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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: Swift ToO observations
  2. GRB 260125A: GOTO candidate optical counterpart
  3. Fermi GRB 260125B: Global MASTER-Net observations report
  4. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 260125B: Fermi GBM Final Real-time Localization
  6. GRB 260125A: Fermi GBM Final Real-time Localization
  7. GRB 260114A: SVOM/VT optical upper limits
  8. GRB 260120A: AstroSat CZTI detection
  9. GRB 260122B: Swift-BAT refined analysis
  10. GRB 260120B: SVOM/GRM observation
  11. GRB 260120A: GECAM-B observation
  12. GRB 260120B: AstroSat CZTI detection
  13. GRB 260114A: Insight-HXMT/HE detection
  14. GRB 260122B: Swift detection of a burst
  15. Swift GRB260122.97: Global MASTER-Net observations report
  16. EP260119a: Assy AZT-20 optical observations
  17. EP260119a: Mondy and SAO RAS optical upper limits
  18. GRB 260122A: Fermi GBM Final Real-time Localization
  19. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  20. EP260119a: Xinglong optical upper limit
  21. The EP-WXT trigger 01709251871 is likely a flaring star
  22. Fermi GRB 260120C: Global MASTER-Net observations report
  23. GRB 260120B: Swift-BAT refined analysis
  24. GRB 260120B: Swift-XRT refined Analysis
  25. EP260116a: COLIBRÍ further observations
  26. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  27. GRB 260120B: Fermi GBM Observation
  28. EP260105a: GTC/HiPERCAM optical observations
  29. GRB 260120B: Swift/UVOT Detection
  30. GRB 260120B: COLIBRÍ optical upper limits
  31. SVOM GRB260121.06: Global MASTER-Net observations report
  32. GRB 260120B: Enhanced Swift-XRT position
  33. GRB 260120B: SVOM/C-GFT optical counterpart detection
  34. GRB 260120C: Fermi GBM Final Real-time Localization
  35. GRB 260101A: 239Alferov CubeSat detection
  36. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  37. GRB 260120B: Swift detection of a burst
  38. Swift GRB260120B: Global MASTER-Net observations report
  39. GRB 260120B: Fermi GBM Final Real-time Localization
  40. EP260119A: Mondy I-Band Observations
  41. Fermi trigger No 790601190: Global MASTER-Net observations report
  42. Fermi trigger No 790570272: Global MASTER-Net observations report
  43. GRB 260114A: Swift/UVOT Upper Limits
  44. EP260119a: Liverpool Telescope optical follow-up observations
  45. GRB 251202A: further radio observations with the VLA
  46. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  47. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  48. EP260119a: KAIT optical observations
  49. GRB 260120A: Fermi GBM Final Real-time Localization
  50. EP260119a: SVOM/VT optical observation
  51. EP260119a: update of EP-FXT follow-up observation
  52. EP260119a: NOT optical observations
  53. EP260119a: SAO RAS optical observations
  54. SVOM GRB260119.92: Global MASTER-Net observations report
  55. SVOM GRB260119.92: Global MASTER-Net observations report
  56. SVOM GRB260119.90: Global MASTER-Net observations report
  57. EP260116a: COLIBRÍ detection of a fading optical source
  58. GRB 251208D: SVOM/ECLAIRs refined analysis
  59. GRB 251208D: SVOM/ECLAIRs refined analysis
  60. GRB 260117A: Swift-XRT afterglow detection
  61. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  62. EP260119a: Global MASTER-Net observations report
  63. GRB 260115A: AstroSat CZTI detection
  64. EP260119a: LCO optical observations
  65. GRB 260117A: ZTSh optical upper limit
  66. EP260119a: COLIBRÍ optical counterpart candidate
  67. EP260119a: preliminary result from the EP-FXT observation
  68. GRB 260110A: SVOM detection of a burst through offline search
  69. EP260119a: EP-WXT detection of a fast X-ray transient
  70. Swift GRB260118.48: Global MASTER-Net observations report
  71. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  72. SVOM GRB260117.82: Global MASTER-Net observations report
  73. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  74. Swift trigger on the HMXB 1A 1118-61
  75. GRB 260117A: SVOM/VT optical candidate
  76. GRB 260117A: SVOM/C-GFT upper limit
  77. GRB 260117A: Swift-XRT observations
  78. GRB 260117A: Swift ToO observations
  79. GRB 260117A: SVOM detection of a long faint burst
  80. EP 260116a: COLIBRÍ optical upper limit
  81. Swift triggered on the HMXB 1A 1118-61
  82. GRB 260115A: GECAM-B observation
  83. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  84. EP260116a: Liverpool Telescope upper limits
  85. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  86. EP260116A: 1.3m DFOT optical upper limit
  87. GRB 260114A: VLT/MUSE spectroscopic observations
  88. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  89. EP260116a: Global MASTER-Net observations report
  90. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  91. EP260116a: Xinglong optical upper limit
  92. EP260116a: Einstein Probe detection of an X-ray transient
  93. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  94. IceCube Alert 260115.73: Global MASTER-Net observations report
  95. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  97. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  98. Fermi GRB 260115A: Global MASTER-Net observations report
  99. GRB 260115A: Fermi GBM Final Real-time Localization
  100. GRB260114A: STEP/T80S optical limits

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