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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. The EP-WXT trigger 01709131196 is likely a flaring star
  2. GRB 250202C: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  4. GRB 250129A: SVOM/C-GFT optical observations
  5. The EP-WXT trigger 01709131153 is not a real source
  6. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  7. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  8. GRB 250202B: Fermi GBM Final Real-time Localization
  9. Swift GRB250129A: MASTER 4 days observations report
  10. GRB 250202A: Fermi GBM Final Real-time Localization
  11. GRB 250201A: INTEGRAL SPI/ACS detection
  12. Konus-Wind detection of GRB 250129A
  13. GRB 250129A: 1.3m DFOT Optical observations
  14. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  15. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  16. GRB 250201A: Fermi GBM Final Real-time Localization
  17. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  18. GRB 250129A: Skynet Continued Optical Observations
  19. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  20. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  21. GRB 250129A: SAO RAS optical observations
  22. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  23. GRB 250129A: optical photometry from Konkoly
  24. GRB 250129A: COLIBRÍ Optical Observations
  25. GRB 250128B: VLA possible radio detection
  26. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  27. GRB 250129A: iTelescope optical observation
  28. GRB 250129A: NOT optical observations of continuining activity
  29. GRB 250129a: Liverpool Telescope optical follow-up
  30. GRB 250129A: TNG NIR afterglow detection
  31. GRB 250129A: AKO Optical Afterglow Detection
  32. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  33. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  34. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  35. GRB 250128B: VLA radio upper limit
  36. Ep250125A: 1.3m DFOT optical upper limit
  37. GRB 250129A: Skynet optical observations
  38. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  39. GRB 250129A: Swift-XRT refined Analysis
  40. GRB 250128B: Gemini-North optical extended source detection
  41. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  42. GRB 250128B: TNG optical upper limit
  43. GRB 250129A: Swift/UVOT Detection
  44. GRB 250128B: VLT/HAWKI near-infrared observations
  45. GRB 250127A: CrAO and Terskol optical upper limits
  46. GRB 250129A: Enhanced Swift-XRT position
  47. GRB 250128B: NOT optical upper limit
  48. GRB 250128B: VLT/FORS2 optical observations
  49. GRB 250129A: REM optical/NIR afterglow detection
  50. GRB 250129A: OHP/T193 optical and spectroscopy observations
  51. GRB 250129A: Early afterglow detection by LCO.
  52. GRB 250128B: OHP/T193 optical upper limit
  53. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  54. GRB 250129A: LCO optical observations
  55. GRB 250129A: NOT optical observations and redshift confirmation
  56. GRB 250129A: GOTO optical observations show brightening afterglow
  57. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  58. Swift GRB 250129A: Global MASTER-Net observations report
  59. GRB 250128B: Enhanced Swift-XRT position
  60. The EP-WXT trigger 01709131085 is likely a flaring star
  61. Fermi GRB 250128B: Global MASTER-Net observations report
  62. GRB 250129A: Swift detection of a burst with an optical counterpart
  63. Swift GRB 250129A: Global MASTER-Net OT detection
  64. GRB 250128B: Swift-XRT refined Analysis
  65. GRB 250128B: Fermi GBM Observation
  66. GRB 250128B: GOTO optical upper limit
  67. Swift GRB 250128B: Global MASTER-Net observations report
  68. EP250125a: Upper limits from Swift/BAT-GUANO
  69. GRB 250128B: LCO optical observations
  70. GRB 250128B: Swift detection of a short burst
  71. GRB 250128B: Fermi GBM Final Real-time Localization
  72. GRB 250127A: Swift-XRT observations
  73. GRB 250127B: DDOTI Upper Limit on the Afterglow
  74. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  75. GRB 250127A: EP-FXT afterglow detection
  76. Fermi GRB 250128A: Global MASTER-Net observations report
  77. GRB 250128A: Fermi GBM Final Real-time Localization
  78. GRB 250117A: Fermi GBM Observation
  79. Fermi GRB 250127B: Global MASTER-Net observations report
  80. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  81. GRB 250127A: SVOM/VT upper limit
  82. GRB 250127B: Fermi GBM Final Real-time Localization
  83. IPN triangulation of GRB 250119C
  84. GRB 250127A: Swift ToO observations
  85. GRB 250127A: LCO optical upper limit
  86. GRB 241223A: cubesat Avion detection
  87. GRB 250127A: SVOM detection of a long burst
  88. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  89. EP250125A: Non-detection from Fermi-GBM Observations
  90. GRB 250126A: MAXI/GSC detection
  91. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  92. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  93. GRB 250126A: Fermi GBM Final Real-time Localization
  94. GECAM-A detection of a bright burst from SGR 1E1841-045
  95. GRB 250118A: Fermi GBM Observation
  96. EP250125a: Optical upper limit with Kinder observations
  97. EP250125a: REM optical counterpart detection
  98. GRB 250119C: Fermi GBM Observation
  99. EP250125a: Swift/XRT detection of a fading counterpart
  100. EP250125a: a new X-ray transient detected by Einstein Probe

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