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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"

38581 results found.

  1. GRB 260504B: SVOM/VT optical upper limits
  2. GRB 260421B: radio observation with the VLA
  3. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  4. Konus-Wind detection of GRB 260504B (short/hard)
  5. GRB 260504B: GECAM-B detection
  6. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  7. GRB 260504C: SVOM/GRM observation of short GRB
  8. GRB 260504B: SVOM/GRM spectral analysis
  9. GRB 260430B: AstroSat CZTI detection of a long burst
  10. GRB 260504B: SVOM/MXT refined analysis and potential detection
  11. GRB 260504B: EP-FXT upper limit
  12. GRB 260502A: SVOM/GRM observation of a short GRB
  13. GRB 260503A: SVOM/GRM observation of a GRB
  14. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  15. Konus-Wind detection of GRB 260415C
  16. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  17. Konus-Wind detection of GRB 260411C
  18. GRB 260504B: REM optical/NIR observations
  19. IPN triangulation of GRB 260429A
  20. IPN triangulation of GRB 260428A
  21. GRB 260504B: AST3-2 i-band upper limit
  22. GRB 260504B: LCO z-band upper limit
  23. SVOM GRB 260504B: MASTER-OAFA optical observations
  24. GRB 260504B: SVOM detection of a short burst
  25. GRB 260504A: Fermi GBM Final Real-time Localization
  26. GRB 260503A: Fermi GBM Final Real-time Localization
  27. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  28. GRB 260502A: GECAM-B observation of a short burst
  29. IPN triangulation of a bright burst from SGR 1E1841-045
  30. GRB 260502A: Fermi GBM Final Localization
  31. The EP-WXT trigger 01709261576 is likely a flaring star
  32. GRB 260429B / EP260429a: EP-FXT follow-up observation
  33. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  34. GRB 260429B / EP260429a: AstroSat CZTI detection
  35. EP260502a: BOOTES-7: early optical upper limit
  36. EP260502a: Einstein Probe detection of an X-ray transient
  37. GRB 260429A: SVOM/GRM observation of a short burst
  38. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  39. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  40. GRB 260424B: AstroSat CZTI detection
  41. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  42. EP260429a: LCO optical upper limits
  43. EP260430a: LCO optical upper limits
  44. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  45. GRB 260429A: Fermi GBM Detection
  46. EP260430a: Einstein Probe detection of an X-ray transient
  47. EP260429a: EP-WXT detection of a fast X-ray transient
  48. GRB 260429A: Fermi GBM Final Real-time Localization
  49. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  50. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  51. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 260428A: AstroSat CZTI detection
  53. EP260416a: Mondy and Terskol optical upper limits
  54. GRB 260424B: Glowbug gamma-ray detection of a short burst
  55. GRB 260424B: COLIBRÍ optical upper limit
  56. Konus-Wind detection of GRB 260424B
  57. GRB 260428A: Fermi GBM Final Real-time Localization
  58. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  59. GRB 260424C: Fermi GBM Final Localization
  60. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  61. IPN triangulation of GRB 260424B (short)
  62. GRB 260424B: SVOM/GRM detection of a short burst
  63. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 260401A: cubesat Avion detection
  65. GRB 260424A: AstroSat CZTI detection of a long burst
  66. EP260321a: Upper limits from ATCA radio observations
  67. GRB 260421B: Kilonova-Catcher optical afterglow detection
  68. GRB 260421B: Insight-HXMT/HE detection
  69. The EP-WXT trigger 01709258652: Mondy optical observations
  70. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  71. EP260416a: Mondy optical observations
  72. GRB 260421B: SVOM/ECLAIRs refined analysis
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP260416a: ZTSh R band observations
  75. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  76. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  77. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  78. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  79. GRB 260419A: AstroSat CZTI detection
  80. GRB 260421B: SVOM/GRM observation
  81. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  82. GRB 260421B: EP-FXT follow-up observation
  83. The EP-WXT trigger 01709260362 is likely a flaring star
  84. GOTO26djh/AT2026jpw: ATCA radio detection
  85. GRB 260421B: LCO optical counterpart detection
  86. GRB 260421B: Fermi GBM Observation
  87. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  88. GRB 260421A: AstroSat CZTI detection
  89. GRB 260412A: SVOM/ECLAIRs refined analysis
  90. GRB 260421B: SVOM/VT optical observations
  91. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  92. GRB 260310A: Late-time Chandra X-ray Detection
  93. GRB 260418A: Insight-HXMT/HE detection
  94. EP260416a: 1.3m DFOT optical observation
  95. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  96. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  97. GRB 260421C: Fermi GBM Final Real-time Localization
  98. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  99. GRB 260421B: BOOTES-7 early optical afterglow detection
  100. GRB 260421B: LCO optical afterglow confirmation

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