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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"

36328 results found.

  1. GRB 251129B: Glowbug gamma-ray detection of a short burst
  2. GRB 251203A: AstroSat CZTI detection
  3. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  4. GRB 251203C: LCO optical afterglow confirmation
  5. GRB 251203C: SVOM/VT optical counterpart
  6. GRB 251203C: EP-FXT follow-up observation
  7. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  8. GRB 251129B: GECAM-B observation of a burst
  9. GRB 251203B: Swift-XRT observations
  10. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  11. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  12. GRB 251203C: LCO optical upper limits
  13. GRB 251203B: LCO optical upper limits
  14. GRB 251203B: SVOM/VT optical observation
  15. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  16. GRB 251203C: SVOM detection of a burst
  17. GRB 251203B: SVOM detection of a burst
  18. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  19. GRB 251201B: Insight-HXMT/HE detection
  20. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  21. GRB 251203A: Fermi GBM Final Real-time Localization
  22. EP251202a / GRB251202A: AstroSat CZTI detection
  23. GRB 251202A / EP251202a: SVOM/VT optical observation
  24. GRB 251201B: Fermi GBM Observation
  25. EP251202a/GRB 251202A: KAIT optical observations
  26. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  27. Fermi GRB 251202B: Global MASTER-Net observations report
  28. GRB 251202B: Fermi GBM Final Real-time Localization
  29. IPN triangulation of GRB 251129B (short/hard)
  30. GRB251129A/EP251129a: Swift UVOT detection
  31. GRB 251129B: AstroSat CZTI detection
  32. GRB 251202A: Fermi GBM Observation
  33. GRB 251202A: Swift/UVOT Detection
  34. GRB 251201B: Kilonova-Catcher optical afterglow detection
  35. GRB 251201B: Swift/UVOT Detection
  36. GRB 251130B: Glowbug gamma-ray detection
  37. GRB 251201B: GECAM-B observation of a long burst
  38. EP251130a: continued NOT optical observations indicate steep fading phase
  39. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  40. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  41. GRB 251202A: GOTO optical afterglow detection
  42. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  43. GRB 251201A: GECAM-B observation of a burst
  44. GRB 251126A: SAO RAS optical marginal detection
  45. GRB 251202A: Swift-XRT afterglow detection
  46. EP251129a/GRB 251129A: NOWT Detection
  47. GRB 251126A: SVOM/VT optical observation
  48. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  49. Fermi GRB 251202A: Global MASTER-Net observations report
  50. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  51. GRB 251201B: Swift-XRT refined Analysis
  52. GRB 251202A: Fermi GBM Final Real-time Localization
  53. GRB 251201A: SVOM/GRM observation of a burst
  54. GRB 251201B: SVOM/VT optical fading
  55. Swift GRB 251201B : MASTER optical counterpart detection
  56. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  57. Swift GRB 251201B: Global MASTER-Net observations report
  58. GRB 251201B: Enhanced Swift-XRT position
  59. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  60. GRB 251130B: AstroSat CZTI detection
  61. GRB 251201B: Swift detection of a burst with an optical counterpart
  62. GRB 251201B: Fermi GBM Final Real-time Localization
  63. EP251130a: Mondy optical observations
  64. EP251130a: Optical detections with Kinder observations
  65. EP251130a: SAO RAS optical observations
  66. EP251130a: KAIT optical observations
  67. GRB 251201A: MAXI/GSC detection
  68. Fermi GRB 251130B: Global MASTER-Net observations report
  69. GRB 251127A: SVOM/GRM observation
  70. GRB 251130B: Fermi GBM Final Localization Correction
  71. GRB 251130B: Fermi GBM Final Real-time Localization
  72. EP251129a/GRB 251129A: EP-FXT follow-up observations
  73. GRB 251130A: Fermi GBM Final Real-time Localization
  74. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  75. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  76. GRB 251128A: AstroSat CZTI detection
  77. GRB 251129A / EP251129a: SAO RAS optical observations
  78. GRB 251126A: SAO RAS optical observations
  79. GRB 251128A: GECAM-B detection
  80. GRB 251128A: SVOM/GRM observation of a long burst
  81. GRB 251128A: Insight-HXMT/HE detection
  82. SVOM GRB 251129A : MASTER optical counterpart detection
  83. GRB 251129A: Swift-XRT afterglow detection
  84. GRB 251129A: Swift ToO observations
  85. GRB 251129A / EP251129a: SVOM/VT optical fading
  86. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  87. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  88. GRB 251129A: Correction to the position of the optical counterpar
  89. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  90. GRB 251128A: Fermi GBM Observation
  91. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  92. GRB 251129A: SVOM detection of a burst
  93. GRB 251129A: SVOM detection of a burst
  94. GRB 251126A: Swift-BAT refined analysis
  95. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  96. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  97. Fermi GRB 251128A: Global MASTER-Net observations report
  98. GRB 251127A: Glowbug gamma-ray detection
  99. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  100. GRB 251126A: further SAO RAS optical observations

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