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

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