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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"

2409 results found.

  1. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  2. GRB 250520A: GRBAlpha detection
  3. GRB 250521B: SVOM/VT optical upper limit
  4. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  5. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  6. GRB 250521D: SVOM/VT optical observations
  7. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  9. GRB 250520A: 10 GHz VLA radio source
  10. GRB 250521B: Swift ToO observations
  11. GRB 250521B: SVOM detection of a burst through offline search
  12. Konus-Wind detection of GRB 250520A (short/hard)
  13. GRB 250520A: VLT/FORS2 Optical Observation
  14. GRB 250502A: Tautenburg observations
  15. GRB 250520A: Swift/UVOT Upper Limits
  16. GRB 250520A: J-band observations with WINTER
  17. GRB 250520A: Gemini-South optical observations
  18. GRB 250520A: REM optical/NIR early observations
  19. GRB 250520A:SVOM/VT optical candidate
  20. GRB 250520A: COLIBRÍ optical upper limit
  21. GRB 250520A: DDOTI Optical Upper Limit
  22. GRB 250520A: AstroSat CZTI detection of a short burst
  23. GRB 250520A: SVOM/GRM observation
  24. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  25. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  26. GRB 250512B / EP250512a: SVOM/GRM analysis
  27. Konus-Wind detection of GRB 250512B / EP250512a
  28. Konus-Wind detection of GRB 250506A
  29. EP250512a/GRB 250512B: REM optical/NIR observations
  30. GRB 250507B: AstroSat CZTI detection
  31. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 250512B/EP250512a: SVOM/VT optical fading
  33. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  34. GRB 250506A: GRBAlpha detection
  35. GRB 250512B: SVOM detection of a burst
  36. GRB 250507B: SVOM/GRM observation of a burst
  37. EP250511a: SVOM/VT optical candidate comfirmation
  38. EP250508a: Gemini NIR upper limits
  39. GRB 250510A: Swift-XRT observations
  40. GRB 250510A: follow-up observation with EP-FXT
  41. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 250510A: SVOM possible detection of a burst
  43. GRB 250507A: J-band observations with WINTER
  44. EP250508a: SVOM/VT optical candidate fading
  45. GRB 250506A: NOT optical upper limits
  46. EP250508a: SVOM/VT optical candidate
  47. GRB 250507A: KAIT optical upper limit
  48. GRB 250505B: SVOM/GRM observation of a short burst
  49. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  50. GRB 250506A: GECAM detection
  51. GRB 250506A: Swift-XRT afterglow detection
  52. GRB 250506A: SVOM/VT optical upper limit
  53. GRB 250507A: Swift-XRT refined Analysis
  54. GRB 250506A: Swift/UVOT Upper Limits
  55. GRB 250427B : SVOM detection of a burst through offline search
  56. GRB 250507A: follow-up observation with EP-FXT
  57. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. GRB 250507A: refined SVOM/MXT data analysis
  59. GRB 250507A: REM optical/NIR observations
  60. GRB 250507A: SVOM/VT optical upper limit
  61. GRB 250506A: Swift-XRT observations
  62. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. GRB 250507A: SVOM detection of a long burst
  64. GRB 250506A: Mephisto optical upper limits
  65. GRB 250506A: Swift ToO observations
  66. GRB 250502A: Bassano Bresciano Observatory upper limit
  67. GRB 250506A: Xinglong 2.16m optical upper limit
  68. SVOM/sb25050601: EP-FXT observations
  69. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  70. GRB 250506A: REM optical/NIR upper limits
  71. GRB 250506A: Fermi GBM Observation
  72. GRB 250506A: Swift XRT observations and possible counterpart detection
  73. GRB 250506A: TRT optical observations
  74. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  75. GRB 250506A: SVOM detection of a burst
  76. GRB 250504A: SVOM/VT upper limit
  77. GRB 250502A: REM optical/NIR observations
  78. GRB 250502A: Swift/UVOT Follow up
  79. GRB 250502A: KAIT optical observations
  80. GRB 250502A: Montarrenti Observatory optical detection
  81. GRB 250502A: Swift-XRT afterglow detection
  82. GRB 250502A: NOT optical observations
  83. GRB 250502a: Liverpool Telescope optical follow-up
  84. GRB 250502A: AKO Optical Afterglow Detection
  85. GRB 250502A: LCO optical counterpart detection
  86. GRB 250502A: Swift ToO observations
  87. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  88. GRB 250407A: VZLUSAT-2 detection
  89. GRB 250502A: Early optical counterpart detection by LCO.
  90. GRB 250502A: SVOM/VT optical bump
  91. GRB 250502A: TRT optical afterglow confirmation
  92. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  93. GRB 250502A: SVOM detection of a burst
  94. GRB 250430A: SVOM/VT optical observations
  95. SVOM/sb25043004: EP-FXT observations
  96. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  97. SVOM/sb25043004: SVOM detection of a X-ray transient
  98. EP250428b: GROWTH-India telescope optical upper limit
  99. EP250428b: SVOM/VT upper limit
  100. GRB 250424A: SVOM/GRM observation of a long burst

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