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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"

36143 results found.

  1. GRB 250828B: Swift-BAT refined analysis
  2. GRB 250808B: SVOM detection of a burst through offline search
  3. Swift GRB 250828B: Global MASTER-Net observations report
  4. EP-WXT trigger 01709200800 : KAIT optical observations
  5. EP250828a: KAIT optical upper limit
  6. GRB 250828B: Swift detection of a burst
  7. GRB 250828A: Fermi GBM Final Localization
  8. GRID detection of GRB 250824A
  9. Fermi GRB 250827A: Global MASTER-Net observations report
  10. EP250827a: GOTO observation of the optical afterglow
  11. GRB 250826A: SVOM/GRM observation
  12. GRB 250827A: Fermi GBM Final Real-time Localization
  13. EP250827A: An optical rebrightening was detected by LCO.
  14. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  15. Fermi GRB 250826A: Global MASTER-Net observations report
  16. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  17. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  18. Fermi Gamma-ray Burst Monitor trigger 777883624/250826283 is not a GRB
  19. GRB 250826A: Fermi GBM Final Real-time Localization
  20. Fermi GRB 250824B: Global MASTER-Net observations report
  21. GRB 250823A: Swift-BAT refined analysis
  22. GRB 250821B: AstroSat CZTI detection
  23. GRB 250819A: AstroSat CZTI detection
  24. GRB 250821B: Insight-HXMT detection
  25. GRB 250823A: Swift-XRT refined Analysis
  26. GRB 250824B: Fermi GBM Final Real-time Localization
  27. GRB 250823A: COLIBRÍ optical observations
  28. GRB 250823A: SVOM/VT optical observation
  29. GRB 250824A: Fermi GBM Final Real-time Localization
  30. GRB 250823A: Swift/UVOT Detection
  31. GRB 250823A: NOT optical observations
  32. GRB 250823A: Fermi GBM Observation
  33. GRB 250818B: MeerKAT Detection
  34. GRB 250823A: Enhanced Swift-XRT position
  35. GRB 250823A: LCOGT Optical Detection
  36. GRB 250823A: BOOTES6/DPRT early optical detection
  37. GRB 250823A: Liverpool Telescope optical detection
  38. GRB 250823A: Swift detection of a burst
  39. GRB 250823A: Fermi GBM Final Real-time Localization
  40. Konus-Wind detection of GRB 250821B
  41. GRB 250806A: Gemini observations of host galaxy candidate
  42. IPN triangulation of GRB 250821B (long/bright)
  43. GRB 250821A: Kilonova-Catcher optical upper limits
  44. GRB 250812A: SVOM/ECLAIRs refined analysis
  45. GRB 250821A: Swift-BAT refined analysis
  46. GRB 250821A: VLT/FORS2 Optical Observation
  47. GRB 250821A: GECAM-B detection
  48. GRB 250821B: SVOM/GRM observation
  49. Fermi GRB 250821B: Global MASTER-Net observations report
  50. GRB 250821A: NOT z-band upper limit
  51. GRB 250821C: Fermi GBM Final Real-time Localization
  52. GRB 250821A: KAIT optical upper limit
  53. GRB 250821A: Swift-XRT refined Analysis
  54. Swift GRB 250821A: Global MASTER-Net observations report
  55. GRB 250821B: Fermi GBM Detection
  56. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  57. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  58. GRB 250821A: Enhanced Swift-XRT position
  59. GRB 250821A: Swift/UVOT Upper Limits
  60. GRB 250821A: LCOGT Optical Upper Limits
  61. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  62. GRB 250821A: Prompt enhanced Swift-XRT position
  63. GRB 250821A: Swift detection of a burst
  64. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  65. GRB 250819A: Insight-HXMT detection
  66. GRB 250818B: 10 GHz VLA detection
  67. GRB 250814A: Swift/UVOT Upper Limits
  68. GRB 250813B: Swift/UVOT Upper Limit
  69. IPN triangulation of GRB 250816A (short)
  70. IPN triangulation of GRB 250814C (short)
  71. IPN triangulation of GRB 250804B (short)
  72. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  73. GRB 250818B: Kilonova-Catcher optical afterglow detection
  74. GRB 250818B: Liverpool Telescope optical detections
  75. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  76. GRB 250818A: AstroSat CZTI detection
  77. GRB 250818B: Swift/UVOT Detection
  78. Fermi Gamma-ray Burst Monitor trigger 777342746/250820022 is not a GRB
  79. GRB 250820A: Fermi GBM Final Real-time Localization
  80. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  81. GRB 250818B: TRT Optical Observation
  82. Fermi GRB 250816A: Global MASTER-Net observations report
  83. GRB 250818B: SAO RAS optical observations
  84. Swift GRB 250818A: Global MASTER-Net observations report
  85. GRB 250818B: NOT optical observations
  86. GRB 250818A: Swift-XRT refined Analysis
  87. GRB 250818B: EP-FXT counterpart detection
  88. GRB 250818A: Swift-BAT refined analysis
  89. Fermi Gamma-ray Burst Monitor trigger 777251788/250818970 is not a GRB
  90. GRB 250818C: Fermi GBM Final Real-time Localization
  91. GRB 250818B: Keck redshift of the optical afterglow
  92. GRB 250818B: KAIT optical observations
  93. GRB 250818A: Swift/UVOT Upper Limits
  94. GRB 250818A: Enhanced Swift-XRT position
  95. GRB 250813B: SVOM/ECLAIRs refined analysis
  96. GRB 250818A: Fermi GBM Observation
  97. GRB 250818B: SVOM/VT optical observation
  98. GRB 250814A: Further GRAWITA TNG NIR observations
  99. GRB 250818B: Swift-XRT afterglow detection
  100. GRB 250818B: GOTO optical counterpart candidate

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