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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 260122A: Fermi GBM Final Real-time Localization
  2. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  3. EP260119a: Xinglong optical upper limit
  4. The EP-WXT trigger 01709251871 is likely a flaring star
  5. Fermi GRB 260120C: Global MASTER-Net observations report
  6. GRB 260120B: Swift-BAT refined analysis
  7. GRB 260120B: Swift-XRT refined Analysis
  8. EP260116a: COLIBRÍ further observations
  9. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  10. GRB 260120B: Fermi GBM Observation
  11. EP260105a: GTC/HiPERCAM optical observations
  12. GRB 260120B: Swift/UVOT Detection
  13. GRB 260120B: COLIBRÍ optical upper limits
  14. SVOM GRB260121.06: Global MASTER-Net observations report
  15. GRB 260120B: Enhanced Swift-XRT position
  16. GRB 260120B: SVOM/C-GFT optical counterpart detection
  17. GRB 260120C: Fermi GBM Final Real-time Localization
  18. GRB 260101A: 239Alferov CubeSat detection
  19. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  20. GRB 260120B: Swift detection of a burst
  21. Swift GRB260120B: Global MASTER-Net observations report
  22. GRB 260120B: Fermi GBM Final Real-time Localization
  23. EP260119A: Mondy I-Band Observations
  24. Fermi trigger No 790601190: Global MASTER-Net observations report
  25. Fermi trigger No 790570272: Global MASTER-Net observations report
  26. GRB 260114A: Swift/UVOT Upper Limits
  27. EP260119a: Liverpool Telescope optical follow-up observations
  28. GRB 251202A: further radio observations with the VLA
  29. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  30. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  31. EP260119a: KAIT optical observations
  32. GRB 260120A: Fermi GBM Final Real-time Localization
  33. EP260119a: SVOM/VT optical observation
  34. EP260119a: update of EP-FXT follow-up observation
  35. EP260119a: NOT optical observations
  36. EP260119a: SAO RAS optical observations
  37. SVOM GRB260119.92: Global MASTER-Net observations report
  38. SVOM GRB260119.92: Global MASTER-Net observations report
  39. SVOM GRB260119.90: Global MASTER-Net observations report
  40. EP260116a: COLIBRÍ detection of a fading optical source
  41. GRB 251208D: SVOM/ECLAIRs refined analysis
  42. GRB 251208D: SVOM/ECLAIRs refined analysis
  43. GRB 260117A: Swift-XRT afterglow detection
  44. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  45. EP260119a: Global MASTER-Net observations report
  46. GRB 260115A: AstroSat CZTI detection
  47. EP260119a: LCO optical observations
  48. GRB 260117A: ZTSh optical upper limit
  49. EP260119a: COLIBRÍ optical counterpart candidate
  50. EP260119a: preliminary result from the EP-FXT observation
  51. GRB 260110A: SVOM detection of a burst through offline search
  52. EP260119a: EP-WXT detection of a fast X-ray transient
  53. Swift GRB260118.48: Global MASTER-Net observations report
  54. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. SVOM GRB260117.82: Global MASTER-Net observations report
  56. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  57. Swift trigger on the HMXB 1A 1118-61
  58. GRB 260117A: SVOM/VT optical candidate
  59. GRB 260117A: SVOM/C-GFT upper limit
  60. GRB 260117A: Swift-XRT observations
  61. GRB 260117A: Swift ToO observations
  62. GRB 260117A: SVOM detection of a long faint burst
  63. EP 260116a: COLIBRÍ optical upper limit
  64. Swift triggered on the HMXB 1A 1118-61
  65. GRB 260115A: GECAM-B observation
  66. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  67. EP260116a: Liverpool Telescope upper limits
  68. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  69. EP260116A: 1.3m DFOT optical upper limit
  70. GRB 260114A: VLT/MUSE spectroscopic observations
  71. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  72. EP260116a: Global MASTER-Net observations report
  73. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  74. EP260116a: Xinglong optical upper limit
  75. EP260116a: Einstein Probe detection of an X-ray transient
  76. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  77. IceCube Alert 260115.73: Global MASTER-Net observations report
  78. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  79. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)
  80. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  81. Fermi GRB 260115A: Global MASTER-Net observations report
  82. GRB 260115A: Fermi GBM Final Real-time Localization
  83. GRB260114A: STEP/T80S optical limits
  84. GRB 251222A: radio detection with the VLA
  85. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  86. Konus-Wind detection of GRB 260114A
  87. GRB 260114A: Swift-XRT refined Analysis
  88. GRB 260114A: 6 GHz VLA observations
  89. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  90. GRB 260114A : MITSuME Akeno optical upper limits
  91. GRB 260114A: COLIBRÍ optical upper limits
  92. GRB 260114A: TNG NIR upper limit
  93. GRB 260114A: NOT optical observations
  94. Konus-Wind detection of GRB 251230A / EP251230a
  95. GRB 260114A: SVOM/GRM observation of a short burst
  96. Swift GRB 260114A: Global MASTER-Net observations report
  97. GRB 260114A: GECAM-B observation of a short burst
  98. GRB 260114A: Mondy optical observations
  99. GRB 260114A: Fermi GBM observation
  100. GRB 260112B: GECAM-B observation

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