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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"

18144 results found.

  1. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  2. GRB 250521D: DDOTI Optical Upper Limit
  3. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  4. GRB 250521D: LAST tentative optical counterpart candidate
  5. GRB 250521B: Swift ToO observations
  6. GRB 250521A: DDOTI Optical Upper Limit
  7. GRB 250521B: SVOM detection of a burst through offline search
  8. GRB 250520A: VLT/FORS2 Optical Observation
  9. GRB 250502A: Tautenburg observations
  10. GRB 250520A: Swift/UVOT Upper Limits
  11. IPN triangulation of GRB 250516B
  12. GRB 250520A: J-band observations with WINTER
  13. GRB 250520A: Gemini-South optical observations
  14. GRB 250520A: REM optical/NIR early observations
  15. GRB 250520A：SVOM/VT optical candidate
  16. GRB 250520A: COLIBRÍ optical upper limit
  17. GRB 250520A: DDOTI Optical Upper Limit
  18. GRB 250520A: Enhanced Swift-XRT position
  19. GRB 250520A: Swift detection of a burst
  20. GRB 250516A: COLIBRÍ optical upper limit
  21. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  22. GRB 250515A: Swift-XRT observations
  23. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  24. GRB 250515A: 1.6m Mephisto optical detection
  25. GRB 250516A: AstroSat CZTI detection
  26. GRB 250516A: Swift/UVOT Detection
  27. GRB 250515A: Swift ToO observations
  28. GRB 250516A: Enhanced Swift-XRT position
  29. GRB 250516A: Swift detection of a burst
  30. GRB 250424A: COLIBRÍ detection of the associated supernova
  31. Konus-Wind detection of GRB 250512B / EP250512a
  32. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  33. EP250512a/GRB 250512B: REM optical/NIR observations
  34. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  35. GRB 250507B: AstroSat CZTI detection
  36. EP250511a: Gemini optical counterpart observation
  37. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  38. EP250511a: Mephisto optical upper limits
  39. GRB 250512B: SVOM detection of a burst
  40. EP250512a: Einstein Probe detection of an X-ray transient
  41. EP250511a: REM optical/NIR observations
  42. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  43. EP250511a: COLIBRÍ optical counterpart candidate
  44. EP250511a: Einstein Probe detection of an X-ray transient
  45. EP250508a: Gemini NIR upper limits
  46. GRB 250510A: Swift-XRT observations
  47. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  48. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  49. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 250507A: J-band observations with WINTER
  51. GRB 250509A: Enhanced Swift-XRT position
  52. GRB 250509A: Swift detection of a burst
  53. GRB 250506A: NOT optical upper limits
  54. EP250508a: Liverpool Telescope optical upper limits
  55. EP250508a: KAIT optical upper limit
  56. GRB 250507A: KAIT optical upper limit
  57. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  58. GRB 250505B: SVOM/GRM observation of a short burst
  59. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  60. EP250508a: REM optical/NIR observations
  61. GRB 250506A: Swift-XRT afterglow detection
  62. EP250508a: COLIBRÍ Optical Limit
  63. EP250508a: Einstein Probe detection of an X-ray transient
  64. GRB 250506A: Swift/UVOT Upper Limits
  65. GRB 250427B : SVOM detection of a burst through offline search
  66. GRB 250430A / EP250430a: AstroSat CZTI detection
  67. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 250507A: REM optical/NIR observations
  69. GRB 250507A: SVOM/VT optical upper limit
  70. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  72. GRB 250507A: SVOM detection of a long burst
  73. GRB 250506A: Mephisto optical upper limits
  74. GRB 250506A: Swift ToO observations
  75. GRB 250502A: Bassano Bresciano Observatory upper limit
  76. GRB 250506A: Xinglong 2.16m optical upper limit
  77. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  78. GRB 250506A: REM optical/NIR upper limits
  79. GRB 250506A: TRT optical observations
  80. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  81. GRB 250506A: SVOM detection of a burst
  82. GRB 250504A: VLT/X-shooter upper limits
  83. GRB 250504A: REM optical/NIR observations
  84. GRB 250502A: REM optical/NIR observations
  85. GRB 250504A: MeerLICHT optical afterglow detection
  86. GRB 250504A: Enhanced Swift-XRT position
  87. GRB 250504A: Swift detection of a burst
  88. GRB 250502A: Swift/UVOT Follow up
  89. GRB 250502A: KAIT optical observations
  90. GRB 250502A: Montarrenti Observatory optical detection
  91. GRB 250502A: Swift-XRT afterglow detection
  92. GRB 250502A: NOT optical observations
  93. GRB 250502A: AKO Optical Afterglow Detection
  94. GRB 250502A: LCO optical counterpart detection
  95. GRB 250502A: Swift ToO observations
  96. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  97. GRB 250502B: DDOTI Optical Observations
  98. GRB 250502A: Early optical counterpart detection by LCO.
  99. GRB 250430A: Swift/UVOT Detection
  100. GRB 250502A: TRT optical afterglow confirmation

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