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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"

26533 results found.

  1. GRB 260208A: NuSTAR detection of prompt emission
  2. GRB 260208A: Fermi GBM Observation
  3. GRB 260208B: Swift-XRT observations
  4. GRB 260131A/B: continued Mondy optical observations
  5. GRB 260204A: Swift/UVOT Upper Limits
  6. GRB 260208B: COLIBRÍ optical observations
  7. GRB 260208A: 1.3m DFOT optical detection
  8. GRB 260208A: COLIBRÍ optical observations
  9. GRB 260208B: EP-FXT observation
  10. GRB 260208A: NOT spectroscopic redshift z = 2.36
  11. GRB 260208B: SVOM/VT optical candidate
  12. GRB 260208A: GECAM-B observation of a bright burst
  13. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  14. GRB 260208A: SVOM/VT optical observation
  15. GRB 260208A: Swift-XRT observations
  16. GRB 260208B: SVOM/GRM observation of a bright burst
  17. GRB 260208B: Fermi GBM Detection
  18. GRB 260208B: Fermi-LAT detection
  19. GRB 260208A: Fermi-LAT detection
  20. GRB 260207B: GECAM-B observation
  21. GRB 260208A: Fermi GBM Classification Correction
  22. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  23. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  24. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  25. GRB 260131A/B: Mondy and Terskol optical observations
  26. GRB 260206A: Swift-XRT observations
  27. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  28. GRB 260204A: Swift-XRT observations
  29. GRB 260204A: LCO optical afterglow detection
  30. GRB 260204A: SVOM/VT optical candidate
  31. GRB 260204A : MASTER Global robotic net optical observations
  32. Fermi GBM Sub-Threshold Detection of GRB 260204A
  33. GRB 260204A: GOTO optical upper limit
  34. GRB 260204A: LCO optical upper limits
  35. EP260110a: Late GTC/EMIR near-infrared observations
  36. GRB 260204A: SVOM detection of a burst
  37. GRB 260121A: 239Alferov CubeSat detection
  38. Konus-Wind detection of GRB 260121A
  39. GRB 260131A/B: OHP/T193 optical observations
  40. GRB 251230A: MeerLICHT afterglow detection
  41. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  42. GRID detection of GRB 260131A/B
  43. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  44. GRB 260130A: Insight-HXMT/HE detection
  45. GRB 260130A: GECAM-B observation of a short burst
  46. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  47. GRB 260131A/B: EP/FXT X-ray afterglow detection
  48. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  49. GRB 260127B: Insight-HXMT/HE detection
  50. GRB 260127B: GECAM-B observation of a short burst
  51. GRB 260127A: GECAM-B observation
  52. EP260131a: Liverpool Telescope optical upper limits
  53. EP260131a: COLIBRÍ further observations
  54. Konus-Wind detection of GRB 260128A / EP260128a
  55. GRB 260131A: Insight-HXMT/HE detection
  56. Konus-Wind detection of GRB 260131A/B
  57. EP260131a: SVOM/VT optical observation
  58. EP260131a: Xinglong optical upper limit
  59. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  60. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  61. GRB 260131A/B: Fermi GBM Observation
  62. EP260131a: COLIBRÍ observations of slow optical fading
  63. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  64. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  65. EP260131a: COLIBRÍ optical observations of the counterpart
  66. GRB 260127B: AstroSat CZTI detection
  67. GRB 260130A: Fermi GBM Detection
  68. EP260131a: Einstein Probe detection of an X-ray transient
  69. GRB 260127B: Fermi GBM Detection
  70. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  71. GRB 260128B: LCO optical upper limits
  72. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  73. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  74. IPN triangulation of GRB 260121A
  75. GRB 260127A: Swift-BAT refined analysis
  76. GRB 260128B: SVOM detection of a burst through offline search
  77. IPN triangulation of GRB 260127B (short)
  78. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  79. EP260128a: NOT optical counterpart candidate
  80. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  81. EP260126a: SVOM/VT optical upperlimit
  82. EP260128a: Einstein Probe detection of an X-ray transient
  83. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  84. GRB 260127A: Fermi GBM Observation
  85. GRB 260127A: COLIBRÍ optical observations
  86. GRB 260127A: NOT optical observations
  87. EP260126a: Seimei/TriCCS optical upper limit
  88. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  89. GRB 260127B: GOTO candidate optical counterpart
  90. GRB 260127A: SVOM/C-GFT optical observations
  91. GRB 260127A: Enhanced Swift-XRT position
  92. GRB 260127A: Prompt enhanced Swift-XRT position
  93. GRB 260127A: LCO optical afterglow discovery
  94. GRB 260127A: Swift detection of a burst
  95. EP260126a: EP-FXT follow-up observation
  96. EP260126a: Optical upper limit with Kinder observations
  97. EP260126a: COLIBRÍ optical upper limits
  98. EP260126a: Einstein Probe detection of a fast X-ray transient
  99. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  100. Konus-Wind detection of GRB 260120B

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