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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"

32571 results found.

  1. GRB 250602A: GECAM detection
  2. GRB 250605A: LT optical observations
  3. Konus-Wind detection of GRB 250601A
  4. IPN triangulation of GRB 250404B
  5. IPN triangulation of GRB 250529A
  6. GRB 250601A: PRIME H band upper limit.
  7. GRB 250530A: SVOM/GRM analysis
  8. GRB 250601A: PRIME J band upper limit.
  9. GRB 250601A: VLT/FORS2 Optical Observation
  10. GRB 250601A: Fermi GBM Observation
  11. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  12. GRB 250603A: Swift/UVOT Upper Limits
  13. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  14. GRB 250602A: Fermi GBM Observation
  15. GRB 250602A: Fermi-LAT detection
  16. GRB 250602A: DDOTI Optical Upper Limit
  17. GRB 250530C: Swift-BAT refined analysis
  18. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  19. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  20. GRB 250601A: Swift/XRT candidate afterglow
  21. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  22. Fermi GRB 250601A: Global MASTER-Net observations report
  23. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  24. GRB 250601A: Swift ToO observations
  25. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  26. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  27. EP#01709177494: SVOM/VT optical observations
  28. Fermi GRB 250531A: Global MASTER-Net observations report
  29. GRB 250530C: BOOTES-7 optical upper limit
  30. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  31. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  32. Swift GRB 250530C: Global MASTER-Net observations report
  33. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  34. GRB 250530A: EP-FXT counterpart detection
  35. GRB 250530A: SVOM/VT optical upper limit
  36. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  37. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  38. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  39. GRB 250527C: Swift/UVOT Upper Limits
  40. EP J1350.0-8622: EP-FXT follow-up observation
  41. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  42. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  43. GRB 250520A: Swift-BAT refined analysis
  44. GRB 250527C: Swift ToO observations
  45. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  46. EP250526a: SVOM/VT optical upper limit
  47. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  48. GRB 250527B: Tiled Swift observations
  49. GRB 250520A: Gemini-South optical afterglow detection
  50. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 250314A: CIDER NB1008 upper limit
  52. EP250526a: COLIBRÍ optical upper limits
  53. EP250526a: Global MASTER-Net observations report
  54. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  55. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  56. GRB 250520A: 3 GHz MeerKAT Detection
  57. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  58. Fermi GRB 250523A: Global MASTER-Net observations report
  59. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  60. GRB 250521A: GRBAlpha detection
  61. GRB 250520A: GRBAlpha detection
  62. GRB 250521B: SVOM/VT optical upper limit
  63. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  64. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  65. Fermi GRB 250522B: Global MASTER-Net observations report
  66. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  67. GRB 250521D: SVOM/VT optical observations
  68. EP#01709176612: Swift-XRT counterpart detection of flaring star
  69. Fermi GRB 250521D: Global MASTER-Net observations report
  70. GRB 250521D: DDOTI Optical Upper Limit
  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 250520A: 10 GHz VLA radio source
  76. GRB 250521B: Swift ToO observations
  77. GRB 250521A: DDOTI Optical Upper Limit
  78. Konus-Wind detection of GRB 250520A (short/hard)
  79. GRB 250520A: VLT/FORS2 Optical Observation
  80. GRB 250502A: Tautenburg observations
  81. GRB 250520A: Swift/UVOT Upper Limits
  82. Konus-Wind detection of GRB 250516B
  83. IPN triangulation of GRB 250516B
  84. GRB 250520A: J-band observations with WINTER
  85. GRB 250520A: Gemini-South optical observations
  86. GRB 250520A: REM optical/NIR early observations
  87. GRB 250520A：SVOM/VT optical candidate
  88. GRB 250520A: COLIBRÍ optical upper limit
  89. GRB 250520A: DDOTI Optical Upper Limit
  90. GRB 250520A: AstroSat CZTI detection of a short burst
  91. GRB 250516B: GRBAlpha detection
  92. GRB 250520A: SVOM/GRM observation
  93. GRB 250520A: GOTO optical upper limit
  94. GRB 250516B: Insight-HXMT detection
  95. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  96. GRB 250516A: Swift-BAT refined analysis
  97. GRB 250516A: COLIBRÍ optical upper limit
  98. Konus-Wind detection of GRB 250516A
  99. GRB 250516B: NuSTAR Detection of the Prompt Emission
  100. Fermi GRB 250516A: Global MASTER-Net observations report

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