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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

32501 results found.

  1. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. EP250610a: TNG NIR upper limit
  3. GRB 250610B: REM optical/NIR observations
  4. EP250610a: Liverpool Telescope optical upper limits
  5. GRB 250610B: SVOM/VT optical shallow decay
  6. GRB 250610B: additional Liverpool Telescope optical observations
  7. GRB 250610B: SVOM/GRM analysis
  8. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  9. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  10. GRB 250610B: Swift-XRT counterpart detection
  11. GRB 250610B: SVOM/VT optical counterpart
  12. GRB 250610B: LT detection of the optical counterpart
  13. GRB 250610B: OHP/T120 optical counterpart candidate
  14. GRB 250610B: GOTO optical upper limit
  15. EP250610a: Global MASTER-Net observations report
  16. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  17. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 250605A: Swift-BAT refined analysis
  19. EP250610a: SVOM/VT optical upper limit
  20. EP250610a: REM optical/NIR observations
  21. GRB 250609A: Fermi GBM Observation
  22. EP250610a: COLIBRÍ optical upper limit
  23. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  24. GRB 250605A: Swift/UVOT Upper Limits
  25. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  26. GRB 250527C: CrAO Optical Upper Limit
  27. GRB 250607A: SVOM/GRM observation of a long burst
  28. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  29. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  30. GRB 250605A: SVOM/VT optical upper limit
  31. Fermi GRB 250606A: Global MASTER-Net observations report
  32. GRB 250602A: GECAM detection
  33. GRB 250605A: LT optical observations
  34. Konus-Wind detection of GRB 250601A
  35. IPN triangulation of GRB 250404B
  36. IPN triangulation of GRB 250529A
  37. GRB 250601A: PRIME H band upper limit.
  38. GRB 250530A: SVOM/GRM analysis
  39. GRB 250601A: PRIME J band upper limit.
  40. GRB 250601A: VLT/FORS2 Optical Observation
  41. GRB 250601A: Fermi GBM Observation
  42. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  43. GRB 250603A: Swift/UVOT Upper Limits
  44. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  45. GRB 250602A: Fermi GBM Observation
  46. GRB 250602A: Fermi-LAT detection
  47. GRB 250602A: DDOTI Optical Upper Limit
  48. GRB 250530C: Swift-BAT refined analysis
  49. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  50. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  51. GRB 250601A: Swift/XRT candidate afterglow
  52. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  53. Fermi GRB 250601A: Global MASTER-Net observations report
  54. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  55. GRB 250601A: Swift ToO observations
  56. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  57. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  58. EP#01709177494: SVOM/VT optical observations
  59. Fermi GRB 250531A: Global MASTER-Net observations report
  60. GRB 250530C: BOOTES-7 optical upper limit
  61. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  62. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  63. Swift GRB 250530C: Global MASTER-Net observations report
  64. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  65. GRB 250530A: EP-FXT counterpart detection
  66. GRB 250530A: SVOM/VT optical upper limit
  67. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  68. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  69. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  70. GRB 250527C: Swift/UVOT Upper Limits
  71. EP J1350.0-8622: EP-FXT follow-up observation
  72. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  73. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  74. GRB 250520A: Swift-BAT refined analysis
  75. GRB 250527C: Swift ToO observations
  76. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  77. EP250526a: SVOM/VT optical upper limit
  78. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  79. GRB 250527B: Tiled Swift observations
  80. GRB 250520A: Gemini-South optical afterglow detection
  81. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  82. GRB 250314A: CIDER NB1008 upper limit
  83. EP250526a: COLIBRÍ optical upper limits
  84. EP250526a: Global MASTER-Net observations report
  85. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  86. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  87. GRB 250520A: 3 GHz MeerKAT Detection
  88. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  89. Fermi GRB 250523A: Global MASTER-Net observations report
  90. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  91. GRB 250521A: GRBAlpha detection
  92. GRB 250520A: GRBAlpha detection
  93. GRB 250521B: SVOM/VT optical upper limit
  94. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  95. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  96. Fermi GRB 250522B: Global MASTER-Net observations report
  97. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  98. GRB 250521D: SVOM/VT optical observations
  99. EP#01709176612: Swift-XRT counterpart detection of flaring star
  100. Fermi GRB 250521D: Global MASTER-Net observations report

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