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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"

37926 results found.

  1. GRB 250821B: Insight-HXMT detection
  2. GRB 250823A: Swift-XRT refined Analysis
  3. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  4. GRB 250824B: Fermi GBM Final Real-time Localization
  5. GRB 250823A: COLIBRÍ optical observations
  6. GRB 250823A: SVOM/VT optical observation
  7. GRB 250824A: Fermi GBM Final Real-time Localization
  8. GRB 250823A: Swift/UVOT Detection
  9. GRB 250823A: NOT optical observations
  10. GRB 250823A: Fermi GBM Observation
  11. GRB 250818B: MeerKAT Detection
  12. GRB 250823A: Enhanced Swift-XRT position
  13. GRB 250823A: LCOGT Optical Detection
  14. GRB 250823A: BOOTES6/DPRT early optical detection
  15. GRB 250823A: Liverpool Telescope optical detection
  16. GRB 250823A: Swift detection of a burst
  17. GRB 250823A: Fermi GBM Final Real-time Localization
  18. Swift GRB250823.84: Global MASTER-Net observations report
  19. Konus-Wind detection of GRB 250821B
  20. GRB 250806A: Gemini observations of host galaxy candidate
  21. IPN triangulation of GRB 250821B (long/bright)
  22. GRB 250821A: Kilonova-Catcher optical upper limits
  23. EP250821a: Swift/XRT counterpart fading
  24. GRB 250812A: SVOM/ECLAIRs refined analysis
  25. GRB 250821A: Swift-BAT refined analysis
  26. EP250821a: Swift/UVOT further observations.
  27. GRB 250821A: VLT/FORS2 Optical Observation
  28. GRB 250821A: GECAM-B detection
  29. GRB 250821B: SVOM/GRM observation
  30. EP250821a: SVOM/VT optical observation
  31. Fermi GRB 250821B: Global MASTER-Net observations report
  32. GRB 250821A: NOT z-band upper limit
  33. GRB 250821C: Fermi GBM Final Real-time Localization
  34. GRB 250821A: KAIT optical upper limit
  35. GRB 250821A: Swift-XRT refined Analysis
  36. Swift GRB 250821A: Global MASTER-Net observations report
  37. GRB 250821B: Fermi GBM Detection
  38. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  39. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  40. GRB 250821A: Enhanced Swift-XRT position
  41. GRB 250821A: Swift/UVOT Upper Limits
  42. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  43. EP250821a: Swift XRT and UVOT counterpart detection
  44. GRB 250821A: LCOGT Optical Upper Limits
  45. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  46. GRB 250821A: Prompt enhanced Swift-XRT position
  47. GRB 250821A: Swift detection of a burst
  48. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  49. GRB 250819A: Insight-HXMT detection
  50. GRB 250818B: 10 GHz VLA detection
  51. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  52. GRB 250814A: Swift/UVOT Upper Limits
  53. GRB 250813B: Swift/UVOT Upper Limit
  54. IPN triangulation of GRB 250816A (short)
  55. IPN triangulation of GRB 250814C (short)
  56. IPN triangulation of GRB 250804B (short)
  57. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  58. GRB 250818B: Kilonova-Catcher optical afterglow detection
  59. GRB 250818B: Liverpool Telescope optical detections
  60. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  61. GRB 250818A: AstroSat CZTI detection
  62. GRB 250818B: Swift/UVOT Detection
  63. Fermi Gamma-ray Burst Monitor trigger 777342746/250820022 is not a GRB
  64. GRB 250820A: Fermi GBM Final Real-time Localization
  65. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  66. GRB 250818B: TRT Optical Observation
  67. Fermi GRB 250816A: Global MASTER-Net observations report
  68. GRB 250818B: SAO RAS optical observations
  69. Swift GRB 250818A: Global MASTER-Net observations report
  70. GRB 250818B: NOT optical observations
  71. GRB 250818A: Swift-XRT refined Analysis
  72. GRB 250818B: EP-FXT counterpart detection
  73. GRB 250818A: Swift-BAT refined analysis
  74. Fermi Gamma-ray Burst Monitor trigger 777251788/250818970 is not a GRB
  75. GRB 250818C: Fermi GBM Final Real-time Localization
  76. GRB 250818B: Keck redshift of the optical afterglow
  77. GRB 250818B: KAIT optical observations
  78. GRB 250818A: Swift/UVOT Upper Limits
  79. GRB 250818A: Enhanced Swift-XRT position
  80. GRB 250813B: SVOM/ECLAIRs refined analysis
  81. GRB 250818A: Fermi GBM Observation
  82. GRB 250818B: SVOM/VT optical observation
  83. GRB 250814A: Further GRAWITA TNG NIR observations
  84. GRB 250818B: Swift-XRT afterglow detection
  85. GRB 250818B: GOTO optical counterpart candidate
  86. GRB 250818B: SVOM detection of a short burst
  87. GRB 250818A: Swift detection of a burst
  88. GRB 250818A: Fermi GBM Final Real-time Localization
  89. sb25081602: Swift-XRT observations
  90. GRB 250816A: SVOM/GRM observation of a short burst
  91. Fermi GRB 250814B: Global MASTER-Net observations report
  92. GRB 250816A: Fermi GBM Final Real-time Localization
  93. GRB 250814A: Swift-BAT refined analysis
  94. GRB 250815A: Fermi GBM Final Localization
  95. GRB 250813B: Liverpool Telescope optical upper limits
  96. GRB 250814A: Further COLIBRÍ optical upper limit
  97. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  98. GRB 250814A: GRAWITA TNG NIR observations
  99. GRB 250812A: SVOM/VT optical continued observation
  100. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg

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