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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"

43914 results found.

  1. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  2. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  3. GRB 250601A: Swift/XRT candidate afterglow
  4. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  5. GRB 250601A: Swift-XRT observations
  6. Fermi GRB 250601A: Global MASTER-Net observations report
  7. GRB 250602A: Fermi GBM Final Real-time Localization
  8. Fermi trigger No 770470765: Global MASTER-Net observations report
  9. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  10. GRB 250601A: Swift ToO observations
  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 250530C: BOOTES-7 optical upper limit
  19. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  20. GRB 250530C: Swift-XRT refined Analysis
  21. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  22. Swift GRB 250530C: Global MASTER-Net observations report
  23. GRB 250530C: Enhanced Swift-XRT position
  24. GRB 250530C: Swift detection of a burst
  25. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  26. GRB 250530A: EP-FXT counterpart detection
  27. GRB 250530A: SVOM/VT optical upper limit
  28. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  29. GRB 250530B: Fermi GBM Final Real-time Localization
  30. GRB 250530A: Swift-XRT counterpart detection
  31. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  32. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  33. GRB 250530A: SVOM detection of a burst
  34. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  35. GRB 250527C: Swift/UVOT Upper Limits
  36. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  37. EP J1350.0-8622: EP-FXT follow-up observation
  38. GRB 250529B: Fermi GBM Final Real-time Localization
  39. GRB 250527B: Swift-XRT observations
  40. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  41. The EP-WXT trigger 01709177124 is likely a flaring star
  42. GRB 250529A: Fermi GBM Final Real-time Localization
  43. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  44. GRB 250520A: Swift-BAT refined analysis
  45. GRB 250527C: Swift ToO observations
  46. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  47. EP250526a: SVOM/VT optical upper limit
  48. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  49. GRB 250527B: Tiled Swift observations
  50. GRB 250520A: Gemini-South optical afterglow detection
  51. Fermi trigger No 770058372: Global MASTER-Net observations report
  52. Fermi trigger No 770047117: Global MASTER-Net observations report
  53. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  54. GRB 250527A: Fermi GBM Final Localization
  55. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 250314A: CIDER NB1008 upper limit
  57. EP250526a: COLIBRÍ optical upper limits
  58. EP250526a: Global MASTER-Net observations report
  59. EP250526a: Einstein Probe detection of a fast X-ray transient
  60. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  61. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  62. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  63. GRB 250520A: 3 GHz MeerKAT Detection
  64. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  65. Fermi GRB 250523A: Global MASTER-Net observations report
  66. Fermi trigger No 769611916: Global MASTER-Net observations report
  67. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  68. GRB 250521A: GRBAlpha detection
  69. GRB 250520A: GRBAlpha detection
  70. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  71. GRB 250523A: Fermi GBM Final Real-time Localization
  72. The EP-WXT trigger 01709176712 is likely a flaring star
  73. GRB 250521B: SVOM/VT optical upper limit
  74. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  75. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  76. Fermi GRB 250522B: Global MASTER-Net observations report
  77. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  78. GRB 250522B: Fermi GBM Final Localization
  79. GRB 250521D: SVOM/VT optical observations
  80. GRB 250522A: Fermi GBM Final Real-time Localization
  81. EP#01709176612: Swift-XRT counterpart detection of flaring star
  82. Fermi GRB 250521D: Global MASTER-Net observations report
  83. Fermi trigger No 769533898: Global MASTER-Net observations report
  84. Fermi trigger No 769499303: Global MASTER-Net observations report
  85. GRB 250521D: DDOTI Optical Upper Limit
  86. The EP-WXT trigger 01709176612 is likely a flaring star
  87. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  88. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  89. GRB 250521D: LAST tentative optical counterpart candidate
  90. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  91. GRB 250520A: 10 GHz VLA radio source
  92. GRB 250521B: Swift ToO observations
  93. GRB 250521D: Fermi GBM Final Real-time Localization
  94. GRB 250521C: Fermi GBM Final Localization
  95. GRB 250521A: DDOTI Optical Upper Limit
  96. GRB 250521B: SVOM detection of a burst through offline search
  97. Konus-Wind detection of GRB 250520A (short/hard)
  98. GRB 250520A: VLT/FORS2 Optical Observation
  99. GRB 250502A: Tautenburg observations
  100. GRB 250520A: Swift/UVOT Upper Limits

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