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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"

25840 results found.

  1. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  2. GRB 251202A: SVOM/GRM observation
  3. GRB 251203A: SVOM/GRM observation
  4. GRB 251201B: SALT spectroscopic redshift z = 1.599
  5. GRB 251203C: J-band observations with WINTER
  6. GRB 251129B: Glowbug gamma-ray detection of a short burst
  7. GRB 251203A: AstroSat CZTI detection
  8. GRB 251203C: SVOM/VT optical counterpart
  9. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  10. GRB 251203B: Swift-XRT observations
  11. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  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. EP251130a: MAO/AZT-22 optical observations
  19. GRB 251201B: Fermi GBM Observation
  20. EP251202a/GRB 251202A: KAIT optical observations
  21. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  22. GRB 251202B: Fermi GBM Final Real-time Localization
  23. IPN triangulation of GRB 251129B (short/hard)
  24. GRB251129A/EP251129a: Swift UVOT detection
  25. GRB 251202A: Fermi GBM Observation
  26. GRB 251202A: Swift/UVOT Detection
  27. GRB 251201B: Kilonova-Catcher optical afterglow detection
  28. GRB 251201B: Swift/UVOT Detection
  29. GRB 251130B: Glowbug gamma-ray detection
  30. EP251130a: continued NOT optical observations indicate steep fading phase
  31. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  32. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  33. GRB 251126A: SAO RAS optical marginal detection
  34. GRB 251202A: Swift-XRT afterglow detection
  35. EP251129a/GRB 251129A: NOWT Detection
  36. GRB 251126A: SVOM/VT optical observation
  37. EP251130a: SVOM/VT optical observation
  38. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  39. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  40. GRB 251201B: Swift-XRT refined Analysis
  41. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  42. GRB 251202A: Fermi GBM Final Real-time Localization
  43. GRB 251201A: SVOM/GRM observation of a burst
  44. GRB 251201B: SVOM/VT optical fading
  45. Swift GRB 251201B : MASTER optical counterpart detection
  46. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  47. GRB 251201B: Enhanced Swift-XRT position
  48. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  49. GRB 251130B: AstroSat CZTI detection
  50. GRB 251201B: Swift detection of a burst with an optical counterpart
  51. EP251130a: Mondy optical observations
  52. EP251130a: Optical detections with Kinder observations
  53. EP251130a: SAO RAS optical observations
  54. EP251130A: Optical observation from 1.3m DFOT
  55. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP251130a: JinShan optical observations
  57. GRB 251127A: SVOM/GRM observation
  58. EP251130a: Swift-XRT counterpart detection
  59. EP251130a: COLIBRÍ optical counterpart candidate
  60. EP251130a: Einstein Probe detection of an X-ray transient
  61. EP251129a/GRB 251129A: EP-FXT follow-up observations
  62. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  63. GRB 251128A: AstroSat CZTI detection
  64. GRB 251129A / EP251129a: SAO RAS optical observations
  65. GRB 251126A: SAO RAS optical observations
  66. GRB 251128A: GECAM-B detection
  67. GRB 251128A: SVOM/GRM observation of a long burst
  68. SVOM GRB 251129A : MASTER optical counterpart detection
  69. GRB 251129A: Swift-XRT afterglow detection
  70. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  71. GRB 251128A: Fermi GBM Observation
  72. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  73. GRB 251129A: SVOM detection of a burst
  74. GRB 251129A: SVOM detection of a burst
  75. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  76. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  77. GRB 251127A: Glowbug gamma-ray detection
  78. GRB 251126A: further SAO RAS optical observations
  79. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  80. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  81. GRB251126A: MAO/AZT-22 optical observations
  82. GRB251126A: Continued optical observation from 1.3m DFOT
  83. GRB 251126A: Swift/UVOT Detection
  84. GRB 251126A: Mondy and SAO RAS optical observations
  85. GRB 251126A: Swift-XRT refined Analysis
  86. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  87. GRB 251126A: 1.3m DFOT optical afterglow detection
  88. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  89. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  90. GRB 251125B: GECAM-B detection
  91. GRB 251126A: Enhanced Swift-XRT position
  92. GRB 251126A: Kilonova-Catcher optical afterglow detection
  93. GRB 251126A: Nanshan/HMT optical afterglow detection
  94. GRB 251121A: Fermi GBM Observation
  95. GRB 251126A: GIT discovery of the likely optical afterglow
  96. GRB 251126A: Swift detection of a burst
  97. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  98. EP251124b follow-up observation by EP-FXT
  99. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  100. EP251124b: NOT r- and z-band optical upper limits

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