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

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