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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"

21760 results found.

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

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