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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').
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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"

45423 results found.

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

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