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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. EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
  2. GRB 261011A: 1.3m DFOT optical upper limit
  3. GRB 261010A: Pan-STARRS z-band imaging and upper limit
  4. EP261015a: SVOM/VT optical observation
  5. EP241111a and EP250125a: Upper limits from SVOM/GRM Observations
  6. GRB 261010A: VLA radio observations
  7. EP261015a: COLIBRÍ optical observations
  8. EP261015c: Einstein Probe detection of a fast X-ray transient
  9. EP261015b: Einstein Probe detection of an X-ray transient
  10. GRB261010A: Keck/MOSFIRE detection of a near-IR source
  11. EP261015a: Einstein Probe detection of a fast X-ray transient
  12. EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
  13. The EP-WXT trigger 01709321333 is likely a flaring star
  14. GRB 261010A: ASKAP non-detection of a radio afterglow
  15. GRB 261010A: LBT tentative near-infrared detection
  16. GRB 261011A: SAO RAS and AbAO optical observations
  17. GRB 261010A: Glowbug gamma-ray detection
  18. GRB 261008A: SVOM/GRM observation
  19. GRB 261009A: GECAM-B detection of a burst
  20. EP261006a : MeerKAT radio observations.
  21. IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
  23. GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
  24. GRB 261013A: Fermi GBM Final Real-time Localization
  25. GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  26. Fermi-LAT Gamma-ray Observations of IceCube-261012A
  27. GRID detection of GRB 261010A
  28. GRB 261011A: GECAM-B observation
  29. GRB 261011B: GECAM-B observation
  30. GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
  31. IceCube-260919A: No transient candidates from the Zwicky Transient Facility
  32. GRB 261010A: Swift-XRT refined Analysis
  33. GRB 261011A: Swift-XRT refined Analysis
  34. GRB 261011A: Enhanced Swift-XRT position
  35. GRB 261010A: a Type I-L (merger-driven) GRB candidate
  36. GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
  37. GRB 261011A: Swift-BAT refined analysis
  38. IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
  39. GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
  40. MAXI GRB261012.23: Global MASTER-Net observations report
  41. GRB 261011A: REM optical/NIR observations
  42. Konus-Wind detection of GRB 261010A
  43. Konus-Wind detection of GRB 261011A
  44. Konus-Wind detection of GRB 261007A/EP261007a
  45. GRB 261011A: SOAR optical afterglow observations at ~17 hours
  46. EP261006a: 10 GHz VLA observations
  47. GRB 261011A: VLT/X-shooter redshift constraints
  48. GRB 261012A: MAXI GSC detection
  49. GRB 261010A: Swift-BAT refined analysis
  50. GRB 261011A : MITSuME Akeno optical afterglow candidate detection
  51. GRB 261011A: Optical followup from Sichuan South Observatory
  52. GRB 261011A: GMG Optical Observation
  53. GRB 261011A: Liverpool Telescope optical observations
  54. GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
  55. GRB 261010A: NOT confirmation of the optical afterglow
  56. GRB 261010A: Fermi GBM Observation
  57. GRB 261011B: Fermi GBM Final Localization
  58. GRB 261011A: continued LCO optical observations
  59. EP261007b: Global MASTER-Net observations report
  60. GRB 261011A: GROWTH-India Telescope optical observations
  61. GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
  62. Swift GRB 261011A: Global MASTER-Net observations report
  63. GRB 261011A: Optical follow-up observations with Kinder
  64. GRB 261011A: SVOM/C-GFT optical observations
  65. EP261007b: Second EP-FXT follow-up observation and a possible X-ray counterpart to the optical transient
  66. GRB 261011A: LCO optical observations
  67. GRB 261011A: SVOM/VT optical observation from VHF data
  68. GRB 261011A: LCO optical observations
  69. GRB 261011A: TRT optical afterglow detection
  70. GRB 261011A: GOTO optical counterpart detection
  71. GRB 261011A: Swift detection of an unusual burst
  72. GRB 261011A: SVOM detection of a long bright burst
  73. GRB 261010A: Enhanced Swift-XRT position
  74. EP261010a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  75. EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
  76. GRB 261010A: possible optical afterglow detected with the 1.5m OSN
  77. GRB 261010A: NOT possible optical counterpart
  78. GRB 261010A: Swift detection of a burst
  79. GRB 261010A: Fermi GBM Final Real-time Localization
  80. EP261006a: Kilonova-Catcher optical follow-up and detection
  81. GRB 261001A: SVOM/GRM observation
  82. EP261006a / AT 2026aetp: Multiband optical follow-up with the PKU 60cm Telescope
  83. EP261010a: SVOM/VT optical upper limits
  84. EP261006a: Liverpool Telescope optical follow-up
  85. EP261010a: NOT optical upper limits
  86. EP261010a: Global MASTER-Net observations report
  87. EP261010a Einstein Probe detection of an X-ray transient
  88. GRB 261009A: Fermi GBM Final Real-time Localization
  89. GRB261007A: Lesedi optical afterglow detection
  90. EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
  91. EP261007b: SVOM/ECLAIRs Upper Limit
  92. GRB 261008A: GECAM-B observation
  93. EP261006a: Optical follow-up observations with MATCH
  94. EP261007b: J-band upper limit by SYSU 80cm infrared telescope
  95. EP261007b: Refined analysis of the EP-WXT and autonomous EP-FXT observations
  96. GRB 261007A: SVOM/ECLAIRs refined analysis
  97. EP261007b: SVOM/VT optical detection of the NOT transient
  98. GRB 261007A / EP261007a: SVOM/GWAC-F60A/B observations
  99. EP261006a / AT 2026aetp: VLT/X-shooter spectroscopic redshift z = 0.1853
  100. GRB 261007A: Glowbug gamma-ray detection

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