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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"

22214 results found.

  1. GRB 260127A: LCO optical afterglow discovery
  2. GRB 260125A: Swift-XRT observations
  3. EP260126a: EP-FXT follow-up observation
  4. EP260126a: Optical upper limit with Kinder observations
  5. EP260126a: Further NOT optical upper limits
  6. EP260126a: NOT optical observations
  7. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  8. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  9. GRB 251222A: SVOM/ECLAIRs refined analysis
  10. GRB 260125A: Swift ToO observations
  11. GRB 260125A: GOTO candidate optical counterpart
  12. Fermi GRB 260125B: Global MASTER-Net observations report
  13. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  14. GRB 260122B: Swift detection of a burst
  15. Swift GRB260122.97: Global MASTER-Net observations report
  16. EP260119a: Assy AZT-20 optical observations
  17. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  18. Fermi GRB 260120C: Global MASTER-Net observations report
  19. EP260116a: COLIBRÍ further observations
  20. EP260105a: GTC/HiPERCAM optical observations
  21. GRB 260120B: Swift/UVOT Detection
  22. SVOM GRB260121.06: Global MASTER-Net observations report
  23. GRB 260101A: 239Alferov CubeSat detection
  24. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  25. Swift GRB260120B: Global MASTER-Net observations report
  26. EP260119A: Mondy I-Band Observations
  27. Fermi trigger No 790601190: Global MASTER-Net observations report
  28. Fermi trigger No 790570272: Global MASTER-Net observations report
  29. GRB 260114A: Swift/UVOT Upper Limits
  30. EP260119a: Liverpool Telescope optical follow-up observations
  31. GRB 251202A: further radio observations with the VLA
  32. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  33. EP260119a: KAIT optical observations
  34. EP260119a: update of EP-FXT follow-up observation
  35. EP260119a: NOT optical observations
  36. EP260119a: SAO RAS optical observations
  37. SVOM GRB260119.92: Global MASTER-Net observations report
  38. SVOM GRB260119.92: Global MASTER-Net observations report
  39. SVOM GRB260119.90: Global MASTER-Net observations report
  40. EP260116a: COLIBRÍ detection of a fading optical source
  41. GRB 251208D: SVOM/ECLAIRs refined analysis
  42. GRB 251208D: SVOM/ECLAIRs refined analysis
  43. GRB 260117A: Swift-XRT afterglow detection
  44. EP260119a: Global MASTER-Net observations report
  45. EP260119a: LCO optical observations
  46. EP260119a: COLIBRÍ optical counterpart candidate
  47. Swift GRB260118.48: Global MASTER-Net observations report
  48. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  49. SVOM GRB260117.82: Global MASTER-Net observations report
  50. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  51. Swift trigger on the HMXB 1A 1118-61
  52. GRB 260117A: SVOM/C-GFT upper limit
  53. GRB 260117A: Swift-XRT observations
  54. GRB 260117A: Swift ToO observations
  55. Swift triggered on the HMXB 1A 1118-61
  56. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  57. EP260116A: 1.3m DFOT optical upper limit
  58. GRB 260114A: VLT/MUSE spectroscopic observations
  59. EP260116a: Global MASTER-Net observations report
  60. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  61. IceCube Alert 260115.73: Global MASTER-Net observations report
  62. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  63. Fermi GRB 260115A: Global MASTER-Net observations report
  64. GRB260114A: STEP/T80S optical limits
  65. GRB 251222A: radio detection with the VLA
  66. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  67. GRB 260114A: 6 GHz VLA observations
  68. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  69. GRB 260114A: TNG NIR upper limit
  70. GRB 260114A: NOT optical observations
  71. Konus-Wind detection of GRB 251230A / EP251230a
  72. Swift GRB 260114A: Global MASTER-Net observations report
  73. GRB 260114A: Mondy optical observations
  74. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  75. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  76. Swift GRB260113.43: Global MASTER-Net observations report
  77. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  78. EP260110a: TRT optical upper limits
  79. Konus-Wind detection of GRB 260101A
  80. GRB 260111A: Swift-XRT observations
  81. GRB 260111A: GOTO optical upper limits
  82. GRB 260111A: Swift ToO observations
  83. GRB 251230A: Mondy Optical Observations
  84. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  85. IceCube Alert 260111A: Global MASTER-Net observations report
  86. EP260110a: Global MASTER-Net observations report
  87. Fermi GRB 260111A: Global MASTER-Net observations report
  88. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  89. EP 260110a: COLIBRÍ optical observations
  90. EP260110a: SVOM/C-GFT upper limit
  91. GRB 260109C: LCO optical upper limits
  92. GRB 260109C: Kilonova-Catcher optical upper limit
  93. GRB 260102A: Swift-XRT afterglow detection
  94. Fermi GRB 260107A: Global MASTER-Net observations report
  95. GRB 260102A: AbAO optical observations
  96. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  97. Fermi GRB 260105A: Global MASTER-Net observations report
  98. EP260105a: FTW optical observations
  99. EP260104a: FTW optical observations
  100. Fermi GRB 260105B: Global MASTER-Net observations report

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