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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"

20967 results found.

  1. GRB 250916A : GIT optical observations
  2. GRB250917B: WFST optical observations
  3. GRB 250916A: Swift ToO observations
  4. GRB 250917B: Swift-XRT observations
  5. Fermi GRB 250917B: Global MASTER-Net observations report
  6. GRB 250916A: GOTO optical counterpart candidate
  7. GRB 250910A: SVOM/ECLAIRs refined analysis
  8. EP250916a: Einstein Probe detection of an X-ray transient
  9. Fermi GRB 250916A: Global MASTER-Net observations report
  10. EP250827b: VLA Observations
  11. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  12. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  13. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  14. GRB 250912A: Swift-XRT observations
  15. GRB250912A: VLT/HAWK-I follow-up observations
  16. GRB 250912A: VLT observations
  17. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  18. Fermi GRB 250912A: Global MASTER-Net observations report
  19. EP250911a: Global MASTER-Net observations report
  20. EP250911a: Upper limit from Fermi-GBM Observations
  21. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 250911A: MASTER optical counterpart observations
  23. EP250911a: SAO RAS optical observations
  24. EP250911a: Swift-XRT observations
  25. EP250911a: Optical detection with Kinder observations
  26. GRB 250911A: Swift/UVOT Detection
  27. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  28. EP250911a: COLIBRÍ optical observations
  29. Fermi GRB 250910B: Global MASTER-Net observations report
  30. EP250910a: Global MASTER-Net observations report
  31. GRB 250903A: SVOM/ECLAIRs refined analysis
  32. GRB 250911A: Swift-XRT observations
  33. GRB 250911A: COLIBRÍ optical counterpart candidate
  34. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  35. GRB 250702B: Late time Chandra observations
  36. EP250908b/EP#01709240653: Swift/UVOT Detection
  37. EP#01709240653: Swift-XRT observations
  38. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  39. EP250908c: Global MASTER-Net observations report
  40. Fermi GRB 250909A: Global MASTER-Net observations report
  41. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  42. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  43. GRB 250903A: Swift-XRT afterglow detection
  44. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  45. EP250905b: EP-FXT follow-up observation
  46. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  47. EP250905a: Liverpool Telescope observations
  48. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  49. EP250905b: Global MASTER-Net observations report
  50. EP250905b: EP-WXT detection of a fast X-ray transient
  51. EP250905a: FTW one optical and multiple NIR counterpart candidates
  52. EP250905a: JinShan likely optical counterpart detection
  53. IceCube Alert 250905.84: Global MASTER-Net observations report
  54. GRB 250905A: Swift/UVOT Upper Limits
  55. EP250905a: Global MASTER-Net observations report
  56. GRB 250901A - SVOM/ECLAIRs refined analysis
  57. GRB 250904A: Swift/UVOT Detection
  58. GRB 250903A: Swift/UVOT detection
  59. Swift GRB250905.09: Global MASTER-Net observations report
  60. Swift GRB 250904A: Global MASTER-Net observations report
  61. GRB 250904A: TRT optical counterpart detection
  62. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  63. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  64. GRB 250903A: Swift-XRT observations
  65. EP250903a: Swift-XRT observations
  66. EP#01709201209: Swift-XRT observations
  67. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  68. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  70. GRB 250903A: LCO optical afterglow detection
  71. EP250903a: SVOM/VT optical confirmation
  72. GRB 250903A: TRT optical counterpart detection
  73. EP250903a: Global MASTER-Net observations report
  74. EP250903a: TRT optical observations
  75. EP 250827B: Detection of supernova counterpart by LCO.
  76. EP/WXT01709201159: GOTO optical follow-up
  77. EP250827b / AT 2025wkm: TRT optical observations
  78. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  79. EP250827b: continued Liverpool Telescope observations
  80. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  81. Fermi GRB 250902B: Global MASTER-Net observations report
  82. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  83. GRB 250901A: Swift/UVOT Upper Limit
  84. GRB 250830B: Swift-XRT afterglow detection
  85. EP250827b: Liverpool Telescope observations
  86. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  87. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  88. GRB 250901A: NOT optical observations
  89. GRB 250901A: Swift-XRT afterglow detection
  90. EP250901a: Swift-XRT observations
  91. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  92. EP250827b: Swift observations of AT 2025wkm
  93. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  94. EP250827b: Gemini Spectroscopy of AT 2025wkm
  95. EP250831a: NOT optical observations and tentative afterglow candidate
  96. EP250827b: FTW Observations of AT 2025wkm
  97. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  98. EP250901a: Mephisto optical upper limits
  99. EP250901a: Global MASTER-Net observations report
  100. EP250831a: Swift-XRT observations

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