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

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