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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-260919A: No transient candidates from the Zwicky Transient Facility
  2. GRB 261010A: Swift-XRT refined Analysis
  3. GRB 261011A: Swift-XRT refined Analysis
  4. GRB 261011A: Enhanced Swift-XRT position
  5. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  6. GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
  7. GRB 261011A: Swift-BAT refined analysis
  8. IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
  10. MAXI GRB261012.23: Global MASTER-Net observations report
  11. GRB 261011A: REM optical/NIR observations
  12. Konus-Wind detection of GRB 261010A
  13. Konus-Wind detection of GRB 261011A
  14. Konus-Wind detection of GRB 261007A/EP261007a
  15. GRB 261011A: SOAR optical afterglow observations at ~17 hours
  16. EP261006a: 10 GHz VLA observations
  17. GRB 261011A: VLT/X-shooter redshift constraints
  18. GRB 261012A: MAXI GSC detection
  19. GRB 261010A: Swift-BAT refined analysis
  20. GRB 261011A : MITSuME Akeno optical afterglow candidate detection
  21. GRB 261011A: Optical followup from Sichuan South Observatory
  22. GRB 261011A: GMG Optical Observation
  23. GRB 261011A: Liverpool Telescope optical observations
  24. GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
  25. GRB 261010A: NOT confirmation of the optical afterglow
  26. GRB 261010A: Fermi GBM Observation
  27. GRB 261011B: Fermi GBM Final Localization
  28. GRB 261011A: continued LCO optical observations
  29. EP261007b: Global MASTER-Net observations report
  30. GRB 261011A: GROWTH-India Telescope optical observations
  31. GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
  32. Swift GRB 261011A: Global MASTER-Net observations report
  33. GRB 261011A: Optical follow-up observations with Kinder
  34. GRB 261011A: SVOM/C-GFT optical observations
  35. EP261007b: Second EP-FXT follow-up observation and a possible X-ray counterpart to the optical transient
  36. GRB 261011A: LCO optical observations
  37. GRB 261011A: SVOM/VT optical observation from VHF data
  38. GRB 261011A: LCO optical observations
  39. GRB 261011A: TRT optical afterglow detection
  40. GRB 261011A: GOTO optical counterpart detection
  41. GRB 261011A: Swift detection of an unusual burst
  42. GRB 261011A: SVOM detection of a long bright burst
  43. GRB 261010A: Enhanced Swift-XRT position
  44. EP261010a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  45. EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
  46. GRB 261010A: possible optical afterglow detected with the 1.5m OSN
  47. GRB 261010A: NOT possible optical counterpart
  48. GRB 261010A: Swift detection of a burst
  49. GRB 261010A: Fermi GBM Final Real-time Localization
  50. EP261006a: Kilonova-Catcher optical follow-up and detection
  51. GRB 261001A: SVOM/GRM observation
  52. EP261006a / AT 2026aetp: Multiband optical follow-up with the PKU 60cm Telescope
  53. EP261010a: SVOM/VT optical upper limits
  54. EP261006a: Liverpool Telescope optical follow-up
  55. EP261010a: NOT optical upper limits
  56. EP261010a: Global MASTER-Net observations report
  57. EP261010a Einstein Probe detection of an X-ray transient
  58. GRB 261009A: Fermi GBM Final Real-time Localization
  59. GRB261007A: Lesedi optical afterglow detection
  60. EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
  61. EP261007b: SVOM/ECLAIRs Upper Limit
  62. GRB 261008A: GECAM-B observation
  63. EP261006a: Optical follow-up observations with MATCH
  64. EP261007b: J-band upper limit by SYSU 80cm infrared telescope
  65. EP261007b: Refined analysis of the EP-WXT and autonomous EP-FXT observations
  66. GRB 261007A: SVOM/ECLAIRs refined analysis
  67. EP261007b: SVOM/VT optical detection of the NOT transient
  68. GRB 261007A / EP261007a: SVOM/GWAC-F60A/B observations
  69. EP261006a / AT 2026aetp: VLT/X-shooter spectroscopic redshift z = 0.1853
  70. GRB 261007A: Glowbug gamma-ray detection
  71. GRB 261008A: Fermi GBM Final Real-time Localization
  72. GRB 261007A: NOT optical observations
  73. EP261007b: NOT optical observations, variable source outside the FXT region
  74. GRB 261007A: SVOM/GRM observation
  75. EP261007b: SVOM/C-GFT optical upper limits
  76. EP261007b: J-band upper limit with WINTER
  77. The EP-WXT trigger 01709321008/EP261007b：Xinglong optical upper limit
  78. GRB 261007A / EP261007a: AstroSat CZTI detection
  79. GRB 261005A: GECAM-B observation
  80. EP261006a: Swift/XRT detection of the fading X-ray counterpart
  81. EP261007a/GRB 261007A：Xinglong optical observation
  82. GRB 261007A/EP261007a: Optical follow-up observations with Kinder
  83. EP261006a: Optical follow-up observations with Kinder
  84. EP261006a: Liverpool Telescope optical observations
  85. EP261006a: Early Optical Observations by WFST
  86. GRB 261007A / EP261007a: SVOM/VT optical observations
  87. GRB 261007A: Swift-XRT afterglow detection
  88. EP261007b: SVOM/VT optical upper limits
  89. GRB 261007A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. EP261007b: Einstein Probe detection of an X-ray transient
  91. GRB 261007A / EP261007a: NuSTAR detection of prompt emission
  92. EP Alert 261007.63: Global MASTER-Net observations report
  93. GRB 261007A / EP261007a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at McDonald Observatory
  94. GRB 261007A: Autonomous identification and follow-up of the counterpart to GRB 261007A by BTSbot with ZTF and P60/SEDM
  95. SVOM GRB261007.27: Global MASTER-Net observations report
  96. GRB 261007A: GROWTH-India Telescope optical observations
  97. GRB 261007A / EP261007a: TRT optical observations
  98. GRB 261007A: Swift ToO observations
  99. GRB 261007A: SVOM/C-GFT optical observations
  100. GRB 261007A / EP261007a: LCO optical observations

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