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

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