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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"

32508 results found.

  1. GRB 251205A: COLIBRÍ optical observations
  2. GRB 251205A: GOTO optical afterglow detection
  3. GRB 251205A: NOT optical observations
  4. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  5. Swift GRB 251205A : MASTER OT detection with host galaxy
  6. GRB 251203A: Insight-HXMT/HE detection
  7. GRB 251203C: SVOM/ECLAIRs refined analysis
  8. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  9. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. GRB 251202A: SVOM/GRM observation
  11. GRB 251203A: GECAM-B observation of a burst
  12. GRB 251203A: SVOM/GRM observation
  13. GRB 251201B: SALT spectroscopic redshift z = 1.599
  14. GRB 251203C: J-band observations with WINTER
  15. GRB 251129B: Glowbug gamma-ray detection of a short burst
  16. GRB 251203A: AstroSat CZTI detection
  17. EP251130a: JinShan near-infrared observations
  18. GRB 251203C: LCO optical afterglow confirmation
  19. GRB 251203C: SVOM/VT optical counterpart
  20. GRB 251203C: EP-FXT follow-up observation
  21. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  22. GRB 251203B: Swift-XRT observations
  23. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  24. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  25. GRB 251203C: LCO optical upper limits
  26. GRB 251203B: LCO optical upper limits
  27. GRB 251203B: SVOM/VT optical observation
  28. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  29. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  30. GRB 251201B: Insight-HXMT/HE detection
  31. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  32. EP251130a: MAO/AZT-22 optical observations
  33. EP251202a / GRB251202A: AstroSat CZTI detection
  34. GRB 251202A / EP251202a: SVOM/VT optical observation
  35. GRB 251201B: Fermi GBM Observation
  36. EP251202a/GRB 251202A: KAIT optical observations
  37. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  38. Fermi GRB 251202B: Global MASTER-Net observations report
  39. IPN triangulation of GRB 251129B (short/hard)
  40. GRB251129A/EP251129a: Swift UVOT detection
  41. GRB 251202A: Fermi GBM Observation
  42. GRB 251202A: Swift/UVOT Detection
  43. GRB 251201B: Kilonova-Catcher optical afterglow detection
  44. GRB 251201B: Swift/UVOT Detection
  45. GRB 251130B: Glowbug gamma-ray detection
  46. GRB 251201B: GECAM-B observation of a long burst
  47. EP251130a: continued NOT optical observations indicate steep fading phase
  48. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  49. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  50. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  51. GRB 251202A: GOTO optical afterglow detection
  52. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  53. GRB 251201A: GECAM-B observation of a burst
  54. GRB 251126A: SAO RAS optical marginal detection
  55. GRB 251202A: Swift-XRT afterglow detection
  56. EP251129a/GRB 251129A: NOWT Detection
  57. GRB 251126A: SVOM/VT optical observation
  58. EP251130a: SVOM/VT optical observation
  59. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  60. Fermi GRB 251202A: Global MASTER-Net observations report
  61. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  62. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 251201A: SVOM/GRM observation of a burst
  64. GRB 251201B: SVOM/VT optical fading
  65. Swift GRB 251201B : MASTER optical counterpart detection
  66. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  67. Swift GRB 251201B: Global MASTER-Net observations report
  68. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  69. GRB 251130B: AstroSat CZTI detection
  70. EP251130a: Mondy optical observations
  71. EP251130a: Optical detections with Kinder observations
  72. EP251130a: SAO RAS optical observations
  73. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  74. EP251130a: KAIT optical observations
  75. EP251130A: Optical observation from 1.3m DFOT
  76. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  77. EP251130a: JinShan optical observations
  78. Fermi GRB 251130B: Global MASTER-Net observations report
  79. GRB 251127A: SVOM/GRM observation
  80. EP251130a: Swift-XRT counterpart detection
  81. EP251130a: Global MASTER-Net observations report
  82. EP251130a: COLIBRÍ optical counterpart candidate
  83. EP251129a/GRB 251129A: EP-FXT follow-up observations
  84. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  85. GRB 251128A: AstroSat CZTI detection
  86. GRB 251129A / EP251129a: SAO RAS optical observations
  87. GRB 251126A: SAO RAS optical observations
  88. GRB 251128A: GECAM-B detection
  89. GRB 251128A: SVOM/GRM observation of a long burst
  90. GRB 251128A: Insight-HXMT/HE detection
  91. SVOM GRB 251129A : MASTER optical counterpart detection
  92. GRB 251129A: Swift-XRT afterglow detection
  93. GRB 251129A: Swift ToO observations
  94. GRB 251129A / EP251129a: SVOM/VT optical fading
  95. EP251129a: Global MASTER-Net observations report
  96. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  97. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  98. GRB 251129A: Correction to the position of the optical counterpar
  99. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  100. GRB 251128A: Fermi GBM Observation

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