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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').

23965 results found.

  1. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  2. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  3. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  4. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  5. GRB 250207A: Swift detection of a burst with optical counterpart
  6. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  7. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  8. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  9. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  10. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  11. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  13. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  14. GRB 250205A: Fermi GBM Observation
  15. GRB 250205A: REM NIR upper limit
  16. GRB 250205A: Swift/UVOT Upper Limits
  17. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  18. EP250205a/GRB 250205A: Einstein Probe observation
  19. GRB 250127C: SVOM/GRM observation of a burst
  20. GRB 250204B: SVOM/GRM observation of a likely short burst
  21. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  22. GRB 250205A: Swift/XRT detection
  23. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  24. GRB250205A: SVOM/VT optical afterglow detection
  25. GRB 250205A: OHP/T193 optical counterpart candidate
  26. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  27. GRB 250205A: SVOM detection of a burst
  28. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  29. IPN triangulation of GRB 250201A
  30. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  31. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  32. GRB 250129A: Swift-BAT refined analysis
  33. EP 250108A: Upper limits from Fermi-GBM Observations
  34. IPN triangulation of GRB 250204B (short/hard)
  35. IPN triangulation of GRB 250202B
  36. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  37. GRB 250204B: AstroSat CZTI detection of a short burst
  38. GRB 250129A: LCO late afterglow detection
  39. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  40. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  41. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  42. GRB 250202B: NuSTAR detection of the prompt emission
  43. GRB 250202B: Fermi GBM Detection
  44. GRB 250129a: Liverpool Telescope optical follow-up
  45. GRB 240129A: further SAO RAS optical observations
  46. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  47. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  48. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  49. GRB 250129A: SVOM/C-GFT optical observations
  50. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  51. Swift GRB250129A: MASTER 4 days observations report
  52. GRB 250129A: 1.3m DFOT Optical observations
  53. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  54. GRB 250201A: Fermi GBM Final Real-time Localization
  55. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  56. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  57. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  58. GRB 250129A: SAO RAS optical observations
  59. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  60. GRB 250129A: COLIBRÍ Optical Observations
  61. GRB 250129A: iTelescope optical observation
  62. GRB 250129a: Liverpool Telescope optical follow-up
  63. GRB 250129A: TNG NIR afterglow detection
  64. GRB 250129A: AKO Optical Afterglow Detection
  65. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  66. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  67. GRB 250128B: VLA radio upper limit
  68. Ep250125A: 1.3m DFOT optical upper limit
  69. GRB 250129A: Skynet optical observations
  70. GRB 250129A: Swift-XRT refined Analysis
  71. GRB 250128B: Gemini-North optical extended source detection
  72. GRB 250128B: TNG optical upper limit
  73. GRB 250129A: Swift/UVOT Detection
  74. GRB 250128B: VLT/HAWKI near-infrared observations
  75. GRB 250127A: CrAO and Terskol optical upper limits
  76. GRB 250129A: Enhanced Swift-XRT position
  77. GRB 250128B: NOT optical upper limit
  78. GRB 250128B: VLT/FORS2 optical observations
  79. GRB 250129A: REM optical/NIR afterglow detection
  80. GRB 250129A: OHP/T193 optical and spectroscopy observations
  81. GRB 250129A: Early afterglow detection by LCO.
  82. GRB 250128B: OHP/T193 optical upper limit
  83. GRB 250129A: LCO optical observations
  84. GRB 250128B: Enhanced Swift-XRT position
  85. GRB 250129A: Swift detection of a burst with an optical counterpart
  86. Swift GRB 250129A: Global MASTER-Net OT detection
  87. GRB 250128B: Swift-XRT refined Analysis
  88. GRB 250128B: GOTO optical upper limit
  89. EP250125a: Upper limits from Swift/BAT-GUANO
  90. GRB 250128B: LCO optical observations
  91. GRB 250128B: Swift detection of a short burst
  92. GRB 250127A: Swift-XRT observations
  93. GRB 250127B: DDOTI Upper Limit on the Afterglow
  94. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  95. Fermi GRB 250128A: Global MASTER-Net observations report
  96. GRB 250117A: Fermi GBM Observation
  97. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  98. IPN triangulation of GRB 250119C
  99. GRB 250127A: LCO optical upper limit
  100. GRB 241223A: cubesat Avion detection

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