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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 231111A: Nanshan/HMT optical observations
  2. GRB 231111A: Swift detection of a burst with an optical counterpart
  3. Swift GRB231111.60: Global MASTER-Net observations report
  4. GRB231110A: WFST Observation and upper limits
  5. Swift GRB231110.89: Global MASTER-Net observations report
  6. GRB 231110A: Swift detection of a burst
  7. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  8. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  9. GRB 231109A: Fermi GBM Final Localization
  10. IceCube-231103A: No candidates from the Zwicky Transient Facility
  11. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  12. Fermi trigger No 721204446: Global MASTER-Net observations report
  13. Fermi GRB 231108A: Global MASTER-Net observations report
  14. GRB 231108A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA O4 Landscape
  16. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  17. GRB 231106A: AstroSat CZTI detection
  18. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  19. GRB 231104A: Swift-BAT refined analysis
  20. Fermi trigger No 721006392: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  22. GRB 231104A: FRAM-ORM optical limit
  23. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  24. Fermi GRB 231106A: Global MASTER-Net observations report
  25. GRB 231104A: Wendelstein Optical/Infrared Observations
  26. GRB 231104A: NuSTAR Observation of the prompt emission
  27. GRB 231106A: Fermi GBM Final Real-time Localization
  28. GRB 231104A: 3.6m DOT optical upper limit
  29. IceCube-231103A: Upper limits from a search for additional neutrino events in IceCube
  30. LIGO/Virgo/KAGRA S231106y: one counterpart neutrino candidate from IceCube neutrino searches
  31. Fermi-LAT gamma-ray observations of IceCube-231103A
  32. GRB 231104A: NOT upper limit
  33. GRB 231104A: Fermi GBM Observation
  34. GRB 231104B: Fermi GBM Final Real-time Localization
  35. Fermi GRB 231103A: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  37. GRB 231104A: AKO Upper Limit
  38. GRB 231104A: AstroSat CZTI detection
  39. GRB 231104A: Swift-XRT refined Analysis
  40. GRB 231104A: Fermi-LAT detection
  41. LIGO/Virgo/KAGRA S231104ac: Identification of a GW compact binary merger candidate
  42. GRB 231104A: Swift/UVOT Upper Limits
  43. GRB 231104A: Enhanced Swift-XRT position
  44. GRB231104A: LCOGT Optical Upper Limits
  45. GRB 231104A: Swift detection of a bright burst
  46. GRB 231104A: Fermi GBM Final Real-time Localization
  47. Swift GRB231104.07: Global MASTER-Net observations report
  48. IceCube Alert 231103.39: Global MASTER-Net observations report
  49. GRB 231103A: Fermi GBM Final Real-time Localization
  50. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  51. Fermi-LAT gamma-ray observations of IceCube-231027A
  52. LIGO/Virgo/KAGRA S231102w: Updated Sky localization
  53. LIGO/Virgo/KAGRA S231102i: Global MASTER-Net observations report
  54. GRB 231101A: Glowbug gamma-ray detection
  55. GRB 231024A: GRANDMA observations of AT2023vuc/GOTO23baj candidate
  56. LIGO/Virgo/KAGRA S231102w: Identification of a GW compact binary merger candidate
  57. New Swift-BAT/GUANO and IceCube Notices Available via GCN Kafka
  58. Fermi trigger No 720498201: Global MASTER-Net observations report
  59. GRB 231101A: Fermi GBM Final Real-time Localization
  60. GRB 231030B: GRBAlpha detection
  61. GRB 231028B: VZLUSAT-2 detection
  62. Fermi trigger No 720415645: Global MASTER-Net observations report
  63. GRB 231030B: Fermi GBM Detection
  64. GRB 231030B: AstroSat CZTI detection
  65. Fermi GRB 231030B: Global MASTER-Net observations report
  66. IPN triangulation of GRB 231020A
  67. GRB 231030B: BALROG localization (Fermi Trigger 720388704 / GRB 231030832)
  68. GRB 231030B: Fermi GBM Final Real-time Localization
  69. GRB 231028A: Swift-BAT refined analysis
  70. IceCube-231027A: Upper limits from a search for additional neutrino events in IceCube
  71. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  72. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  73. GRB 231024A: AKO Optical Counterpart Candidate
  74. GRB 231028A: CALET Gamma-Ray Burst Monitor detection
  75. Fermi GRB 231030A: Global MASTER-Net observations report
  76. GRB 231030A: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  78. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  80. GRID detection of GRB 231020A
  81. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  82. GRB 231028A: AstroSat CZTI detection
  83. GRB 231028A: Glowbug gamma-ray detection
  84. GRB 231028A: Fermi GBM Detection
  85. Fermi trigger No 720224759: Global MASTER-Net observations report
  86. Swift GRB 231028A: Global MASTER-Net observations report
  87. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  88. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  89. GRB 231028A: Swift detection of a burst
  90. GRB 231028A: Fermi GBM Final Real-time Localization
  91. IceCube Alert 231027.18: Global MASTER-Net observations report
  92. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  93. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  95. GRB 231019A: Glowbug gamma-ray detection
  96. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  97. GRB 231025A: Fermi GBM Observation
  98. GRB 231024A: Fermi GBM Observation
  99. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  100. GRB 231025A: Fermi GBM Final Localization

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