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

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