOTES-7 early optical afterglow detection
  99. GRB 260421B: LCO optical afterglow confirmation
  100. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart

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