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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"
  1. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  2. The EP-WXT trigger 01709259112 is likely a flaring star
  3. Fermi GRB 260323A: Global MASTER-Net observations report
  4. GRB 260323A: Fermi GBM Final Real-time Localization
  5. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  6. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  7. GRB 260322A: Fermi GBM Final Localization
  8. GRB 260320A: Glowbug gamma-ray detection
  9. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  10. EP260321a: COLIBRÍ further optical observations and brightening
  11. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  12. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  13. EP260214b: ATCA 6 GHz detection
  14. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  15. GRB 260321A: EP-FXT follow-up observation
  16. The EP-WXT trigger 01709259045 is likely a flaring star
  17. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  18. EP260321a: GOTO detection of blue variable source
  19. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  20. EP260321a: further Kinder optical observations
  21. GRB 260321A: SVOM/VT optical upper limits
  22. EP260321a: Las Cumbres upper limit
  23. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  24. GRB 260320A: Insight-HXMT/HE detection
  25. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  26. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  27. EP260321a: SVOM/VT optical upper limit
  28. GRB 260310A: continued optical observation at Mondy
  29. Fermi GBM Sub-Threshold Detection of GRB 260321A
  30. GRB 260321A: SVOM detection of a burst
  31. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  32. EP260321a: Global MASTER-Net observations report
  33. EP260321a: Einstein Probe detection of an X-ray transient
  34. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  35. GRB 260318A: Glowbug gamma-ray detection
  36. GRB 260310A / AT 2026fgk: KAIT optical observations
  37. GRB 260320A: NuSTAR detection of prompt emission
  38. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  39. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  40. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  41. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  42. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  43. GRB 260310A/AT2026fgk: LBT near-infrared observations
  44. NOEMA Detection of GRB 260310A / AT 2026fgk
  45. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  46. GRB 260318A: SVOM/GRM observation
  47. The EP-WXT trigger 01709258989 is likely a flaring star
  48. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  49. GRB 260318A: GECAM-B observation
  50. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  51. Fermi GRB 260318A: Global MASTER-Net observations report
  52. GRB 260318A: Fermi GBM Final Real-time Localization
  53. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  54. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  55. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  56. GRB 260310A / AT 2026fgk: radio detection with the VLA
  57. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  58. GRB 260310A / AT2026fgk: LCO optical observations
  59. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  60. GRB 260317A: Fermi GBM Final Localization
  61. GRB 260316B: GECAM-B observation
  62. GRB 260316B: SVOM/GRM observation
  63. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  64. EP260316a: COLIBRÍ faint optical counterpart candidate
  65. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  66. GRB 260316B: AstroSat CZTI detection
  67. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  68. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  69. EP260316a: Xinglong optical upper limit
  70. GRB 260316B: Fermi GBM Final Real-time Localization
  71. EP260316a: optical upper limit with Kinder observations
  72. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  73. GRB 260314A: Glowbug gamma-ray detection
  74. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  75. IceCube-260315A: COLIBRÍ optical observations
  76. EP260314a: Xinglong optical upper limit
  77. EP260314a: optical upper limit with Kinder observations
  78. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  79. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  80. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  81. GRB 260310A / AT 2026fgk: iTelescope optical observations
  82. EP260314a: COLIBRÍ optical upper limit
  83. GRID detection of GRB 260312B
  84. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  85. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP260314a: BOOTES-6/DPR optical upper limits at early times
  87. EP260314a: Global MASTER-Net observations report
  88. EP260314a: SVOM/VT optical candidate
  89. Fermi trigger No 795185313: Global MASTER-Net observations report
  90. IceCube Alert 260315A: Global MASTER-Net observations report
  91. EP260314a: Einstein Probe detection of an X-ray transient
  92. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  93. GRB 260314A: GECAM-B observation of a burst
  94. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  95. GRB 260310A / AT2026fgk: SAO RAS optical observations
  96. GRB 260310A/AT2026fgk: radio detection at 15GHz
  97. GRB 260310A / AT2026fgk: TNG NIR detection
  98. GRB 260310A / AT2026fgk: OASDG optical observations
  99. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  100. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations

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