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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').
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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"

20977 results found.

  1. Fermi GRB 250919A: Global MASTER-Net observations report
  2. GRB 250916A: KAIT optical observations
  3. GRB 250917B: VLT/HAWK-I near-infrared observations
  4. GRB 250916A: further SAO RAS optical observations
  5. GRB 250912A: SVOM/ECLAIRs refined analysis
  6. GRB 250917B: Swift/UVOT Upper Limits
  7. GRB 250916A: Swift-XRT observations
  8. EP250916a: EP-FXT follow-up observation
  9. GRB 250916A: MAO/AZT-22 optical observations
  10. GRB 250916A: SAO RAS optical observations
  11. GRB 250916A : GIT optical observations
  12. GRB250917B: WFST optical observations
  13. GRB 250916A: Swift ToO observations
  14. GRB 250917B: Swift-XRT observations
  15. Fermi GRB 250917B: Global MASTER-Net observations report
  16. GRB 250916A: GOTO optical counterpart candidate
  17. GRB 250910A: SVOM/ECLAIRs refined analysis
  18. EP250916a: Einstein Probe detection of an X-ray transient
  19. Fermi GRB 250916A: Global MASTER-Net observations report
  20. EP250827b: VLA Observations
  21. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  22. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  23. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  24. GRB 250912A: Swift-XRT observations
  25. GRB250912A: VLT/HAWK-I follow-up observations
  26. GRB 250912A: VLT observations
  27. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  28. Fermi GRB 250912A: Global MASTER-Net observations report
  29. EP250911a: Global MASTER-Net observations report
  30. EP250911a: Upper limit from Fermi-GBM Observations
  31. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 250911A: MASTER optical counterpart observations
  33. EP250911a: SAO RAS optical observations
  34. EP250911a: Swift-XRT observations
  35. EP250911a: Optical detection with Kinder observations
  36. GRB 250911A: Swift/UVOT Detection
  37. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  38. EP250911a: COLIBRÍ optical observations
  39. Fermi GRB 250910B: Global MASTER-Net observations report
  40. EP250910a: Global MASTER-Net observations report
  41. GRB 250903A: SVOM/ECLAIRs refined analysis
  42. GRB 250911A: Swift-XRT observations
  43. GRB 250911A: COLIBRÍ optical counterpart candidate
  44. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  45. GRB 250702B: Late time Chandra observations
  46. EP250908b/EP#01709240653: Swift/UVOT Detection
  47. EP#01709240653: Swift-XRT observations
  48. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  49. EP250908c: Global MASTER-Net observations report
  50. Fermi GRB 250909A: Global MASTER-Net observations report
  51. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  52. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  53. GRB 250903A: Swift-XRT afterglow detection
  54. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  55. EP250905b: EP-FXT follow-up observation
  56. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  57. EP250905a: Liverpool Telescope observations
  58. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  59. EP250905b: Global MASTER-Net observations report
  60. EP250905b: EP-WXT detection of a fast X-ray transient
  61. EP250905a: FTW one optical and multiple NIR counterpart candidates
  62. EP250905a: JinShan likely optical counterpart detection
  63. IceCube Alert 250905.84: Global MASTER-Net observations report
  64. GRB 250905A: Swift/UVOT Upper Limits
  65. EP250905a: Global MASTER-Net observations report
  66. GRB 250901A - SVOM/ECLAIRs refined analysis
  67. GRB 250904A: Swift/UVOT Detection
  68. GRB 250903A: Swift/UVOT detection
  69. Swift GRB250905.09: Global MASTER-Net observations report
  70. Swift GRB 250904A: Global MASTER-Net observations report
  71. GRB 250904A: TRT optical counterpart detection
  72. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  73. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  74. GRB 250903A: Swift-XRT observations
  75. EP250903a: Swift-XRT observations
  76. EP#01709201209: Swift-XRT observations
  77. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  78. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  80. GRB 250903A: LCO optical afterglow detection
  81. EP250903a: SVOM/VT optical confirmation
  82. GRB 250903A: TRT optical counterpart detection
  83. EP250903a: Global MASTER-Net observations report
  84. EP250903a: TRT optical observations
  85. EP 250827B: Detection of supernova counterpart by LCO.
  86. EP/WXT01709201159: GOTO optical follow-up
  87. EP250827b / AT 2025wkm: TRT optical observations
  88. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  89. EP250827b: continued Liverpool Telescope observations
  90. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  91. Fermi GRB 250902B: Global MASTER-Net observations report
  92. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  93. GRB 250901A: Swift/UVOT Upper Limit
  94. GRB 250830B: Swift-XRT afterglow detection
  95. EP250827b: Liverpool Telescope observations
  96. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  97. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  98. GRB 250901A: NOT optical observations
  99. GRB 250901A: Swift-XRT afterglow detection
  100. EP250901a: Swift-XRT observations

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