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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"

18693 results found.

  1. GRB 250430A: Swift-XRT refined Analysis
  2. GRB 250430A: Swift/UVOT Detection
  3. GRB 250430A: Enhanced Swift-XRT position
  4. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  5. GRB 250430A: DDOTI Optical Observations
  6. GRB 250430A: Leavitt Observatory optical upper limit
  7. GRB 250430A: Bassano Bresciano Observatory upper limit
  8. GRB 250430A : MITSuME Akeno optical upper limits
  9. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  10. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  11. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  12. GRB 250430A: AKO Optical Afterglow Detection
  13. GRB 250430A: Swift detection of a burst with optical counterpart
  14. Swift GRB250430.73: Global MASTER-Net observations report
  15. GRB 250427A: Swift/UVOT Detection
  16. EP250427a: EP-FXT follow-up observations
  17. GRB 250427A: Swift-XRT refined Analysis
  18. GRB 250424A: LCO optical observation
  19. GRB 250424A: Swift-BAT refined analysis
  20. GRB 250424A: SVOM/GRM observation of a long burst
  21. GRB 250424A: PRIME near-infrared detection
  22. GRB 250424A: WINTER J-band detection
  23. GRB 250424A: EIRSAT-1 GMOD Detection
  24. GRB 250424A: Swift/UVOT Detection
  25. Konus-Wind detection of GRB 250424A
  26. GRB 250424A: Skynet Optical Observations
  27. GRB 250424A: Kilonova-Catcher optical afterglow detection
  28. GRB 250424A: Swift-XRT refined Analysis
  29. GRB 250424A: Enhanced Swift-XRT position
  30. GRB 250424A: AstroSat CZTI detection of a bright long burst
  31. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  32. GRB 250424A: BlackGEM optical afterglow detection
  33. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  34. GRB 250424A: likely host galaxy
  35. GRB 250424A: DDOTI Afterglow Detection
  36. GRB 250424A: REM optical/NIR afterglow detection
  37. GRB 250424A: Swift detection of a burst with an optical counterpart
  38. Swift GRB250424A: Global MASTER-Net observations report
  39. Swift GRB250424A: Global MASTER-Net OT detection
  40. SVOM/sb25042207: XRT observations
  41. EP250421a: NOT optical observations
  42. EP250421a: Swift/XRT counterpart detection
  43. GRB 250419A: Swift/UVOT Follow up
  44. GRB 250419A: LCO optical afterglow multi-band observations
  45. GRB 250419A: Mondy and AbAO Optical Observations
  46. GRB 250419A: Swift-XRT localisation
  47. GRB 250419A: Swift-XRT refined Analysis
  48. EP250416a: Swift/XRT counterpart fading
  49. EP20250416a: Swift/XRT counterpart detection
  50. GRB 250407A: Mondy and AbAO Optical Observations
  51. IceCube-250406A: Swift-XRT observations
  52. IPN triangulation of GRB 250407A
  53. GRB 250407A: LCO detection of a fading optical counterpart
  54. EP250407a: Swift-XRT observations
  55. Konus-Wind detection of GRB 250407A
  56. GRB 250407A: SVOM/GRM observation of a bright long burst
  57. GRB 250407A: EP-WXT afterglow detection
  58. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  59. GRB 250407A: Fermi GBM Detection
  60. GRB 250407A: Swift-XRT afterglow detection
  61. GRB 250407A: Swift ToO observations
  62. GRB 250407A: SRG/ART-XC afterglow detection
  63. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  64. IPN triangulation of GRB 250406B (short/hard)
  65. GRB 250331D: Swift-XRT afterglow detection
  66. GRB 250403A: Montarrenti Observatory optical detection
  67. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  68. GRB 250331C Swift-BAT refined analysis
  69. GRB 250331B Swift-BAT refined analysis
  70. GRB 250330A Swift-BAT refined analysis
  71. EP250321A: J band upper limit by SYSU 80cm telescope
  72. GRB 250403A: Swift/UVOT Detection
  73. GRB 250402A: Swift/UVOT Upper Limits
  74. GRB 250403A: LCO optical counterpart detection
  75. GRB 250402A: EP-FXT afterglow detection
  76. GRB 250403A: Swift-XRT observations
  77. GRB 250402A: Swift-XRT observations
  78. GRB 250225B: VLT host galaxy redshift z = 0.950
  79. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  80. GRB 250329B: Swift/UVOT Upper Limit
  81. GRB 250329A: Swift/UVOT Upper Limit
  82. GRB 250327B: Swift/UVOT Detection
  83. GRB 250327A: Swift/UVOT Upper Limits
  84. GRB250331D: AbAO optical observations
  85. GRB 250331D: Fermi GBM observation
  86. GRB 250331C: Swift/UVOT Upper Limits
  87. GRB 250331B: Swift/UVOT Upper Limits
  88. GRB 250331D: Swift-XRT observations
  89. GRB 250331C: Swift-XRT refined Analysis
  90. GRB 250331B: Swift-XRT refined Analysis
  91. GRB 250331B: Swift-XRT refined Analysis
  92. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  93. GRB 250327A Swift-BAT refined analysis
  94. GRB 250329B: CAHA 2.2m telescope optical limit
  95. GRB 250331D: Swift ToO observations
  96. Swift GRB 250331C: Global MASTER-Net observations report
  97. Swift GRB 250331B: Global MASTER-Net observations report
  98. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  99. GRB 250331C: Enhanced Swift-XRT position
  100. GRB 250331B: Enhanced Swift-XRT position

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