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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"

19936 results found.

  1. GRB 260925A: Swift-XRT refined Analysis
  2. Swift Trigger 1513439 is probably not a GRB
  3. GRB 260925A: Swift/UVOT Upper Limits
  4. Konus-Wind detection of GRB 260924A
  5. GRB 260922A: Glowbug gamma-ray detection
  6. GRB 260925A: Enhanced Swift-XRT position
  7. GRB 260925A: COLIBRÍ optical upper limits
  8. GRB 260925A: FRAM-Auger optical limit
  9. GRB 260924A: Ondrejov D50 optical afterglow detection
  10. GRB 260924A: SVOM/GRM observation
  11. GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
  12. GRB 260925A: Swift detection of a burst
  13. GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
  14. GRB 260924A: Swift/UVOT Detection
  15. GRB 260924A: Swift-BAT refined analysis
  16. GRB 260924A: NuSTAR detection of prompt emission
  17. GRB 260924A: Swift/UVOT Upper Limits
  18. GRB 260924A: Swift-XRT refined Analysis
  19. Konus-Wind detection of GRB 260922A
  20. GRB 260922A: NuSTAR detection of prompt emission
  21. GRB 260921A: NuSTAR detection of prompt emission
  22. GRB 260921A: SVOM/GRM observation
  23. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  24. GRB 260924A: Fermi GRB Observation
  25. Konus-Wind detection of GRB 260921A (possible merger-origin)
  26. GRB 260924A: Fermi-LAT detection of a bright burst
  27. GRB 260924A: AstroSat CZTI detection
  28. GRB 260924A: NOT optical counterpart confirmation
  29. GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
  30. GRB 260922A: CALET Gamma-Ray Burst Monitor detection
  31. GRB 260924A: Enhanced Swift-XRT position
  32. GRB 260924A: Swift detection of a burst
  33. Trigger_21914: Swift ToO observations
  34. GRB 260922A: Ondrejov D50 optical limit
  35. GRB 260922A: Swift-BAT refined analysis
  36. GRB 260922A: Swift/UVOT Upper Limits
  37. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  38. GRB 260922A: COLIBRÍ optical upper limits
  39. GRB 260922A: Swift-XRT refined Analysis
  40. GRB 260922A: Enhanced Swift-XRT position
  41. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  42. GRB 260922A: SVOM/C-GFT optical upper limit
  43. GRB 260922A: Swift detection of a burst
  44. GRB 260921A: AstroSat CZTI detection
  45. GRB 260921A: Swift-BAT refined analysis
  46. GRB 260921A: Fermi GBM Observation
  47. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  48. Swift GRB 260921A: Global MASTER-Net observations report
  49. GRB 260921A: Swift detection of a burst
  50. GRB 260915A: VLT optical and near-infrared upper limits
  51. GRB 260915A: Swift-XRT afterglow detection
  52. GRB 260909A: Swift-XRT observations
  53. GRB 260915A: Swift ToO observations
  54. GRB 260909A: Swift ToO observations
  55. GRB 260903A: Swift-XRT observations
  56. GRB 260903A: Swift ToO observations
  57. NuSTAR 260828: a 1100s hard X-ray transient
  58. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  59. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  60. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  61. AT2026nik: EP-FXT X-ray counterpart
  62. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  63. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  64. IPN triangulation of a bright burst from SGR 1E1841-045
  65. EP260321a: Chandra X-ray Non-detection
  66. Swift BAT trigger 1500295: A solar flare
  67. Swift BAT trigger 1500287: A solar flare
  68. Swift BAT trigger 1500148: A solar flare
  69. Retraction of GCN 43965: GRB is actually solar flare
  70. GRB 260312A: Swift detection of a burst
  71. GRB 260208A: radio detection with the VLA
  72. IPN triangulation of GRB 260212A
  73. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  74. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  75. GRB 260208A: Swift UVOT detection
  76. GRB 260208A: LCO detection of the optical counterpart
  77. GRB 260208B: refined analysis of the EP-FXT observation
  78. GRB 260204A: Swift-XRT afterglow detection
  79. GRB 260208A: Fermi GBM Observation
  80. GRB 260208B: Swift-XRT observations
  81. GRB 260204A: Swift/UVOT Upper Limits
  82. GRB 260208B: EP-FXT observation
  83. GRB 260208B: SVOM/VT optical candidate
  84. GRB 260208A: SVOM/VT optical observation
  85. GRB 260208A: Swift-XRT observations
  86. GRB 260208B: Swift ToO observations
  87. GRB 260208B: Fermi-LAT detection
  88. GRB 260208A: Fermi-LAT detection
  89. GRB 260208A: Swift ToO observations
  90. GRB 260206A: Swift-XRT observations
  91. GRB 260206A: Tiled Swift observations
  92. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  93. GRB 260204A: Swift-XRT observations
  94. GRB 260204A: SVOM/VT optical candidate
  95. GRB 251230A: MeerLICHT afterglow detection
  96. GRB 260127A: GECAM-B observation
  97. GRB 260127B: AstroSat CZTI detection
  98. IPN triangulation of GRB 260121A
  99. GRB 260127A: Swift-BAT refined analysis
  100. GRB 260127B: Swift-XRT observations

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