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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"

25028 results found.

  1. GRB 250530C: Swift-XRT refined Analysis
  2. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  3. GRB 250530C: Enhanced Swift-XRT position
  4. GRB 250530C: Swift detection of a burst
  5. GRB 250530A: EP-FXT counterpart detection
  6. GRB 250530A: SVOM/VT optical upper limit
  7. GRB 250530A: Swift-XRT counterpart detection
  8. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  9. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  10. GRB 250530A: SVOM detection of a burst
  11. GRB 250527C: Swift/UVOT Upper Limits
  12. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  13. GRB 250527B: Swift-XRT observations
  14. GRB 250520A: Swift-BAT refined analysis
  15. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  16. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  17. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  18. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  19. GRB 250314A: CIDER NB1008 upper limit
  20. EP250526a: COLIBRÍ optical upper limits
  21. EP250526a: Einstein Probe detection of a fast X-ray transient
  22. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  23. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  24. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  25. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  26. EP#01709176612: Swift-XRT counterpart detection of flaring star
  27. GRB 250521D: DDOTI Optical Upper Limit
  28. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 250521D: LAST tentative optical counterpart candidate
  30. GRB 250521A: DDOTI Optical Upper Limit
  31. GRB 250520A: VLT/FORS2 Optical Observation
  32. GRB 250502A: Tautenburg observations
  33. GRB 250520A: Swift/UVOT Upper Limits
  34. IPN triangulation of GRB 250516B
  35. GRB 250520A: J-band observations with WINTER
  36. GRB 250520A: Gemini-South optical observations
  37. GRB 250520A: Swift-XRT refined Analysis
  38. GRB 250520A: REM optical/NIR early observations
  39. GRB 250520A:SVOM/VT optical candidate
  40. GRB 250520A: COLIBRÍ optical upper limit
  41. GRB 250520A: DDOTI Optical Upper Limit
  42. GRB 250520A: AstroSat CZTI detection of a short burst
  43. GRB 250520A: Enhanced Swift-XRT position
  44. GRB 250520A: Swift detection of a burst
  45. GRB 250516A: Swift-BAT refined analysis
  46. GRB 250516A: COLIBRÍ optical upper limit
  47. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  48. GRB 250515A: Swift-XRT observations
  49. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  50. GRB 250515A: 1.6m Mephisto optical detection
  51. GRB 250516A: Fermi GBM Observation
  52. GRB 250516A: Swift-XRT refined Analysis
  53. GRB 250516A: Swift/UVOT Detection
  54. GRB 250516B: GECAM-B detection of a bright long burst
  55. GRB 250516A: Enhanced Swift-XRT position
  56. GRB 250516A: Swift detection of a burst
  57. MAXI GRB250515.65: Global MASTER-Net observations report
  58. GRB 250424A: COLIBRÍ detection of the associated supernova
  59. GRB 250502A: TESS observations
  60. GRB 250509A: Swift-BAT refined analysis
  61. Fermi GRB 250512A: Global MASTER-Net observations report
  62. EP250512a/GRB 250512B: REM optical/NIR observations
  63. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  64. GRB 250507B: AstroSat CZTI detection
  65. EP250511a: Gemini optical counterpart observation
  66. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  67. EP250511a: Mephisto optical upper limits
  68. GRB 250512B: SVOM detection of a burst
  69. EP250512a: Einstein Probe detection of an X-ray transient
  70. EP250511a: REM optical/NIR observations
  71. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  72. EP250511a: COLIBRÍ optical counterpart candidate
  73. EP250511a: BOOTES-5 optical upper limit
  74. EP250511a: Einstein Probe detection of an X-ray transient
  75. EP250508a: Gemini NIR upper limits
  76. GRB 250510B: Fermi GBM Observation
  77. GRB 250510A: Swift-XRT observations
  78. GRB 250509A: Fermi GBM Observation
  79. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  80. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  81. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. GRB 250509A: Swift-XRT refined Analysis
  83. GRB 250510A: SVOM possible detection of a burst
  84. GRB 250507A: J-band observations with WINTER
  85. GRB 250509A: Enhanced Swift-XRT position
  86. GRB 250509A: Swift detection of a burst
  87. GRB 250506A: NOT optical upper limits
  88. EP250508a: Liverpool Telescope optical upper limits
  89. EP250508a: KAIT optical upper limit
  90. GRB 250507A: KAIT optical upper limit
  91. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250505B: SVOM/GRM observation of a short burst
  93. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  94. EP250508a: REM optical/NIR observations
  95. GRB 250506A: Swift-XRT afterglow detection
  96. EP250508a: COLIBRÍ Optical Limit
  97. EP250508a: Einstein Probe detection of an X-ray transient
  98. GRB 250507A: Swift-XRT refined Analysis
  99. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 250506A: Swift/UVOT Upper Limits

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