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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 S250207bg: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  3. GRB 250207A: Swift/UVOT Detection
  4. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  5. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  6. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  7. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  8. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  9. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  10. GRB 250129A: Continued AbAO and Mondy optical observations
  11. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  12. GRB 250207B: MAXI/GSC detection
  13. The EP-WXT trigger 01709131347 is likely a flaring star
  14. The EP-WXT trigger 01709131332 is likely a flaring star
  15. The EP-WXT trigger 01709131290 is likely a flaring star
  16. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  17. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  18. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  19. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  20. GRB 250207A: Swift detection of a burst with optical counterpart
  21. GRB 250207A: Fermi GBM Final Real-time Localization
  22. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  23. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  24. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  25. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  26. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  27. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  28. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  29. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  30. GRB 250206A: Fermi GBM Final Real-time Localization
  31. GRB 250205A: Fermi GBM Observation
  32. GRB 250205A: REM NIR upper limit
  33. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  34. GRB 250205A: Swift/UVOT Upper Limits
  35. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  36. EP250205a/GRB 250205A: correction to the source localization
  37. EP250205a/GRB 250205A: Einstein Probe observation
  38. GRB 250127C: SVOM/GRM observation of a burst
  39. GRB 250204B: SVOM/GRM observation of a likely short burst
  40. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  41. GRB 250205A: Swift/XRT detection
  42. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  43. GRB250205A: SVOM/VT optical afterglow detection
  44. GRB 250205A: GOTO optical upper limits
  45. GRB 250205A: OHP/T193 optical counterpart candidate
  46. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  47. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  48. GRB 250205A: SVOM detection of a burst
  49. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  50. Konus-Wind detection of GRB 250201A
  51. IPN triangulation of GRB 250201A
  52. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  53. Konus-Wind detection of GRB 250202B
  54. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  55. GRB 250129A: Swift-BAT refined analysis
  56. EP 250108A: Upper limits from Fermi-GBM Observations
  57. IPN triangulation of GRB 250204B (short/hard)
  58. IPN triangulation of GRB 250202B
  59. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  60. GRB 250204B: AstroSat CZTI detection of a short burst
  61. GRB 250204B: Fermi GBM Final Localization
  62. GRB 250129A: LCO late afterglow detection
  63. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  64. GRB 250204A: Fermi GBM Final Real-time Localization
  65. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  66. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  67. GRB 250202B: NuSTAR detection of the prompt emission
  68. GRB 250202C: GRBAlpha detection
  69. GRB 250202B: Fermi GBM Detection
  70. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  71. GRB 250129a: Liverpool Telescope optical follow-up
  72. GRB 240129A: further SAO RAS optical observations
  73. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  74. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  75. The EP-WXT trigger 01709131196 is likely a flaring star
  76. GRB 250202C: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  78. GRB 250129A: SVOM/C-GFT optical observations
  79. The EP-WXT trigger 01709131153 is not a real source
  80. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  81. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  82. GRB 250202B: Fermi GBM Final Real-time Localization
  83. Swift GRB250129A: MASTER 4 days observations report
  84. GRB 250202A: Fermi GBM Final Real-time Localization
  85. GRB 250201A: INTEGRAL SPI/ACS detection
  86. Konus-Wind detection of GRB 250129A
  87. GRB 250129A: 1.3m DFOT Optical observations
  88. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  89. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  90. GRB 250201A: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  92. GRB 250129A: Skynet Continued Optical Observations
  93. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  94. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  95. GRB 250129A: SAO RAS optical observations
  96. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  97. GRB 250129A: optical photometry from Konkoly
  98. GRB 250129A: COLIBRÍ Optical Observations
  99. GRB 250128B: VLA possible radio detection
  100. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h

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