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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"

19316 results found.

  1. EP260131a: COLIBRÍ observations of slow optical fading
  2. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  3. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  4. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  5. GRB 260131B: MAXI/GSC detection
  6. GRB 260131A: Fermi GBM Final Real-time Localization
  7. EP260131a: COLIBRÍ optical observations of the counterpart
  8. EP260131a: Las Cumbres detection of an optical counterpart
  9. GRB 260127B: AstroSat CZTI detection
  10. GRB 260130A: Fermi GBM Detection
  11. EP260131a: Einstein Probe detection of an X-ray transient
  12. GRB 260127B: Fermi GBM Detection
  13. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  14. Fermi GRB 260130A: Global MASTER-Net observations report
  15. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  16. GRB 260130A: Fermi GBM Final Real-time Localization
  17. Fermi GRB 260129A: Global MASTER-Net observations report
  18. GRB 260128B: LCO optical upper limits
  19. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  20. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  21. GRB 260127A: Swift-BAT refined analysis
  22. GRB 260129B: Fermi GBM Final Localization
  23. GRB 260128B: SVOM detection of a burst through offline search
  24. GRB 260129A: Fermi GBM Final Localization
  25. GRB 260127B: Swift-XRT observations
  26. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  27. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  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. EP260126a: SVOM/VT optical upperlimit
  33. EP260128a: Global MASTER-Net observations report
  34. EP260128a: Einstein Probe detection of an X-ray transient
  35. Fermi GRB 260127A: Global MASTER-Net observations report
  36. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  37. GRB 260127A: Fermi GBM Observation
  38. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  39. GRB 260127A: COLIBRÍ optical observations
  40. EP260126a: Seimei/TriCCS optical upper limit
  41. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  42. GRB 260127A: Swift-XRT refined Analysis
  43. GRB 260127B: GOTO candidate optical counterpart
  44. GRB 260127A: SVOM/C-GFT optical observations
  45. The EP-WXT trigger 01709253145 is likely a flaring star
  46. Fermi GRB 260127B: Global MASTER-Net observations report
  47. GRB 260127B: Fermi GBM Final Real-time Localization
  48. Swift GRB 260127A: Global MASTER-Net observations report
  49. GRB 260127A: LCO optical afterglow discovery
  50. GRB 260127A: Swift detection of a burst
  51. GRB 260127A: Fermi GBM Final Real-time Localization
  52. GRB 260125A: Swift-XRT observations
  53. EP260126a: Optical upper limit with Kinder observations
  54. EP260126a: Liverpool Telescope optical upper limits
  55. EP260126a: Further NOT optical upper limits
  56. EP260126a: COLIBRÍ optical upper limits
  57. EP260126a: NOT optical observations
  58. EP260126a: Einstein Probe detection of a fast X-ray transient
  59. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  60. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  61. GRB 251222A: SVOM/ECLAIRs refined analysis
  62. GRB 260125A: GOTO candidate optical counterpart
  63. Fermi GRB 260125B: Global MASTER-Net observations report
  64. GRB 260125B: Fermi GBM Final Real-time Localization
  65. GRB 260125A: Fermi GBM Final Real-time Localization
  66. GRB 260114A: SVOM/VT optical upper limits
  67. GRB 260120A: AstroSat CZTI detection
  68. GRB 260122B: Swift-BAT refined analysis
  69. GRB 260120B: SVOM/GRM observation
  70. GRB 260120A: GECAM-B observation
  71. GRB 260120B: AstroSat CZTI detection
  72. GRB 260114A: Insight-HXMT/HE detection
  73. GRB 260122B: Swift detection of a burst
  74. Swift GRB260122.97: Global MASTER-Net observations report
  75. EP260119a: Assy AZT-20 optical observations
  76. EP260119a: Mondy and SAO RAS optical upper limits
  77. GRB 260122A: Fermi GBM Final Real-time Localization
  78. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  79. EP260119a: Xinglong optical upper limit
  80. The EP-WXT trigger 01709251871 is likely a flaring star
  81. Fermi GRB 260120C: Global MASTER-Net observations report
  82. GRB 260120B: Swift-BAT refined analysis
  83. GRB 260120B: Swift-XRT refined Analysis
  84. EP260116a: COLIBRÍ further observations
  85. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  86. GRB 260120B: Fermi GBM Observation
  87. EP260105a: GTC/HiPERCAM optical observations
  88. GRB 260120B: COLIBRÍ optical upper limits
  89. SVOM GRB260121.06: Global MASTER-Net observations report
  90. GRB 260120B: Enhanced Swift-XRT position
  91. GRB 260120B: SVOM/C-GFT optical counterpart detection
  92. GRB 260120C: Fermi GBM Final Real-time Localization
  93. GRB 260101A: 239Alferov CubeSat detection
  94. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  95. GRB 260120B: Swift detection of a burst
  96. Swift GRB260120B: Global MASTER-Net observations report
  97. GRB 260120B: Fermi GBM Final Real-time Localization
  98. EP260119A: Mondy I-Band Observations
  99. Fermi trigger No 790601190: Global MASTER-Net observations report
  100. Fermi trigger No 790570272: Global MASTER-Net observations report

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