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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"
  1. IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
  2. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  3. GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
  4. GRB 261013A: Fermi GBM Final Real-time Localization
  5. GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  6. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  7. GRID detection of GRB 261010A
  8. GRB 261011A: GECAM-B observation
  9. GRB 261011B: GECAM-B observation
  10. GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
  11. IceCube-260919A: No transient candidates from the Zwicky Transient Facility
  12. GRB 261010A: Swift-XRT refined Analysis
  13. GRB 261011A: Swift-XRT refined Analysis
  14. GRB 261011A: Enhanced Swift-XRT position
  15. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  16. GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
  17. GRB 261011A: Swift-BAT refined analysis
  18. IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
  20. MAXI GRB261012.23: Global MASTER-Net observations report
  21. GRB 261011A: REM optical/NIR observations
  22. Konus-Wind detection of GRB 261010A
  23. Konus-Wind detection of GRB 261011A
  24. Konus-Wind detection of GRB 261007A/EP261007a
  25. GRB 261011A: SOAR optical afterglow observations at ~17 hours
  26. EP261006a: 10 GHz VLA observations
  27. GRB 261011A: VLT/X-shooter redshift constraints
  28. GRB 261012A: MAXI GSC detection
  29. GRB 261010A: Swift-BAT refined analysis
  30. GRB 261011A : MITSuME Akeno optical afterglow candidate detection
  31. GRB 261011A: Optical followup from Sichuan South Observatory
  32. GRB 261011A: GMG Optical Observation
  33. GRB 261011A: Liverpool Telescope optical observations
  34. GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
  35. GRB 261010A: NOT confirmation of the optical afterglow
  36. GRB 261010A: Fermi GBM Observation
  37. GRB 261011B: Fermi GBM Final Localization
  38. GRB 261011A: continued LCO optical observations
  39. EP261007b: Global MASTER-Net observations report
  40. GRB 261011A: GROWTH-India Telescope optical observations
  41. GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
  42. Swift GRB 261011A: Global MASTER-Net observations report
  43. GRB 261011A: Optical follow-up observations with Kinder
  44. GRB 261011A: SVOM/C-GFT optical observations
  45. EP261007b: Second EP-FXT follow-up observation and a possible X-ray counterpart to the optical transient
  46. GRB 261011A: LCO optical observations
  47. GRB 261011A: SVOM/VT optical observation from VHF data
  48. GRB 261011A: LCO optical observations
  49. GRB 261011A: TRT optical afterglow detection
  50. GRB 261011A: GOTO optical counterpart detection
  51. GRB 261011A: Swift detection of an unusual burst
  52. GRB 261011A: SVOM detection of a long bright burst
  53. GRB 261010A: Enhanced Swift-XRT position
  54. EP261010a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  55. EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
  56. GRB 261010A: possible optical afterglow detected with the 1.5m OSN
  57. GRB 261010A: NOT possible optical counterpart
  58. GRB 261010A: Swift detection of a burst
  59. GRB 261010A: Fermi GBM Final Real-time Localization
  60. EP261006a: Kilonova-Catcher optical follow-up and detection
  61. GRB 261001A: SVOM/GRM observation
  62. EP261006a / AT 2026aetp: Multiband optical follow-up with the PKU 60cm Telescope
  63. EP261010a: SVOM/VT optical upper limits
  64. EP261006a: Liverpool Telescope optical follow-up
  65. EP261010a: NOT optical upper limits
  66. EP261010a: Global MASTER-Net observations report
  67. EP261010a Einstein Probe detection of an X-ray transient
  68. GRB 261009A: Fermi GBM Final Real-time Localization
  69. GRB261007A: Lesedi optical afterglow detection
  70. EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
  71. EP261007b: SVOM/ECLAIRs Upper Limit
  72. GRB 261008A: GECAM-B observation
  73. EP261006a: Optical follow-up observations with MATCH
  74. EP261007b: J-band upper limit by SYSU 80cm infrared telescope
  75. EP261007b: Refined analysis of the EP-WXT and autonomous EP-FXT observations
  76. GRB 261007A: SVOM/ECLAIRs refined analysis
  77. EP261007b: SVOM/VT optical detection of the NOT transient
  78. GRB 261007A / EP261007a: SVOM/GWAC-F60A/B observations
  79. EP261006a / AT 2026aetp: VLT/X-shooter spectroscopic redshift z = 0.1853
  80. GRB 261007A: Glowbug gamma-ray detection
  81. GRB 261008A: Fermi GBM Final Real-time Localization
  82. GRB 261007A: NOT optical observations
  83. EP261007b: NOT optical observations, variable source outside the FXT region
  84. GRB 261007A: SVOM/GRM observation
  85. EP261007b: SVOM/C-GFT optical upper limits
  86. EP261007b: J-band upper limit with WINTER
  87. The EP-WXT trigger 01709321008/EP261007b：Xinglong optical upper limit
  88. GRB 261007A / EP261007a: AstroSat CZTI detection
  89. GRB 261005A: GECAM-B observation
  90. EP261006a: Swift/XRT detection of the fading X-ray counterpart
  91. EP261007a/GRB 261007A：Xinglong optical observation
  92. GRB 261007A/EP261007a: Optical follow-up observations with Kinder
  93. EP261006a: Optical follow-up observations with Kinder
  94. EP261006a: Liverpool Telescope optical observations
  95. EP261006a: Early Optical Observations by WFST
  96. GRB 261007A / EP261007a: SVOM/VT optical observations
  97. GRB 261007A: Swift-XRT afterglow detection
  98. EP261007b: SVOM/VT optical upper limits
  99. GRB 261007A: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. EP261007b: Einstein Probe detection of an X-ray transient

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