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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

27188 results found.

  1. GRB 250424A: REM optical/NIR afterglow detection
  2. GRB 250424A: Swift detection of a burst with an optical counterpart
  3. Swift GRB 250424A: Global MASTER-Net observations report
  4. Swift GRB 250424A: Global MASTER-Net OT detection
  5. EP250421a: Nickel optical upper limit
  6. EP250421a: Upper limits from Fermi-GBM Observations
  7. SVOM/sb25042207: XRT observations
  8. SVOM/sb25042207: GOTO optical upper limits
  9. SVOM/sb25042207: SVOM detection of an X-ray transient
  10. IceCube-250421A: DDOTI Detection of the LAST Candidate
  11. GRB 250419A: Mephisto Multi-band Optical Detection
  12. EP250421a: NOT optical observations
  13. EP250421a: REM optical upper limit
  14. EP250421a: Swift/XRT counterpart detection
  15. EP250421A: COLIBRÍ Optical Upper Limit
  16. GRB 250419A: Mondy Continued Optical Observations
  17. Fermi GRB 250421A: Global MASTER-Net observations report
  18. EP250421a: Global MASTER-Net observations report
  19. EP250421a: Einstein Probe detection of an X-ray transient
  20. EP250421a: Mephisto optical counterpart confirmation
  21. IceCube Alert 250421.71: Global MASTER-Net observations report
  22. EP250421a: JinShan likely optical counterpart
  23. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  24. GRB 250421A: Fermi GBM Final Real-time Localization
  25. GRB 250419A: Liverpool Telescope observations
  26. GRB 250419A: LCO optical observation
  27. GRB 250419A: JinShan optical observations
  28. GRB 250419A: SVOM/VT optical continuous observations
  29. GRB 250419A: SVOM/C-GFT optical observations
  30. GRB 250419A: Swift/UVOT Follow up
  31. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  32. GRB 250419A: LCO optical afterglow multi-band observations
  33. GRB 250419A: Mondy and AbAO Optical Observations
  34. GRB 250419A: AKO Optical Afterglow Detection
  35. GRB 250419A: MASTER optical afterglow observation
  36. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  37. GRB 250419A: Swift-XRT refined Analysis
  38. GRB 250419A: GOTO optical counterpart detection
  39. GRB 250419A: KAIT optical afterglow observations
  40. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  41. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  42. GRB 250419A: SVOM detection of a soft burst
  43. EP250416a: Swift/XRT counterpart fading
  44. EP250416a: refined EP-WXT and EP-FXT analysis
  45. EP20250416a: Swift/XRT counterpart detection
  46. IceCube-250416A: DDOTI Optical Observations
  47. EP250225a: SVOM/VT optical brightening
  48. SVOM/sb25041603 is not a GRB
  49. EP250416a: GSP optical upper limit
  50. EP250416a: Global MASTER-Net observations report
  51. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  52. EP250416a: Einstein Probe detection of an X-ray transient
  53. IceCube-250416A: Global MASTER-Net observations report
  54. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  55. GRB 250416B: Fermi GBM Final Real-time Localization
  56. GRB 250416A: Fermi GBM Final Real-time Localization
  57. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  58. SVOM/sb25041603: SVOM detection of an X-ray transient
  59. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  60. IceCube 250414.324: DDOTI Optical Observations
  61. EP250304a: ATCA radio observations
  62. GRB 250412A: AstroSat CZTI detection
  63. EP250404a: Nanshan 0.43m Telescope optical observatios
  64. Fermi trigger No 766148493: Global MASTER-Net observations report
  65. Fermi trigger No 766173972: Global MASTER-Net observations report
  66. GRB 250411A: DDOTI Optical Observations
  67. Fermi GRB 250411A: Global MASTER-Net observations report
  68. GRB 250411A: Fermi GBM Final Real-time Localization
  69. GRB 250407A: Mondy and AbAO Optical Observations
  70. EP250227a: Further NOT optical observations
  71. IceCube-250406A: Swift-XRT observations
  72. IPN triangulation of GRB 250407A
  73. EP250407a: Global MASTER-Net observations report
  74. GRB 250407A: LCO detection of a fading optical counterpart
  75. GRB 250407A: SVOM/GRM observation of a bright long burst
  76. GRB 250407A: EP-WXT afterglow detection
  77. EP250407a: EP-WXT detection of a fast X-ray transient
  78. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  79. GRB 250407A: Fermi GBM Detection
  80. Fermi GRB 250407A: Global MASTER-Net observations report
  81. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  82. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  83. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  84. GRB 250407A: Fermi GBM Final Real-time Localization
  85. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  86. IceCube 250406.951: DDOTI Optical Observations
  87. IceCube Alert 250406.95: Global MASTER-Net observations report
  88. Fermi trigger No 765663719: Global MASTER-Net observations report
  89. Fermi GRB 250406A: Global MASTER-Net observations report
  90. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  91. GRB 250406A: Fermi GBM Final Real-time Localization
  92. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  93. Fermi trigger No 765619921: Global MASTER-Net observations report
  94. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  95. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  96. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  98. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  99. EP250402a: Optical upper limit with PD 1.3m observations
  100. GRB 250404A / EP250404a: NOT optical observations

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