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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"
  1. GRB260511B: MAO/AZT-22 optical observations
  2. GRB 260511A: SVOM/VT optical observations
  3. GRB 260511B: LCO optical observations
  4. GRB 260511B: OHP/T193 spectroscopic observations
  5. GRB 260511B: GOTO optical counterpart detection
  6. GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation
  7. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  8. GRB 260510A: AstroSat CZTI detection (Erroneous Submission)
  9. GRB 260511B: SVOM/VT optical observations
  10. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  11. GRB 260510B: EP-FXT follow-up observation
  12. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  13. GRB 260510C: Fermi GBM Observation
  14. GRB 260509A: SAO RAS optical observations
  15. GRB 260511A: REM near-infrared detection
  16. GRB 260511B: GROWTH-India Telescope optical observations
  17. GRB 260511B: AstroSat CZTI detection
  18. GRB 260506B: Glowbug gamma-ray detection
  19. GRB 260506A: Glowbug gamma-ray detection of a short burst
  20. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  21. GRB 260511B: NuSTAR detection of prompt emission
  22. GRB 260511A: NuSTAR detection of prompt emission
  23. GRB 260511B: Fermi GBM Detection
  24. GRB 260511C: Fermi GBM Final Real-time Localization
  25. GRB 260511B: SVOM/VT optical observation with VHF data
  26. GRB 260511B: TRT optical observation
  27. GRB 260510B: SVOM/ECLAIRs refined analysis
  28. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  29. GRB 260511A: Fermi GBM Detection
  30. GRB 260511B SVOM/C-GFT optical counterpart detection
  31. EP260509a: LCO optical upper limits
  32. GRB 260511A: UTGO H50 optical afterglow observation
  33. GRB 260510C: AstroSat CZTI detection
  34. GRB 260511B: SVOM detection of a burst
  35. GRB 260511B: Fermi GBM Final Real-time Localization
  36. GRB 260510C: EP-FXT follow-up observation
  37. GRB 260510C: SVOM/VT optical counterpart confirmation
  38. EP260509a: EP-FXT non-detection and upper limit
  39. GRB 260511A: SVOM/VT optical observation with VHF data
  40. Fermi GRB 260511A: Global MASTER-Net observations report
  41. GRB 260511A: KAIT optical afterglow observations
  42. GRB 260511A: LCO optical afterglow detection
  43. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  44. GRB 260511A: TRT optical counterpart detection
  45. GRB 260511A: SVOM detection of a bright burst
  46. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  47. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  48. GRB 260511A: Fermi GBM Final Real-time Localization
  49. GRB 260510B: SVOM/VT optical upper limits
  50. GRB 260510C: SVOM/VT optical upper limits
  51. GRB 260510C: MAXI/GSC detection
  52. EP260509a: Global MASTER-Net observations report
  53. Fermi GBM Sub-Threshold Detection of GRB 260510B
  54. GRB 260510D: Fermi GBM Final Real-time Localization
  55. GRB 260510B: GOTO early upper limit
  56. GRB 260510C: SVOM detection of a burst
  57. GRB 260510C: Fermi GBM Final Real-time Localization
  58. GRB 260510A: GECAM-B observation
  59. GRB 260510B: LCO optical upper limits
  60. EP260509a: Einstein Probe detection of an X-ray transient
  61. GRB 260509A: Liverpool Telescope optical observations
  62. GRB 260510B: SVOM detection of a burst
  63. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  64. GRB 260509A: LCO optical observations
  65. SVOM GRB 260509A: MASTER-OAFA optical observation
  66. Fermi GRB 260510A: Global MASTER-Net observations report
  67. GRB 260509A: KAIT optical observations
  68. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  69. GRB 260510A: Fermi GBM Final Real-time Localization
  70. GRB 260509A: SVOM/VT optical candidate with VHF data
  71. GRB 260509A: LCO optical counterpart detection
  72. GRB 260509A: GOTO optical counterpart candidate
  73. GRB 260509A: SVOM detection of a burst
  74. GRB 260506B: AstroSat CZTI detection
  75. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  76. EP260507a: REM optical/NIR observations
  77. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  79. EP260507a: COLIBRÍ optical observations
  80. EP260507a: SVOM/VT optical observations
  81. EP260507a: NOT optical observations
  82. EP260507a: further Liverpool Telescope observations
  83. EP260507a: Liverpool Telescope optical upper limits
  84. GRB 260507A: Fermi GBM Final Real-time Localization
  85. EP260507a: GOTO optical counterpart detection
  86. EP260507a: TRT optical counterpart detection
  87. EP260507a: Kinder optical counterpart candidate
  88. EP260507a: LCO optical counterpart
  89. EP260507a: Einstein Probe detection of an X-ray transient
  90. GRB 260504B: AstroSat CZTI detection
  91. GRB 260504B: SVOM/ECLAIRs refined analysis
  92. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  93. GRB 260506B: Fermi GBM Final Real-time Localization
  94. EP260502a is likely a flaring star
  95. Fermi GRB 260506A: Global MASTER-Net observations report
  96. GRB 260506A: Fermi GBM Final Real-time Localization
  97. GRB 260503A: GECAM-B observation of a burst
  98. IceCube Alert 260505A: Global MASTER-Net observations report
  99. GRB 260430B: Glowbug gamma-ray detection
  100. GRB 260504B: SVOM/VT optical upper limits

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