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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 231129C: AGILE detection
  2. GRB 231129A : MITSuME Akeno optical upper limits
  3. GRB 231129C: Swift/BAT-GUANO localization of a burst outside the coded FOV
  4. GRB 231129A: Swift-BAT refined analysis
  5. GRB 231129C: MASTER OT detection
  6. GRB 231129A: BOOTES-5/JGT optical upper limit
  7. GRB 231129C: Fermi-LAT detection
  8. GRB 231129A: JinShan optical upper limit
  9. GRB 231129C: GRBAlpha detection
  10. GRB 231129C: Glowbug gamma-ray detection
  11. GRB 231129C: Swift-XRT observations
  12. GRB 231129A: Swift/UVOT Upper Limits
  13. GRB 231129A: optical upper limit in Mondy observatory
  14. GRB 231129C: GECAM-B detection of a bright burst
  15. GRB 231129C: AstroSat CZTI detection
  16. GRB 231129C: iTelescope OT retraction
  17. GRB 231129C: CALET Gamma-Ray Burst Monitor detection
  18. GRB 231129C: Fermi GBM Observation of a very bright GRB
  19. GRB 231129C: iTelescope likely optical afterglow AT 2023yph discovery
  20. GRB 231129C: Tiled Swift observations
  21. GRB 231127A: GRBAlpha detection
  22. GRB 231129C: MAXI/GSC detection
  23. GRB 231129C: BALROG localization (Fermi Trigger / GRB 231129799)
  24. GRB 231129C: Fermi GBM detection of a very bright burst
  25. GRB 231129A: Enhanced Swift-XRT position
  26. LIGO/Virgo/KAGRA S231129ac: Updated Sky localization
  27. GRB 231129A: Swift-XRT refined Analysis
  28. GRB 231129C: Fermi GBM Final Real-time Localization
  29. Fermi trigger No 722977823: Global MASTER-Net observations report
  30. GRB 231129B: Tiled Swift observations
  31. GRB 231129B: MAXI/GSC detection
  32. Fermi-LAT gamma-ray observations of IceCube-231125A
  33. Integral GRB231129.21: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S231129ac: Identification of a GW compact binary merger candidate
  35. GRB 231129A: GECAM-C detection of a long burst
  36. GRB 231129A: INTEGRAL detection of a long GRB
  37. GRB 231129A: Swift detection of a burst
  38. LIGO/Virgo/KAGRA S231127cg: Updated Sky localization
  39. GRB 231128A: Fermi GBM Final Real-time Localization
  40. GRB 231123C: Fermi GBM Observation
  41. GRB 231123B: Fermi GBM Observation
  42. IceCube-231125A: Upper limits from a search for additional neutrino events in IceCube
  43. LIGO/Virgo/KAGRA S231127cg: Identification of a GW compact binary merger candidate
  44. GRB 231117A: MeerKAT 1.3GHz detection
  45. GRB 231127A: CALET Gamma-Ray Burst Monitor detection
  46. GRB 231125A: GRBAlpha detection
  47. GRB 231125A: CALET Gamma-Ray Burst Monitor detection
  48. GRB 231127A: AstroSat CZTI detection
  49. GRB 231125A (short): Glowbug gamma-ray detection
  50. GRB 231123B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  51. Update of IceCube-231125A - Corrected errors
  52. GRB 231124A: GRBAlpha detection
  53. IceCube-231125A - IceCube observation of a high-energy neutrino candidate track-like event
  54. Fermi trigger No 722653947: Global MASTER-Net observations report
  55. GRB 231125A: AstroSat CZTI detection of a short burst
  56. GRB 231111A: Optical follow-up observations at Terskol, AbAO, Maidanak, Mondy, Assy
  57. GRB 231126A: Fermi GBM Final Real-time Localization
  58. GRB 231123C: Insight-HXMT/HE detection
  59. Fermi trigger No 722460326: Global MASTER-Net observations report
  60. Fermi trigger No 722507896: Global MASTER-Net observations report
  61. GRB 231123C (short): Glowbug gamma-ray detection
  62. GRB 231124A: Glowbug gamma-ray detection
  63. GRB230728A: VIRT optical upper limit
  64. GRB230506C: VIRT optical upper limit
  65. GRB230506B: VIRT optical upper limit
  66. GRB 231123C: Swift/BAT-GUANO detection of a short burst likely outside the coded FOV
  67. Fermi trigger No 722462310: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S231118an: Updated Sky localization and EM Bright Classification
  69. GRB 231124A: CALET Gamma-Ray Burst Monitor detection
  70. GRB 231115A: XMM-Newton observation
  71. GRB 231124A: Fermi GBM Final Real-time Localization
  72. GRB 231123A: AstroSat CZTI detection
  73. GRB 231117A: Mondy optical observations
  74. GRB 231123C: Fermi GBM Final Real-time Localization
  75. GRB 231123B: Fermi GBM Final Real-time Localization
  76. Fermi trigger No 722400249: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S231123cg: Identification of a GW compact binary merger candidate
  78. GRB 231118A: REM optical afterglow detection
  79. GRB 231122B: AstroSat CZTI detection
  80. GRB 231122B: CALET Gamma-Ray Burst Monitor detection
  81. GRB 231122B: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  82. GRB 231117A: Chandra afterglow detection
  83. GRB 231123A: Fermi GBM Final Real-time Localization
  84. GRB 231122B: Glowbug gamma-ray detection
  85. GRB 231117A: Continued GTC Observations
  86. Fermi trigger No 722349867: Global MASTER-Net observations report
  87. GRB 231122A: GECAM detection
  88. GRB 231122B: GECAM detection
  89. GRB 231122A: Fermi GBM Final Real-time Localization
  90. GRB 231118A: ATCA detection of radio counterpart
  91. GRB 231117A: Swift/UVOT late time observations
  92. GRB 231117A: GTC Near-Infrared Observations
  93. GRB 231117A: Swift-BAT refined analysis
  94. GRB 231118A: GRBAlpha detection
  95. LIGO/Virgo/KAGRA S231118d: Upper limits from Swift/BAT-GUANO
  96. LIGO/Virgo/KAGRA S231118an: Upper limits from Swift/BAT-GUANO
  97. LIGO/Virgo/KAGRA S231114n: Upper limits from Swift/BAT-GUANO
  98. LIGO/Virgo/KAGRA S231113bb: Upper limits from Swift/BAT-GUANO
  99. LIGO/Virgo/KAGRA S231119u: Updated Sky localization and Source Classification
  100. LIGO/Virgo/KAGRA S231118ab: Updated Sky localization and Source Classification

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