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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"

24927 results found.

  1. GRB 251203B: SVOM/VT optical observation
  2. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  3. GRB 251203C: SVOM detection of a burst
  4. GRB 251203B: SVOM detection of a burst
  5. EP251130a: MAO/AZT-22 optical observations
  6. GRB 251201B: Fermi GBM Observation
  7. EP251202a/GRB 251202A: KAIT optical observations
  8. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  9. GRB 251202B: Fermi GBM Final Real-time Localization
  10. IPN triangulation of GRB 251129B (short/hard)
  11. GRB251129A/EP251129a: Swift UVOT detection
  12. GRB 251202A: Fermi GBM Observation
  13. GRB 251202A: Swift/UVOT Detection
  14. GRB 251201B: Kilonova-Catcher optical afterglow detection
  15. GRB 251201B: Swift/UVOT Detection
  16. GRB 251130B: Glowbug gamma-ray detection
  17. EP251130a: continued NOT optical observations indicate steep fading phase
  18. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  19. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  20. GRB 251126A: SAO RAS optical marginal detection
  21. GRB 251202A: Swift-XRT afterglow detection
  22. EP251129a/GRB 251129A: NOWT Detection
  23. GRB 251126A: SVOM/VT optical observation
  24. EP251130a: SVOM/VT optical observation
  25. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  26. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  27. GRB 251201B: Swift-XRT refined Analysis
  28. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 251202A: Fermi GBM Final Real-time Localization
  30. GRB 251201A: SVOM/GRM observation of a burst
  31. GRB 251201B: SVOM/VT optical fading
  32. Swift GRB 251201B : MASTER optical counterpart detection
  33. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  34. GRB 251201B: Enhanced Swift-XRT position
  35. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  36. GRB 251130B: AstroSat CZTI detection
  37. GRB 251201B: Swift detection of a burst with an optical counterpart
  38. EP251130a: Mondy optical observations
  39. EP251130a: Optical detections with Kinder observations
  40. EP251130a: SAO RAS optical observations
  41. EP251130A: Optical observation from 1.3m DFOT
  42. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  43. EP251130a: JinShan optical observations
  44. GRB 251127A: SVOM/GRM observation
  45. EP251130a: Swift-XRT counterpart detection
  46. EP251130a: COLIBRÍ optical counterpart candidate
  47. EP251130a: Einstein Probe detection of an X-ray transient
  48. EP251129a/GRB 251129A: EP-FXT follow-up observations
  49. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  50. GRB 251128A: AstroSat CZTI detection
  51. GRB 251129A / EP251129a: SAO RAS optical observations
  52. GRB 251126A: SAO RAS optical observations
  53. GRB 251128A: GECAM-B detection
  54. GRB 251128A: SVOM/GRM observation of a long burst
  55. SVOM GRB 251129A : MASTER optical counterpart detection
  56. GRB 251129A: Swift-XRT afterglow detection
  57. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  58. GRB 251128A: Fermi GBM Observation
  59. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  60. GRB 251129A: SVOM detection of a burst
  61. GRB 251129A: SVOM detection of a burst
  62. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  63. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  64. GRB 251127A: Glowbug gamma-ray detection
  65. GRB 251126A: further SAO RAS optical observations
  66. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  67. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  68. GRB251126A: MAO/AZT-22 optical observations
  69. GRB251126A: Continued optical observation from 1.3m DFOT
  70. GRB 251126A: Swift/UVOT Detection
  71. GRB 251126A: Mondy and SAO RAS optical observations
  72. GRB 251126A: Swift-XRT refined Analysis
  73. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  74. GRB 251126A: 1.3m DFOT optical afterglow detection
  75. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  76. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  77. GRB 251125B: GECAM-B detection
  78. GRB 251126A: Enhanced Swift-XRT position
  79. GRB 251126A: Kilonova-Catcher optical afterglow detection
  80. GRB 251126A: Nanshan/HMT optical afterglow detection
  81. GRB 251121A: Fermi GBM Observation
  82. GRB 251126A: GIT discovery of the likely optical afterglow
  83. GRB 251126A: Swift detection of a burst
  84. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  85. EP251124b follow-up observation by EP-FXT
  86. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  87. EP251124b: NOT r- and z-band optical upper limits
  88. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  89. EP251124b: EP-WXT detection of a fast X-ray transient
  90. EP251124a: Xinglong GWAC-F60A optical observation
  91. EP251124a: NOT r- and z-band optical upper limits
  92. EP251124a: Swift-XRT observations
  93. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  94. EP251124a: Optical upper limit with Kinder observations
  95. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  96. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  97. EP251124a: GROWTH-India Telescope optical upper limits
  98. EP251124a: Einstein Probe detection of an X-ray transient
  99. GRB 251116C: Swift-XRT confirmation of fading
  100. GRB 251122A/EP251122A: 1.3m DFOT optical detection

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