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

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