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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: Swift detection of a bright burst
  2. GRB 231104A: Fermi GBM Final Real-time Localization
  3. Swift GRB231104.07: Global MASTER-Net observations report
  4. IceCube Alert 231103.39: Global MASTER-Net observations report
  5. GRB 231103A: Fermi GBM Final Real-time Localization
  6. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  7. Fermi-LAT gamma-ray observations of IceCube-231027A
  8. LIGO/Virgo/KAGRA S231102w: Updated Sky localization
  9. LIGO/Virgo/KAGRA S231102i: Global MASTER-Net observations report
  10. GRB 231101A: Glowbug gamma-ray detection
  11. GRB 231024A: GRANDMA observations of AT2023vuc/GOTO23baj candidate
  12. LIGO/Virgo/KAGRA S231102w: Identification of a GW compact binary merger candidate
  13. New Swift-BAT/GUANO and IceCube Notices Available via GCN Kafka
  14. Fermi trigger No 720498201: Global MASTER-Net observations report
  15. GRB 231101A: Fermi GBM Final Real-time Localization
  16. GRB 231030B: GRBAlpha detection
  17. GRB 231028B: VZLUSAT-2 detection
  18. Fermi trigger No 720415645: Global MASTER-Net observations report
  19. GRB 231030B: Fermi GBM Detection
  20. GRB 231030B: AstroSat CZTI detection
  21. Fermi GRB 231030B: Global MASTER-Net observations report
  22. IPN triangulation of GRB 231020A
  23. GRB 231030B: BALROG localization (Fermi Trigger 720388704 / GRB 231030832)
  24. GRB 231030B: Fermi GBM Final Real-time Localization
  25. GRB 231028A: Swift-BAT refined analysis
  26. IceCube-231027A: Upper limits from a search for additional neutrino events in IceCube
  27. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  28. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  29. GRB 231024A: AKO Optical Counterpart Candidate
  30. GRB 231028A: CALET Gamma-Ray Burst Monitor detection
  31. Fermi GRB 231030A: Global MASTER-Net observations report
  32. GRB 231030A: Fermi GBM Final Real-time Localization
  33. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  34. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  35. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  36. GRID detection of GRB 231020A
  37. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  38. GRB 231028A: AstroSat CZTI detection
  39. GRB 231028A: Glowbug gamma-ray detection
  40. GRB 231028A: Fermi GBM Detection
  41. Fermi trigger No 720224759: Global MASTER-Net observations report
  42. Swift GRB 231028A: Global MASTER-Net observations report
  43. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  44. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  45. GRB 231028A: Swift detection of a burst
  46. GRB 231028A: Fermi GBM Final Real-time Localization
  47. IceCube Alert 231027.18: Global MASTER-Net observations report
  48. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  49. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  51. GRB 231019A: Glowbug gamma-ray detection
  52. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  53. GRB 231025A: Fermi GBM Observation
  54. GRB 231024A: Fermi GBM Observation
  55. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  56. GRB 231025A: Fermi GBM Final Localization
  57. GRB 231024A: X-shooter spectroscopy of AT2023vuc/GOTO23baj reveals a young supernova with flash ionisation features
  58. GRB 231024A: LCOGT and ZTF detections of the GOTO optical counterpart candidate
  59. GRB 231020A: AstroSat CZTI detection
  60. GRB 231020B: AstroSat CZTI detection
  61. GRB 231024A: GOTO optical counterpart candidate
  62. LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches
  63. GRB 231024A: Fermi GBM Final Localization
  64. Fermi trigger No 719846439: Global MASTER-Net observations report
  65. The photometry of the transient in Messier 31 field: GMG observation
  66. GRB 231018A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  67. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  68. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  69. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  70. GRB 231020A: Fermi GBM Detection
  71. GRID detection of GRB 231004A
  72. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  73. GRB 231019A: VZLUSAT-2 detection
  74. GRB 231018A: VZLUSAT-2 detection
  75. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  76. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  77. GRB 231020B: Fermi GBM Final Real-time Localization
  78. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  79. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  80. GRB 231015A: NuSTAR Detection of Prompt Emission
  81. Fermi GRB 231020A: Global MASTER-Net observations report
  82. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  83. GRB 231020A: Fermi GBM Final Real-time Localization
  84. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  85. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  86. GRB 231017A: 1.3m DFOT Optical upper limit
  87. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  88. IceCube-231004A: Upper limits from Fermi-GBM Observations
  89. GRB 231018A: GRBAlpha detection
  90. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  91. Fermi GRB 231019A: Global MASTER-Net observations report
  92. GRB 231018A: Glowbug gamma-ray detection
  93. Konus-Wind detection of GRB 231018A
  94. IPN triangulation of GRB 231018A
  95. GRB 231017A: Swift/UVOT Upper Limit
  96. GRB 230911C: ATCA detection of possible radio counterpart
  97. GRB 231019A: Fermi GBM Final Real-time Localization
  98. GRB 231017A: GOTO optical upper limits
  99. GRB 231017A: JinShan optical upper limit
  100. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB

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