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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"

18632 results found.

  1. Konus-Wind detection of GRB 250424A
  2. GRB 250424A: Skynet Optical Observations
  3. GRB 250424A: Kilonova-Catcher optical afterglow detection
  4. GRB 250424A: Swift-XRT refined Analysis
  5. GRB 250424A: Enhanced Swift-XRT position
  6. GRB 250424A: AstroSat CZTI detection of a bright long burst
  7. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  8. GRB 250424A: BlackGEM optical afterglow detection
  9. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  10. GRB 250424A: likely host galaxy
  11. GRB 250424A: DDOTI Afterglow Detection
  12. GRB 250424A: REM optical/NIR afterglow detection
  13. GRB 250424A: Swift detection of a burst with an optical counterpart
  14. Swift GRB 250424A: Global MASTER-Net observations report
  15. Swift GRB 250424A: Global MASTER-Net OT detection
  16. SVOM/sb25042207: XRT observations
  17. EP250421a: NOT optical observations
  18. EP250421a: Swift/XRT counterpart detection
  19. GRB 250419A: Swift/UVOT Follow up
  20. GRB 250419A: LCO optical afterglow multi-band observations
  21. GRB 250419A: Mondy and AbAO Optical Observations
  22. GRB 250419A: Swift-XRT localisation
  23. GRB 250419A: Swift-XRT refined Analysis
  24. EP250416a: Swift/XRT counterpart fading
  25. EP20250416a: Swift/XRT counterpart detection
  26. GRB 250407A: Mondy and AbAO Optical Observations
  27. IceCube-250406A: Swift-XRT observations
  28. IPN triangulation of GRB 250407A
  29. GRB 250407A: LCO detection of a fading optical counterpart
  30. EP250407a: Swift-XRT observations
  31. Konus-Wind detection of GRB 250407A
  32. GRB 250407A: SVOM/GRM observation of a bright long burst
  33. GRB 250407A: EP-WXT afterglow detection
  34. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  35. GRB 250407A: Fermi GBM Detection
  36. GRB 250407A: Swift-XRT afterglow detection
  37. GRB 250407A: Swift ToO observations
  38. GRB 250407A: SRG/ART-XC afterglow detection
  39. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  40. IPN triangulation of GRB 250406B (short/hard)
  41. GRB 250331D: Swift-XRT afterglow detection
  42. GRB 250403A: Montarrenti Observatory optical detection
  43. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  44. GRB 250331C Swift-BAT refined analysis
  45. GRB 250331B Swift-BAT refined analysis
  46. GRB 250330A Swift-BAT refined analysis
  47. EP250321A: J band upper limit by SYSU 80cm telescope
  48. GRB 250403A: Swift/UVOT Detection
  49. GRB 250402A: Swift/UVOT Upper Limits
  50. GRB 250403A: LCO optical counterpart detection
  51. GRB 250402A: EP-FXT afterglow detection
  52. GRB 250403A: Swift-XRT observations
  53. GRB 250402A: Swift-XRT observations
  54. GRB 250225B: VLT host galaxy redshift z = 0.950
  55. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  56. GRB 250329B: Swift/UVOT Upper Limit
  57. GRB 250329A: Swift/UVOT Upper Limit
  58. GRB 250327B: Swift/UVOT Detection
  59. GRB 250327A: Swift/UVOT Upper Limits
  60. GRB250331D: AbAO optical observations
  61. GRB 250331D: Fermi GBM observation
  62. GRB 250331C: Swift/UVOT Upper Limits
  63. GRB 250331B: Swift/UVOT Upper Limits
  64. GRB 250331D: Swift-XRT observations
  65. GRB 250331C: Swift-XRT refined Analysis
  66. GRB 250331B: Swift-XRT refined Analysis
  67. GRB 250331B: Swift-XRT refined Analysis
  68. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  69. GRB 250327A Swift-BAT refined analysis
  70. GRB 250329B: CAHA 2.2m telescope optical limit
  71. GRB 250331D: Swift ToO observations
  72. Swift GRB 250331C: Global MASTER-Net observations report
  73. Swift GRB 250331B: Global MASTER-Net observations report
  74. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  75. GRB 250331C: Enhanced Swift-XRT position
  76. GRB 250331B: Enhanced Swift-XRT position
  77. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  78. GRB 250329B: Swift-XRT confirmation of fading
  79. GRB20250327B: 45th Parallel Observatory upper limit
  80. GRB 250328A: Swift/UVOT Detection
  81. GRB 250328A: Swift-XRT refined Analysis
  82. GRB 250330A: Fermi GBM Observation
  83. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  84. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  85. GRB 250331C: Prompt enhanced Swift-XRT position
  86. GRB 250331C: Swift detection of a burst
  87. GRB 250331B: Swift detection of a burst
  88. GRB 250330A: SVOM/VT optical upper limit
  89. GRB 250330A: BOOTES-7 early optical upper limit
  90. GRB 250330A: Swift/UVOT Upper Limits
  91. GRB 250330A: Swift-XRT afterglow detection
  92. GRB 250330A: Fermi GBM Final Localization
  93. GRB 250330A: Prompt Swift-XRT position
  94. GRB 250329B: Swift-XRT afterglow detection
  95. GRB 250330A: Swift detection of a burst
  96. Swift GRB250330.26: Global MASTER-Net observations report
  97. GRB 250329B: SVOM/C-GFT optical upper limit
  98. GRB 250329B: SVOM/VT optical upper limit
  99. GRB 250329A: Swift-XRT afterglow detection
  100. GRB 250328A: SVOM/C-GFT optical upper limit

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