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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 231203A: Fermi GBM Observation
  2. GRB 231204A: Fermi GBM Final Real-time Localization
  3. GRB 231203A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  4. Konus-Wind detection of GRB 231129C
  5. IceCube-231202A - IceCube observation of a high-energy neutrino candidate track-like event
  6. Fermi trigger No 723279695: Global MASTER-Net observations report
  7. The Fermi GBM team reports the detection of a likely SHORT GRB
  8. GRB 231203A: Fermi GBM Final Real-time Localization
  9. GRB 231129C: Swift-XRT afterglow detection
  10. Fermi trigger No 723149952: Global MASTER-Net observations report
  11. GRB 231129C: PROMPT optical upper limits for the MAXI/GSC X-ray counterpart and the MASTER afterglow candidate
  12. GRB 231129A: VZLUSAT-2 detection
  13. GRB 231129B: Swift-XRT observations
  14. GRB 231128A: VZLUSAT-2 detection
  15. Optical transient in the field of Messier 31, likely a new blazar: back to bright state
  16. GRB 231129C: AGILE detection
  17. GRB 231129A : MITSuME Akeno optical upper limits
  18. GRB 231129C: Swift/BAT-GUANO localization of a burst outside the coded FOV
  19. GRB 231129A: Swift-BAT refined analysis
  20. GRB 231129C: MASTER OT detection
  21. GRB 231129A: BOOTES-5/JGT optical upper limit
  22. GRB 231129C: Fermi-LAT detection
  23. GRB 231129A: JinShan optical upper limit
  24. GRB 231129C: GRBAlpha detection
  25. GRB 231129C: Glowbug gamma-ray detection
  26. GRB 231129C: Swift-XRT observations
  27. GRB 231129A: Swift/UVOT Upper Limits
  28. GRB 231129A: optical upper limit in Mondy observatory
  29. GRB 231129C: GECAM-B detection of a bright burst
  30. GRB 231129C: AstroSat CZTI detection
  31. GRB 231129C: iTelescope OT retraction
  32. GRB 231129C: CALET Gamma-Ray Burst Monitor detection
  33. GRB 231129C: Fermi GBM Observation of a very bright GRB
  34. GRB 231129C: iTelescope likely optical afterglow AT 2023yph discovery
  35. GRB 231129C: Tiled Swift observations
  36. GRB 231127A: GRBAlpha detection
  37. GRB 231129C: MAXI/GSC detection
  38. GRB 231129C: BALROG localization (Fermi Trigger / GRB 231129799)
  39. GRB 231129C: Fermi GBM detection of a very bright burst
  40. GRB 231129A: Enhanced Swift-XRT position
  41. LIGO/Virgo/KAGRA S231129ac: Updated Sky localization
  42. GRB 231129A: Swift-XRT refined Analysis
  43. GRB 231129C: Fermi GBM Final Real-time Localization
  44. Fermi trigger No 722977823: Global MASTER-Net observations report
  45. GRB 231129B: Tiled Swift observations
  46. GRB 231129B: MAXI/GSC detection
  47. Fermi-LAT gamma-ray observations of IceCube-231125A
  48. Integral GRB231129.21: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S231129ac: Identification of a GW compact binary merger candidate
  50. GRB 231129A: GECAM-C detection of a long burst
  51. GRB 231129A: INTEGRAL detection of a long GRB
  52. GRB 231129A: Swift detection of a burst
  53. LIGO/Virgo/KAGRA S231127cg: Updated Sky localization
  54. GRB 231128A: Fermi GBM Final Real-time Localization
  55. GRB 231123C: Fermi GBM Observation
  56. GRB 231123B: Fermi GBM Observation
  57. IceCube-231125A: Upper limits from a search for additional neutrino events in IceCube
  58. LIGO/Virgo/KAGRA S231127cg: Identification of a GW compact binary merger candidate
  59. GRB 231117A: MeerKAT 1.3GHz detection
  60. GRB 231127A: CALET Gamma-Ray Burst Monitor detection
  61. GRB 231125A: GRBAlpha detection
  62. GRB 231125A: CALET Gamma-Ray Burst Monitor detection
  63. GRB 231127A: AstroSat CZTI detection
  64. GRB 231125A (short): Glowbug gamma-ray detection
  65. GRB 231123B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  66. Update of IceCube-231125A - Corrected errors
  67. GRB 231124A: GRBAlpha detection
  68. IceCube-231125A - IceCube observation of a high-energy neutrino candidate track-like event
  69. Fermi trigger No 722653947: Global MASTER-Net observations report
  70. GRB 231125A: AstroSat CZTI detection of a short burst
  71. GRB 231111A: Optical follow-up observations at Terskol, AbAO, Maidanak, Mondy, Assy
  72. GRB 231126A: Fermi GBM Final Real-time Localization
  73. GRB 231123C: Insight-HXMT/HE detection
  74. Fermi trigger No 722460326: Global MASTER-Net observations report
  75. Fermi trigger No 722507896: Global MASTER-Net observations report
  76. GRB 231123C (short): Glowbug gamma-ray detection
  77. GRB 231124A: Glowbug gamma-ray detection
  78. GRB230728A: VIRT optical upper limit
  79. GRB230506C: VIRT optical upper limit
  80. GRB230506B: VIRT optical upper limit
  81. GRB 231123C: Swift/BAT-GUANO detection of a short burst likely outside the coded FOV
  82. Fermi trigger No 722462310: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S231118an: Updated Sky localization and EM Bright Classification
  84. GRB 231124A: CALET Gamma-Ray Burst Monitor detection
  85. GRB 231115A: XMM-Newton observation
  86. GRB 231124A: Fermi GBM Final Real-time Localization
  87. GRB 231123A: AstroSat CZTI detection
  88. GRB 231117A: Mondy optical observations
  89. GRB 231123C: Fermi GBM Final Real-time Localization
  90. GRB 231123B: Fermi GBM Final Real-time Localization
  91. Fermi trigger No 722400249: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S231123cg: Identification of a GW compact binary merger candidate
  93. GRB 231118A: REM optical afterglow detection
  94. GRB 231122B: AstroSat CZTI detection
  95. GRB 231122B: CALET Gamma-Ray Burst Monitor detection
  96. GRB 231122B: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  97. GRB 231117A: Chandra afterglow detection
  98. GRB 231123A: Fermi GBM Final Real-time Localization
  99. GRB 231122B: Glowbug gamma-ray detection
  100. GRB 231117A: Continued GTC Observations

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