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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"

12321 results found.

  1. GRB 250812A: Swift/UVOT Detection
  2. EP250812a: Liverpool Telescope upper limits
  3. IceCube Alert 250813.14: Global MASTER-Net observations report
  4. EP 250812a: GOTO optical upper limit
  5. EP250812a: Swift-XRT counterpart detection
  6. GRB 250812A: Swift-XRT afterglow detection
  7. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  8. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  9. GRB 250809A: Swift/UVOT Detection
  10. EP250807a: EP-FXT follow-up observation upper limit
  11. GRB 250809A: LCOGT Optical Upper Limits
  12. EP250807a: Global MASTER-Net observations report
  13. Fermi GRB 250808A: Global MASTER-Net observations report
  14. GRB 250809A: Swift detection of a gamma ray burst
  15. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  16. GRB 250808A: Swift-XRT candidate counterpart detection
  17. Konus-Wind detection of GRB 250807A
  18. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250807A: Swift/UVOT Detection
  20. EP250807a: NTT z-band optical upper limit
  21. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  22. Swift GRB250807.45: Global MASTER-Net observations report
  23. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  24. EP250807a: EP-WXT detection of a fast X-ray transient
  25. EP 250807.979: GOTO optical upper limit
  26. EP250807a: COLIBRÍ optical upper limit
  27. EP250806a: Upper limit from Fermi-GBM Observations
  28. Swift GRB250807.65: Global MASTER-Net observations report
  29. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 250805A: Kilonova-Catcher optical upper limits
  31. GRB 250805A: Swift/UVOT Upper Limits
  32. GRB 250806A: Swift/UVOT U-band detection
  33. EP250806a: Liverpool telescope optical upper limit
  34. IceCube Alert 250804.84: Global MASTER-Net observations report
  35. EP#01709198415/EP250806a: Swift-XRT observations
  36. EP250806a: Global MASTER-Net observations report
  37. GRB 250806A: J-band upper limit from WINTER
  38. GRB 250806A: KAIT optical upper limit
  39. GRB 250806A: SVOM/VT refined analysis
  40. EP250806a: COLIBRÍ optical upper limit
  41. GRB 250806A: Kilonova-Catcher optical upper limits
  42. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 250806A: SVOM/VT optical upper limit
  44. GRB 250804B: Swift-XRT observations
  45. GRB 250805A: TRT optical upper limits
  46. Swift GRB250805.26: Global MASTER-Net observations report
  47. Fermi trigger No 776041355: Global MASTER-Net observations report
  48. EP250802a: additional Liverpool Telescope upper limits
  49. EP250730a: SVOM/VT optical upper limit
  50. EP250802a: Liverpool Telescope optical upper limits
  51. EP250802a: Global MASTER-Net observations report
  52. EP250802a: GROWTH-India Telescope optical upper limit
  53. GRB 250702B: SMA observations
  54. EP250730a: Global MASTER-Net observations report
  55. EP250730a: COLIBRÍ optical upper limit
  56. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  57. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  58. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  59. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  60. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  61. GRB 250727A: EP-FXT follow-up observation
  62. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  63. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  64. GRB 250728A: Swift-XRT observations
  65. GRB 250728A: COLIBRÍ optical upper limit
  66. Fermi trigger No 775387550: Global MASTER-Net observations report
  67. GRB 250727A: AST3-2 Upper limit
  68. GRB250727A: SVOM/VT optical upper limit
  69. GRB 250727A: Swift-XRT observations
  70. GRB 250725A: Swift/UVOT Upper Limits
  71. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  72. GRB 250725A: Swift detection of a burst
  73. Swift GRB 250725A: Global MASTER-Net OT detection
  74. Fermi GRB 250725A: Global MASTER-Net observations report
  75. Swift GRB 250725A: Global MASTER-Net observations report
  76. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  77. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  78. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  79. GRB 250721A: Swift-XRT observations
  80. GRB 250721A: MAXI/GSC detection
  81. Fermi trigger No 774730635: Global MASTER-Net observations report
  82. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  83. GRB 250717B: COLIBRÍ optical upper limit
  84. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  85. GRB 250717B: Swift-XRT observations
  86. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  87. Swift GRB250718.01: Global MASTER-Net observations report
  88. GRB 250716A: Swift-XRT afterglow detection
  89. Fermi GRB 250716A: Global MASTER-Net observations report
  90. Fermi GRB 250715A: Global MASTER-Net observations report
  91. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  92. GRB 250713A: Mephisto optical upper limits
  93. Fermi GRB 250714A: Global MASTER-Net observations report
  94. GRB 250713A: SVOM/VT optical upper limit
  95. GRB 250713A: NOT optical upper limits
  96. GRB 250713A: OHP/T193 upper limit
  97. GRB 250713A: SVOM/C-GFT upper limit
  98. GRB 250706B/C: 7DT Follow-up Observations
  99. GRB 250713A: Swift-XRT observations
  100. GRB 250713A: JinShan optical upper limits

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