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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"

45409 results found.

  1. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  2. GRB 250812A: NTT spectroscopic redshift z = 2.57
  3. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  4. EP250812a: NOT, NTT, and GS observations
  5. GRB 250812A: Swift/UVOT Detection
  6. GRB 250813A: Fermi GBM Final Localization
  7. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  8. EP250812a: Liverpool Telescope upper limits
  9. EP250812a: SVOM/VT optical counterpart
  10. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  11. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  12. IceCube Alert 250813.14: Global MASTER-Net observations report
  13. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  14. GRB 250812A: EP-FXT counterpart detection
  15. GRB 250812A: Swift ToO observations
  16. GRB 250807B: Swift-BAT refined analysis
  17. EP 250812a: GOTO optical upper limit
  18. GRB 250812A: Kilonova-Catcher optical afterglow detection
  19. EP250812a: Swift-XRT counterpart detection
  20. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  21. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  22. EP250812a: Einstein Probe detection of an X-ray transient
  23. GRB 250812A: SVOM/VT optical afterglow confirmation
  24. GRB 250812A: Swift-XRT afterglow detection
  25. GRB 250812A: TRT likely optical counterpart detection
  26. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB 250812A: SVOM detection of a faint long burst
  28. GRB 250809A: Swift-BAT refined analysis
  29. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  30. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  31. GRB 250807A: Swift-BAT refined analysis
  32. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  33. GRB 250809A: Swift/UVOT Detection
  34. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  35. Corrected Swift-XRT Refined Analysis of GRB 250809A
  36. GRB 250809A: Swift-XRT refined Analysis
  37. GRB 250807B: SVOM/VT optical observation
  38. EP250807a: EP-FXT follow-up observation upper limit
  39. GRB 250809A: LCOGT Optical Upper Limits
  40. GRB 250702B: Chandra X-ray Detection
  41. EP250807a: Global MASTER-Net observations report
  42. Fermi GRB 250808A: Global MASTER-Net observations report
  43. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  44. GRB 250808A: VLT X-shooter candidate counterpart
  45. GRB 250809A: Prompt enhanced Swift-XRT position
  46. GRB 250809A: Swift detection of a gamma ray burst
  47. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. GRB 250808A: Fermi GBM Observation
  49. GRB 250808A: Swift-XRT candidate counterpart detection
  50. GRB 250807A: SVOM/VT optical continued observation
  51. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  52. GRB 250808A: SVOM detection of a long burst
  53. GRB 250808A: Fermi GBM Final Real-time Localization
  54. Konus-Wind detection of GRB 250807A
  55. GRB 250807B: Swift/UVOT Detection
  56. GRB 250807B: Kilonova-Catcher optical afterglow detection
  57. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 250807A: Swift/UVOT Detection
  59. GRB 250807A: Swift-XRT refined Analysis
  60. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  61. GRB 250806A: SVOM/MXT refined analysis
  62. GRB 250806A: SVOM/ECLAIRs refined analysis
  63. EP250807a: NTT z-band optical upper limit
  64. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  65. GRB 250804B: Insight-HXMT detection
  66. GRB 250807A: SVOM/GRM observation
  67. Swift GRB250807.45: Global MASTER-Net observations report
  68. GRB 250807A: AstroSat CZTI detection of bright long burst
  69. GRB 250807B: Swift-XRT refined Analysis
  70. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  71. GRB 250807B: NTT optical observations
  72. EP250807a: EP-WXT detection of a fast X-ray transient
  73. EP 250807.979: GOTO optical upper limit
  74. EP250807a: COLIBRÍ optical upper limit
  75. GRB 250807A: SVOM/VT optical observation
  76. EP250806a: Upper limit from Fermi-GBM Observations
  77. GRB 250807B: Enhanced Swift-XRT position
  78. Swift GRB250807.65: Global MASTER-Net observations report
  79. GRB 250807A: Enhanced Swift-XRT position
  80. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 250807B: Swift detection of a burst with an optical counterpart.
  82. GRB 250805A: Kilonova-Catcher optical upper limits
  83. EP250806a:SVOM/VT refined analysis
  84. GRB 250805A: Swift/UVOT Upper Limits
  85. GRB 250806A: Swift/UVOT U-band detection
  86. EP250806a: Liverpool telescope optical upper limit
  87. GRB 250807A: Swift detection of a burst with an optical counterpart
  88. IceCube Alert 250804.84: Global MASTER-Net observations report
  89. GRB 250806A: EP-FXT observation
  90. EP#01709198415/EP250806a: Swift-XRT observations
  91. EP250806a: Global MASTER-Net observations report
  92. EP250802a: EP-FXT follow-up observation
  93. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  94. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  95. EP250806a: SVOM /VT optical candidate
  96. GRB 250806A: J-band upper limit from WINTER
  97. GRB 250805A: Swift-BAT refined analysis
  98. GRB 250806A: KAIT optical upper limit
  99. GRB 250806A: SVOM/VT refined analysis
  100. GRB 250806A: Swift-XRT counterpart detection

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