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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"
  1. GRB 250515A: GOTO candidate optical counterpart
  2. MAXI GRB250515.65: Global MASTER-Net observations report
  3. GRB 250515A: Fermi GBM Final Localization
  4. GRB 250424A: COLIBRÍ detection of the associated supernova
  5. Konus-Wind detection of GRB 250512B / EP250512a
  6. GRB 250502A: TESS observations
  7. Fermi trigger No 768922089: Global MASTER-Net observations report
  8. GRB 250511A: GECAM-A detection of a short burst
  9. GRB 250509A: Swift-BAT refined analysis
  10. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  11. Fermi GRB 250512A: Global MASTER-Net observations report
  12. Konus-Wind detection of GRB 250506A
  13. EP250512a/GRB 250512B: REM optical/NIR observations
  14. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  15. GRB 250507B: AstroSat CZTI detection
  16. EP250511a: Gemini optical counterpart observation
  17. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  18. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  19. EP250512a: Global MASTER-Net observations report
  20. EP250511a: FTW optical and NIR observations
  21. GRB 250512B/EP250512a: SVOM/VT optical fading
  22. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  23. EP250511a: Mephisto optical upper limits
  24. GRB 250507B: GRBAlpha detection
  25. GRB 250506A: GRBAlpha detection
  26. GRB 250512B: SVOM detection of a burst
  27. GRB 250507B: SVOM/GRM observation of a burst
  28. EP250512a: Einstein Probe detection of an X-ray transient
  29. GRB 250512A: Fermi GBM Final Real-time Localization
  30. EP250511a: REM optical/NIR observations
  31. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  32. EP250511a: SVOM/VT optical candidate comfirmation
  33. EP250511a: Global MASTER-Net observations report
  34. EP250511a: COLIBRÍ optical counterpart candidate
  35. EP250511a: BOOTES-5 optical upper limit
  36. EP250511a: Einstein Probe detection of an X-ray transient
  37. EP250508a: Gemini NIR upper limits
  38. GRB 250510B: Fermi GBM Observation
  39. Fermi GRB 250510C: Global MASTER-Net observations report
  40. Fermi GRB 250510B: Global MASTER-Net observations report
  41. GRB 250510C: Fermi GBM Final Real-time Localization
  42. GRB 250510A: Swift-XRT observations
  43. GRB 250509A: Fermi GBM Observation
  44. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  45. GRB 250510A: follow-up observation with EP-FXT
  46. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  47. GRB 250510B: Fermi GBM Final Localization
  48. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  49. GRB 250509A: Swift-XRT refined Analysis
  50. GRB 250510A: SVOM possible detection of a burst
  51. GRB 250507A: J-band observations with WINTER (duplicate submission)
  52. GRB 250507A: J-band observations with WINTER
  53. EP250508a: SVOM/VT optical candidate fading
  54. GRB 250509A: Enhanced Swift-XRT position
  55. GRB 250509A: Prompt enhanced Swift-XRT position
  56. Fermi GRB 250509A: Global MASTER-Net observations report
  57. Swift GRB 250509A: Global MASTER-Net observations report
  58. GRB 250509A: Swift detection of a burst
  59. GRB 250509A: Fermi GBM Final Real-time Localization
  60. GRB 250506A: NOT optical upper limits
  61. EP250508a: Liverpool Telescope optical upper limits
  62. EP250508a: follow-up observation with EP-FXT
  63. EP250508a: SVOM/VT optical candidate
  64. EP250508a: KAIT optical upper limit
  65. GRB 250507A: KAIT optical upper limit
  66. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 250505B: SVOM/GRM observation of a short burst
  68. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  69. GRB 250506A: GECAM detection
  70. EP250508a: REM optical/NIR observations
  71. GRB 250506A: Swift-XRT afterglow detection
  72. EP250508a: Global MASTER-Net observations report
  73. GRB 250506A: SVOM/VT optical upper limit
  74. EP250508a: COLIBRÍ Optical Limit
  75. EP250508a: Einstein Probe detection of an X-ray transient
  76. GRB 250507A: Swift-XRT refined Analysis
  77. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 250506A: Swift/UVOT Upper Limits
  79. GRB 250427B : SVOM detection of a burst through offline search
  80. GRB 250507A: follow-up observation with EP-FXT
  81. GRB 250430A / EP250430a: AstroSat CZTI detection
  82. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  83. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 250507A: refined SVOM/MXT data analysis
  85. GRB 250507A: REM optical/NIR observations
  86. GRB 250507A: SVOM/VT optical upper limit
  87. GRB 250506A: Swift-XRT observations
  88. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  89. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  91. GRB 250507A: SVOM detection of a long burst
  92. GRB 250506A: Mephisto optical upper limits
  93. GRB 250504A: EIRSAT-1 GMOD Detection
  94. GRB 250506A: Swift ToO observations
  95. GRB 250502A: Bassano Bresciano Observatory upper limit
  96. IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
  97. IceCube Alert 250506.59: Global MASTER-Net observations report
  98. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  99. GRB 250506A: Xinglong 2.16m optical upper limit
  100. SVOM/sb25050601: EP-FXT observations

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