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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. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  2. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  3. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  5. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  6. GRB 250206A: Fermi GBM Final Real-time Localization
  7. GRB 250205A: Fermi GBM Observation
  8. GRB 250205A: REM NIR upper limit
  9. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  10. GRB 250205A: Swift/UVOT Upper Limits
  11. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  12. EP250205a/GRB 250205A: correction to the source localization
  13. EP250205a/GRB 250205A: Einstein Probe observation
  14. GRB 250127C: SVOM/GRM observation of a burst
  15. GRB 250204B: SVOM/GRM observation of a likely short burst
  16. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  17. GRB 250205A: Swift/XRT detection
  18. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  19. GRB250205A: SVOM/VT optical afterglow detection
  20. GRB 250205A: GOTO optical upper limits
  21. GRB 250205A: OHP/T193 optical counterpart candidate
  22. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  23. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  24. GRB 250205A: SVOM detection of a burst
  25. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  26. Konus-Wind detection of GRB 250201A
  27. IPN triangulation of GRB 250201A
  28. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  29. Konus-Wind detection of GRB 250202B
  30. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  31. GRB 250129A: Swift-BAT refined analysis
  32. EP 250108A: Upper limits from Fermi-GBM Observations
  33. IPN triangulation of GRB 250204B (short/hard)
  34. IPN triangulation of GRB 250202B
  35. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  36. GRB 250204B: AstroSat CZTI detection of a short burst
  37. GRB 250204B: Fermi GBM Final Localization
  38. GRB 250129A: LCO late afterglow detection
  39. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  40. GRB 250204A: Fermi GBM Final Real-time Localization
  41. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  42. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  43. GRB 250202B: NuSTAR detection of the prompt emission
  44. GRB 250202C: GRBAlpha detection
  45. GRB 250202B: Fermi GBM Detection
  46. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  47. GRB 250129a: Liverpool Telescope optical follow-up
  48. GRB 240129A: further SAO RAS optical observations
  49. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  50. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  51. The EP-WXT trigger 01709131196 is likely a flaring star
  52. GRB 250202C: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  54. GRB 250129A: SVOM/C-GFT optical observations
  55. The EP-WXT trigger 01709131153 is not a real source
  56. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  57. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  58. GRB 250202B: Fermi GBM Final Real-time Localization
  59. Swift GRB250129A: MASTER 4 days observations report
  60. GRB 250202A: Fermi GBM Final Real-time Localization
  61. GRB 250201A: INTEGRAL SPI/ACS detection
  62. Konus-Wind detection of GRB 250129A
  63. GRB 250129A: 1.3m DFOT Optical observations
  64. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  65. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  66. GRB 250201A: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  68. GRB 250129A: Skynet Continued Optical Observations
  69. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  70. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  71. GRB 250129A: SAO RAS optical observations
  72. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  73. GRB 250129A: optical photometry from Konkoly
  74. GRB 250129A: COLIBRÍ Optical Observations
  75. GRB 250128B: VLA possible radio detection
  76. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  77. GRB 250129A: iTelescope optical observation
  78. GRB 250129A: NOT optical observations of continuining activity
  79. GRB 250129a: Liverpool Telescope optical follow-up
  80. GRB 250129A: TNG NIR afterglow detection
  81. GRB 250129A: AKO Optical Afterglow Detection
  82. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  83. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  84. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  85. GRB 250128B: VLA radio upper limit
  86. Ep250125A: 1.3m DFOT optical upper limit
  87. GRB 250129A: Skynet optical observations
  88. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  89. GRB 250129A: Swift-XRT refined Analysis
  90. GRB 250128B: Gemini-North optical extended source detection
  91. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  92. GRB 250128B: TNG optical upper limit
  93. GRB 250129A: Swift/UVOT Detection
  94. GRB 250128B: VLT/HAWKI near-infrared observations
  95. GRB 250127A: CrAO and Terskol optical upper limits
  96. GRB 250129A: Enhanced Swift-XRT position
  97. GRB 250128B: NOT optical upper limit
  98. GRB 250128B: VLT/FORS2 optical observations
  99. GRB 250129A: REM optical/NIR afterglow detection
  100. GRB 250129A: OHP/T193 optical and spectroscopy observations

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