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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"
  1. GRB 231110A: GOTO optical upper limits
  2. GRB 231110A: SAO RAS optical observations
  3. GRB 231110A: Swift-XRT afterglow detection
  4. GRB231111A: YAHPT Observations
  5. GRB231111A: GIT confirmation of the optical afterglow
  6. GRB 231111A: MASTER OT earlier detection
  7. GRB 231111A: Nanshan/HMT optical observations
  8. GRB 231111A: Swift detection of a burst with an optical counterpart
  9. Swift GRB231111.60: Global MASTER-Net observations report
  10. GRB231110A: WFST Observation and upper limits
  11. Swift GRB231110.89: Global MASTER-Net observations report
  12. GRB 231110A: Swift detection of a burst
  13. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  14. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  15. GRB 231109A: Fermi GBM Final Localization
  16. IceCube-231103A: No candidates from the Zwicky Transient Facility
  17. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  18. Fermi trigger No 721204446: Global MASTER-Net observations report
  19. Fermi GRB 231108A: Global MASTER-Net observations report
  20. GRB 231108A: Fermi GBM Final Real-time Localization
  21. LIGO/Virgo/KAGRA O4 Landscape
  22. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  23. GRB 231106A: AstroSat CZTI detection
  24. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  25. GRB 231104A: Swift-BAT refined analysis
  26. Fermi trigger No 721006392: Global MASTER-Net observations report
  27. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  28. GRB 231104A: FRAM-ORM optical limit
  29. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  30. Fermi GRB 231106A: Global MASTER-Net observations report
  31. GRB 231104A: Wendelstein Optical/Infrared Observations
  32. GRB 231104A: NuSTAR Observation of the prompt emission
  33. GRB 231106A: Fermi GBM Final Real-time Localization
  34. GRB 231104A: 3.6m DOT optical upper limit
  35. IceCube-231103A: Upper limits from a search for additional neutrino events in IceCube
  36. LIGO/Virgo/KAGRA S231106y: one counterpart neutrino candidate from IceCube neutrino searches
  37. Fermi-LAT gamma-ray observations of IceCube-231103A
  38. GRB 231104A: NOT upper limit
  39. GRB 231104A: Fermi GBM Observation
  40. GRB 231104B: Fermi GBM Final Real-time Localization
  41. Fermi GRB 231103A: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  43. GRB 231104A: AKO Upper Limit
  44. GRB 231104A: AstroSat CZTI detection
  45. GRB 231104A: Swift-XRT refined Analysis
  46. GRB 231104A: Fermi-LAT detection
  47. LIGO/Virgo/KAGRA S231104ac: Identification of a GW compact binary merger candidate
  48. GRB 231104A: Swift/UVOT Upper Limits
  49. GRB 231104A: Enhanced Swift-XRT position
  50. GRB231104A: LCOGT Optical Upper Limits
  51. GRB 231104A: Swift detection of a bright burst
  52. GRB 231104A: Fermi GBM Final Real-time Localization
  53. Swift GRB231104.07: Global MASTER-Net observations report
  54. IceCube Alert 231103.39: Global MASTER-Net observations report
  55. GRB 231103A: Fermi GBM Final Real-time Localization
  56. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  57. Fermi-LAT gamma-ray observations of IceCube-231027A
  58. LIGO/Virgo/KAGRA S231102w: Updated Sky localization
  59. LIGO/Virgo/KAGRA S231102i: Global MASTER-Net observations report
  60. GRB 231101A: Glowbug gamma-ray detection
  61. GRB 231024A: GRANDMA observations of AT2023vuc/GOTO23baj candidate
  62. LIGO/Virgo/KAGRA S231102w: Identification of a GW compact binary merger candidate
  63. New Swift-BAT/GUANO and IceCube Notices Available via GCN Kafka
  64. Fermi trigger No 720498201: Global MASTER-Net observations report
  65. GRB 231101A: Fermi GBM Final Real-time Localization
  66. GRB 231030B: GRBAlpha detection
  67. GRB 231028B: VZLUSAT-2 detection
  68. Fermi trigger No 720415645: Global MASTER-Net observations report
  69. GRB 231030B: Fermi GBM Detection
  70. GRB 231030B: AstroSat CZTI detection
  71. Fermi GRB 231030B: Global MASTER-Net observations report
  72. IPN triangulation of GRB 231020A
  73. GRB 231030B: BALROG localization (Fermi Trigger 720388704 / GRB 231030832)
  74. GRB 231030B: Fermi GBM Final Real-time Localization
  75. GRB 231028A: Swift-BAT refined analysis
  76. IceCube-231027A: Upper limits from a search for additional neutrino events in IceCube
  77. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  78. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  79. GRB 231024A: AKO Optical Counterpart Candidate
  80. GRB 231028A: CALET Gamma-Ray Burst Monitor detection
  81. Fermi GRB 231030A: Global MASTER-Net observations report
  82. GRB 231030A: Fermi GBM Final Real-time Localization
  83. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  84. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  86. GRID detection of GRB 231020A
  87. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  88. GRB 231028A: AstroSat CZTI detection
  89. GRB 231028A: Glowbug gamma-ray detection
  90. GRB 231028A: Fermi GBM Detection
  91. Fermi trigger No 720224759: Global MASTER-Net observations report
  92. Swift GRB 231028A: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  94. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  95. GRB 231028A: Swift detection of a burst
  96. GRB 231028A: Fermi GBM Final Real-time Localization
  97. IceCube Alert 231027.18: Global MASTER-Net observations report
  98. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  99. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report

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