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

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