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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

21263 results found.

  1. EP260210a: refined analysis of the EP-FXT observation
  2. GRB 260208A: LCO detection of the optical counterpart
  3. EP260209a: Einstein Probe detection of a fast X-ray transient
  4. EP260210a: Optical upper limits with Kinder observations
  5. GRB 260210A: AstroSat CZTI detection
  6. EP260210a: COLIBRÍ optical upper limit
  7. EP260210a: SVOM/C-GFT upper limit
  8. EP260210a: Einstein Probe detection of an X-ray transient
  9. GRB 260208C: SVOM/GRM observation
  10. GRB 260204A: Swift-XRT afterglow detection
  11. GRB 260208B: AstroSat CZTI detection of a bright long burst
  12. GRB260208A: Liverpool Telescope optical follow-up observations
  13. GRB 260208A: NuSTAR detection of prompt emission
  14. Fermi GRB 260209A: Global MASTER-Net observations report
  15. GRB 260131A/B: continued Mondy optical observations
  16. GRB 260204A: Swift/UVOT Upper Limits
  17. GRB 260208B: COLIBRÍ optical observations
  18. GRB 260208A: Mondy optical observations
  19. GRB 260208A: 1.3m DFOT optical detection
  20. GRB 260208A: COLIBRÍ optical observations
  21. GRB 260208A: Liverpool Telescope optical detection
  22. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  23. GRB 260208A: SVOM/VT optical observation
  24. GRB 260208B: SVOM/GRM observation of a bright burst
  25. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  26. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  27. GRB 260131A/B: Mondy and Terskol optical observations
  28. GRB 260206A: Swift-XRT observations
  29. GRB 260204A: LCO optical afterglow detection
  30. GRB 260204A: SVOM/VT optical candidate
  31. GRB 260204A: GOTO optical upper limit
  32. GRB 260204A: LCO optical upper limits
  33. EP260110a: Late GTC/EMIR near-infrared observations
  34. GRB 260204A: SVOM detection of a burst
  35. Konus-Wind detection of GRB 260121A
  36. GRB 260131A: KAIT optical observations
  37. GRB 251230A: MeerLICHT afterglow detection
  38. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  39. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  40. EP260131a: Liverpool Telescope optical upper limits
  41. EP260131a: COLIBRÍ further observations
  42. Konus-Wind detection of GRB 260131A/B
  43. EP260131a: SVOM/VT optical observation
  44. EP260131a: Xinglong optical upper limit
  45. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  46. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  47. EP260131a: COLIBRÍ observations of slow optical fading
  48. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  49. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  50. EP260131a: COLIBRÍ optical observations of the counterpart
  51. EP260131a: Einstein Probe detection of an X-ray transient
  52. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  53. GRB 260128B: LCO optical upper limits
  54. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  55. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  56. GRB 260127A: Swift-BAT refined analysis
  57. GRB 260127B: Swift-XRT observations
  58. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  59. EP260128a: NOT optical counterpart candidate
  60. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. EP260128a: Liverpool Telescope optical observations and possible counterpart
  62. EP260128a: LCO optical upper limits
  63. EP260128a: Einstein Probe detection of an X-ray transient
  64. GRB 260127A: COLIBRÍ optical observations
  65. EP260126a: Seimei/TriCCS optical upper limit
  66. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  67. GRB 260127B: GOTO candidate optical counterpart
  68. GRB 260127A: SVOM/C-GFT optical observations
  69. GRB 260127A: Enhanced Swift-XRT position
  70. GRB 260127A: LCO optical afterglow discovery
  71. GRB 260127A: Swift detection of a burst
  72. GRB 260125A: Swift-XRT observations
  73. EP260126a: Optical upper limit with Kinder observations
  74. EP260126a: Liverpool Telescope optical upper limits
  75. EP260126a: Further NOT optical upper limits
  76. EP260126a: COLIBRÍ optical upper limits
  77. EP260126a: NOT optical observations
  78. EP260126a: Einstein Probe detection of a fast X-ray transient
  79. GRB 251222A: SVOM/ECLAIRs refined analysis
  80. GRB 260125A: GOTO candidate optical counterpart
  81. GRB 260114A: SVOM/VT optical upper limits
  82. GRB 260120A: AstroSat CZTI detection
  83. GRB 260120B: SVOM/GRM observation
  84. EP260119a: Assy AZT-20 optical observations
  85. EP260119a: Mondy and SAO RAS optical upper limits
  86. EP260119a: Xinglong optical upper limit
  87. EP260116a: COLIBRÍ further observations
  88. EP260105a: GTC/HiPERCAM optical observations
  89. GRB 260120B: Swift/UVOT Detection
  90. GRB 260120B: COLIBRÍ optical upper limits
  91. GRB 260120B: Enhanced Swift-XRT position
  92. GRB 260120B: SVOM/C-GFT optical counterpart detection
  93. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  94. GRB 260120B: Swift detection of a burst
  95. EP260119A: Mondy I-Band Observations
  96. GRB 260114A: Swift/UVOT Upper Limits
  97. EP260119a: Liverpool Telescope optical follow-up observations
  98. GRB 251202A: further radio observations with the VLA
  99. EP260119a: KAIT optical observations
  100. EP260119a: SVOM/VT optical observation

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