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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"

15714 results found.

  1. GRB 260131A: FTW optical and NIR observations
  2. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  3. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  4. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  5. GRB 260131A/B: EP/FXT X-ray afterglow detection
  6. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  7. GRB 260131A: NOT spectroscopic redshift z = 1.434
  8. EP260131a: Liverpool Telescope optical upper limits
  9. EP260131a: COLIBRÍ further observations
  10. EP260131a: SVOM/VT optical observation
  11. EP260131a: Xinglong optical upper limit
  12. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  13. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  14. EP260131a: COLIBRÍ observations of slow optical fading
  15. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  16. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  17. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  18. EP260131a: COLIBRÍ optical observations of the counterpart
  19. EP260131a: Las Cumbres detection of an optical counterpart
  20. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  21. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  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. IPN triangulation of GRB 260127B (short)
  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: Liverpool Telescope optical observations and possible counterpart
  30. EP260128a: LCO optical upper limits
  31. EP260126a: SVOM/VT optical upperlimit
  32. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  33. GRB 260127A: COLIBRÍ optical observations
  34. GRB 260127A: NOT optical observations
  35. EP260126a: Seimei/TriCCS optical upper limit
  36. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  37. GRB 260127B: GOTO candidate optical counterpart
  38. GRB 260127A: SVOM/C-GFT optical observations
  39. GRB 260127A: LCO optical afterglow discovery
  40. EP260126a: Optical upper limit with Kinder observations
  41. EP260126a: Liverpool Telescope optical upper limits
  42. EP260126a: Further NOT optical upper limits
  43. EP260126a: COLIBRÍ optical upper limits
  44. EP260126a: NOT optical observations
  45. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  46. GRB 260125A: GOTO candidate optical counterpart
  47. GRB 260114A: SVOM/VT optical upper limits
  48. GRB 260120B: SVOM/GRM observation
  49. EP260119a: Assy AZT-20 optical observations
  50. EP260119a: Mondy and SAO RAS optical upper limits
  51. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  52. EP260119a: Xinglong optical upper limit
  53. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  54. EP260105a: GTC/HiPERCAM optical observations
  55. GRB 260120B: Swift/UVOT Detection
  56. GRB 260120B: COLIBRÍ optical upper limits
  57. GRB 260120B: SVOM/C-GFT optical counterpart detection
  58. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  59. GRB 260114A: Swift/UVOT Upper Limits
  60. EP260119a: Liverpool Telescope optical follow-up observations
  61. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  62. EP260119a: KAIT optical observations
  63. EP260119a: SVOM/VT optical observation
  64. EP260119a: NOT optical observations
  65. EP260119a: SAO RAS optical observations
  66. EP260116a: COLIBRÍ detection of a fading optical source
  67. GRB 260117A: Swift-XRT afterglow detection
  68. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  69. EP260119a: LCO optical observations
  70. GRB 260117A: ZTSh optical upper limit
  71. EP260119a: COLIBRÍ optical counterpart candidate
  72. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. GRB 260117A: SVOM/VT optical candidate
  74. GRB 260117A: SVOM detection of a long faint burst
  75. EP 260116a: COLIBRÍ optical upper limit
  76. EP260116a: Liverpool Telescope upper limits
  77. EP260116A: 1.3m DFOT optical upper limit
  78. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  79. EP260116a: Xinglong optical upper limit
  80. GRB260114A: STEP/T80S optical limits
  81. GRB 251222A: radio detection with the VLA
  82. GRB 260114A : MITSuME Akeno optical upper limits
  83. GRB 260114A: COLIBRÍ optical upper limits
  84. GRB 260114A: TNG NIR upper limit
  85. GRB 260114A: NOT optical observations
  86. GRB 260114A: SVOM/GRM observation of a short burst
  87. GRB 260114A: Mondy optical observations
  88. GRB 260114A: GMG Optical Observation
  89. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  90. EP260110a: TRT optical upper limits
  91. GRB 260111A: Swift-XRT observations
  92. GRB 260111A: COLIBRÍ optical afterglow candidate
  93. GRB 260111A: GOTO optical upper limits
  94. GRB 251230A: Mondy Optical Observations
  95. EP260110a: SVOM/VT optical upper limits
  96. EP260110a: KAIT optical upper limit
  97. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP 260110a: COLIBRÍ optical observations
  99. EP260110a: BOOTES-5/JGU optical upper limit
  100. GRB 260109C: LCO optical upper limits

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