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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"

32720 results found.

  1. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  2. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  3. EP260131a: COLIBRÍ optical observations of the counterpart
  4. GRB 260127B: AstroSat CZTI detection
  5. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  6. Fermi GRB 260130A: Global MASTER-Net observations report
  7. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  8. Fermi GRB 260129A: Global MASTER-Net observations report
  9. GRB 260128B: LCO optical upper limits
  10. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  11. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  12. IPN triangulation of GRB 260121A
  13. GRB 260127A: Swift-BAT refined analysis
  14. IPN triangulation of GRB 260127B (short)
  15. GRB 260127B: Swift-XRT observations
  16. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  17. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  18. EP260128a: NOT optical counterpart candidate
  19. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  20. EP260128a: Liverpool Telescope optical observations and possible counterpart
  21. EP260128a: LCO optical upper limits
  22. EP260126a: SVOM/VT optical upperlimit
  23. EP260128a: Global MASTER-Net observations report
  24. Fermi GRB 260127A: Global MASTER-Net observations report
  25. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  26. GRB 260127A: Fermi GBM Observation
  27. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  28. GRB 260127A: COLIBRÍ optical observations
  29. GRB 260127A: NOT optical observations
  30. GRB 260127B: Swift ToO observations
  31. EP260126a: Seimei/TriCCS optical upper limit
  32. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  33. GRB 260127B: GOTO candidate optical counterpart
  34. GRB 260127A: SVOM/C-GFT optical observations
  35. Fermi GRB 260127B: Global MASTER-Net observations report
  36. Swift GRB 260127A: Global MASTER-Net observations report
  37. GRB 260127A: LCO optical afterglow discovery
  38. GRB 260125A: Swift-XRT observations
  39. EP260126a: EP-FXT follow-up observation
  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. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  46. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  47. Konus-Wind detection of GRB 260120B
  48. GRB 251222A: SVOM/ECLAIRs refined analysis
  49. GRB 260125A: Swift ToO observations
  50. GRB 260125A: GOTO candidate optical counterpart
  51. Fermi GRB 260125B: Global MASTER-Net observations report
  52. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 260114A: SVOM/VT optical upper limits
  54. GRB 260120A: AstroSat CZTI detection
  55. GRB 260122B: Swift-BAT refined analysis
  56. GRB 260120B: SVOM/GRM observation
  57. GRB 260120A: GECAM-B observation
  58. GRB 260120B: AstroSat CZTI detection
  59. GRB 260114A: Insight-HXMT/HE detection
  60. EP260119a: Assy AZT-20 optical observations
  61. EP260119a: Mondy and SAO RAS optical upper limits
  62. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  63. EP260119a: Xinglong optical upper limit
  64. Fermi GRB 260120C: Global MASTER-Net observations report
  65. GRB 260120B: Swift-BAT refined analysis
  66. EP260116a: COLIBRÍ further observations
  67. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  68. GRB 260120B: Fermi GBM Observation
  69. EP260105a: GTC/HiPERCAM optical observations
  70. GRB 260120B: Swift/UVOT Detection
  71. GRB 260120B: COLIBRÍ optical upper limits
  72. GRB 260120B: SVOM/C-GFT optical counterpart detection
  73. GRB 260101A: 239Alferov CubeSat detection
  74. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  75. EP260119A: Mondy I-Band Observations
  76. GRB 260114A: Swift/UVOT Upper Limits
  77. EP260119a: Liverpool Telescope optical follow-up observations
  78. GRB 251202A: further radio observations with the VLA
  79. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  80. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  81. EP260119a: KAIT optical observations
  82. EP260119a: SVOM/VT optical observation
  83. EP260119a: update of EP-FXT follow-up observation
  84. EP260119a: NOT optical observations
  85. EP260119a: SAO RAS optical observations
  86. EP260116a: COLIBRÍ detection of a fading optical source
  87. GRB 251208D: SVOM/ECLAIRs refined analysis
  88. GRB 251208D: SVOM/ECLAIRs refined analysis
  89. GRB 260117A: Swift-XRT afterglow detection
  90. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  91. EP260119a: Global MASTER-Net observations report
  92. GRB 260115A: AstroSat CZTI detection
  93. EP260119a: LCO optical observations
  94. GRB 260117A: ZTSh optical upper limit
  95. EP260119a: COLIBRÍ optical counterpart candidate
  96. EP260119a: preliminary result from the EP-FXT observation
  97. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  98. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  99. Swift trigger on the HMXB 1A 1118-61
  100. GRB 260117A: SVOM/VT optical candidate

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