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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').
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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"

28089 results found.

  1. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  2. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. GRB 260510B: EP-FXT follow-up observation
  4. GRB 260510C: Fermi GBM Observation
  5. GRB 260509A: SAO RAS optical observations
  6. GRB 260511A: REM near-infrared detection
  7. GRB 260511B: GROWTH-India Telescope optical observations
  8. GRB 260506B: Glowbug gamma-ray detection
  9. GRB 260506A: Glowbug gamma-ray detection of a short burst
  10. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  11. GRB 260511B: NuSTAR detection of prompt emission
  12. GRB 260511A: NuSTAR detection of prompt emission
  13. GRB 260511B: Fermi GBM Detection
  14. GRB 260511B: SVOM/VT optical observation with VHF data
  15. GRB 260511B: TRT optical observation
  16. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  17. GRB 260511A: Fermi GBM Detection
  18. GRB 260511B SVOM/C-GFT optical counterpart detection
  19. EP260509a: LCO optical upper limits
  20. GRB 260511A: UTGO H50 optical afterglow observation
  21. GRB 260511B: SVOM detection of a burst
  22. GRB 260510C: EP-FXT follow-up observation
  23. EP260509a: EP-FXT non-detection and upper limit
  24. GRB 260511A: SVOM/VT optical observation with VHF data
  25. Fermi GRB 260511A: Global MASTER-Net observations report
  26. GRB 260511A: KAIT optical afterglow observations
  27. GRB 260511A: LCO optical afterglow detection
  28. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  29. GRB 260511A: TRT optical counterpart detection
  30. GRB 260511A: SVOM detection of a bright burst
  31. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  32. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  33. GRB 260510C: MAXI/GSC detection
  34. EP260509a: Global MASTER-Net observations report
  35. Fermi GBM Sub-Threshold Detection of GRB 260510B
  36. GRB 260510C: SVOM detection of a burst
  37. GRB 260510B: LCO optical upper limits
  38. EP260509a: Einstein Probe detection of an X-ray transient
  39. GRB 260509A: Liverpool Telescope optical observations
  40. GRB 260510B: SVOM detection of a burst
  41. GRB 260509A: LCO optical observations
  42. SVOM GRB 260509A: MASTER-OAFA optical observation
  43. Fermi GRB 260510A: Global MASTER-Net observations report
  44. GRB 260509A: KAIT optical observations
  45. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  46. GRB 260509A: SVOM/VT optical candidate with VHF data
  47. GRB 260509A: LCO optical counterpart detection
  48. GRB 260509A: SVOM detection of a burst
  49. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  50. EP260507a: REM optical/NIR observations
  51. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  52. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  53. EP260507a: COLIBRÍ optical observations
  54. EP260507a: NOT optical observations
  55. EP260507a: further Liverpool Telescope observations
  56. EP260507a: Liverpool Telescope optical upper limits
  57. EP260507a: TRT optical counterpart detection
  58. EP260507a: Kinder optical counterpart candidate
  59. EP260507a: LCO optical counterpart
  60. EP260507a: Einstein Probe detection of an X-ray transient
  61. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  62. Fermi GRB 260506A: Global MASTER-Net observations report
  63. IceCube Alert 260505A: Global MASTER-Net observations report
  64. GRB 260430B: Glowbug gamma-ray detection
  65. GRB 260421B: radio observation with the VLA
  66. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  67. GRB 260430B: AstroSat CZTI detection of a long burst
  68. GRB 260502A: SVOM/GRM observation of a short GRB
  69. GRB 260503A: SVOM/GRM observation of a GRB
  70. Konus-Wind detection of GRB 260411C
  71. GRB 260504B: REM optical/NIR observations
  72. GRB 260504B: LCO z-band upper limit
  73. SVOM GRB 260504B: MASTER-OAFA optical observations
  74. GRB 260504B: SVOM detection of a short burst
  75. Fermi GRB 260504A: Global MASTER-Net observations report
  76. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  77. GRB 260429B / EP260429a: EP-FXT follow-up observation
  78. EP260502a: Einstein Probe detection of an X-ray transient
  79. GRB 260429A: SVOM/GRM observation of a short burst
  80. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  81. EP260429a: Global MASTER-Net observations report
  82. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  83. GRB 260424B: AstroSat CZTI detection
  84. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  85. EP260429a: LCO optical upper limits
  86. EP260430a: LCO optical upper limits
  87. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  88. GRB 260429A: Fermi GBM Detection
  89. Fermi GRB 260429A: Global MASTER-Net observations report
  90. EP260430a: Global MASTER-Net observations report
  91. EP260430a: Einstein Probe detection of an X-ray transient
  92. EP260429a: EP-WXT detection of a fast X-ray transient
  93. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  94. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  95. Fermi GRB 260428A: Global MASTER-Net observations report
  96. EP260416a: Mondy and Terskol optical upper limits
  97. GRB 260424B: Glowbug gamma-ray detection of a short burst
  98. GRB 260424B: COLIBRÍ optical upper limit
  99. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  100. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position

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