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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"

32570 results found.

  1. GRB 250605A: LT optical observations
  2. Konus-Wind detection of GRB 250601A
  3. IPN triangulation of GRB 250404B
  4. IPN triangulation of GRB 250529A
  5. GRB 250601A: PRIME H band upper limit.
  6. GRB 250530A: SVOM/GRM analysis
  7. GRB 250601A: PRIME J band upper limit.
  8. GRB 250601A: VLT/FORS2 Optical Observation
  9. GRB 250601A: Fermi GBM Observation
  10. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  11. GRB 250603A: Swift/UVOT Upper Limits
  12. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  13. GRB 250602A: Fermi GBM Observation
  14. GRB 250602A: Fermi-LAT detection
  15. GRB 250602A: DDOTI Optical Upper Limit
  16. GRB 250530C: Swift-BAT refined analysis
  17. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  18. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  19. GRB 250601A: Swift/XRT candidate afterglow
  20. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  21. Fermi GRB 250601A: Global MASTER-Net observations report
  22. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  23. GRB 250601A: Swift ToO observations
  24. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  25. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  26. EP#01709177494: SVOM/VT optical observations
  27. Fermi GRB 250531A: Global MASTER-Net observations report
  28. GRB 250530C: BOOTES-7 optical upper limit
  29. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  30. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  31. Swift GRB 250530C: Global MASTER-Net observations report
  32. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  33. GRB 250530A: EP-FXT counterpart detection
  34. GRB 250530A: SVOM/VT optical upper limit
  35. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  36. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  37. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  38. GRB 250527C: Swift/UVOT Upper Limits
  39. EP J1350.0-8622: EP-FXT follow-up observation
  40. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  41. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  42. GRB 250520A: Swift-BAT refined analysis
  43. GRB 250527C: Swift ToO observations
  44. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  45. EP250526a: SVOM/VT optical upper limit
  46. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  47. GRB 250527B: Tiled Swift observations
  48. GRB 250520A: Gemini-South optical afterglow detection
  49. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  50. GRB 250314A: CIDER NB1008 upper limit
  51. EP250526a: COLIBRÍ optical upper limits
  52. EP250526a: Global MASTER-Net observations report
  53. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  54. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  55. GRB 250520A: 3 GHz MeerKAT Detection
  56. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  57. Fermi GRB 250523A: Global MASTER-Net observations report
  58. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  59. GRB 250521A: GRBAlpha detection
  60. GRB 250520A: GRBAlpha detection
  61. GRB 250521B: SVOM/VT optical upper limit
  62. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  63. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  64. Fermi GRB 250522B: Global MASTER-Net observations report
  65. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  66. GRB 250521D: SVOM/VT optical observations
  67. EP#01709176612: Swift-XRT counterpart detection of flaring star
  68. Fermi GRB 250521D: Global MASTER-Net observations report
  69. GRB 250521D: DDOTI Optical Upper Limit
  70. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  71. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. GRB 250521D: LAST tentative optical counterpart candidate
  73. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  74. GRB 250520A: 10 GHz VLA radio source
  75. GRB 250521B: Swift ToO observations
  76. GRB 250521A: DDOTI Optical Upper Limit
  77. Konus-Wind detection of GRB 250520A (short/hard)
  78. GRB 250520A: VLT/FORS2 Optical Observation
  79. GRB 250502A: Tautenburg observations
  80. GRB 250520A: Swift/UVOT Upper Limits
  81. Konus-Wind detection of GRB 250516B
  82. IPN triangulation of GRB 250516B
  83. GRB 250520A: J-band observations with WINTER
  84. GRB 250520A: Gemini-South optical observations
  85. GRB 250520A: REM optical/NIR early observations
  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 250516B: Insight-HXMT detection
  94. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  95. GRB 250516A: Swift-BAT refined analysis
  96. GRB 250516A: COLIBRÍ optical upper limit
  97. Konus-Wind detection of GRB 250516A
  98. GRB 250516B: NuSTAR Detection of the Prompt Emission
  99. Fermi GRB 250516A: Global MASTER-Net observations report
  100. GRB 250515A: Swift-XRT observations

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