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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. Swift GRB260122.97: Global MASTER-Net observations report
  2. EP260119a: Assy AZT-20 optical observations
  3. EP260119a: Mondy and SAO RAS optical upper limits
  4. GRB 260122A: Fermi GBM Final Real-time Localization
  5. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  6. EP260119a: Xinglong optical upper limit
  7. The EP-WXT trigger 01709251871 is likely a flaring star
  8. Fermi GRB 260120C: Global MASTER-Net observations report
  9. GRB 260120B: Swift-BAT refined analysis
  10. GRB 260120B: Swift-XRT refined Analysis
  11. EP260116a: COLIBRÍ further observations
  12. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  13. GRB 260120B: Fermi GBM Observation
  14. EP260105a: GTC/HiPERCAM optical observations
  15. GRB 260120B: Swift/UVOT Detection
  16. GRB 260120B: COLIBRÍ optical upper limits
  17. SVOM GRB260121.06: Global MASTER-Net observations report
  18. GRB 260120B: Enhanced Swift-XRT position
  19. GRB 260120B: SVOM/C-GFT optical counterpart detection
  20. GRB 260120C: Fermi GBM Final Real-time Localization
  21. GRB 260101A: 239Alferov CubeSat detection
  22. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  23. GRB 260120B: Swift detection of a burst
  24. Swift GRB260120B: Global MASTER-Net observations report
  25. GRB 260120B: Fermi GBM Final Real-time Localization
  26. EP260119A: Mondy I-Band Observations
  27. Fermi trigger No 790601190: Global MASTER-Net observations report
  28. Fermi trigger No 790570272: Global MASTER-Net observations report
  29. GRB 260114A: Swift/UVOT Upper Limits
  30. EP260119a: Liverpool Telescope optical follow-up observations
  31. GRB 251202A: further radio observations with the VLA
  32. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  33. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  34. EP260119a: KAIT optical observations
  35. GRB 260120A: Fermi GBM Final Real-time Localization
  36. EP260119a: SVOM/VT optical observation
  37. EP260119a: update of EP-FXT follow-up observation
  38. EP260119a: NOT optical observations
  39. EP260119a: SAO RAS optical observations
  40. SVOM GRB260119.92: Global MASTER-Net observations report
  41. SVOM GRB260119.92: Global MASTER-Net observations report
  42. SVOM GRB260119.90: Global MASTER-Net observations report
  43. EP260116a: COLIBRÍ detection of a fading optical source
  44. GRB 251208D: SVOM/ECLAIRs refined analysis
  45. GRB 251208D: SVOM/ECLAIRs refined analysis
  46. GRB 260117A: Swift-XRT afterglow detection
  47. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  48. EP260119a: Global MASTER-Net observations report
  49. GRB 260115A: AstroSat CZTI detection
  50. EP260119a: LCO optical observations
  51. GRB 260117A: ZTSh optical upper limit
  52. EP260119a: COLIBRÍ optical counterpart candidate
  53. EP260119a: preliminary result from the EP-FXT observation
  54. GRB 260110A: SVOM detection of a burst through offline search
  55. EP260119a: EP-WXT detection of a fast X-ray transient
  56. Swift GRB260118.48: Global MASTER-Net observations report
  57. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. SVOM GRB260117.82: Global MASTER-Net observations report
  59. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  60. Swift trigger on the HMXB 1A 1118-61
  61. GRB 260117A: SVOM/VT optical candidate
  62. GRB 260117A: SVOM/C-GFT upper limit
  63. GRB 260117A: Swift-XRT observations
  64. GRB 260117A: Swift ToO observations
  65. GRB 260117A: SVOM detection of a long faint burst
  66. EP 260116a: COLIBRÍ optical upper limit
  67. Swift triggered on the HMXB 1A 1118-61
  68. GRB 260115A: GECAM-B observation
  69. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  70. EP260116a: Liverpool Telescope upper limits
  71. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  72. EP260116A: 1.3m DFOT optical upper limit
  73. GRB 260114A: VLT/MUSE spectroscopic observations
  74. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  75. EP260116a: Global MASTER-Net observations report
  76. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  77. EP260116a: Xinglong optical upper limit
  78. EP260116a: Einstein Probe detection of an X-ray transient
  79. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  80. IceCube Alert 260115.73: Global MASTER-Net observations report
  81. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  83. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  84. Fermi GRB 260115A: Global MASTER-Net observations report
  85. GRB 260115A: Fermi GBM Final Real-time Localization
  86. GRB260114A: STEP/T80S optical limits
  87. GRB 251222A: radio detection with the VLA
  88. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  89. Konus-Wind detection of GRB 260114A
  90. GRB 260114A: Swift-XRT refined Analysis
  91. GRB 260114A: 6 GHz VLA observations
  92. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  93. GRB 260114A : MITSuME Akeno optical upper limits
  94. GRB 260114A: COLIBRÍ optical upper limits
  95. GRB 260114A: TNG NIR upper limit
  96. GRB 260114A: NOT optical observations
  97. Konus-Wind detection of GRB 251230A / EP251230a
  98. GRB 260114A: SVOM/GRM observation of a short burst
  99. Swift GRB 260114A: Global MASTER-Net observations report
  100. GRB 260114A: GECAM-B observation of a short burst

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