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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"

21577 results found.

  1. GRB 260208B: SVOM/VT optical candidate
  2. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  3. GRB 260208A: SVOM/VT optical observation
  4. Fermi GRB 260208D: Global MASTER-Net observations report
  5. GRB 260208A: Swift-XRT observations
  6. GRB 260208B: Swift ToO observations
  7. LAT GRB 260208B: Global MASTER-Net observations report
  8. GRB 260208A: Swift ToO observations
  9. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  10. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  11. Fermi GRB 260208A: Global MASTER-Net observations report
  12. GRB 260207A : MASTER optical counterpart discovery
  13. GRB 260131A/B: Mondy and Terskol optical observations
  14. Fermi GRB 260207B: Global MASTER-Net observations report
  15. GRB 260206A: Swift-XRT observations
  16. Fermi trigger No 792135758: Global MASTER-Net observations report
  17. EP260131a: VLA detection
  18. GRB 260206A: Tiled Swift observations
  19. GRB 260204A: Swift-XRT observations
  20. GRB 260204A: LCO optical afterglow detection
  21. GRB 260204A : MASTER Global robotic net optical observations
  22. GRB 260204A: GOTO optical upper limit
  23. EP260110a: Late GTC/EMIR near-infrared observations
  24. GRB 260204A: SVOM detection of a burst
  25. GRB 260121A: 239Alferov CubeSat detection
  26. Konus-Wind detection of GRB 260121A
  27. GRB 260131A/B: OHP/T193 optical observations
  28. GRB 260131A: KAIT optical observations
  29. GRB 251230A: MeerLICHT afterglow detection
  30. GRB 260131A: FTW optical and NIR observations
  31. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  32. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  33. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  34. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  35. EP260131a: COLIBRÍ further observations
  36. Konus-Wind detection of GRB 260128A / EP260128a
  37. Konus-Wind detection of GRB 260131A/B
  38. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  39. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  40. EP260131a: COLIBRÍ observations of slow optical fading
  41. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  43. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  44. EP260131a: COLIBRÍ optical observations of the counterpart
  45. Fermi GRB 260130A: Global MASTER-Net observations report
  46. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  47. Fermi GRB 260129A: Global MASTER-Net observations report
  48. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  49. GRB 260127B: Swift-XRT observations
  50. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  51. EP260128a: NOT optical counterpart candidate
  52. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  53. EP260128a: Liverpool Telescope optical observations and possible counterpart
  54. EP260128a: Global MASTER-Net observations report
  55. Fermi GRB 260127A: Global MASTER-Net observations report
  56. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  57. GRB 260127A: COLIBRÍ optical observations
  58. GRB 260127A: NOT optical observations
  59. GRB 260127B: Swift ToO observations
  60. GRB 260127B: GOTO candidate optical counterpart
  61. GRB 260127A: SVOM/C-GFT optical observations
  62. Fermi GRB 260127B: Global MASTER-Net observations report
  63. Swift GRB 260127A: Global MASTER-Net observations report
  64. GRB 260127A: LCO optical afterglow discovery
  65. GRB 260125A: Swift-XRT observations
  66. EP260126a: EP-FXT follow-up observation
  67. EP260126a: Optical upper limit with Kinder observations
  68. EP260126a: Further NOT optical upper limits
  69. EP260126a: NOT optical observations
  70. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  71. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  72. GRB 251222A: SVOM/ECLAIRs refined analysis
  73. GRB 260125A: Swift ToO observations
  74. GRB 260125A: GOTO candidate optical counterpart
  75. Fermi GRB 260125B: Global MASTER-Net observations report
  76. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  77. GRB 260122B: Swift detection of a burst
  78. Swift GRB260122.97: Global MASTER-Net observations report
  79. EP260119a: Assy AZT-20 optical observations
  80. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  81. Fermi GRB 260120C: Global MASTER-Net observations report
  82. EP260116a: COLIBRÍ further observations
  83. EP260105a: GTC/HiPERCAM optical observations
  84. GRB 260120B: Swift/UVOT Detection
  85. SVOM GRB260121.06: Global MASTER-Net observations report
  86. GRB 260101A: 239Alferov CubeSat detection
  87. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  88. Swift GRB260120B: Global MASTER-Net observations report
  89. EP260119A: Mondy I-Band Observations
  90. Fermi trigger No 790601190: Global MASTER-Net observations report
  91. Fermi trigger No 790570272: Global MASTER-Net observations report
  92. GRB 260114A: Swift/UVOT Upper Limits
  93. EP260119a: Liverpool Telescope optical follow-up observations
  94. GRB 251202A: further radio observations with the VLA
  95. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  96. EP260119a: KAIT optical observations
  97. EP260119a: update of EP-FXT follow-up observation
  98. EP260119a: NOT optical observations
  99. EP260119a: SAO RAS optical observations
  100. SVOM GRB260119.92: Global MASTER-Net observations report

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