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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"

45431 results found.

  1. GRB 250910A: SVOM/MXT possible afterglow detection
  2. GRB 250910A: SVOM detection of a faint burst
  3. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  4. GRB 250702B: Late time Chandra observations
  5. EP250908b/EP#01709240653: Swift/UVOT Detection
  6. EP#01709240653: Swift-XRT observations
  7. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  8. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 250907A: CALET Gamma-Ray Burst Monitor detection
  10. EP250908c: SVOM/VT optical observation
  11. EP250908c: VLT/FORS2 optical counterpart identification
  12. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  13. EP250908b: SVOM/VT optical candidate
  14. The EP-WXT trigger EP250908a/01709240652 is not a real source
  15. EP250908c: Global MASTER-Net observations report
  16. Fermi GRB 250909A: Global MASTER-Net observations report
  17. EP250908c: Einstein Probe detection of an X-ray transient
  18. GRB 250909A: Fermi GBM Final Real-time Localization
  19. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  20. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  21. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  22. GRB 250907A: GECAM-B detection
  23. GRB 250905A: Swift-BAT refined analysis
  24. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  25. GRB 250903A: Swift-XRT afterglow detection
  26. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  27. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  28. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  29. EP250905a: Liverpool Telescope i-band upper limits
  30. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  31. EP250905b: EP-FXT follow-up observation
  32. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  33. EP250905a: Liverpool Telescope observations
  34. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  35. EP250905b: Global MASTER-Net observations report
  36. EP250905b: EP-WXT detection of a fast X-ray transient
  37. EP250905a: FTW one optical and multiple NIR counterpart candidates
  38. GRB 250905A: Swift-XRT refined Analysis
  39. EP250905a: JinShan likely optical counterpart detection
  40. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  41. GRB 250904A: Swift-BAT refined analysis
  42. IceCube Alert 250905.84: Global MASTER-Net observations report
  43. GRB 250905A: Swift/UVOT Upper Limits
  44. EP250905a: Global MASTER-Net observations report
  45. GRB 250901A - SVOM/ECLAIRs refined analysis
  46. EP250905a: Einstein Probe detection of an X-ray transient
  47. GRB 250905B: Fermi GBM Final Localization
  48. GRB250904A: Liverpool Telescope upper limits
  49. GRB 250905A: Enhanced Swift-XRT position
  50. GRB 250904A: Swift/UVOT Detection
  51. GRB 250903A: Swift/UVOT detection
  52. GRB 250904A: Swift-XRT refined Analysis
  53. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  54. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  55. EP detected a brightening of LMXB 1ES 1735-26.9
  56. GRB 250905A: KAIT optical upper limit
  57. GRB 250905A: Swift detection of a burst
  58. Swift GRB250905.09: Global MASTER-Net observations report
  59. Swift GRB 250904A: Global MASTER-Net observations report
  60. GRB 250904A: Enhanced Swift-XRT position
  61. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 250904A: TRT optical counterpart detection
  63. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  64. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  65. GRB 250904A: Prompt enhanced Swift-XRT position
  66. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  67. GRB 250904A: Swift detection of a burst
  68. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  69. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  70. GRB 250902A: VZLUSAT-2 detection
  71. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  72. GRB 250903A: Swift-XRT observations
  73. EP250903a: Swift-XRT observations
  74. EP#01709201209: Swift-XRT observations
  75. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  76. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  77. GRB 250830C: VZLUSAT-2 detection
  78. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  79. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  80. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  81. The EP-WXT trigger 01709201209 is likely a flaring star
  82. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  83. GRB 250903A: EP-FXT counterpart detection
  84. GRB 250902A: GECAM-B detection
  85. GRB 250903A: LCO optical observation
  86. GRB 250903A: LCO optical afterglow detection
  87. GRB 250903A: SVOM/VT optical confirmation with VHF data
  88. EP250903a: SVOM/VT optical confirmation
  89. EP250901a: Mondy, Assy and SAO RAS optical limits
  90. Subject GRB 250903A: SVOM/MXT afterglow detection
  91. EP250903a: LCO candidate counterpart discovery
  92. GRB 250903A: TRT optical counterpart detection
  93. GRB 250902B: AstroSat CZTI detection
  94. GRB 250903A: SVOM detection of a burst
  95. EP250903a: Global MASTER-Net observations report
  96. EP250903a: TRT optical observations
  97. EP250903a: Einstein Probe detection of an X-ray transient
  98. EP 250827B: Detection of supernova counterpart by LCO.
  99. EP/WXT01709201159: GOTO optical follow-up
  100. EP250827b / AT 2025wkm: TRT optical observations

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