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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: GOTO candidate optical counterpart
  2. Fermi GRB 260125B: Global MASTER-Net observations report
  3. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  4. GRB 260125B: Fermi GBM Final Real-time Localization
  5. GRB 260125A: Fermi GBM Final Real-time Localization
  6. GRB 260114A: SVOM/VT optical upper limits
  7. GRB 260120A: AstroSat CZTI detection
  8. GRB 260122B: Swift-BAT refined analysis
  9. GRB 260120B: SVOM/GRM observation
  10. GRB 260120A: GECAM-B observation
  11. GRB 260120B: AstroSat CZTI detection
  12. GRB 260114A: Insight-HXMT/HE detection
  13. GRB 260122B: Swift detection of a burst
  14. Swift GRB260122.97: Global MASTER-Net observations report
  15. EP260119a: Assy AZT-20 optical observations
  16. EP260119a: Mondy and SAO RAS optical upper limits
  17. GRB 260122A: Fermi GBM Final Real-time Localization
  18. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  19. EP260119a: Xinglong optical upper limit
  20. The EP-WXT trigger 01709251871 is likely a flaring star
  21. Fermi GRB 260120C: Global MASTER-Net observations report
  22. GRB 260120B: Swift-BAT refined analysis
  23. GRB 260120B: Swift-XRT refined Analysis
  24. EP260116a: COLIBRÍ further observations
  25. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  26. GRB 260120B: Fermi GBM Observation
  27. EP260105a: GTC/HiPERCAM optical observations
  28. GRB 260120B: Swift/UVOT Detection
  29. GRB 260120B: COLIBRÍ optical upper limits
  30. SVOM GRB260121.06: Global MASTER-Net observations report
  31. GRB 260120B: Enhanced Swift-XRT position
  32. GRB 260120B: SVOM/C-GFT optical counterpart detection
  33. GRB 260120C: Fermi GBM Final Real-time Localization
  34. GRB 260101A: 239Alferov CubeSat detection
  35. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  36. GRB 260120B: Swift detection of a burst
  37. Swift GRB260120B: Global MASTER-Net observations report
  38. GRB 260120B: Fermi GBM Final Real-time Localization
  39. EP260119A: Mondy I-Band Observations
  40. Fermi trigger No 790601190: Global MASTER-Net observations report
  41. Fermi trigger No 790570272: Global MASTER-Net observations report
  42. GRB 260114A: Swift/UVOT Upper Limits
  43. EP260119a: Liverpool Telescope optical follow-up observations
  44. GRB 251202A: further radio observations with the VLA
  45. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  46. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  47. EP260119a: KAIT optical observations
  48. GRB 260120A: Fermi GBM Final Real-time Localization
  49. EP260119a: SVOM/VT optical observation
  50. EP260119a: update of EP-FXT follow-up observation
  51. EP260119a: NOT optical observations
  52. EP260119a: SAO RAS optical observations
  53. SVOM GRB260119.92: Global MASTER-Net observations report
  54. SVOM GRB260119.92: Global MASTER-Net observations report
  55. SVOM GRB260119.90: Global MASTER-Net observations report
  56. EP260116a: COLIBRÍ detection of a fading optical source
  57. GRB 251208D: SVOM/ECLAIRs refined analysis
  58. GRB 251208D: SVOM/ECLAIRs refined analysis
  59. GRB 260117A: Swift-XRT afterglow detection
  60. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  61. EP260119a: Global MASTER-Net observations report
  62. GRB 260115A: AstroSat CZTI detection
  63. EP260119a: LCO optical observations
  64. GRB 260117A: ZTSh optical upper limit
  65. EP260119a: COLIBRÍ optical counterpart candidate
  66. EP260119a: preliminary result from the EP-FXT observation
  67. GRB 260110A: SVOM detection of a burst through offline search
  68. EP260119a: EP-WXT detection of a fast X-ray transient
  69. Swift GRB260118.48: Global MASTER-Net observations report
  70. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. SVOM GRB260117.82: Global MASTER-Net observations report
  72. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  73. Swift trigger on the HMXB 1A 1118-61
  74. GRB 260117A: SVOM/VT optical candidate
  75. GRB 260117A: SVOM/C-GFT upper limit
  76. GRB 260117A: Swift-XRT observations
  77. GRB 260117A: Swift ToO observations
  78. GRB 260117A: SVOM detection of a long faint burst
  79. EP 260116a: COLIBRÍ optical upper limit
  80. Swift triggered on the HMXB 1A 1118-61
  81. GRB 260115A: GECAM-B observation
  82. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  83. EP260116a: Liverpool Telescope upper limits
  84. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  85. EP260116A: 1.3m DFOT optical upper limit
  86. GRB 260114A: VLT/MUSE spectroscopic observations
  87. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  88. EP260116a: Global MASTER-Net observations report
  89. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  90. EP260116a: Xinglong optical upper limit
  91. EP260116a: Einstein Probe detection of an X-ray transient
  92. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  93. IceCube Alert 260115.73: Global MASTER-Net observations report
  94. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  96. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  97. Fermi GRB 260115A: Global MASTER-Net observations report
  98. GRB 260115A: Fermi GBM Final Real-time Localization
  99. GRB260114A: STEP/T80S optical limits
  100. GRB 251222A: radio detection with the VLA

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