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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').
  1. GRB 231129C: CALET Gamma-Ray Burst Monitor detection
  2. GRB 231129C: Fermi GBM Observation of a very bright GRB
  3. GRB 231129C: iTelescope likely optical afterglow AT 2023yph discovery
  4. GRB 231129C: Tiled Swift observations
  5. GRB 231127A: GRBAlpha detection
  6. GRB 231129C: MAXI/GSC detection
  7. GRB 231129C: BALROG localization (Fermi Trigger / GRB 231129799)
  8. GRB 231129C: Fermi GBM detection of a very bright burst
  9. GRB 231129A: Enhanced Swift-XRT position
  10. LIGO/Virgo/KAGRA S231129ac: Updated Sky localization
  11. GRB 231129A: Swift-XRT refined Analysis
  12. GRB 231129C: Fermi GBM Final Real-time Localization
  13. Fermi trigger No 722977823: Global MASTER-Net observations report
  14. GRB 231129B: Tiled Swift observations
  15. GRB 231129B: MAXI/GSC detection
  16. Fermi-LAT gamma-ray observations of IceCube-231125A
  17. Integral GRB231129.21: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S231129ac: Identification of a GW compact binary merger candidate
  19. GRB 231129A: GECAM-C detection of a long burst
  20. GRB 231129A: INTEGRAL detection of a long GRB
  21. GRB 231129A: Swift detection of a burst
  22. LIGO/Virgo/KAGRA S231127cg: Updated Sky localization
  23. GRB 231128A: Fermi GBM Final Real-time Localization
  24. GRB 231123C: Fermi GBM Observation
  25. GRB 231123B: Fermi GBM Observation
  26. IceCube-231125A: Upper limits from a search for additional neutrino events in IceCube
  27. LIGO/Virgo/KAGRA S231127cg: Identification of a GW compact binary merger candidate
  28. GRB 231117A: MeerKAT 1.3GHz detection
  29. GRB 231127A: CALET Gamma-Ray Burst Monitor detection
  30. GRB 231125A: GRBAlpha detection
  31. GRB 231125A: CALET Gamma-Ray Burst Monitor detection
  32. GRB 231127A: AstroSat CZTI detection
  33. GRB 231125A (short): Glowbug gamma-ray detection
  34. GRB 231123B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  35. Update of IceCube-231125A - Corrected errors
  36. GRB 231124A: GRBAlpha detection
  37. IceCube-231125A - IceCube observation of a high-energy neutrino candidate track-like event
  38. Fermi trigger No 722653947: Global MASTER-Net observations report
  39. GRB 231125A: AstroSat CZTI detection of a short burst
  40. GRB 231111A: Optical follow-up observations at Terskol, AbAO, Maidanak, Mondy, Assy
  41. GRB 231126A: Fermi GBM Final Real-time Localization
  42. GRB 231123C: Insight-HXMT/HE detection
  43. Fermi trigger No 722460326: Global MASTER-Net observations report
  44. Fermi trigger No 722507896: Global MASTER-Net observations report
  45. GRB 231123C (short): Glowbug gamma-ray detection
  46. GRB 231124A: Glowbug gamma-ray detection
  47. GRB230728A: VIRT optical upper limit
  48. GRB230506C: VIRT optical upper limit
  49. GRB230506B: VIRT optical upper limit
  50. GRB 231123C: Swift/BAT-GUANO detection of a short burst likely outside the coded FOV
  51. Fermi trigger No 722462310: Global MASTER-Net observations report
  52. LIGO/Virgo/KAGRA S231118an: Updated Sky localization and EM Bright Classification
  53. GRB 231124A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 231115A: XMM-Newton observation
  55. GRB 231124A: Fermi GBM Final Real-time Localization
  56. GRB 231123A: AstroSat CZTI detection
  57. GRB 231117A: Mondy optical observations
  58. GRB 231123C: Fermi GBM Final Real-time Localization
  59. GRB 231123B: Fermi GBM Final Real-time Localization
  60. Fermi trigger No 722400249: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S231123cg: Identification of a GW compact binary merger candidate
  62. GRB 231118A: REM optical afterglow detection
  63. GRB 231122B: AstroSat CZTI detection
  64. GRB 231122B: CALET Gamma-Ray Burst Monitor detection
  65. GRB 231122B: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  66. GRB 231117A: Chandra afterglow detection
  67. GRB 231123A: Fermi GBM Final Real-time Localization
  68. GRB 231122B: Glowbug gamma-ray detection
  69. GRB 231117A: Continued GTC Observations
  70. Fermi trigger No 722349867: Global MASTER-Net observations report
  71. GRB 231122A: GECAM detection
  72. GRB 231122B: GECAM detection
  73. GRB 231122A: Fermi GBM Final Real-time Localization
  74. GRB 231118A: ATCA detection of radio counterpart
  75. GRB 231117A: Swift/UVOT late time observations
  76. GRB 231117A: GTC Near-Infrared Observations
  77. GRB 231117A: Swift-BAT refined analysis
  78. GRB 231118A: GRBAlpha detection
  79. LIGO/Virgo/KAGRA S231118d: Upper limits from Swift/BAT-GUANO
  80. LIGO/Virgo/KAGRA S231118an: Upper limits from Swift/BAT-GUANO
  81. LIGO/Virgo/KAGRA S231114n: Upper limits from Swift/BAT-GUANO
  82. LIGO/Virgo/KAGRA S231113bb: Upper limits from Swift/BAT-GUANO
  83. LIGO/Virgo/KAGRA S231119u: Updated Sky localization and Source Classification
  84. LIGO/Virgo/KAGRA S231118ab: Updated Sky localization and Source Classification
  85. LIGO/Virgo/KAGRA S231118d: Updated Sky localization and Source Classification
  86. GRB 231118A: VZLUSAT-2 detection
  87. GRB 231117A: AMI-LA radio observations
  88. GRB 231118A: Swift-BAT refined analysis
  89. Konus-Wind detection of GRB 231020A
  90. GRB 231117A: LDT Confirmation of Optical Fading
  91. GRB 231117A: Wendelstein Confirmation of Fading of the Optical Afterglow
  92. GRB 231118B: CALET Gamma-Ray Burst Monitor detection
  93. GRB 231117A: CALET Gamma-Ray Burst Monitor detection
  94. 231118A: Swift-UVOT Detection
  95. GRB231117A: Swift-UVOT detection
  96. GRB 231117A : MITSuME Akeno optical afterglow candidate detection
  97. GRB 231118B: Fermi GBM observation
  98. GRB 231118A: Fermi GBM observation
  99. LIGO/Virgo/KAGRA S231119ab: Coverage and upper limits from MAXI/GSC observations
  100. GRB 231120A: Fermi GBM Final Real-time Localization

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