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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"

22856 results found.

  1. GRB 250520A: Swift/UVOT Upper Limits
  2. IPN triangulation of GRB 250516B
  3. GRB 250520A: J-band observations with WINTER
  4. GRB 250520A: Gemini-South optical observations
  5. GRB 250520A: REM optical/NIR early observations
  6. GRB 250520A：SVOM/VT optical candidate
  7. GRB 250520A: COLIBRÍ optical upper limit
  8. GRB 250520A: DDOTI Optical Upper Limit
  9. GRB 250520A: Enhanced Swift-XRT position
  10. GRB 250520A: GOTO optical upper limit
  11. GRB 250520A: Swift detection of a burst
  12. GRB 250516A: COLIBRÍ optical upper limit
  13. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  14. GRB 250515A: Swift-XRT observations
  15. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  16. GRB 250515A: 1.6m Mephisto optical detection
  17. GRB 250516A: Swift-XRT refined Analysis
  18. GRB 250516A: Swift/UVOT Detection
  19. GRB 250516A: Enhanced Swift-XRT position
  20. GRB 250516A: Swift detection of a burst
  21. GRB 250512B / EP250512a: SVOM/GRM analysis
  22. GRB 250515A: GOTO candidate optical counterpart
  23. GRB 250424A: COLIBRÍ detection of the associated supernova
  24. GRB 250502A: TESS observations
  25. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  26. EP250512a/GRB 250512B: REM optical/NIR observations
  27. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  28. EP250511a: Gemini optical counterpart observation
  29. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  30. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  31. EP250511a: FTW optical and NIR observations
  32. EP250511a: Mephisto optical upper limits
  33. GRB 250512B: SVOM detection of a burst
  34. EP250512a: Einstein Probe detection of an X-ray transient
  35. EP250511a: REM optical/NIR observations
  36. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  37. EP250511a: COLIBRÍ optical counterpart candidate
  38. EP250511a: Einstein Probe detection of an X-ray transient
  39. EP250508a: Gemini NIR upper limits
  40. GRB 250510A: Swift-XRT observations
  41. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  42. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  43. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. GRB 250509A: Swift-XRT refined Analysis
  45. GRB 250507A: J-band observations with WINTER
  46. GRB 250509A: Enhanced Swift-XRT position
  47. GRB 250509A: Swift detection of a burst
  48. GRB 250506A: NOT optical upper limits
  49. EP250508a: Liverpool Telescope optical upper limits
  50. EP250508a: KAIT optical upper limit
  51. GRB 250507A: KAIT optical upper limit
  52. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  53. GRB 250505B: SVOM/GRM observation of a short burst
  54. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  55. EP250508a: REM optical/NIR observations
  56. GRB 250506A: Swift-XRT afterglow detection
  57. GRB 250506A: SVOM/VT optical upper limit
  58. EP250508a: COLIBRÍ Optical Limit
  59. EP250508a: Einstein Probe detection of an X-ray transient
  60. GRB 250506A: Swift/UVOT Upper Limits
  61. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. GRB 250507A: REM optical/NIR observations
  63. GRB 250507A: SVOM/VT optical upper limit
  64. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  66. GRB 250507A: SVOM detection of a long burst
  67. GRB 250506A: Mephisto optical upper limits
  68. GRB 250502A: Bassano Bresciano Observatory upper limit
  69. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  70. GRB 250506A: Xinglong 2.16m optical upper limit
  71. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  72. GRB 250506A: REM optical/NIR upper limits
  73. GRB 250506A: Swift XRT observations and possible counterpart detection
  74. GRB 250506A: TRT optical observations
  75. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  76. GRB 250506A: SVOM detection of a burst
  77. GRB 250504A: Swift-XRT refined Analysis
  78. GRB 250504A: VLT/X-shooter upper limits
  79. Fermi GRB 250505A: Global MASTER-Net observations report
  80. GRB 250504A: SVOM/VT upper limit
  81. GRB 250504A: REM optical/NIR observations
  82. GRB 250502A: REM optical/NIR observations
  83. GRB 250504A: MeerLICHT optical afterglow detection
  84. GRB 250504A: Enhanced Swift-XRT position
  85. GRB 250504A: Swift detection of a burst
  86. GRB 250502A: Swift/UVOT Follow up
  87. GRB 250502A: KAIT optical observations
  88. GRB 250502A: Montarrenti Observatory optical detection
  89. GRB 250502A: Swift-XRT afterglow detection
  90. GRB 250502A: NOT optical observations
  91. GRB 250502B: AstroSat CZTI detection
  92. GRB 250502A: AKO Optical Afterglow Detection
  93. GRB 250502A: LCO optical counterpart detection
  94. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  95. GRB 250502B: DDOTI Optical Observations
  96. GRB 250502A: Early optical counterpart detection by LCO.
  97. GRB 250430A: Swift/UVOT Detection
  98. GRB 250502A: TRT optical afterglow confirmation
  99. GRB 250430A: Enhanced Swift-XRT position
  100. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate

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