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

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