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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"

19603 results found.

  1. GRB 250516A: Fermi GBM Observation
  2. GRB 250516A: Swift-XRT refined Analysis
  3. GRB 250516A: Swift/UVOT Detection
  4. GRB 250515A: Swift ToO observations
  5. GRB 250516A: Enhanced Swift-XRT position
  6. GRB 250516A: Swift detection of a burst
  7. GRB 250509A: Swift-BAT refined analysis
  8. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  9. GRB 250510B: Fermi GBM Observation
  10. GRB 250510A: Swift-XRT observations
  11. GRB 250509A: Fermi GBM Observation
  12. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  13. GRB 250509A: Swift-XRT refined Analysis
  14. GRB 250507A: J-band observations with WINTER
  15. GRB 250509A: Enhanced Swift-XRT position
  16. GRB 250509A: Prompt enhanced Swift-XRT position
  17. Swift GRB 250509A: Global MASTER-Net observations report
  18. GRB 250509A: Swift detection of a burst
  19. GRB 250506A: NOT optical upper limits
  20. GRB 250506A: GECAM detection
  21. GRB 250506A: Swift-XRT afterglow detection
  22. GRB 250507A: Swift-XRT refined Analysis
  23. GRB 250506A: Swift/UVOT Upper Limits
  24. GRB 250430A / EP250430a: AstroSat CZTI detection
  25. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  26. GRB 250506A: Swift-XRT observations
  27. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  28. GRB 250504A: EIRSAT-1 GMOD Detection
  29. GRB 250506A: Swift ToO observations
  30. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  31. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  32. GRB 250506A: Swift XRT observations and possible counterpart detection
  33. GRB 250506A: TRT optical observations
  34. GRB 250504A: Swift-BAT refined analysis
  35. GRB 250430A: Swift-BAT refined analysis
  36. GRB 250504A: Swift-XRT refined Analysis
  37. GRB 250504A: VLT/X-shooter upper limits
  38. GRB 250504A: SVOM/VT upper limit
  39. GRB 250504A: REM optical/NIR observations
  40. GRB 250504A: MeerLICHT optical afterglow detection
  41. GRB 250504A: Fermi GBM Observation
  42. GRB 250504A: Enhanced Swift-XRT position
  43. GRB 250504A: Swift detection of a burst
  44. Swift GRB250504.98: Global MASTER-Net observations report
  45. GRB 250502A: Swift/UVOT Follow up
  46. GRB 250502A: Swift-XRT afterglow detection
  47. GRB 250502A: Swift ToO observations
  48. GRB 250430A: Swift-XRT refined Analysis
  49. GRB 250430A: Swift/UVOT Detection
  50. GRB 250430A: Enhanced Swift-XRT position
  51. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  52. GRB 250430A: DDOTI Optical Observations
  53. GRB 250430A: Leavitt Observatory optical upper limit
  54. GRB 250430A: Bassano Bresciano Observatory upper limit
  55. GRB 250430A : MITSuME Akeno optical upper limits
  56. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  57. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  58. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  59. GRB 250430A: AKO Optical Afterglow Detection
  60. GRB 250430A: Swift detection of a burst with optical counterpart
  61. Swift GRB250430.73: Global MASTER-Net observations report
  62. GRB 250427A: Swift/UVOT Detection
  63. EP250427a: EP-FXT follow-up observations
  64. GRB 250427A: Swift-XRT refined Analysis
  65. GRB 250424A: LCO optical observation
  66. GRB 250424A: Swift-BAT refined analysis
  67. GRB 250424A: SVOM/GRM observation of a long burst
  68. GRB 250424A: PRIME near-infrared detection
  69. GRB 250424A: WINTER J-band detection
  70. GRB 250424A: EIRSAT-1 GMOD Detection
  71. GRB 250424A: Swift/UVOT Detection
  72. Konus-Wind detection of GRB 250424A
  73. GRB 250424A: Skynet Optical Observations
  74. GRB 250424A: Kilonova-Catcher optical afterglow detection
  75. GRB 250424A: Swift-XRT refined Analysis
  76. GRB 250424A: Enhanced Swift-XRT position
  77. GRB 250424A: AstroSat CZTI detection of a bright long burst
  78. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  79. GRB 250424A: BlackGEM optical afterglow detection
  80. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  81. GRB 250424A: likely host galaxy
  82. GRB 250424A: DDOTI Afterglow Detection
  83. GRB 250424A: REM optical/NIR afterglow detection
  84. GRB 250424A: Swift detection of a burst with an optical counterpart
  85. Swift GRB 250424A: Global MASTER-Net observations report
  86. Swift GRB 250424A: Global MASTER-Net OT detection
  87. SVOM/sb25042207: XRT observations
  88. EP250421a: NOT optical observations
  89. EP250421a: Swift/XRT counterpart detection
  90. GRB 250419A: Swift/UVOT Follow up
  91. GRB 250419A: LCO optical afterglow multi-band observations
  92. GRB 250419A: Mondy and AbAO Optical Observations
  93. GRB 250419A: Swift-XRT localisation
  94. GRB 250419A: Swift-XRT refined Analysis
  95. EP250416a: Swift/XRT counterpart fading
  96. EP20250416a: Swift/XRT counterpart detection
  97. GRB 250407A: Mondy and AbAO Optical Observations
  98. IceCube-250406A: Swift-XRT observations
  99. IPN triangulation of GRB 250407A
  100. GRB 250407A: LCO detection of a fading optical counterpart

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