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

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