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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"

20515 results found.

  1. GRB 260204B: Fermi GBM Final Real-time Localization
  2. Konus-Wind detection of GRB 260121A
  3. GRB 260131A: KAIT optical observations
  4. GRB 251230A: MeerLICHT afterglow detection
  5. GRID detection of GRB 260131A/B
  6. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  7. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  8. GRB 260131A: NOT spectroscopic redshift z = 1.434
  9. EP260131a: Liverpool Telescope optical upper limits
  10. EP260131a: COLIBRÍ further observations
  11. Konus-Wind detection of GRB 260128A / EP260128a
  12. EP260131a: SVOM/VT optical observation
  13. EP260131a: Xinglong optical upper limit
  14. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  15. EP260131a: COLIBRÍ observations of slow optical fading
  16. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  18. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  19. EP260131a: COLIBRÍ optical observations of the counterpart
  20. EP260131a: Einstein Probe detection of an X-ray transient
  21. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  22. GRB 260128B: LCO optical upper limits
  23. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  24. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  25. GRB 260128B: SVOM detection of a burst through offline search
  26. GRB 260127B: Swift-XRT observations
  27. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  28. EP260128a: NOT optical counterpart candidate
  29. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. EP260128a: Liverpool Telescope optical observations and possible counterpart
  31. EP260128a: LCO optical upper limits
  32. EP260128a: Einstein Probe detection of an X-ray transient
  33. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  34. GRB 260127A: COLIBRÍ optical observations
  35. EP260126a: Seimei/TriCCS optical upper limit
  36. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  37. GRB 260127A: SVOM/C-GFT optical observations
  38. GRB 260127A: Enhanced Swift-XRT position
  39. GRB 260127A: LCO optical afterglow discovery
  40. GRB 260127A: Swift detection of a burst
  41. GRB 260125A: Swift-XRT observations
  42. EP260126a: Optical upper limit with Kinder observations
  43. EP260126a: Liverpool Telescope optical upper limits
  44. EP260126a: Further NOT optical upper limits
  45. EP260126a: COLIBRÍ optical upper limits
  46. EP260126a: NOT optical observations
  47. EP260126a: Einstein Probe detection of a fast X-ray transient
  48. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  49. GRB 251222A: SVOM/ECLAIRs refined analysis
  50. GRB 260125A: GOTO candidate optical counterpart
  51. GRB 260114A: SVOM/VT optical upper limits
  52. GRB 260120B: SVOM/GRM observation
  53. GRB 260120B: AstroSat CZTI detection
  54. EP260119a: Assy AZT-20 optical observations
  55. EP260119a: Mondy and SAO RAS optical upper limits
  56. EP260119a: Xinglong optical upper limit
  57. EP260116a: COLIBRÍ further observations
  58. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  59. GRB 260120B: Fermi GBM Observation
  60. EP260105a: GTC/HiPERCAM optical observations
  61. GRB 260120B: Swift/UVOT Detection
  62. GRB 260120B: COLIBRÍ optical upper limits
  63. GRB 260120B: Enhanced Swift-XRT position
  64. GRB 260120B: SVOM/C-GFT optical counterpart detection
  65. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  66. GRB 260120B: Swift detection of a burst
  67. EP260119A: Mondy I-Band Observations
  68. GRB 260114A: Swift/UVOT Upper Limits
  69. EP260119a: Liverpool Telescope optical follow-up observations
  70. GRB 251202A: further radio observations with the VLA
  71. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  72. EP260119a: KAIT optical observations
  73. EP260119a: SVOM/VT optical observation
  74. EP260119a: NOT optical observations
  75. EP260119a: SAO RAS optical observations
  76. EP260116a: COLIBRÍ detection of a fading optical source
  77. GRB 251208D: SVOM/ECLAIRs refined analysis
  78. GRB 251208D: SVOM/ECLAIRs refined analysis
  79. GRB 260117A: Swift-XRT afterglow detection
  80. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  81. EP260119a: LCO optical observations
  82. GRB 260117A: ZTSh optical upper limit
  83. EP260119a: COLIBRÍ optical counterpart candidate
  84. GRB 260110A: SVOM detection of a burst through offline search
  85. EP260119a: EP-WXT detection of a fast X-ray transient
  86. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  87. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  88. Swift trigger on the HMXB 1A 1118-61
  89. GRB 260117A: SVOM/C-GFT upper limit
  90. GRB 260117A: SVOM detection of a long faint burst
  91. EP 260116a: COLIBRÍ optical upper limit
  92. Swift triggered on the HMXB 1A 1118-61
  93. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  94. EP260116a: Liverpool Telescope upper limits
  95. EP260116A: 1.3m DFOT optical upper limit
  96. GRB 260114A: VLT/MUSE spectroscopic observations
  97. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  99. EP260116a: Xinglong optical upper limit
  100. EP260116a: Einstein Probe detection of an X-ray transient

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