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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"

27174 results found.

  1. GRB 250602A: Fermi GBM Observation
  2. GRB 250602A: Fermi-LAT detection
  3. GRB 250602A: DDOTI Optical Upper Limit
  4. GRB 250530C: Swift-BAT refined analysis
  5. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  6. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  7. Fermi GRB 250601A: Global MASTER-Net observations report
  8. GRB 250602A: Fermi GBM Final Real-time Localization
  9. Fermi trigger No 770470765: Global MASTER-Net observations report
  10. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  11. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  12. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  13. GRB 250601A: Fermi GBM Final Real-time Localization
  14. EP#01709177494: SVOM/VT optical observations
  15. Fermi GRB 250531A: Global MASTER-Net observations report
  16. GRB 250531A: Fermi GBM Final Real-time Localization
  17. EP#01709177494: Swift-XRT counterpart detection of known source
  18. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  19. GRB 250530C: Swift-XRT refined Analysis
  20. Swift GRB 250530C: Global MASTER-Net observations report
  21. GRB 250530C: Swift detection of a burst
  22. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  23. GRB 250530A: EP-FXT counterpart detection
  24. GRB 250530A: SVOM/VT optical upper limit
  25. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  26. GRB 250530B: Fermi GBM Final Real-time Localization
  27. GRB 250530A: Swift-XRT counterpart detection
  28. GRB 250530A: SVOM detection of a burst
  29. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  30. GRB 250527C: Swift/UVOT Upper Limits
  31. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  32. EP J1350.0-8622: EP-FXT follow-up observation
  33. GRB 250529B: Fermi GBM Final Real-time Localization
  34. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  35. The EP-WXT trigger 01709177124 is likely a flaring star
  36. GRB 250529A: Fermi GBM Final Real-time Localization
  37. GRB 250520A: Swift-BAT refined analysis
  38. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  39. EP250526a: SVOM/VT optical upper limit
  40. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  41. Fermi trigger No 770058372: Global MASTER-Net observations report
  42. Fermi trigger No 770047117: Global MASTER-Net observations report
  43. GRB 250527A: Fermi GBM Final Localization
  44. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP250526a: COLIBRÍ optical upper limits
  46. EP250526a: Global MASTER-Net observations report
  47. EP250526a: Einstein Probe detection of a fast X-ray transient
  48. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  49. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  50. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  51. Fermi GRB 250523A: Global MASTER-Net observations report
  52. Fermi trigger No 769611916: Global MASTER-Net observations report
  53. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  54. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  55. GRB 250523A: Fermi GBM Final Real-time Localization
  56. The EP-WXT trigger 01709176712 is likely a flaring star
  57. GRB 250521B: SVOM/VT optical upper limit
  58. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  59. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  60. Fermi GRB 250522B: Global MASTER-Net observations report
  61. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  62. GRB 250522B: Fermi GBM Final Localization
  63. GRB 250521D: SVOM/VT optical observations
  64. GRB 250522A: Fermi GBM Final Real-time Localization
  65. EP#01709176612: Swift-XRT counterpart detection of flaring star
  66. Fermi GRB 250521D: Global MASTER-Net observations report
  67. Fermi trigger No 769533898: Global MASTER-Net observations report
  68. Fermi trigger No 769499303: Global MASTER-Net observations report
  69. GRB 250521D: DDOTI Optical Upper Limit
  70. The EP-WXT trigger 01709176612 is likely a flaring star
  71. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  72. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. GRB 250521D: LAST tentative optical counterpart candidate
  74. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  75. GRB 250521D: Fermi GBM Final Real-time Localization
  76. GRB 250521C: Fermi GBM Final Localization
  77. GRB 250521A: DDOTI Optical Upper Limit
  78. GRB 250521B: SVOM detection of a burst through offline search
  79. GRB 250520A: VLT/FORS2 Optical Observation
  80. GRB 250502A: Tautenburg observations
  81. GRB 250520A: Swift/UVOT Upper Limits
  82. GRB 250521A: Fermi GBM Final Real-time Localization
  83. GRB 250520A: Swift-XRT refined Analysis
  84. GRB 250520A: REM optical/NIR early observations
  85. GRB 250520B: Fermi GBM Final Real-time Localization
  86. GRB 250520A：SVOM/VT optical candidate
  87. GRB 250520A: COLIBRÍ optical upper limit
  88. GRB 250520A: DDOTI Optical Upper Limit
  89. GRB 250520A: AstroSat CZTI detection of a short burst
  90. GRB 250516B: GRBAlpha detection
  91. GRB 250520A: SVOM/GRM observation
  92. GRB 250520A: GOTO optical upper limit
  93. GRB 250520A: Swift detection of a burst
  94. Swift GRB 250520A: Global MASTER-Net observations report
  95. GRB 250516A: Swift-BAT refined analysis
  96. GRB 250516A: COLIBRÍ optical upper limit
  97. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  98. Fermi GRB 250516A: Global MASTER-Net observations report
  99. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  100. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB

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