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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"

39166 results found.

  1. GRB 250206A: Tiled Swift observations
  2. GRB 250206A: EIRSAT-1 GMOD Detection
  3. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  4. GRB 250206A: Fermi-LAT detection
  5. GRB 250207B: Swift-XRT observations
  6. GRB 250208A: Fermi GBM Final Real-time Localization
  7. GRB 250207A: Swift-XRT refined Analysis
  8. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  9. GRB 250207A: Enhanced Swift-XRT position
  10. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  11. GRB 250207A: REM IR afterglow detection
  12. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  13. GRB 250207A: FRAM-Auger optical detection
  14. GRB 250207B: Tiled Swift observations
  15. Konus-Wind detection of GRB 250204B
  16. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  17. GRB 250207A: REM optical afterglow detection
  18. GRB 250207A: Swift/UVOT Detection
  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. GRB 250129A: Continued AbAO and Mondy optical observations
  22. GRB 250207B: MAXI/GSC detection
  23. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  24. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  25. GRB 250207A: Swift detection of a burst with optical counterpart
  26. GRB 250207A: Fermi GBM Final Real-time Localization
  27. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  28. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  29. GRB 250206A: Fermi GBM Final Real-time Localization
  30. GRB 250205A: Fermi GBM Observation
  31. GRB 250205A: REM NIR upper limit
  32. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  33. GRB 250205A: Swift/UVOT Upper Limits
  34. EP250205a/GRB 250205A: correction to the source localization
  35. EP250205a/GRB 250205A: Einstein Probe observation
  36. GRB 250127C: SVOM/GRM observation of a burst
  37. GRB 250204B: SVOM/GRM observation of a likely short burst
  38. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  39. GRB 250205A: Swift/XRT detection
  40. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  41. GRB250205A: SVOM/VT optical afterglow detection
  42. GRB 250205A: GOTO optical upper limits
  43. GRB 250205A: OHP/T193 optical counterpart candidate
  44. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  45. GRB 250205A: SVOM detection of a burst
  46. Konus-Wind detection of GRB 250201A
  47. IPN triangulation of GRB 250201A
  48. Konus-Wind detection of GRB 250202B
  49. GRB 250129A: Swift-BAT refined analysis
  50. EP 250108A: Upper limits from Fermi-GBM Observations
  51. IPN triangulation of GRB 250204B (short/hard)
  52. IPN triangulation of GRB 250202B
  53. GRB 250204B: AstroSat CZTI detection of a short burst
  54. GRB 250204B: Fermi GBM Final Localization
  55. GRB 250129A: LCO late afterglow detection
  56. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  57. GRB 250204A: Fermi GBM Final Real-time Localization
  58. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  59. GRB 250202B: NuSTAR detection of the prompt emission
  60. GRB 250202C: GRBAlpha detection
  61. GRB 250202B: Fermi GBM Detection
  62. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  63. GRB 250129a: Liverpool Telescope optical follow-up
  64. GRB 240129A: further SAO RAS optical observations
  65. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  66. GRB 250202C: Fermi GBM Final Real-time Localization
  67. GRB 250129A: SVOM/C-GFT optical observations
  68. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  69. GRB 250202B: Fermi GBM Final Real-time Localization
  70. Swift GRB250129A: MASTER 4 days observations report
  71. GRB 250202A: Fermi GBM Final Real-time Localization
  72. GRB 250201A: INTEGRAL SPI/ACS detection
  73. Konus-Wind detection of GRB 250129A
  74. GRB 250129A: 1.3m DFOT Optical observations
  75. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  76. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  77. GRB 250201A: Fermi GBM Final Real-time Localization
  78. GRB 250129A: Skynet Continued Optical Observations
  79. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  80. GRB 250129A: SAO RAS optical observations
  81. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  82. GRB 250129A: optical photometry from Konkoly
  83. GRB 250129A: COLIBRÍ Optical Observations
  84. GRB 250128B: VLA possible radio detection
  85. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  86. GRB 250129A: iTelescope optical observation
  87. GRB 250129A: NOT optical observations of continuining activity
  88. GRB 250129a: Liverpool Telescope optical follow-up
  89. GRB 250129A: TNG NIR afterglow detection
  90. GRB 250129A: AKO Optical Afterglow Detection
  91. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  92. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  93. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  94. GRB 250128B: VLA radio upper limit
  95. Ep250125A: 1.3m DFOT optical upper limit
  96. GRB 250129A: Skynet optical observations
  97. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  98. GRB 250129A: Swift-XRT refined Analysis
  99. GRB 250128B: Gemini-North optical extended source detection
  100. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare

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