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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. IPN triangulation of GRB 250201A
  2. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  3. Konus-Wind detection of GRB 250202B
  4. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  5. GRB 250129A: Swift-BAT refined analysis
  6. EP 250108A: Upper limits from Fermi-GBM Observations
  7. IPN triangulation of GRB 250204B (short/hard)
  8. IPN triangulation of GRB 250202B
  9. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  10. GRB 250204B: AstroSat CZTI detection of a short burst
  11. GRB 250204B: Fermi GBM Final Localization
  12. GRB 250129A: LCO late afterglow detection
  13. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  14. GRB 250204A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  16. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  17. GRB 250202B: NuSTAR detection of the prompt emission
  18. GRB 250202C: GRBAlpha detection
  19. GRB 250202B: Fermi GBM Detection
  20. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  21. GRB 250129a: Liverpool Telescope optical follow-up
  22. GRB 240129A: further SAO RAS optical observations
  23. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  24. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  25. The EP-WXT trigger 01709131196 is likely a flaring star
  26. GRB 250202C: Fermi GBM Final Real-time Localization
  27. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  28. GRB 250129A: SVOM/C-GFT optical observations
  29. The EP-WXT trigger 01709131153 is not a real source
  30. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  31. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  32. GRB 250202B: Fermi GBM Final Real-time Localization
  33. Swift GRB250129A: MASTER 4 days observations report
  34. GRB 250202A: Fermi GBM Final Real-time Localization
  35. GRB 250201A: INTEGRAL SPI/ACS detection
  36. Konus-Wind detection of GRB 250129A
  37. GRB 250129A: 1.3m DFOT Optical observations
  38. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  39. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  40. GRB 250201A: Fermi GBM Final Real-time Localization
  41. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  42. GRB 250129A: Skynet Continued Optical Observations
  43. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  44. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  45. GRB 250129A: SAO RAS optical observations
  46. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  47. GRB 250129A: optical photometry from Konkoly
  48. GRB 250129A: COLIBRÍ Optical Observations
  49. GRB 250128B: VLA possible radio detection
  50. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  51. GRB 250129A: iTelescope optical observation
  52. GRB 250129A: NOT optical observations of continuining activity
  53. GRB 250129a: Liverpool Telescope optical follow-up
  54. GRB 250129A: TNG NIR afterglow detection
  55. GRB 250129A: AKO Optical Afterglow Detection
  56. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  57. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  58. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  59. GRB 250128B: VLA radio upper limit
  60. Ep250125A: 1.3m DFOT optical upper limit
  61. GRB 250129A: Skynet optical observations
  62. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  63. GRB 250129A: Swift-XRT refined Analysis
  64. GRB 250128B: Gemini-North optical extended source detection
  65. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  66. GRB 250128B: TNG optical upper limit
  67. GRB 250129A: Swift/UVOT Detection
  68. GRB 250128B: VLT/HAWKI near-infrared observations
  69. GRB 250127A: CrAO and Terskol optical upper limits
  70. GRB 250129A: Enhanced Swift-XRT position
  71. GRB 250128B: NOT optical upper limit
  72. GRB 250128B: VLT/FORS2 optical observations
  73. GRB 250129A: REM optical/NIR afterglow detection
  74. GRB 250129A: OHP/T193 optical and spectroscopy observations
  75. GRB 250129A: Early afterglow detection by LCO.
  76. GRB 250128B: OHP/T193 optical upper limit
  77. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  78. GRB 250129A: LCO optical observations
  79. GRB 250129A: NOT optical observations and redshift confirmation
  80. GRB 250129A: GOTO optical observations show brightening afterglow
  81. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  82. Swift GRB 250129A: Global MASTER-Net observations report
  83. GRB 250128B: Enhanced Swift-XRT position
  84. The EP-WXT trigger 01709131085 is likely a flaring star
  85. Fermi GRB 250128B: Global MASTER-Net observations report
  86. GRB 250129A: Swift detection of a burst with an optical counterpart
  87. Swift GRB 250129A: Global MASTER-Net OT detection
  88. GRB 250128B: Swift-XRT refined Analysis
  89. GRB 250128B: Fermi GBM Observation
  90. GRB 250128B: GOTO optical upper limit
  91. Swift GRB 250128B: Global MASTER-Net observations report
  92. EP250125a: Upper limits from Swift/BAT-GUANO
  93. GRB 250128B: LCO optical observations
  94. GRB 250128B: Swift detection of a short burst
  95. GRB 250128B: Fermi GBM Final Real-time Localization
  96. GRB 250127A: Swift-XRT observations
  97. GRB 250127B: DDOTI Upper Limit on the Afterglow
  98. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  99. GRB 250127A: EP-FXT afterglow detection
  100. Fermi GRB 250128A: Global MASTER-Net observations report

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