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

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