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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"

26206 results found.

  1. GRB 251201B: SALT spectroscopic redshift z = 1.599
  2. GRB 251203C: J-band observations with WINTER
  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. SVOM GRB251203.77: Global MASTER-Net observations report
  18. SVOM GRB251203B: Global MASTER-Net observations report
  19. GRB 251203B: SVOM detection of a burst
  20. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  21. GRB 251203A: Fermi GBM Final Real-time Localization
  22. GRB 251202A / EP251202a: SVOM/VT optical observation
  23. GRB 251201B: Fermi GBM Observation
  24. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  25. Fermi GRB 251202B: Global MASTER-Net observations report
  26. GRB 251202B: Fermi GBM Final Real-time Localization
  27. GRB251129A/EP251129a: Swift UVOT detection
  28. GRB 251202A: Fermi GBM Observation
  29. GRB 251202A: Swift/UVOT Detection
  30. GRB 251201B: Kilonova-Catcher optical afterglow detection
  31. GRB 251201B: Swift/UVOT Detection
  32. GRB 251130B: Glowbug gamma-ray detection
  33. GRB 251201B: GECAM-B observation of a long burst
  34. EP251130a: continued NOT optical observations indicate steep fading phase
  35. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  36. GRB 251202A: GOTO optical afterglow detection
  37. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  38. GRB 251201A: GECAM-B observation of a burst
  39. GRB 251126A: SVOM/VT optical observation
  40. EP251130a: SVOM/VT optical observation
  41. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  42. Fermi GRB 251202A: Global MASTER-Net observations report
  43. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  44. GRB 251201B: Swift-XRT refined Analysis
  45. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  46. GRB 251202A: Fermi GBM Final Real-time Localization
  47. GRB 251201A: SVOM/GRM observation of a burst
  48. GRB 251201B: SVOM/VT optical fading
  49. Swift GRB 251201B : MASTER optical counterpart detection
  50. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  51. Swift GRB 251201B: Global MASTER-Net observations report
  52. GRB 251201B: Swift detection of a burst with an optical counterpart
  53. GRB 251201B: Fermi GBM Final Real-time Localization
  54. EP251130a: Optical detections with Kinder observations
  55. SVOM GRB251201.19: Global MASTER-Net observations report
  56. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  57. EP251130A: Optical observation from 1.3m DFOT
  58. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  59. Fermi GRB 251130B: Global MASTER-Net observations report
  60. GRB 251127A: SVOM/GRM observation
  61. IceCube Alert 251130.75: Global MASTER-Net observations report
  62. EP251130a: Swift-XRT counterpart detection
  63. GRB 251130B: Fermi GBM Final Localization Correction
  64. EP251130a: Global MASTER-Net observations report
  65. GRB 251130B: Fermi GBM Final Real-time Localization
  66. EP251130a: COLIBRÍ optical counterpart candidate
  67. EP251130a: Einstein Probe detection of an X-ray transient
  68. EP251129a/GRB 251129A: EP-FXT follow-up observations
  69. GRB 251130A: Fermi GBM Final Real-time Localization
  70. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  71. GRB 251128A: GECAM-B detection
  72. GRB 251128A: SVOM/GRM observation of a long burst
  73. SVOM GRB 251129A : MASTER optical counterpart detection
  74. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  75. Swift trigger 1418333 is not an astrophysical source
  76. GRB 251129A / EP251129a: SVOM/VT optical fading
  77. EP251129a: Global MASTER-Net observations report
  78. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  79. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  80. GRB 251128A: Fermi GBM Observation
  81. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  82. GRB 251129A: SVOM detection of a burst
  83. SVOM GRB251129A: Global MASTER-Net observations report
  84. GRB 251129A: SVOM detection of a burst
  85. GRB 251126A: Swift-BAT refined analysis
  86. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  87. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  88. Fermi GRB 251128A: Global MASTER-Net observations report
  89. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  90. GRB 251126A NUTTelA-TAO Early Measurements
  91. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  92. GRB251126A: MAO/AZT-22 optical observations
  93. GRB 251128A: Fermi GBM Final Real-time Localization
  94. GRB251126A: Continued optical observation from 1.3m DFOT
  95. GRB 251126A: Swift/UVOT Detection
  96. GRB 251126A: Mondy and SAO RAS optical observations
  97. GRB 251126A: Swift-XRT refined Analysis
  98. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  99. GRB 251126A: NOT optical observations
  100. GRB 251126A: 1.3m DFOT optical afterglow detection

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