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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"

19546 results found.

  1. GRB 260921A: Fermi GBM Observation
  2. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  3. Swift GRB 260921A: Global MASTER-Net observations report
  4. GRB 260921A: Swift detection of a burst
  5. GRB 260915A: VLT optical and near-infrared upper limits
  6. GRB 260915A: Swift-XRT afterglow detection
  7. GRB 260909A: Swift-XRT observations
  8. GRB 260915A: Swift ToO observations
  9. GRB 260909A: Swift ToO observations
  10. GRB 260903A: Swift-XRT observations
  11. GRB 260903A: Swift ToO observations
  12. NuSTAR 260828: a 1100s hard X-ray transient
  13. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  14. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  15. AT2026nik: EP-FXT X-ray counterpart
  16. SVOM GRB 260515A: Global MASTER-Net observations report
  17. EP260321a: Chandra X-ray Non-detection
  18. Swift BAT trigger 1500295: A solar flare
  19. Swift BAT trigger 1500287: A solar flare
  20. Swift BAT trigger 1500148: A solar flare
  21. Retraction of GCN 43965: GRB is actually solar flare
  22. GRB 260312A: Swift detection of a burst
  23. GRB 260208A: radio detection with the VLA
  24. IPN triangulation of GRB 260212A
  25. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  26. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  27. GRB 260208A: Swift UVOT detection
  28. GRB 260208A: LCO detection of the optical counterpart
  29. GRB 260208B: refined analysis of the EP-FXT observation
  30. GRB 260204A: Swift-XRT afterglow detection
  31. GRB 260208A: Fermi GBM Observation
  32. GRB 260208B: Swift-XRT observations
  33. GRB 260204A: Swift/UVOT Upper Limits
  34. GRB 260208B: EP-FXT observation
  35. GRB 260208B: SVOM/VT optical candidate
  36. GRB 260208A: SVOM/VT optical observation
  37. GRB 260208A: Swift-XRT observations
  38. GRB 260208B: Swift ToO observations
  39. GRB 260208B: Fermi-LAT detection
  40. GRB 260208A: Fermi-LAT detection
  41. GRB 260208A: Swift ToO observations
  42. GRB 260206A: Swift-XRT observations
  43. GRB 260206A: Tiled Swift observations
  44. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  45. GRB 260204A: Swift-XRT observations
  46. GRB 260204A: SVOM/VT optical candidate
  47. GRB 251230A: MeerLICHT afterglow detection
  48. GRB 260127A: GECAM-B observation
  49. GRB 260127B: AstroSat CZTI detection
  50. IPN triangulation of GRB 260121A
  51. GRB 260127A: Swift-BAT refined analysis
  52. GRB 260127B: Swift-XRT observations
  53. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  54. GRB 260127A: Fermi GBM Observation
  55. GRB 260127A: COLIBRÍ optical observations
  56. GRB 260127B: Swift ToO observations
  57. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  58. GRB 260127A: Swift-XRT refined Analysis
  59. GRB 260127A: SVOM/C-GFT optical observations
  60. GRB 260127A: Enhanced Swift-XRT position
  61. GRB 260127A: Prompt enhanced Swift-XRT position
  62. Swift GRB 260127A: Global MASTER-Net observations report
  63. GRB 260127A: Swift detection of a burst
  64. GRB 260125A: Swift-XRT observations
  65. Konus-Wind detection of GRB 260120B
  66. GRB 260125A: Swift ToO observations
  67. GRB 260114A: SVOM/VT optical upper limits
  68. GRB 260122B: Swift-BAT refined analysis
  69. GRB 260120B: SVOM/GRM observation
  70. GRB 260120B: AstroSat CZTI detection
  71. GRB 260114A: Insight-HXMT/HE detection
  72. GRB 260122B: Swift detection of a burst
  73. Swift GRB260122.97: Global MASTER-Net observations report
  74. GRB 260120B: Swift-BAT refined analysis
  75. GRB 260120B: Swift-XRT refined Analysis
  76. GRB 260120B: Fermi GBM Observation
  77. GRB 260120B: Swift/UVOT Detection
  78. GRB 260120B: COLIBRÍ optical upper limits
  79. GRB 260120B: Enhanced Swift-XRT position
  80. GRB 260120B: SVOM/C-GFT optical counterpart detection
  81. GRB 260101A: 239Alferov CubeSat detection
  82. GRB 260120B: Swift detection of a burst
  83. Swift GRB260120B: Global MASTER-Net observations report
  84. GRB 260114A: Swift/UVOT Upper Limits
  85. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  86. GRB 260117A: Swift-XRT afterglow detection
  87. GRB 260117A: ZTSh optical upper limit
  88. Swift GRB260118.48: Global MASTER-Net observations report
  89. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. Swift trigger on the HMXB 1A 1118-61
  91. GRB 260117A: SVOM/VT optical candidate
  92. GRB 260117A: SVOM/C-GFT upper limit
  93. GRB 260117A: Swift-XRT observations
  94. GRB 260117A: Swift ToO observations
  95. Swift triggered on the HMXB 1A 1118-61
  96. GRB 260114A: VLT/MUSE spectroscopic observations
  97. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  98. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  99. GRB260114A: STEP/T80S optical limits
  100. GRB 251222A: radio detection with the VLA

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