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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: SOAR galaxy targeted observations
  2. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  3. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  4. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  5. GRB 250129A: Continued AbAO and Mondy optical observations
  6. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  7. GRB 250207B: MAXI/GSC detection
  8. The EP-WXT trigger 01709131347 is likely a flaring star
  9. The EP-WXT trigger 01709131332 is likely a flaring star
  10. The EP-WXT trigger 01709131290 is likely a flaring star
  11. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  12. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  13. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  14. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  15. GRB 250207A: Swift detection of a burst with optical counterpart
  16. GRB 250207A: Fermi GBM Final Real-time Localization
  17. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  18. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  19. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  20. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  21. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  22. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  24. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  25. GRB 250206A: Fermi GBM Final Real-time Localization
  26. GRB 250205A: Fermi GBM Observation
  27. GRB 250205A: REM NIR upper limit
  28. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  29. GRB 250205A: Swift/UVOT Upper Limits
  30. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  31. EP250205a/GRB 250205A: correction to the source localization
  32. EP250205a/GRB 250205A: Einstein Probe observation
  33. GRB 250127C: SVOM/GRM observation of a burst
  34. GRB 250204B: SVOM/GRM observation of a likely short burst
  35. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  36. GRB 250205A: Swift/XRT detection
  37. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  38. GRB250205A: SVOM/VT optical afterglow detection
  39. GRB 250205A: GOTO optical upper limits
  40. GRB 250205A: OHP/T193 optical counterpart candidate
  41. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  42. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  43. GRB 250205A: SVOM detection of a burst
  44. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  45. Konus-Wind detection of GRB 250201A
  46. IPN triangulation of GRB 250201A
  47. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  48. Konus-Wind detection of GRB 250202B
  49. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  50. GRB 250129A: Swift-BAT refined analysis
  51. EP 250108A: Upper limits from Fermi-GBM Observations
  52. IPN triangulation of GRB 250204B (short/hard)
  53. IPN triangulation of GRB 250202B
  54. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  55. GRB 250204B: AstroSat CZTI detection of a short burst
  56. GRB 250204B: Fermi GBM Final Localization
  57. GRB 250129A: LCO late afterglow detection
  58. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  59. GRB 250204A: Fermi GBM Final Real-time Localization
  60. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  61. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  62. GRB 250202B: NuSTAR detection of the prompt emission
  63. GRB 250202C: GRBAlpha detection
  64. GRB 250202B: Fermi GBM Detection
  65. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  66. GRB 250129a: Liverpool Telescope optical follow-up
  67. GRB 240129A: further SAO RAS optical observations
  68. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  69. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  70. The EP-WXT trigger 01709131196 is likely a flaring star
  71. GRB 250202C: Fermi GBM Final Real-time Localization
  72. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  73. GRB 250129A: SVOM/C-GFT optical observations
  74. The EP-WXT trigger 01709131153 is not a real source
  75. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  76. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  77. GRB 250202B: Fermi GBM Final Real-time Localization
  78. Swift GRB250129A: MASTER 4 days observations report
  79. GRB 250202A: Fermi GBM Final Real-time Localization
  80. GRB 250201A: INTEGRAL SPI/ACS detection
  81. Konus-Wind detection of GRB 250129A
  82. GRB 250129A: 1.3m DFOT Optical observations
  83. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  84. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  85. GRB 250201A: Fermi GBM Final Real-time Localization
  86. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  87. GRB 250129A: Skynet Continued Optical Observations
  88. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  89. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  90. GRB 250129A: SAO RAS optical observations
  91. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  92. GRB 250129A: optical photometry from Konkoly
  93. GRB 250129A: COLIBRÍ Optical Observations
  94. GRB 250128B: VLA possible radio detection
  95. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  96. GRB 250129A: iTelescope optical observation
  97. GRB 250129A: NOT optical observations of continuining activity
  98. GRB 250129a: Liverpool Telescope optical follow-up
  99. GRB 250129A: TNG NIR afterglow detection
  100. GRB 250129A: AKO Optical Afterglow Detection

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