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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"
  1. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  2. Konus-Wind detection of GRB 260120B
  3. GRB 251222A: SVOM/ECLAIRs refined analysis
  4. GRB 260125A: Swift ToO observations
  5. GRB 260125A: GOTO candidate optical counterpart
  6. Fermi GRB 260125B: Global MASTER-Net observations report
  7. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  8. GRB 260125B: Fermi GBM Final Real-time Localization
  9. GRB 260125A: Fermi GBM Final Real-time Localization
  10. GRB 260114A: SVOM/VT optical upper limits
  11. GRB 260120A: AstroSat CZTI detection
  12. GRB 260122B: Swift-BAT refined analysis
  13. GRB 260120B: SVOM/GRM observation
  14. GRB 260120A: GECAM-B observation
  15. GRB 260120B: AstroSat CZTI detection
  16. GRB 260114A: Insight-HXMT/HE detection
  17. GRB 260122B: Swift detection of a burst
  18. Swift GRB260122.97: Global MASTER-Net observations report
  19. EP260119a: Assy AZT-20 optical observations
  20. EP260119a: Mondy and SAO RAS optical upper limits
  21. GRB 260122A: Fermi GBM Final Real-time Localization
  22. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  23. EP260119a: Xinglong optical upper limit
  24. The EP-WXT trigger 01709251871 is likely a flaring star
  25. Fermi GRB 260120C: Global MASTER-Net observations report
  26. GRB 260120B: Swift-BAT refined analysis
  27. GRB 260120B: Swift-XRT refined Analysis
  28. EP260116a: COLIBRÍ further observations
  29. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  30. GRB 260120B: Fermi GBM Observation
  31. EP260105a: GTC/HiPERCAM optical observations
  32. GRB 260120B: Swift/UVOT Detection
  33. GRB 260120B: COLIBRÍ optical upper limits
  34. SVOM GRB260121.06: Global MASTER-Net observations report
  35. GRB 260120B: Enhanced Swift-XRT position
  36. GRB 260120B: SVOM/C-GFT optical counterpart detection
  37. GRB 260120C: Fermi GBM Final Real-time Localization
  38. GRB 260101A: 239Alferov CubeSat detection
  39. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  40. GRB 260120B: Swift detection of a burst
  41. Swift GRB260120B: Global MASTER-Net observations report
  42. GRB 260120B: Fermi GBM Final Real-time Localization
  43. EP260119A: Mondy I-Band Observations
  44. Fermi trigger No 790601190: Global MASTER-Net observations report
  45. Fermi trigger No 790570272: Global MASTER-Net observations report
  46. GRB 260114A: Swift/UVOT Upper Limits
  47. EP260119a: Liverpool Telescope optical follow-up observations
  48. GRB 251202A: further radio observations with the VLA
  49. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  50. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  51. EP260119a: KAIT optical observations
  52. GRB 260120A: Fermi GBM Final Real-time Localization
  53. EP260119a: SVOM/VT optical observation
  54. EP260119a: update of EP-FXT follow-up observation
  55. EP260119a: NOT optical observations
  56. EP260119a: SAO RAS optical observations
  57. SVOM GRB260119.92: Global MASTER-Net observations report
  58. SVOM GRB260119.92: Global MASTER-Net observations report
  59. SVOM GRB260119.90: Global MASTER-Net observations report
  60. EP260116a: COLIBRÍ detection of a fading optical source
  61. GRB 251208D: SVOM/ECLAIRs refined analysis
  62. GRB 251208D: SVOM/ECLAIRs refined analysis
  63. GRB 260117A: Swift-XRT afterglow detection
  64. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  65. EP260119a: Global MASTER-Net observations report
  66. GRB 260115A: AstroSat CZTI detection
  67. EP260119a: LCO optical observations
  68. GRB 260117A: ZTSh optical upper limit
  69. EP260119a: COLIBRÍ optical counterpart candidate
  70. EP260119a: preliminary result from the EP-FXT observation
  71. GRB 260110A: SVOM detection of a burst through offline search
  72. EP260119a: EP-WXT detection of a fast X-ray transient
  73. Swift GRB260118.48: Global MASTER-Net observations report
  74. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. SVOM GRB260117.82: Global MASTER-Net observations report
  76. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  77. Swift trigger on the HMXB 1A 1118-61
  78. GRB 260117A: SVOM/VT optical candidate
  79. GRB 260117A: SVOM/C-GFT upper limit
  80. GRB 260117A: Swift-XRT observations
  81. GRB 260117A: Swift ToO observations
  82. GRB 260117A: SVOM detection of a long faint burst
  83. EP 260116a: COLIBRÍ optical upper limit
  84. Swift triggered on the HMXB 1A 1118-61
  85. GRB 260115A: GECAM-B observation
  86. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  87. EP260116a: Liverpool Telescope upper limits
  88. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  89. EP260116A: 1.3m DFOT optical upper limit
  90. GRB 260114A: VLT/MUSE spectroscopic observations
  91. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  92. EP260116a: Global MASTER-Net observations report
  93. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  94. EP260116a: Xinglong optical upper limit
  95. EP260116a: Einstein Probe detection of an X-ray transient
  96. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  97. IceCube Alert 260115.73: Global MASTER-Net observations report
  98. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  100. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka

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