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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"

43616 results found.

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