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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"

32581 results found.

  1. GRB 250609A: Fermi GBM Observation
  2. EP250610a: COLIBRÍ optical upper limit
  3. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  4. GRB 250605A: Swift/UVOT Upper Limits
  5. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  6. GRB 250527C: CrAO Optical Upper Limit
  7. GRB 250607A: SVOM/GRM observation of a long burst
  8. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  9. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  10. GRB 250605A: SVOM/VT optical upper limit
  11. Fermi GRB 250606A: Global MASTER-Net observations report
  12. GRB 250602A: GECAM detection
  13. GRB 250605A: LT optical observations
  14. Konus-Wind detection of GRB 250601A
  15. IPN triangulation of GRB 250404B
  16. IPN triangulation of GRB 250529A
  17. GRB 250601A: PRIME H band upper limit.
  18. GRB 250530A: SVOM/GRM analysis
  19. GRB 250601A: PRIME J band upper limit.
  20. GRB 250601A: VLT/FORS2 Optical Observation
  21. GRB 250601A: Fermi GBM Observation
  22. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  23. GRB 250603A: Swift/UVOT Upper Limits
  24. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  25. GRB 250602A: Fermi GBM Observation
  26. GRB 250602A: Fermi-LAT detection
  27. GRB 250602A: DDOTI Optical Upper Limit
  28. GRB 250530C: Swift-BAT refined analysis
  29. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  30. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  31. GRB 250601A: Swift/XRT candidate afterglow
  32. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  33. Fermi GRB 250601A: Global MASTER-Net observations report
  34. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  35. GRB 250601A: Swift ToO observations
  36. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  37. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  38. EP#01709177494: SVOM/VT optical observations
  39. Fermi GRB 250531A: Global MASTER-Net observations report
  40. GRB 250530C: BOOTES-7 optical upper limit
  41. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  42. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  43. Swift GRB 250530C: Global MASTER-Net observations report
  44. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  45. GRB 250530A: EP-FXT counterpart detection
  46. GRB 250530A: SVOM/VT optical upper limit
  47. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  48. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  49. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  50. GRB 250527C: Swift/UVOT Upper Limits
  51. EP J1350.0-8622: EP-FXT follow-up observation
  52. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  53. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  54. GRB 250520A: Swift-BAT refined analysis
  55. GRB 250527C: Swift ToO observations
  56. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  57. EP250526a: SVOM/VT optical upper limit
  58. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  59. GRB 250527B: Tiled Swift observations
  60. GRB 250520A: Gemini-South optical afterglow detection
  61. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  62. GRB 250314A: CIDER NB1008 upper limit
  63. EP250526a: COLIBRÍ optical upper limits
  64. EP250526a: Global MASTER-Net observations report
  65. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  66. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  67. GRB 250520A: 3 GHz MeerKAT Detection
  68. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  69. Fermi GRB 250523A: Global MASTER-Net observations report
  70. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  71. GRB 250521A: GRBAlpha detection
  72. GRB 250520A: GRBAlpha detection
  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 250521D: SVOM/VT optical observations
  79. EP#01709176612: Swift-XRT counterpart detection of flaring star
  80. Fermi GRB 250521D: Global MASTER-Net observations report
  81. GRB 250521D: DDOTI Optical Upper Limit
  82. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  83. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 250521D: LAST tentative optical counterpart candidate
  85. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  86. GRB 250520A: 10 GHz VLA radio source
  87. GRB 250521B: Swift ToO observations
  88. GRB 250521A: DDOTI Optical Upper Limit
  89. Konus-Wind detection of GRB 250520A (short/hard)
  90. GRB 250520A: VLT/FORS2 Optical Observation
  91. GRB 250502A: Tautenburg observations
  92. GRB 250520A: Swift/UVOT Upper Limits
  93. Konus-Wind detection of GRB 250516B
  94. IPN triangulation of GRB 250516B
  95. GRB 250520A: J-band observations with WINTER
  96. GRB 250520A: Gemini-South optical observations
  97. GRB 250520A: REM optical/NIR early observations
  98. GRB 250520A：SVOM/VT optical candidate
  99. GRB 250520A: COLIBRÍ optical upper limit
  100. GRB 250520A: DDOTI Optical Upper Limit

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