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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"

19539 results found.

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

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