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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"

23838 results found.

  1. GRB 250502A: TESS observations
  2. Fermi trigger No 768922089: Global MASTER-Net observations report
  3. GRB 250509A: Swift-BAT refined analysis
  4. Fermi GRB 250512A: Global MASTER-Net observations report
  5. EP250512a/GRB 250512B: REM optical/NIR observations
  6. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  7. EP250511a: Gemini optical counterpart observation
  8. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  9. EP250512a: Global MASTER-Net observations report
  10. EP250511a: FTW optical and NIR observations
  11. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  12. EP250511a: Mephisto optical upper limits
  13. GRB 250507B: GRBAlpha detection
  14. GRB 250512B: SVOM detection of a burst
  15. GRB 250507B: SVOM/GRM observation of a burst
  16. GRB 250512A: Fermi GBM Final Real-time Localization
  17. EP250511a: REM optical/NIR observations
  18. EP250511a: SVOM/VT optical candidate comfirmation
  19. EP250511a: Global MASTER-Net observations report
  20. EP250511a: COLIBRÍ optical counterpart candidate
  21. EP250508a: Gemini NIR upper limits
  22. GRB 250510B: Fermi GBM Observation
  23. Fermi GRB 250510C: Global MASTER-Net observations report
  24. Fermi GRB 250510B: Global MASTER-Net observations report
  25. GRB 250510C: Fermi GBM Final Real-time Localization
  26. GRB 250510A: Swift-XRT observations
  27. GRB 250509A: Fermi GBM Observation
  28. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  29. GRB 250510B: Fermi GBM Final Localization
  30. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 250509A: Swift-XRT refined Analysis
  32. GRB 250510A: SVOM possible detection of a burst
  33. EP250508a: SVOM/VT optical candidate fading
  34. Fermi GRB 250509A: Global MASTER-Net observations report
  35. Swift GRB 250509A: Global MASTER-Net observations report
  36. GRB 250509A: Swift detection of a burst
  37. GRB 250509A: Fermi GBM Final Real-time Localization
  38. GRB 250506A: NOT optical upper limits
  39. EP250508a: SVOM/VT optical candidate
  40. EP250508a: REM optical/NIR observations
  41. EP250508a: Global MASTER-Net observations report
  42. GRB 250506A: SVOM/VT optical upper limit
  43. EP250508a: COLIBRÍ Optical Limit
  44. GRB 250507A: Swift-XRT refined Analysis
  45. GRB 250427B : SVOM detection of a burst through offline search
  46. GRB 250507A: follow-up observation with EP-FXT
  47. GRB 250430A / EP250430a: AstroSat CZTI detection
  48. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  49. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 250507A: refined SVOM/MXT data analysis
  51. GRB 250507A: REM optical/NIR observations
  52. GRB 250507A: SVOM/VT optical upper limit
  53. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  55. GRB 250507A: SVOM detection of a long burst
  56. GRB 250506A: Mephisto optical upper limits
  57. GRB 250504A: EIRSAT-1 GMOD Detection
  58. GRB 250502A: Bassano Bresciano Observatory upper limit
  59. IceCube Alert 250506.59: Global MASTER-Net observations report
  60. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  61. GRB 250506A: Xinglong 2.16m optical upper limit
  62. SVOM/sb25050601: EP-FXT observations
  63. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  64. GRB 250506A: REM optical/NIR upper limits
  65. GRB 250506A: Fermi GBM Observation
  66. GRB 250506A: Swift XRT observations and possible counterpart detection
  67. GRB 250506A: TRT optical observations
  68. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  69. GRB 250506A: SVOM detection of a burst
  70. GRB 250504A: Swift-BAT refined analysis
  71. GRB 250430A: Swift-BAT refined analysis
  72. GRB 250506A: Fermi GBM Final Real-time Localization
  73. GRB 250504A: Swift-XRT refined Analysis
  74. GRB 250504A: VLT/X-shooter upper limits
  75. Fermi GRB 250505A: Global MASTER-Net observations report
  76. GRB 250504A: REM optical/NIR observations
  77. GRB 250502A: REM optical/NIR observations
  78. GRB 250505A: Fermi GBM Final Real-time Localization
  79. GRB 250504A: MeerLICHT optical afterglow detection
  80. GRB 250504A: Fermi GBM Observation
  81. Fermi GRB 250504A: Global MASTER-Net observations report
  82. GRB 250504A: Swift detection of a burst
  83. GRB 250504A: Fermi GBM Final Real-time Localization
  84. Swift GRB250504.98: Global MASTER-Net observations report
  85. GRB 250502A: Swift/UVOT Follow up
  86. Fermi trigger No 767975731: Global MASTER-Net observations report
  87. GRB 250502A: NOT optical observations
  88. GRB 250502a: Liverpool Telescope optical follow-up
  89. GRB 250502A: AKO Optical Afterglow Detection
  90. GRB 250502A: LCO optical counterpart detection
  91. GRB 250502C: Fermi GBM Final Localization
  92. GRB 250502B: DDOTI Optical Observations
  93. GRB 250430A: Swift-XRT refined Analysis
  94. GRB 250502A: Early optical counterpart detection by LCO.
  95. GRB 250430A: Swift/UVOT Detection
  96. GRB 250502A: TRT optical afterglow confirmation
  97. Fermi GRB 250502B: Global MASTER-Net observations report
  98. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  99. GRB 250502B: Fermi GBM Final Real-time Localization
  100. GRB 250502A: SVOM detection of a burst

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