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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"

38260 results found.

  1. GRB 260326A: Fermi GBM Detection
  2. EP260321a: JinShan near-infrared observations
  3. GRB 260325A: Fermi GBM Final Localization
  4. GRB 260326A: Fermi GBM Final Real-time Localization
  5. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  6. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  7. IPN triangulation of GRB 260316B
  8. GRID detection of GRB 260320A
  9. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  10. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  11. GRB 260310A: LBT optical observations
  12. EP260321A: Mondy optical observations
  13. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  14. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  15. Fermi GRB 260323A: Global MASTER-Net observations report
  16. GRB 260323A: Fermi GBM Final Real-time Localization
  17. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  18. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  19. GRB 260322A: Fermi GBM Final Localization
  20. GRB 260320A: Glowbug gamma-ray detection
  21. EP260321a: COLIBRÍ further optical observations and brightening
  22. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  23. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  24. GRB 260321A: EP-FXT follow-up observation
  25. GRB 260321A: SVOM/VT optical upper limits
  26. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 260320A: Insight-HXMT/HE detection
  28. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  29. GRB 260310A: continued optical observation at Mondy
  30. Fermi GBM Sub-Threshold Detection of GRB 260321A
  31. GRB 260321A: SVOM detection of a burst
  32. EP260321a: Global MASTER-Net observations report
  33. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  34. GRB 260318A: Glowbug gamma-ray detection
  35. GRB 260310A / AT 2026fgk: KAIT optical observations
  36. GRB 260320A: NuSTAR detection of prompt emission
  37. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  38. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  39. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  40. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  41. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  42. GRB 260310A/AT2026fgk: LBT near-infrared observations
  43. NOEMA Detection of GRB 260310A / AT 2026fgk
  44. GRB 260318A: SVOM/GRM observation
  45. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  46. GRB 260318A: GECAM-B observation
  47. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  48. Fermi GRB 260318A: Global MASTER-Net observations report
  49. GRB 260318A: Fermi GBM Final Real-time Localization
  50. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  51. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  52. GRB 260310A / AT 2026fgk: radio detection with the VLA
  53. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  54. GRB 260310A / AT2026fgk: LCO optical observations
  55. GRB 260317A: Fermi GBM Final Localization
  56. GRB 260316B: GECAM-B observation
  57. GRB 260316B: SVOM/GRM observation
  58. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  59. EP260316a: COLIBRÍ faint optical counterpart candidate
  60. GRB 260316B: AstroSat CZTI detection
  61. GRB 260316B: Fermi GBM Final Real-time Localization
  62. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  63. GRB 260314A: Glowbug gamma-ray detection
  64. IceCube-260315A: COLIBRÍ optical observations
  65. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  66. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  67. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  68. GRB 260310A / AT 2026fgk: iTelescope optical observations
  69. EP260314a: COLIBRÍ optical upper limit
  70. GRID detection of GRB 260312B
  71. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  72. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  73. EP260314a: Global MASTER-Net observations report
  74. Fermi trigger No 795185313: Global MASTER-Net observations report
  75. IceCube Alert 260315A: Global MASTER-Net observations report
  76. GRB 260314A: GECAM-B observation of a burst
  77. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  78. GRB 260310A / AT2026fgk: SAO RAS optical observations
  79. GRB 260310A/AT2026fgk: radio detection at 15GHz
  80. GRB 260310A / AT2026fgk: TNG NIR detection
  81. GRB 260310A / AT2026fgk: OASDG optical observations
  82. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  83. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  84. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  85. Fermi GRB 260314A: Global MASTER-Net observations report
  86. Fermi GRB 260313A: Global MASTER-Net observations report
  87. GRB 260314A: Fermi GBM Final Real-time Localization
  88. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  89. GRB 260313A: A Correction to the Fermi GBM Final Localization
  90. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  91. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  92. GRB 260310B: Insight-HXMT/HE detection
  93. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  94. GRB 260310A: NOT optical polarimetry
  95. GRB 260312B: AstroSat CZTI detection
  96. Swift BAT trigger 1500295: A solar flare
  97. GRB 260313A: Fermi GBM Final Real-time Localization
  98. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  99. Swift BAT trigger 1500287: A solar flare
  100. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153

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