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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

1096 results found.

  1. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  2. EP250916a: EP-FXT follow-up observation
  3. The EP-WXT trigger 01709241037 is likely a flaring star
  4. EP250916a: Einstein Probe detection of an X-ray transient
  5. The EP-WXT trigger 01709240768 is likely a flaring star
  6. EP250911a: Upper limit from Fermi-GBM Observations
  7. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  8. EP250911a: Swift-XRT observations
  9. EP250911a: Einstein Probe detection of an X-ray transient
  10. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  11. EP250908C: GROND observation of the fading optical counterpart
  12. EP#01709240653: Swift-XRT observations
  13. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  14. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  15. The EP-WXT trigger EP250908a/01709240652 is not a real source
  16. EP250908c: Einstein Probe detection of an X-ray transient
  17. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  18. EP250905b: EP-FXT follow-up observation
  19. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  20. EP250905b: EP-WXT detection of a fast X-ray transient
  21. EP250905a: JinShan likely optical counterpart detection
  22. EP250905a: Einstein Probe detection of an X-ray transient
  23. EP detected a brightening of LMXB 1ES 1735-26.9
  24. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  25. EP250903a: Swift-XRT observations
  26. EP#01709201209: Swift-XRT observations
  27. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  28. The EP-WXT trigger 01709201209 is likely a flaring star
  29. GRB 250903A: EP-FXT counterpart detection
  30. EP250903a: Einstein Probe detection of an X-ray transient
  31. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  32. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  33. GRB 250901A: EP-FXT follow-up observation
  34. EP250901a: Swift-XRT observations
  35. EP250827b: Gemini Spectroscopy of AT 2025wkm
  36. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  37. EP250901a: Einstein Probe detection of an X-ray transient
  38. EP250831a: EP-FXT follow-up observation
  39. EP250831a: Swift-XRT observations
  40. EP250831a: EP-WXT detection of a fast X-ray transient
  41. GRB 250830B: Swift-XRT observations
  42. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  43. The EP-WXT trigger 01709200994 is likely a flaring star
  44. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  45. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  46. EP250828a: Seimei/TriCCS optical counterpart detection
  47. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  48. EP250828a: Einstein Probe detection of an X-ray transient
  49. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  50. EP250827a: confirmation of optical rebrightening with LCO
  51. EP250827A: An optical rebrightening was detected by LCO.
  52. EP250827a: Swift-XRT counterpart detection
  53. The EP-WXT trigger 01709200800 is likely a flaring star
  54. EP250827a: BOOTES-7 early optical dectection
  55. EP250827a: Einstein Probe detection of an X-ray transient
  56. EP250821a: MeerKAT radio counterpart
  57. The EP-WXT trigger 01709200707 is likely a flaring star
  58. The EP-WXT trigger 01709200706 is likely a flaring star
  59. EP250821a: Swift/UVOT further observations.
  60. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  61. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  62. EP250821a: Swift XRT and UVOT counterpart detection
  63. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  64. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  65. EP250821a: Einstein Probe detection of an X-ray transient
  66. GRB 250818B: EP-FXT counterpart detection
  67. GRB 250813B: EP-FXT counterpart detection
  68. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250812A: EP-FXT counterpart detection
  70. EP250812a: Swift-XRT counterpart detection
  71. EP250812a: Einstein Probe detection of an X-ray transient
  72. EP250807a: EP-FXT follow-up observation upper limit
  73. GRB 250806A: SVOM/MXT refined analysis
  74. EP250807a: EP-WXT detection of a fast X-ray transient
  75. EP250806a: Upper limit from Fermi-GBM Observations
  76. GRB 250806A: EP-FXT observation
  77. EP#01709198415/EP250806a: Swift-XRT observations
  78. EP250802a: EP-FXT follow-up observation
  79. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  80. EP250806a: Einstein Probe detection of an X-ray transient
  81. EP250802a: Einstein Probe detection of an X-ray transient
  82. The EP-WXT trigger 01709198251 is likely a flaring star
  83. The EP-WXT trigger 01709198202 is likely a flaring star
  84. EP250730a: Einstein Probe detection of an X-ray transient
  85. GRB 250727A: EP-FXT follow-up observation
  86. GRB 250727A: EP-FXT counterpart detection
  87. The EP-WXT trigger 01709195487 is likely a flaring star
  88. GRB 250713A: EP-FXT counterpart detection
  89. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  90. GRB 250702B,D,E / EP250702a: ALMA detection
  91. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  92. The EP-WXT trigger 01709181970 is likely a flaring star
  93. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  94. IceCube-250706A: EP-FXT follow-up observations
  95. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  96. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  97. The EP-WXT trigger 01709181580 is likely a flaring star
  98. GRB 250704B: Swift-XRT refined Analysis
  99. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  100. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array

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