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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"

28056 results found.

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

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