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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. GRB 261011A: continued LCO optical observations
  2. EP261007b: Global MASTER-Net observations report
  3. GRB 261011A: GROWTH-India Telescope optical observations
  4. GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
  5. Swift GRB 261011A: Global MASTER-Net observations report
  6. GRB 261011A: Optical follow-up observations with Kinder
  7. GRB 261011A: SVOM/C-GFT optical observations
  8. EP261007b: Second EP-FXT follow-up observation and a possible X-ray counterpart to the optical transient
  9. GRB 261011A: LCO optical observations
  10. GRB 261011A: SVOM/VT optical observation from VHF data
  11. GRB 261011A: LCO optical observations
  12. GRB 261011A: TRT optical afterglow detection
  13. GRB 261011A: GOTO optical counterpart detection
  14. GRB 261011A: Swift detection of an unusual burst
  15. GRB 261011A: SVOM detection of a long bright burst
  16. GRB 261010A: Enhanced Swift-XRT position
  17. EP261010a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
  19. GRB 261010A: possible optical afterglow detected with the 1.5m OSN
  20. GRB 261010A: NOT possible optical counterpart
  21. GRB 261010A: Swift detection of a burst
  22. GRB 261010A: Fermi GBM Final Real-time Localization
  23. EP261006a: Kilonova-Catcher optical follow-up and detection
  24. GRB 261001A: SVOM/GRM observation
  25. EP261006a / AT 2026aetp: Multiband optical follow-up with the PKU 60cm Telescope
  26. EP261010a: SVOM/VT optical upper limits
  27. EP261006a: Liverpool Telescope optical follow-up
  28. EP261010a: NOT optical upper limits
  29. EP261010a: Global MASTER-Net observations report
  30. EP261010a Einstein Probe detection of an X-ray transient
  31. GRB 261009A: Fermi GBM Final Real-time Localization
  32. GRB261007A: Lesedi optical afterglow detection
  33. EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
  34. EP261007b: SVOM/ECLAIRs Upper Limit
  35. GRB 261008A: GECAM-B observation
  36. EP261006a: Optical follow-up observations with MATCH
  37. EP261007b: J-band upper limit by SYSU 80cm infrared telescope
  38. EP261007b: Refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. GRB 261007A: SVOM/ECLAIRs refined analysis
  40. EP261007b: SVOM/VT optical detection of the NOT transient
  41. GRB 261007A / EP261007a: SVOM/GWAC-F60A/B observations
  42. EP261006a / AT 2026aetp: VLT/X-shooter spectroscopic redshift z = 0.1853
  43. GRB 261007A: Glowbug gamma-ray detection
  44. GRB 261008A: Fermi GBM Final Real-time Localization
  45. GRB 261007A: NOT optical observations
  46. EP261007b: NOT optical observations, variable source outside the FXT region
  47. GRB 261007A: SVOM/GRM observation
  48. EP261007b: SVOM/C-GFT optical upper limits
  49. EP261007b: J-band upper limit with WINTER
  50. The EP-WXT trigger 01709321008/EP261007b：Xinglong optical upper limit
  51. GRB 261007A / EP261007a: AstroSat CZTI detection
  52. GRB 261005A: GECAM-B observation
  53. EP261006a: Swift/XRT detection of the fading X-ray counterpart
  54. EP261007a/GRB 261007A：Xinglong optical observation
  55. GRB 261007A/EP261007a: Optical follow-up observations with Kinder
  56. EP261006a: Optical follow-up observations with Kinder
  57. EP261006a: Liverpool Telescope optical observations
  58. EP261006a: Early Optical Observations by WFST
  59. GRB 261007A / EP261007a: SVOM/VT optical observations
  60. GRB 261007A: Swift-XRT afterglow detection
  61. EP261007b: SVOM/VT optical upper limits
  62. GRB 261007A: SVOM/COLIBRÍ (FM-GFT) optical observations
  63. EP261007b: Einstein Probe detection of an X-ray transient
  64. GRB 261007A / EP261007a: NuSTAR detection of prompt emission
  65. EP Alert 261007.63: Global MASTER-Net observations report
  66. GRB 261007A / EP261007a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at McDonald Observatory
  67. GRB 261007A: Autonomous identification and follow-up of the counterpart to GRB 261007A by BTSbot with ZTF and P60/SEDM
  68. SVOM GRB261007.27: Global MASTER-Net observations report
  69. GRB 261007A: GROWTH-India Telescope optical observations
  70. GRB 261007A / EP261007a: TRT optical observations
  71. GRB 261007A: Swift ToO observations
  72. GRB 261007A: SVOM/C-GFT optical observations
  73. GRB 261007A / EP261007a: LCO optical observations
  74. GRB 261007B: Fermi GBM Final Real-time Localization
  75. SVOM GRB261007.23: Global MASTER-Net observations report
  76. GRB 261005B: Swift-BAT refined analysis
  77. EP261006a: NOT spectroscopy of a blue continuum
  78. GRB 261007A: WINTER J-band observations
  79. EP261006a: LT and NOT discovery of an optical counterpart
  80. GRB 261007A: Fermi GBM observation
  81. GRB 261007A / EP261007a: VLT/X-shooter spectroscopic redshift z = 2.101
  82. EP261007a/GRB 261007A: Einstein Probe detection of an X-ray transient
  83. EP261006a: SVOM/VT optical upper limits
  84. EP261006a: Einstein Probe detection of an X-ray transient
  85. GRB 261007A: KAIT optical counterpart candidate
  86. GRB 261007A: SVOM detection of a burst
  87. EP trigger 01709320985: SVOM/C-GFT optical upper limits
  88. GRB 261005B: Swift-XRT refined Analysis
  89. EP trigger 01709320985: Ondrejov D50 optical upper limits
  90. GRB 261005A: Glowbug gamma-ray detection
  91. GRB 261005B: Swift/UVOT Upper Limits
  92. GRB 261005B: J-band upper limit with WINTER
  93. GRB 261001A: GECAM-B observation of a likely long GRB
  94. GRB 261005B: Fermi GBM Observation
  95. GRB 261005B: Enhanced Swift-XRT position
  96. The EP-WXT trigger 01709320908 is likely a flaring star
  97. EP trigger 01709320908: Ondrejov D50 observation, fading star suggests stellar flare
  98. GRB 261005B: Swift detection of a burst
  99. GRB 261005A: Fermi GBM Final Real-time Localization
  100. GRB 261003A: Glowbug gamma-ray detection of a likely short burst

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