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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 231104B: Fermi GBM Final Real-time Localization
  2. Fermi GRB 231103A: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  4. GRB 231104A: AKO Upper Limit
  5. GRB 231104A: AstroSat CZTI detection
  6. GRB 231104A: Swift-XRT refined Analysis
  7. GRB 231104A: Fermi-LAT detection
  8. LIGO/Virgo/KAGRA S231104ac: Identification of a GW compact binary merger candidate
  9. GRB 231104A: Swift/UVOT Upper Limits
  10. GRB 231104A: Enhanced Swift-XRT position
  11. GRB231104A: LCOGT Optical Upper Limits
  12. GRB 231104A: Swift detection of a bright burst
  13. GRB 231104A: Fermi GBM Final Real-time Localization
  14. Swift GRB231104.07: Global MASTER-Net observations report
  15. IceCube Alert 231103.39: Global MASTER-Net observations report
  16. GRB 231103A: Fermi GBM Final Real-time Localization
  17. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  18. Fermi-LAT gamma-ray observations of IceCube-231027A
  19. LIGO/Virgo/KAGRA S231102w: Updated Sky localization
  20. LIGO/Virgo/KAGRA S231102i: Global MASTER-Net observations report
  21. GRB 231101A: Glowbug gamma-ray detection
  22. GRB 231024A: GRANDMA observations of AT2023vuc/GOTO23baj candidate
  23. LIGO/Virgo/KAGRA S231102w: Identification of a GW compact binary merger candidate
  24. New Swift-BAT/GUANO and IceCube Notices Available via GCN Kafka
  25. Fermi trigger No 720498201: Global MASTER-Net observations report
  26. GRB 231101A: Fermi GBM Final Real-time Localization
  27. GRB 231030B: GRBAlpha detection
  28. GRB 231028B: VZLUSAT-2 detection
  29. Fermi trigger No 720415645: Global MASTER-Net observations report
  30. GRB 231030B: Fermi GBM Detection
  31. GRB 231030B: AstroSat CZTI detection
  32. Fermi GRB 231030B: Global MASTER-Net observations report
  33. IPN triangulation of GRB 231020A
  34. GRB 231030B: BALROG localization (Fermi Trigger 720388704 / GRB 231030832)
  35. GRB 231030B: Fermi GBM Final Real-time Localization
  36. GRB 231028A: Swift-BAT refined analysis
  37. IceCube-231027A: Upper limits from a search for additional neutrino events in IceCube
  38. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  39. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  40. GRB 231024A: AKO Optical Counterpart Candidate
  41. GRB 231028A: CALET Gamma-Ray Burst Monitor detection
  42. Fermi GRB 231030A: Global MASTER-Net observations report
  43. GRB 231030A: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  45. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  47. GRID detection of GRB 231020A
  48. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  49. GRB 231028A: AstroSat CZTI detection
  50. GRB 231028A: Glowbug gamma-ray detection
  51. GRB 231028A: Fermi GBM Detection
  52. Fermi trigger No 720224759: Global MASTER-Net observations report
  53. Swift GRB 231028A: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  55. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  56. GRB 231028A: Swift detection of a burst
  57. GRB 231028A: Fermi GBM Final Real-time Localization
  58. IceCube Alert 231027.18: Global MASTER-Net observations report
  59. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  60. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  62. GRB 231019A: Glowbug gamma-ray detection
  63. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  64. GRB 231025A: Fermi GBM Observation
  65. GRB 231024A: Fermi GBM Observation
  66. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  67. GRB 231025A: Fermi GBM Final Localization
  68. GRB 231024A: X-shooter spectroscopy of AT2023vuc/GOTO23baj reveals a young supernova with flash ionisation features
  69. GRB 231024A: LCOGT and ZTF detections of the GOTO optical counterpart candidate
  70. GRB 231020A: AstroSat CZTI detection
  71. GRB 231020B: AstroSat CZTI detection
  72. GRB 231024A: GOTO optical counterpart candidate
  73. LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches
  74. GRB 231024A: Fermi GBM Final Localization
  75. Fermi trigger No 719846439: Global MASTER-Net observations report
  76. The photometry of the transient in Messier 31 field: GMG observation
  77. GRB 231018A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  78. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  79. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  80. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  81. GRB 231020A: Fermi GBM Detection
  82. GRID detection of GRB 231004A
  83. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  84. GRB 231019A: VZLUSAT-2 detection
  85. GRB 231018A: VZLUSAT-2 detection
  86. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  87. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  88. GRB 231020B: Fermi GBM Final Real-time Localization
  89. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  90. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  91. GRB 231015A: NuSTAR Detection of Prompt Emission
  92. Fermi GRB 231020A: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  94. GRB 231020A: Fermi GBM Final Real-time Localization
  95. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  96. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  97. GRB 231017A: 1.3m DFOT Optical upper limit
  98. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  99. IceCube-231004A: Upper limits from Fermi-GBM Observations
  100. GRB 231018A: GRBAlpha detection

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