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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"

5401 results found.

  1. GRB 260326A: Insight-HXMT/HE detection
  2. EP260329b: Einstein Probe detection of an X-ray transient
  3. EP260329a: Einstein Probe detection of an X-ray transient
  4. EP-WXT trigger 01709259209: TRT optical counterpart detection
  5. GRID detection of GRB 260326A
  6. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  7. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  8. EP260327a: SVOM/VT optical upper limits
  9. EP260327a: WINTER J-band upper limit
  10. EP260327a: COLIBRÍ optical upper limits
  11. GRB 260327A: AstroSat CZTI detection of a long burst
  12. EP260327a: Gemini-North optical upper limits
  13. EP260324a: GROWTH-India Telescope optical observation
  14. EP260327a: Global MASTER-Net observations report
  15. EP260327a: Einstein Probe detection of an X-ray transient
  16. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  17. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  18. The EP-WXT trigger 01709259173 is likely a flaring star
  19. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  20. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  21. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  22. EP260321a: JinShan near-infrared observations
  23. EP260321a: Upper limits from a neutrino search with IceCube
  24. GRID detection of GRB 260320A
  25. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  26. GRB 260310A: LBT optical observations
  27. EP260321A: Mondy optical observations
  28. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  29. The EP-WXT trigger 01709259112 is likely a flaring star
  30. Fermi GRB 260323A: Global MASTER-Net observations report
  31. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  32. GRB 260320A: Glowbug gamma-ray detection
  33. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  34. EP260321a: COLIBRÍ further optical observations and brightening
  35. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  36. GRB 260321A: EP-FXT follow-up observation
  37. The EP-WXT trigger 01709259045 is likely a flaring star
  38. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  39. EP260321a: GOTO detection of blue variable source
  40. GRB 260321A: SVOM/VT optical upper limits
  41. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 260320A: Insight-HXMT/HE detection
  43. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  44. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  45. EP260321a: SVOM/VT optical upper limit
  46. GRB 260310A: continued optical observation at Mondy
  47. Fermi GBM Sub-Threshold Detection of GRB 260321A
  48. GRB 260321A: SVOM detection of a burst
  49. EP260321a: Global MASTER-Net observations report
  50. EP260321a: Einstein Probe detection of an X-ray transient
  51. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  52. GRB 260318A: Glowbug gamma-ray detection
  53. GRB 260320A: NuSTAR detection of prompt emission
  54. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  55. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  56. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  57. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  58. GRB 260310A/AT2026fgk: LBT near-infrared observations
  59. GRB 260318A: SVOM/GRM observation
  60. The EP-WXT trigger 01709258989 is likely a flaring star
  61. GRB 260318A: GECAM-B observation
  62. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  63. Fermi GRB 260318A: Global MASTER-Net observations report
  64. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  65. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  66. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  67. GRB 260310A / AT2026fgk: LCO optical observations
  68. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  69. GRB 260316B: GECAM-B observation
  70. GRB 260316B: SVOM/GRM observation
  71. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  72. EP260316a: COLIBRÍ faint optical counterpart candidate
  73. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  74. GRB 260316B: AstroSat CZTI detection
  75. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  76. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  77. EP260316a: Xinglong optical upper limit
  78. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  79. GRB 260314A: Glowbug gamma-ray detection
  80. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  81. IceCube-260315A: COLIBRÍ optical observations
  82. EP260314a: Xinglong optical upper limit
  83. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  84. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  85. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  86. GRB 260310A / AT 2026fgk: iTelescope optical observations
  87. EP260314a: COLIBRÍ optical upper limit
  88. GRID detection of GRB 260312B
  89. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  90. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP260314a: BOOTES-6/DPR optical upper limits at early times
  92. EP260314a: Global MASTER-Net observations report
  93. EP260314a: SVOM/VT optical candidate
  94. Fermi trigger No 795185313: Global MASTER-Net observations report
  95. IceCube Alert 260315A: Global MASTER-Net observations report
  96. EP260314a: Einstein Probe detection of an X-ray transient
  97. GRB 260314A: GECAM-B observation of a burst
  98. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  99. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  100. Fermi GRB 260314A: Global MASTER-Net observations report

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