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GCN Circulars are now part of the new GCN! See news and announcements

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. VIRT optical transient detection
  2. GRB 230414B: 3.6m DOT Optical observations, slow decay at early epochs
  3. GRB 230307A: iTelescope optical upper limit (likely)
  4. GRB 230414B: Montarrenti Observatory late time optical afterglow detection
  5. IceCube-230416A: IceCube observation of a high-energy neutrino candidate
  6. Fermi trigger No 703284533: Global MASTER-Net observations report
  7. GRB 230414B: Lulin 40cm-SLT optical limit
  8. GRB 230414B: Bassano Bresciano Observatory optical observations
  9. GRB 230414B: Redshift from OSIRIS/GTC
  10. GRB 230414B: AbAO optical observations
  11. GRB 230409B: 3.6m DOT near-infrared detection, afterglow confirmation
  12. GRB 230414B: Swift-XRT refined Analysis
  13. GRB 230414B: Dabancheng/GHOST optical observations
  14. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230414A
  15. GRB 230414B: slow optical light curve decay
  16. GRB 230414B: SAO RAS optical observations
  17. GRB 230414B: Enhanced Swift-XRT position
  18. GRB 230414B: 1.3m DFOT Optical observations
  19. Fermi GRB 230414A: Global MASTER-Net observations report
  20. GRB 230414B: GROWTH India Telescope afterglow confirmation
  21. GRB 230414B (correction GRB name in the GCN 33615): Mondy optical afterglow candidate
  22. GRB 230414B: Nanshan/HMT optical afterglow detection
  23. GRB 230414A: Mondy optical afterglow candidate
  24. Swift GRB 230414B: Global MASTER-Net observations report
  25. GRB 230414B: Prompt enhanced Swift-XRT position
  26. GRB 230414B: Swift detection of a burst
  27. IceCube-230405A: BOOTES-4/MET Optical Upper Limits
  28. GRB 230414A: Fermi GBM Final Real-time Localization
  29. GRB 230328B: redshift lower limit estimating
  30. GRB 230409B: Mondy optical upper limit
  31. GRB 230409B: OHP/T193 optical upper limit
  32. GRB 230410B: VZLUSAT-2 detection
  33. GRB 230409D: VZLUSAT-2 detection
  34. GRB 230410B: AGILE detection of a burst
  35. GRB 230410A: Fermi GBM Final Real-time Localization
  36. Fermi GRB 230409C: Global MASTER-Net observations report
  37. Fermi GRB 230409A: Global MASTER-Net observations report
  38. GRB 230409C: Fermi GBM Final Real-time Localization
  39. GRB 230409B: Swift-XRT refined Analysis
  40. GRB 230409B: Swift-BAT refined analysis
  41. Fermi trigger No 702745263: Global MASTER-Net observations report
  42. Swift GRB 230409B: Global MASTER-Net observations report
  43. GRB 230409B: Swift/UVOT Detection
  44. GRB 230409B: Enhanced Swift-XRT position
  45. MAXI GRB230408.82: Global MASTER-Net observations report
  46. GRB 230409B: Swift detection of a burst
  47. GRB 230409A: Fermi GBM Final Real-time Localization
  48. GRB 230405B: VZLUSAT-2 detection
  49. IceCube-230405A: Upper limits from a search for additional neutrino events in IceCube
  50. Fermi-LAT gamma-ray observations of IceCube-230405A
  51. Konus-Wind detection of GRB 230405B
  52. GRB 230405B: AGILE detection
  53. GRB 230405B: Swift-XRT refined Analysis
  54. GRB 230405B: Fermi GBM Observation
  55. GRB 230405B: MeerLICHT upper limits
  56. IceCube Alert 230405.56: Global MASTER-Net observations report
  57. GRB 230307A: JWST NIRSpec observations, possible higher redshift
  58. GRB 230307A: further analysis of the Konus-Wind detection and rest-frame energetics
  59. GRB 230307A: good match with kilonova models
  60. GRB 230307A: short mininum variability timescale compatible with a merger origin
  61. GRB 230405B: Swift/UVOT Upper Limits
  62. GRB 230405B: AstroSat CZTI detection
  63. GRB 230405B: Enhanced Swift-XRT position
  64. Swift GRB 230405B: Global MASTER-Net observations report
  65. GRB 230405B: Prompt enhanced Swift-XRT position
  66. GRB 230405B: Swift detection of a burst
  67. GRB 230405B: Fermi GBM Final Real-time Localization
  68. GRB 230307A: JWST observations consistent with the presence of a kilonova
  69. Fermi GRB 230405A: Global MASTER-Net observations report
  70. IceCube-230405A: IceCube observation of a high-energy neutrino candidate
  71. GRB 230405A: Fermi GBM Final Real-time Localization
  72. GRB 230404A: AstroSat CZTI detection
  73. GRB 230404A: Fermi GBM Final Real-time Localization
  74. GRB 230402A: CALET Gamma-Ray Burst Monitor detection
  75. GRB 230402A: AstroSat CZTI detection
  76. Fermi-LAT gamma-ray observations of IceCube-230401A and detection of Fermi J0030.2+0005
  77. IceCube-230401A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 230328B: Multa observatory optical afterglow observation
  79. GRB 230307A: Chandra late-time detection of the X-ray afterglow
  80. GRB 230228A: detection by GTC of the potential host galaxy
  81. GRB 230328B: Swift/UVOT Detection
  82. GRB 230402A: AGILE detection
  83. Fermi GRB 230402A: Global MASTER-Net observations report
  84. GRB 230402A: Fermi GBM Final Real-time Localization
  85. IceCube-230401A: IceCube observation of a high-energy neutrino candidate
  86. GRB 230307A: Bad Time Intervals for Fermi GBM data
  87. GRB 230328B : GRANDMA/Kilonova-Catcher optical detection
  88. GRB 230328B: CAHA 2.2m/CAFOS detection
  89. IceCube-Cascade 230329A: Upper limits from a search for additional neutrino events in IceCube
  90. GRB 230328B: 3.6m DOT multiband optical observation
  91. Fermi trigger No 701883729: Global MASTER-Net observations report
  92. GRB 230330B: Fermi GBM Final Localization
  93. Konus-Wind detection of GRB 230328B
  94. GRB 230328B: GRBAlpha detection
  95. GRB 230330A: Fermi GBM Final Real-time Localization
  96. GRB 230328B: Swift-BAT refined analysis
  97. GRB 230328B: Nanshan/NEXT 2nd optical observation
  98. GRB 230328B NUTTelA-TAO / BSTI Early Measurements
  99. GRB 230328B: Liverpool Telescope afterglow detection
  100. GRB 230328B: OHP/T120 optical observations
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