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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"

2380 results found.

  1. GRB260511B: MAO/AZT-22 optical observations
  2. GRB 260511A: SVOM/VT optical observations
  3. GRB 260511B: LCO optical observations
  4. GRB 260511B: GOTO optical counterpart detection
  5. GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation
  6. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  7. GRB 260511B: SVOM/VT optical observations
  8. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  9. GRB 260510B: EP-FXT follow-up observation
  10. GRB 260510C: Fermi GBM Observation
  11. GRB 260511A: REM near-infrared detection
  12. GRB 260511B: AstroSat CZTI detection
  13. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  14. GRB 260511B: NuSTAR detection of prompt emission
  15. GRB 260511A: NuSTAR detection of prompt emission
  16. GRB 260511B: Fermi GBM Detection
  17. GRB 260511B: SVOM/VT optical observation with VHF data
  18. GRB 260511B: TRT optical observation
  19. GRB 260510B: SVOM/ECLAIRs refined analysis
  20. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  21. GRB 260511A: Fermi GBM Detection
  22. GRB 260511B SVOM/C-GFT optical counterpart detection
  23. GRB 260511A: UTGO H50 optical afterglow observation
  24. GRB 260510C: AstroSat CZTI detection
  25. GRB 260511B: SVOM detection of a burst
  26. GRB 260510C: EP-FXT follow-up observation
  27. GRB 260510C: SVOM/VT optical counterpart confirmation
  28. GRB 260511A: SVOM/VT optical observation with VHF data
  29. GRB 260511A: KAIT optical afterglow observations
  30. GRB 260511A: LCO optical afterglow detection
  31. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  32. GRB 260511A: TRT optical counterpart detection
  33. GRB 260511A: SVOM detection of a bright burst
  34. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  35. GRB 260510B: SVOM/VT optical upper limits
  36. GRB 260510C: SVOM/VT optical upper limits
  37. GRB 260510C: MAXI/GSC detection
  38. Fermi GBM Sub-Threshold Detection of GRB 260510B
  39. GRB 260510B: GOTO early upper limit
  40. GRB 260510C: SVOM detection of a burst
  41. GRB 260510B: LCO optical upper limits
  42. GRB 260510B: SVOM detection of a burst
  43. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  44. GRB 260509A: LCO optical observations
  45. SVOM GRB 260509A: MASTER-OAFA optical observation
  46. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  47. GRB 260509A: SVOM/VT optical candidate with VHF data
  48. GRB 260509A: LCO optical counterpart detection
  49. GRB 260509A: GOTO optical counterpart candidate
  50. GRB 260509A: SVOM detection of a burst
  51. EP260507a: SVOM/VT optical observations
  52. GRB 260504B: AstroSat CZTI detection
  53. GRB 260504B: SVOM/ECLAIRs refined analysis
  54. GRB 260430B: Glowbug gamma-ray detection
  55. GRB 260504B: SVOM/VT optical upper limits
  56. GRB 260421B: radio observation with the VLA
  57. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  58. Konus-Wind detection of GRB 260504B (short/hard)
  59. GRB 260504B: GECAM-B detection
  60. GRB 260504C: SVOM/GRM observation of short GRB
  61. GRB 260504B: SVOM/GRM spectral analysis
  62. GRB 260504B: SVOM/MXT refined analysis and potential detection
  63. GRB 260502A: SVOM/GRM observation of a short GRB
  64. GRB 260503A: SVOM/GRM observation of a GRB
  65. GRB 260504B: REM optical/NIR observations
  66. IPN triangulation of GRB 260429A
  67. IPN triangulation of GRB 260428A
  68. GRB 260504B: AST3-2 i-band upper limit
  69. GRB 260504B: LCO z-band upper limit
  70. SVOM GRB 260504B: MASTER-OAFA optical observations
  71. GRB 260504B: SVOM detection of a short burst
  72. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  73. IPN triangulation of a bright burst from SGR 1E1841-045
  74. GRB 260429A: SVOM/GRM observation of a short burst
  75. GRB 260424B: AstroSat CZTI detection
  76. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  77. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  78. GRB 260424B: Glowbug gamma-ray detection of a short burst
  79. GRB 260424B: COLIBRÍ optical upper limit
  80. Konus-Wind detection of GRB 260424B
  81. IPN triangulation of GRB 260424B (short)
  82. GRB 260424B: SVOM/GRM detection of a short burst
  83. GRB 260401A: cubesat Avion detection
  84. GRB 260421B: Kilonova-Catcher optical afterglow detection
  85. GRB 260421B: Insight-HXMT/HE detection
  86. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  87. GRB 260421B: SVOM/ECLAIRs refined analysis
  88. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  89. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  90. GRB 260421B: SVOM/GRM observation
  91. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  92. GRB 260421B: EP-FXT follow-up observation
  93. GRB 260421B: LCO optical counterpart detection
  94. GRB 260421B: Fermi GBM Observation
  95. GRB 260412A: SVOM/ECLAIRs refined analysis
  96. GRB 260421B: SVOM/VT optical observations
  97. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  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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