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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"

36155 results found.

  1. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  2. Swift GRB 250516A: Global MASTER-Net observations report
  3. GRB 250515A: 1.6m Mephisto optical detection
  4. GRB 250516A: AstroSat CZTI detection
  5. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  6. GRB 250516A: Fermi GBM Observation
  7. GRB 250516A: Swift-XRT refined Analysis
  8. GRB 250516A: Swift/UVOT Detection
  9. GRB 250515A: Swift ToO observations
  10. GRB 250516B: GECAM-B detection of a bright long burst
  11. GRB 250516A: Enhanced Swift-XRT position
  12. GRB 250516A: Swift detection of a burst
  13. GRB 250516A: Fermi GBM Final Real-time Localization
  14. GRB 250512B / EP250512a: SVOM/GRM analysis
  15. GRB 250515A: GOTO candidate optical counterpart
  16. GRB 250515A: Fermi GBM Final Localization
  17. GRB 250424A: COLIBRÍ detection of the associated supernova
  18. Konus-Wind detection of GRB 250512B / EP250512a
  19. GRB 250502A: TESS observations
  20. GRB 250511A: GECAM-A detection of a short burst
  21. GRB 250509A: Swift-BAT refined analysis
  22. Fermi GRB 250512A: Global MASTER-Net observations report
  23. Konus-Wind detection of GRB 250506A
  24. EP250512a/GRB 250512B: REM optical/NIR observations
  25. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  26. GRB 250507B: AstroSat CZTI detection
  27. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  28. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  29. GRB 250512B/EP250512a: SVOM/VT optical fading
  30. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  31. GRB 250507B: GRBAlpha detection
  32. GRB 250506A: GRBAlpha detection
  33. GRB 250512B: SVOM detection of a burst
  34. GRB 250507B: SVOM/GRM observation of a burst
  35. GRB 250512A: Fermi GBM Final Real-time Localization
  36. EP250511a: REM optical/NIR observations
  37. EP250511a: BOOTES-5 optical upper limit
  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. GRB 250510A: follow-up observation with EP-FXT
  45. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  46. GRB 250510B: Fermi GBM Final Localization
  47. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. GRB 250509A: Swift-XRT refined Analysis
  49. GRB 250510A: SVOM possible detection of a burst
  50. GRB 250507A: J-band observations with WINTER (duplicate submission)
  51. GRB 250507A: J-band observations with WINTER
  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: KAIT optical upper limit
  60. GRB 250507A: KAIT optical upper limit
  61. GRB 250505B: SVOM/GRM observation of a short burst
  62. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  63. GRB 250506A: GECAM detection
  64. EP250508a: REM optical/NIR observations
  65. GRB 250506A: Swift-XRT afterglow detection
  66. GRB 250506A: SVOM/VT optical upper limit
  67. GRB 250507A: Swift-XRT refined Analysis
  68. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 250506A: Swift/UVOT Upper Limits
  70. GRB 250427B : SVOM detection of a burst through offline search
  71. GRB 250507A: follow-up observation with EP-FXT
  72. GRB 250430A / EP250430a: AstroSat CZTI detection
  73. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. GRB 250507A: refined SVOM/MXT data analysis
  75. GRB 250507A: REM optical/NIR observations
  76. GRB 250507A: SVOM/VT optical upper limit
  77. GRB 250506A: Swift-XRT observations
  78. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  79. GRB 250507A: SVOM detection of a long burst
  80. GRB 250506A: Mephisto optical upper limits
  81. GRB 250504A: EIRSAT-1 GMOD Detection
  82. GRB 250506A: Swift ToO observations
  83. GRB 250502A: Bassano Bresciano Observatory upper limit
  84. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  85. GRB 250506A: Xinglong 2.16m optical upper limit
  86. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  87. GRB 250506A: REM optical/NIR upper limits
  88. GRB 250506A: Fermi GBM Observation
  89. GRB 250506A: Swift XRT observations and possible counterpart detection
  90. GRB 250506A: TRT optical observations
  91. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  92. GRB 250506A: SVOM detection of a burst
  93. GRB 250504A: Swift-BAT refined analysis
  94. GRB 250430A: Swift-BAT refined analysis
  95. GRB 250506A: Fermi GBM Final Real-time Localization
  96. GRB 250504A: Swift-XRT refined Analysis
  97. GRB 250504A: VLT/X-shooter upper limits
  98. Fermi GRB 250505A: Global MASTER-Net observations report
  99. GRB 250504A: SVOM/VT upper limit
  100. GRB 250504A: REM optical/NIR observations

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