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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"

3402 results found.

  1. GRB 250706B: Swift/UVOT Detection
  2. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  3. GRB 250706A: Swift-XRT refined Analysis
  4. GRB 250706B: refined SVOM/MXT data analysis
  5. GRB250706B: Swift-XRT counterpart detection
  6. GRB 250704B: Swift-XRT refined Analysis
  7. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  8. GRB 250704B: Swift/UVOT Upper Limits
  9. GRB 250704A: Swift/UVOT Detection
  10. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  11. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  12. EP250704a / GRB250704B: Swift-XRT counterpart detection
  13. GRB 250704A: Swift-XRT afterglow detection
  14. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  15. GRB 250702F: Swift-XRT refined Analysis
  16. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  17. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  18. GRB 250628B: Swift-XRT observations
  19. GRB 250628A: Swift-XRT refined Analysis
  20. GRB 250625A: Swift-XRT refined Analysis
  21. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  22. GRB 250617B: Swift-XRT refined Analysis
  23. EP#01709178975: Swift-XRT counterpart detection
  24. GRB 250615A: Swift-XRT refined Analysis
  25. GRB 250615A: Prompt enhanced Swift-XRT position
  26. sb25061218: Swift-XRT observations
  27. sb25061207: EP-FXT follow-up observation and afterglow candidate
  28. sb25061207: Swift-XRT observations
  29. GRB 250610B: Swift-XRT refined Analysis
  30. GRB 250610B: Swift/UVOT Detection
  31. EP250610A: Swift/UVOT Upper limits
  32. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  33. GRB 250610B: Swift-XRT counterpart detection
  34. EP250610a: Swift-XRT counterpart detection
  35. GRB 250605A: Swift-XRT refined Analysis
  36. GRB 250603A: Swift-XRT refined Analysis
  37. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  38. GRB 250601A: Swift-XRT observations
  39. EP#01709177494: Swift-XRT counterpart detection of known source
  40. GRB 250530C: Swift-XRT refined Analysis
  41. GRB 250530A: Swift-XRT counterpart detection
  42. GRB 250527C: Swift/UVOT Upper Limits
  43. EP J1350.0-8622: EP-FXT follow-up observation
  44. GRB 250527B: Swift-XRT observations
  45. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  46. EP#01709176612: Swift-XRT counterpart detection of flaring star
  47. GRB 250520A: Swift-XRT refined Analysis
  48. GRB 250520A: Prompt enhanced Swift-XRT position
  49. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  50. GRB 250515A: Swift-XRT observations
  51. GRB 250516A: Swift-XRT refined Analysis
  52. GRB 250516A: Swift/UVOT Detection
  53. EP250508a: Gemini NIR upper limits
  54. GRB 250510A: Swift-XRT observations
  55. GRB 250509A: Swift-XRT refined Analysis
  56. GRB 250506A: Swift-XRT afterglow detection
  57. GRB 250507A: Swift-XRT refined Analysis
  58. GRB 250506A: Swift/UVOT Upper Limits
  59. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  60. GRB 250507A: refined SVOM/MXT data analysis
  61. GRB 250506A: Swift-XRT observations
  62. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  63. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  64. GRB 250506A: Swift XRT observations and possible counterpart detection
  65. GRB 250504A: Swift-XRT refined Analysis
  66. GRB 250502A: Swift-XRT afterglow detection
  67. GRB 250430A: Swift-XRT refined Analysis
  68. EP250428b: refined analysis of the EP-FXT follow-up observation
  69. GRB 250427A: Swift/UVOT Detection
  70. EP250427a: EP-FXT follow-up observations
  71. GRB 250427A: Swift-XRT refined Analysis
  72. GRB 250424A: Swift-XRT refined Analysis
  73. SVOM/sb25042207: XRT observations
  74. EP250421a: Swift/XRT counterpart detection
  75. GRB 250419A: Swift-XRT refined Analysis
  76. EP250416a: Swift/XRT counterpart fading
  77. EP20250416a: Swift/XRT counterpart detection
  78. SVOM/sb25041603 is not a GRB
  79. IceCube-250406A: Swift-XRT observations
  80. EP250407a: Swift-XRT observations
  81. GRB 250407A: Swift-XRT afterglow detection
  82. GRB 250331D: Swift-XRT afterglow detection
  83. EP250402a: EP-FXT follow-up observations
  84. GRB 250403A: Swift-XRT observations
  85. GRB 250402A: Swift-XRT observations
  86. GRB 250402A: refined SVOM/MXT data analysis
  87. GRB 250329B: Swift/UVOT Upper Limit
  88. GRB 250327A: Swift/UVOT Upper Limits
  89. GRB 250331D: Swift-XRT observations
  90. GRB 250331C: Swift-XRT refined Analysis
  91. GRB 250331B: Swift-XRT refined Analysis
  92. GRB 250331B: Swift-XRT refined Analysis
  93. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  94. GRB 250328A: Swift-XRT refined Analysis
  95. GRB 250331C: Prompt enhanced Swift-XRT position
  96. GRB 250330A: Swift-XRT afterglow detection
  97. GRB 250330A: Prompt Swift-XRT position
  98. GRB 250329B: Swift-XRT afterglow detection
  99. GRB 250329A: Swift-XRT afterglow detection
  100. GRB 250327A: SVOM/VT upper limits on the XRT position

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