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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"

18400 results found.

  1. GRB 250509A: Swift-BAT refined analysis
  2. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  3. GRB 250510B: Fermi GBM Observation
  4. GRB 250510A: Swift-XRT observations
  5. GRB 250509A: Fermi GBM Observation
  6. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  7. GRB 250509A: Swift-XRT refined Analysis
  8. GRB 250507A: J-band observations with WINTER
  9. GRB 250509A: Enhanced Swift-XRT position
  10. GRB 250509A: Prompt enhanced Swift-XRT position
  11. Swift GRB 250509A: Global MASTER-Net observations report
  12. GRB 250509A: Swift detection of a burst
  13. GRB 250506A: NOT optical upper limits
  14. GRB 250506A: GECAM detection
  15. GRB 250506A: Swift-XRT afterglow detection
  16. GRB 250507A: Swift-XRT refined Analysis
  17. GRB 250506A: Swift/UVOT Upper Limits
  18. GRB 250430A / EP250430a: AstroSat CZTI detection
  19. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  20. GRB 250506A: Swift-XRT observations
  21. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  22. GRB 250504A: EIRSAT-1 GMOD Detection
  23. GRB 250506A: Swift ToO observations
  24. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  25. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  26. GRB 250506A: Swift XRT observations and possible counterpart detection
  27. GRB 250506A: TRT optical observations
  28. GRB 250504A: Swift-BAT refined analysis
  29. GRB 250430A: Swift-BAT refined analysis
  30. GRB 250504A: Swift-XRT refined Analysis
  31. GRB 250504A: VLT/X-shooter upper limits
  32. GRB 250504A: SVOM/VT upper limit
  33. GRB 250504A: REM optical/NIR observations
  34. GRB 250504A: MeerLICHT optical afterglow detection
  35. GRB 250504A: Fermi GBM Observation
  36. GRB 250504A: Enhanced Swift-XRT position
  37. GRB 250504A: Swift detection of a burst
  38. Swift GRB250504.98: Global MASTER-Net observations report
  39. GRB 250502A: Swift/UVOT Follow up
  40. GRB 250502A: Swift-XRT afterglow detection
  41. GRB 250502A: Swift ToO observations
  42. GRB 250430A: Swift-XRT refined Analysis
  43. GRB 250430A: Swift/UVOT Detection
  44. GRB 250430A: Enhanced Swift-XRT position
  45. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  46. GRB 250430A: DDOTI Optical Observations
  47. GRB 250430A: Leavitt Observatory optical upper limit
  48. GRB 250430A: Bassano Bresciano Observatory upper limit
  49. GRB 250430A : MITSuME Akeno optical upper limits
  50. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  51. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  52. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  53. GRB 250430A: AKO Optical Afterglow Detection
  54. GRB 250430A: Swift detection of a burst with optical counterpart
  55. Swift GRB250430.73: Global MASTER-Net observations report
  56. GRB 250427A: Swift/UVOT Detection
  57. EP250427a: EP-FXT follow-up observations
  58. GRB 250427A: Swift-XRT refined Analysis
  59. GRB 250424A: LCO optical observation
  60. GRB 250424A: Swift-BAT refined analysis
  61. GRB 250424A: SVOM/GRM observation of a long burst
  62. GRB 250424A: PRIME near-infrared detection
  63. GRB 250424A: WINTER J-band detection
  64. GRB 250424A: EIRSAT-1 GMOD Detection
  65. GRB 250424A: Swift/UVOT Detection
  66. Konus-Wind detection of GRB 250424A
  67. GRB 250424A: Skynet Optical Observations
  68. GRB 250424A: Kilonova-Catcher optical afterglow detection
  69. GRB 250424A: Swift-XRT refined Analysis
  70. GRB 250424A: Enhanced Swift-XRT position
  71. GRB 250424A: AstroSat CZTI detection of a bright long burst
  72. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  73. GRB 250424A: BlackGEM optical afterglow detection
  74. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  75. GRB 250424A: likely host galaxy
  76. GRB 250424A: DDOTI Afterglow Detection
  77. GRB 250424A: REM optical/NIR afterglow detection
  78. GRB 250424A: Swift detection of a burst with an optical counterpart
  79. Swift GRB250424A: Global MASTER-Net observations report
  80. Swift GRB250424A: Global MASTER-Net OT detection
  81. SVOM/sb25042207: XRT observations
  82. EP250421a: NOT optical observations
  83. EP250421a: Swift/XRT counterpart detection
  84. GRB 250419A: Swift/UVOT Follow up
  85. GRB 250419A: LCO optical afterglow multi-band observations
  86. GRB 250419A: Mondy and AbAO Optical Observations
  87. GRB 250419A: Swift-XRT localisation
  88. GRB 250419A: Swift-XRT refined Analysis
  89. EP250416a: Swift/XRT counterpart fading
  90. EP20250416a: Swift/XRT counterpart detection
  91. GRB 250407A: Mondy and AbAO Optical Observations
  92. IceCube-250406A: Swift-XRT observations
  93. IPN triangulation of GRB 250407A
  94. GRB 250407A: LCO detection of a fading optical counterpart
  95. EP250407a: Swift-XRT observations
  96. Konus-Wind detection of GRB 250407A
  97. GRB 250407A: SVOM/GRM observation of a bright long burst
  98. GRB 250407A: EP-WXT afterglow detection
  99. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  100. GRB 250407A: Fermi GBM Detection

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