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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: Afterglow redshift from OSIRIS+/GTC
  2. GRB 231104A: VZLUSAT-2 detection
  3. GRB 231111A: TNG tentative redshift
  4. GRB 231110A: Glowbug gamma-ray detection
  5. GRB 231110A: AstroSat CZTI detection
  6. GRB 231111A NUTTelA-TAO / BSTI Early Measurements
  7. GRB 231111A: Leavitt Observatory optical observations
  8. GRB231111A: Optical follow-up observations with Mephisto
  9. GRB 231111A: GMG observation (correction)
  10. LIGO/Virgo/KAGRA S231112ag: Retraction of GW compact binary merger candidate
  11. GRB 231111A: GMG observation upper limit
  12. GRB 231106B: GRBAlpha detection
  13. GRB 231111A: Osservatorio Astronomico "Nastro Verde" optical observations with detection of an optical counterpart
  14. GRB 231110A: Terskol Zeiss-2000 optical upper limit
  15. GRB 231111A: Swift-XRT refined Analysis
  16. GRB 231111A: Mondy optical observations
  17. GRB 231111A: GECAM-C detection of a long burst (correction)
  18. GRB 231110A: GECAM-B detection (correction)
  19. GRB 231111A: Enhanced Swift-XRT position
  20. GRB 231111A: GECAM-C detection of a long burst
  21. GRB 231110A: GECAM detection
  22. GRB 231110A: GOTO optical upper limits
  23. GRB 231110A: SAO RAS optical observations
  24. GRB 231110A: Swift-XRT afterglow detection
  25. GRB231111A: YAHPT Observations
  26. GRB231111A: GIT confirmation of the optical afterglow
  27. GRB 231111A: MASTER OT earlier detection
  28. GRB 231111A: Nanshan/HMT optical observations
  29. GRB 231111A: Swift detection of a burst with an optical counterpart
  30. Swift GRB231111.60: Global MASTER-Net observations report
  31. GRB231110A: WFST Observation and upper limits
  32. Swift GRB231110.89: Global MASTER-Net observations report
  33. GRB 231110A: Swift detection of a burst
  34. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  35. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  36. GRB 231109A: Fermi GBM Final Localization
  37. IceCube-231103A: No candidates from the Zwicky Transient Facility
  38. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  39. Fermi trigger No 721204446: Global MASTER-Net observations report
  40. Fermi GRB 231108A: Global MASTER-Net observations report
  41. GRB 231108A: Fermi GBM Final Real-time Localization
  42. LIGO/Virgo/KAGRA O4 Landscape
  43. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  44. GRB 231106A: AstroSat CZTI detection
  45. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  46. GRB 231104A: Swift-BAT refined analysis
  47. Fermi trigger No 721006392: Global MASTER-Net observations report
  48. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  49. GRB 231104A: FRAM-ORM optical limit
  50. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  51. Fermi GRB 231106A: Global MASTER-Net observations report
  52. GRB 231104A: Wendelstein Optical/Infrared Observations
  53. GRB 231104A: NuSTAR Observation of the prompt emission
  54. GRB 231106A: Fermi GBM Final Real-time Localization
  55. GRB 231104A: 3.6m DOT optical upper limit
  56. IceCube-231103A: Upper limits from a search for additional neutrino events in IceCube
  57. LIGO/Virgo/KAGRA S231106y: one counterpart neutrino candidate from IceCube neutrino searches
  58. Fermi-LAT gamma-ray observations of IceCube-231103A
  59. GRB 231104A: NOT upper limit
  60. GRB 231104A: Fermi GBM Observation
  61. GRB 231104B: Fermi GBM Final Real-time Localization
  62. Fermi GRB 231103A: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  64. GRB 231104A: AKO Upper Limit
  65. GRB 231104A: AstroSat CZTI detection
  66. GRB 231104A: Swift-XRT refined Analysis
  67. GRB 231104A: Fermi-LAT detection
  68. LIGO/Virgo/KAGRA S231104ac: Identification of a GW compact binary merger candidate
  69. GRB 231104A: Swift/UVOT Upper Limits
  70. GRB 231104A: Enhanced Swift-XRT position
  71. GRB231104A: LCOGT Optical Upper Limits
  72. GRB 231104A: Swift detection of a bright burst
  73. GRB 231104A: Fermi GBM Final Real-time Localization
  74. Swift GRB231104.07: Global MASTER-Net observations report
  75. IceCube Alert 231103.39: Global MASTER-Net observations report
  76. GRB 231103A: Fermi GBM Final Real-time Localization
  77. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  78. Fermi-LAT gamma-ray observations of IceCube-231027A
  79. LIGO/Virgo/KAGRA S231102w: Updated Sky localization
  80. LIGO/Virgo/KAGRA S231102i: Global MASTER-Net observations report
  81. GRB 231101A: Glowbug gamma-ray detection
  82. GRB 231024A: GRANDMA observations of AT2023vuc/GOTO23baj candidate
  83. LIGO/Virgo/KAGRA S231102w: Identification of a GW compact binary merger candidate
  84. New Swift-BAT/GUANO and IceCube Notices Available via GCN Kafka
  85. Fermi trigger No 720498201: Global MASTER-Net observations report
  86. GRB 231101A: Fermi GBM Final Real-time Localization
  87. GRB 231030B: GRBAlpha detection
  88. GRB 231028B: VZLUSAT-2 detection
  89. Fermi trigger No 720415645: Global MASTER-Net observations report
  90. GRB 231030B: Fermi GBM Detection
  91. GRB 231030B: AstroSat CZTI detection
  92. Fermi GRB 231030B: Global MASTER-Net observations report
  93. IPN triangulation of GRB 231020A
  94. GRB 231030B: BALROG localization (Fermi Trigger 720388704 / GRB 231030832)
  95. GRB 231030B: Fermi GBM Final Real-time Localization
  96. GRB 231028A: Swift-BAT refined analysis
  97. IceCube-231027A: Upper limits from a search for additional neutrino events in IceCube
  98. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  99. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  100. GRB 231024A: AKO Optical Counterpart Candidate

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