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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 250202C: Fermi GBM Final Real-time Localization
  2. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  3. GRB 250129A: SVOM/C-GFT optical observations
  4. The EP-WXT trigger 01709131153 is not a real source
  5. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  6. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  7. GRB 250202B: Fermi GBM Final Real-time Localization
  8. Swift GRB250129A: MASTER 4 days observations report
  9. GRB 250202A: Fermi GBM Final Real-time Localization
  10. GRB 250201A: INTEGRAL SPI/ACS detection
  11. Konus-Wind detection of GRB 250129A
  12. GRB 250129A: 1.3m DFOT Optical observations
  13. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  14. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  15. GRB 250201A: Fermi GBM Final Real-time Localization
  16. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  17. GRB 250129A: Skynet Continued Optical Observations
  18. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  19. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  20. GRB 250129A: SAO RAS optical observations
  21. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  22. GRB 250129A: optical photometry from Konkoly
  23. GRB 250129A: COLIBRÍ Optical Observations
  24. GRB 250128B: VLA possible radio detection
  25. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  26. GRB 250129A: iTelescope optical observation
  27. GRB 250129A: NOT optical observations of continuining activity
  28. GRB 250129a: Liverpool Telescope optical follow-up
  29. GRB 250129A: TNG NIR afterglow detection
  30. GRB 250129A: AKO Optical Afterglow Detection
  31. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  32. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  33. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  34. GRB 250128B: VLA radio upper limit
  35. Ep250125A: 1.3m DFOT optical upper limit
  36. GRB 250129A: Skynet optical observations
  37. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  38. GRB 250129A: Swift-XRT refined Analysis
  39. GRB 250128B: Gemini-North optical extended source detection
  40. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  41. GRB 250128B: TNG optical upper limit
  42. GRB 250129A: Swift/UVOT Detection
  43. GRB 250128B: VLT/HAWKI near-infrared observations
  44. GRB 250127A: CrAO and Terskol optical upper limits
  45. GRB 250129A: Enhanced Swift-XRT position
  46. GRB 250128B: NOT optical upper limit
  47. GRB 250128B: VLT/FORS2 optical observations
  48. GRB 250129A: REM optical/NIR afterglow detection
  49. GRB 250129A: OHP/T193 optical and spectroscopy observations
  50. GRB 250129A: Early afterglow detection by LCO.
  51. GRB 250128B: OHP/T193 optical upper limit
  52. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  53. GRB 250129A: LCO optical observations
  54. GRB 250129A: NOT optical observations and redshift confirmation
  55. GRB 250129A: GOTO optical observations show brightening afterglow
  56. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  57. Swift GRB 250129A: Global MASTER-Net observations report
  58. GRB 250128B: Enhanced Swift-XRT position
  59. The EP-WXT trigger 01709131085 is likely a flaring star
  60. Fermi GRB 250128B: Global MASTER-Net observations report
  61. GRB 250129A: Swift detection of a burst with an optical counterpart
  62. Swift GRB 250129A: Global MASTER-Net OT detection
  63. GRB 250128B: Swift-XRT refined Analysis
  64. GRB 250128B: Fermi GBM Observation
  65. GRB 250128B: GOTO optical upper limit
  66. Swift GRB 250128B: Global MASTER-Net observations report
  67. EP250125a: Upper limits from Swift/BAT-GUANO
  68. GRB 250128B: LCO optical observations
  69. GRB 250128B: Swift detection of a short burst
  70. GRB 250128B: Fermi GBM Final Real-time Localization
  71. GRB 250127A: Swift-XRT observations
  72. GRB 250127B: DDOTI Upper Limit on the Afterglow
  73. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  74. GRB 250127A: EP-FXT afterglow detection
  75. Fermi GRB 250128A: Global MASTER-Net observations report
  76. GRB 250128A: Fermi GBM Final Real-time Localization
  77. GRB 250117A: Fermi GBM Observation
  78. Fermi GRB 250127B: Global MASTER-Net observations report
  79. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  80. GRB 250127A: SVOM/VT upper limit
  81. GRB 250127B: Fermi GBM Final Real-time Localization
  82. IPN triangulation of GRB 250119C
  83. GRB 250127A: Swift ToO observations
  84. GRB 250127A: LCO optical upper limit
  85. GRB 241223A: cubesat Avion detection
  86. GRB 250127A: SVOM detection of a long burst
  87. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  88. EP250125A: Non-detection from Fermi-GBM Observations
  89. GRB 250126A: MAXI/GSC detection
  90. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  91. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  92. GRB 250126A: Fermi GBM Final Real-time Localization
  93. GECAM-A detection of a bright burst from SGR 1E1841-045
  94. GRB 250118A: Fermi GBM Observation
  95. EP250125a: Optical upper limit with Kinder observations
  96. EP250125a: REM optical counterpart detection
  97. GRB 250119C: Fermi GBM Observation
  98. EP250125a: Swift/XRT detection of a fading counterpart
  99. EP250125a: a new X-ray transient detected by Einstein Probe
  100. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89

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