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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 250205A: Swift/UVOT Upper Limits
  2. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  3. EP250205a/GRB 250205A: correction to the source localization
  4. EP250205a/GRB 250205A: Einstein Probe observation
  5. GRB 250127C: SVOM/GRM observation of a burst
  6. GRB 250204B: SVOM/GRM observation of a likely short burst
  7. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  8. GRB 250205A: Swift/XRT detection
  9. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  10. GRB250205A: SVOM/VT optical afterglow detection
  11. GRB 250205A: GOTO optical upper limits
  12. GRB 250205A: OHP/T193 optical counterpart candidate
  13. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  14. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  15. GRB 250205A: SVOM detection of a burst
  16. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  17. Konus-Wind detection of GRB 250201A
  18. IPN triangulation of GRB 250201A
  19. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  20. Konus-Wind detection of GRB 250202B
  21. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  22. GRB 250129A: Swift-BAT refined analysis
  23. EP 250108A: Upper limits from Fermi-GBM Observations
  24. IPN triangulation of GRB 250204B (short/hard)
  25. IPN triangulation of GRB 250202B
  26. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  27. GRB 250204B: AstroSat CZTI detection of a short burst
  28. GRB 250204B: Fermi GBM Final Localization
  29. GRB 250129A: LCO late afterglow detection
  30. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  31. GRB 250204A: Fermi GBM Final Real-time Localization
  32. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  33. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  34. GRB 250202B: NuSTAR detection of the prompt emission
  35. GRB 250202C: GRBAlpha detection
  36. GRB 250202B: Fermi GBM Detection
  37. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 250129a: Liverpool Telescope optical follow-up
  39. GRB 240129A: further SAO RAS optical observations
  40. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  41. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  42. The EP-WXT trigger 01709131196 is likely a flaring star
  43. GRB 250202C: Fermi GBM Final Real-time Localization
  44. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  45. GRB 250129A: SVOM/C-GFT optical observations
  46. The EP-WXT trigger 01709131153 is not a real source
  47. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  48. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  49. GRB 250202B: Fermi GBM Final Real-time Localization
  50. Swift GRB250129A: MASTER 4 days observations report
  51. GRB 250202A: Fermi GBM Final Real-time Localization
  52. GRB 250201A: INTEGRAL SPI/ACS detection
  53. Konus-Wind detection of GRB 250129A
  54. GRB 250129A: 1.3m DFOT Optical observations
  55. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  56. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  57. GRB 250201A: Fermi GBM Final Real-time Localization
  58. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  59. GRB 250129A: Skynet Continued Optical Observations
  60. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  61. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  62. GRB 250129A: SAO RAS optical observations
  63. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  64. GRB 250129A: optical photometry from Konkoly
  65. GRB 250129A: COLIBRÍ Optical Observations
  66. GRB 250128B: VLA possible radio detection
  67. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  68. GRB 250129A: iTelescope optical observation
  69. GRB 250129A: NOT optical observations of continuining activity
  70. GRB 250129a: Liverpool Telescope optical follow-up
  71. GRB 250129A: TNG NIR afterglow detection
  72. GRB 250129A: AKO Optical Afterglow Detection
  73. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  74. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  75. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  76. GRB 250128B: VLA radio upper limit
  77. Ep250125A: 1.3m DFOT optical upper limit
  78. GRB 250129A: Skynet optical observations
  79. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  80. GRB 250129A: Swift-XRT refined Analysis
  81. GRB 250128B: Gemini-North optical extended source detection
  82. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  83. GRB 250128B: TNG optical upper limit
  84. GRB 250129A: Swift/UVOT Detection
  85. GRB 250128B: VLT/HAWKI near-infrared observations
  86. GRB 250127A: CrAO and Terskol optical upper limits
  87. GRB 250129A: Enhanced Swift-XRT position
  88. GRB 250128B: NOT optical upper limit
  89. GRB 250128B: VLT/FORS2 optical observations
  90. GRB 250129A: REM optical/NIR afterglow detection
  91. GRB 250129A: OHP/T193 optical and spectroscopy observations
  92. GRB 250129A: Early afterglow detection by LCO.
  93. GRB 250128B: OHP/T193 optical upper limit
  94. Swift GRB250129A: Global MASTER-Net Slowly evolving LC detection
  95. GRB 250129A: LCO optical observations
  96. GRB 250129A: NOT optical observations and redshift confirmation
  97. GRB 250129A: GOTO optical observations show brightening afterglow
  98. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  99. Swift GRB 250129A: Global MASTER-Net observations report
  100. GRB 250128B: Enhanced Swift-XRT position

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