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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"

12334 results found.

  1. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  2. GRB 250814A: KAIT optical upper limit
  3. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  4. Fermi trigger No 776818276: Global MASTER-Net observations report
  5. Swift GRB250814.32: Global MASTER-Net observations report
  6. GRB 250814A: J-band upper limit from WINTER
  7. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 250814A: COLIBRÍ optical upper limit
  9. GRB 250814A: DDOTI Optical Upper Limit
  10. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  11. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  12. EP250812a: Nickel optical upper limit
  13. EP250812a: NOT, NTT, and GS observations
  14. GRB 250812A: Swift/UVOT Detection
  15. EP250812a: Liverpool Telescope upper limits
  16. IceCube Alert 250813.14: Global MASTER-Net observations report
  17. EP 250812a: GOTO optical upper limit
  18. EP250812a: Swift-XRT counterpart detection
  19. GRB 250812A: Swift-XRT afterglow detection
  20. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  21. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  22. GRB 250809A: Swift/UVOT Detection
  23. EP250807a: EP-FXT follow-up observation upper limit
  24. GRB 250809A: LCOGT Optical Upper Limits
  25. EP250807a: Global MASTER-Net observations report
  26. Fermi GRB 250808A: Global MASTER-Net observations report
  27. GRB 250809A: Swift detection of a gamma ray burst
  28. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 250808A: Swift-XRT candidate counterpart detection
  30. Konus-Wind detection of GRB 250807A
  31. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 250807A: Swift/UVOT Detection
  33. EP250807a: NTT z-band optical upper limit
  34. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  35. Swift GRB250807.45: Global MASTER-Net observations report
  36. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  37. EP250807a: EP-WXT detection of a fast X-ray transient
  38. EP 250807.979: GOTO optical upper limit
  39. EP250807a: COLIBRÍ optical upper limit
  40. EP250806a: Upper limit from Fermi-GBM Observations
  41. Swift GRB250807.65: Global MASTER-Net observations report
  42. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 250805A: Kilonova-Catcher optical upper limits
  44. GRB 250805A: Swift/UVOT Upper Limits
  45. GRB 250806A: Swift/UVOT U-band detection
  46. EP250806a: Liverpool telescope optical upper limit
  47. IceCube Alert 250804.84: Global MASTER-Net observations report
  48. EP#01709198415/EP250806a: Swift-XRT observations
  49. EP250806a: Global MASTER-Net observations report
  50. GRB 250806A: J-band upper limit from WINTER
  51. GRB 250806A: KAIT optical upper limit
  52. GRB 250806A: SVOM/VT refined analysis
  53. EP250806a: COLIBRÍ optical upper limit
  54. GRB 250806A: Kilonova-Catcher optical upper limits
  55. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  56. GRB 250806A: SVOM/VT optical upper limit
  57. GRB 250804B: Swift-XRT observations
  58. GRB 250805A: TRT optical upper limits
  59. Swift GRB250805.26: Global MASTER-Net observations report
  60. Fermi trigger No 776041355: Global MASTER-Net observations report
  61. EP250802a: additional Liverpool Telescope upper limits
  62. EP250730a: SVOM/VT optical upper limit
  63. EP250802a: Liverpool Telescope optical upper limits
  64. EP250802a: Global MASTER-Net observations report
  65. EP250802a: GROWTH-India Telescope optical upper limit
  66. GRB 250702B: SMA observations
  67. EP250730a: Global MASTER-Net observations report
  68. EP250730a: COLIBRÍ optical upper limit
  69. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  70. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  71. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  72. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  73. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  74. GRB 250727A: EP-FXT follow-up observation
  75. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  76. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  77. GRB 250728A: Swift-XRT observations
  78. GRB 250728A: COLIBRÍ optical upper limit
  79. Fermi trigger No 775387550: Global MASTER-Net observations report
  80. GRB 250727A: AST3-2 Upper limit
  81. GRB250727A: SVOM/VT optical upper limit
  82. GRB 250727A: Swift-XRT observations
  83. GRB 250725A: Swift/UVOT Upper Limits
  84. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  85. GRB 250725A: Swift detection of a burst
  86. Swift GRB 250725A: Global MASTER-Net OT detection
  87. Fermi GRB 250725A: Global MASTER-Net observations report
  88. Swift GRB 250725A: Global MASTER-Net observations report
  89. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  90. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  91. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  92. GRB 250721A: Swift-XRT observations
  93. GRB 250721A: MAXI/GSC detection
  94. Fermi trigger No 774730635: Global MASTER-Net observations report
  95. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  96. GRB 250717B: COLIBRÍ optical upper limit
  97. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  98. GRB 250717B: Swift-XRT observations
  99. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  100. Swift GRB250718.01: Global MASTER-Net observations report

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