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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"

28053 results found.

  1. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  2. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  3. EP260128a: NOT optical counterpart candidate
  4. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  5. EP260128a: Liverpool Telescope optical observations and possible counterpart
  6. EP260128a: LCO optical upper limits
  7. EP260128a: Global MASTER-Net observations report
  8. EP260128a: Einstein Probe detection of an X-ray transient
  9. Fermi GRB 260127A: Global MASTER-Net observations report
  10. GRB 260127A: Fermi GBM Observation
  11. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  12. GRB 260127A: COLIBRÍ optical observations
  13. EP260126a: Seimei/TriCCS optical upper limit
  14. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  15. GRB 260127A: Swift-XRT refined Analysis
  16. GRB 260127A: SVOM/C-GFT optical observations
  17. GRB 260127A: Enhanced Swift-XRT position
  18. Fermi GRB 260127B: Global MASTER-Net observations report
  19. Swift GRB 260127A: Global MASTER-Net observations report
  20. GRB 260127A: LCO optical afterglow discovery
  21. GRB 260127A: Swift detection of a burst
  22. GRB 260125A: Swift-XRT observations
  23. EP260126a: Optical upper limit with Kinder observations
  24. EP260126a: Liverpool Telescope optical upper limits
  25. EP260126a: Further NOT optical upper limits
  26. EP260126a: COLIBRÍ optical upper limits
  27. EP260126a: NOT optical observations
  28. EP260126a: Einstein Probe detection of a fast X-ray transient
  29. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  30. GRB 251222A: SVOM/ECLAIRs refined analysis
  31. GRB 260125A: GOTO candidate optical counterpart
  32. Fermi GRB 260125B: Global MASTER-Net observations report
  33. GRB 260114A: SVOM/VT optical upper limits
  34. GRB 260122B: Swift-BAT refined analysis
  35. GRB 260120B: SVOM/GRM observation
  36. Swift GRB260122.97: Global MASTER-Net observations report
  37. EP260119a: Assy AZT-20 optical observations
  38. EP260119a: Mondy and SAO RAS optical upper limits
  39. EP260119a: Xinglong optical upper limit
  40. Fermi GRB 260120C: Global MASTER-Net observations report
  41. GRB 260120B: Swift-BAT refined analysis
  42. GRB 260120B: Swift-XRT refined Analysis
  43. EP260116a: COLIBRÍ further observations
  44. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  45. GRB 260120B: Fermi GBM Observation
  46. EP260105a: GTC/HiPERCAM optical observations
  47. GRB 260120B: Swift/UVOT Detection
  48. GRB 260120B: COLIBRÍ optical upper limits
  49. SVOM GRB260121.06: Global MASTER-Net observations report
  50. GRB 260120B: Enhanced Swift-XRT position
  51. GRB 260120B: SVOM/C-GFT optical counterpart detection
  52. GRB 260101A: 239Alferov CubeSat detection
  53. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  54. GRB 260120B: Swift detection of a burst
  55. Swift GRB260120B: Global MASTER-Net observations report
  56. EP260119A: Mondy I-Band Observations
  57. Fermi trigger No 790601190: Global MASTER-Net observations report
  58. Fermi trigger No 790570272: Global MASTER-Net observations report
  59. GRB 260114A: Swift/UVOT Upper Limits
  60. EP260119a: Liverpool Telescope optical follow-up observations
  61. GRB 251202A: further radio observations with the VLA
  62. EP260119a: KAIT optical observations
  63. EP260119a: SVOM/VT optical observation
  64. EP260119a: NOT optical observations
  65. EP260119a: SAO RAS optical observations
  66. SVOM GRB260119.92: Global MASTER-Net observations report
  67. SVOM GRB260119.92: Global MASTER-Net observations report
  68. SVOM GRB260119.90: Global MASTER-Net observations report
  69. EP260116a: COLIBRÍ detection of a fading optical source
  70. GRB 260117A: Swift-XRT afterglow detection
  71. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  72. EP260119a: Global MASTER-Net observations report
  73. EP260119a: LCO optical observations
  74. GRB 260117A: ZTSh optical upper limit
  75. EP260119a: COLIBRÍ optical counterpart candidate
  76. EP260119a: EP-WXT detection of a fast X-ray transient
  77. Swift GRB260118.48: Global MASTER-Net observations report
  78. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. SVOM GRB260117.82: Global MASTER-Net observations report
  80. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  81. Swift trigger on the HMXB 1A 1118-61
  82. GRB 260117A: SVOM/VT optical candidate
  83. GRB 260117A: SVOM/C-GFT upper limit
  84. GRB 260117A: Swift-XRT observations
  85. GRB 260117A: SVOM detection of a long faint burst
  86. EP 260116a: COLIBRÍ optical upper limit
  87. Swift triggered on the HMXB 1A 1118-61
  88. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  89. EP260116a: Liverpool Telescope upper limits
  90. FRB 20251229A: Updated CHIME/FRB Baseband Localization of FRB 20251229A
  91. EP260116A: 1.3m DFOT optical upper limit
  92. GRB 260114A: VLT/MUSE spectroscopic observations
  93. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  94. EP260116a: Global MASTER-Net observations report
  95. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  96. EP260116a: Xinglong optical upper limit
  97. EP260116a: Einstein Probe detection of an X-ray transient
  98. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  99. IceCube Alert 260115.73: Global MASTER-Net observations report
  100. GRB 260115A: BALROG localization (Fermi Trigger 790192010 / GRB 260115741)

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