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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. EP260321A: Mondy optical observations
  2. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  3. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  4. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  5. The EP-WXT trigger 01709259112 is likely a flaring star
  6. Fermi GRB 260323A: Global MASTER-Net observations report
  7. GRB 260323A: Fermi GBM Final Real-time Localization
  8. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  9. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  10. GRB 260322A: Fermi GBM Final Localization
  11. GRB 260320A: Glowbug gamma-ray detection
  12. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  13. EP260321a: COLIBRÍ further optical observations and brightening
  14. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  15. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  16. EP260214b: ATCA 6 GHz detection
  17. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  18. GRB 260321A: EP-FXT follow-up observation
  19. The EP-WXT trigger 01709259045 is likely a flaring star
  20. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  21. EP260321a: GOTO detection of blue variable source
  22. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  23. EP260321a: further Kinder optical observations
  24. GRB 260321A: SVOM/VT optical upper limits
  25. EP260321a: Las Cumbres upper limit
  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. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  30. EP260321a: SVOM/VT optical upper limit
  31. GRB 260310A: continued optical observation at Mondy
  32. Fermi GBM Sub-Threshold Detection of GRB 260321A
  33. GRB 260321A: SVOM detection of a burst
  34. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  35. EP260321a: Global MASTER-Net observations report
  36. EP260321a: Einstein Probe detection of an X-ray transient
  37. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  38. GRB 260318A: Glowbug gamma-ray detection
  39. GRB 260310A / AT 2026fgk: KAIT optical observations
  40. GRB 260320A: NuSTAR detection of prompt emission
  41. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  42. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  43. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  44. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  45. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  46. GRB 260310A/AT2026fgk: LBT near-infrared observations
  47. NOEMA Detection of GRB 260310A / AT 2026fgk
  48. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  49. GRB 260318A: SVOM/GRM observation
  50. The EP-WXT trigger 01709258989 is likely a flaring star
  51. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  52. GRB 260318A: GECAM-B observation
  53. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  54. Fermi GRB 260318A: Global MASTER-Net observations report
  55. GRB 260318A: Fermi GBM Final Real-time Localization
  56. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  57. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  58. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  59. GRB 260310A / AT 2026fgk: radio detection with the VLA
  60. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  61. GRB 260310A / AT2026fgk: LCO optical observations
  62. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  63. GRB 260317A: Fermi GBM Final Localization
  64. GRB 260316B: GECAM-B observation
  65. GRB 260316B: SVOM/GRM observation
  66. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  67. EP260316a: COLIBRÍ faint optical counterpart candidate
  68. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  69. GRB 260316B: AstroSat CZTI detection
  70. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  71. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  72. EP260316a: Xinglong optical upper limit
  73. GRB 260316B: Fermi GBM Final Real-time Localization
  74. EP260316a: optical upper limit with Kinder observations
  75. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  76. GRB 260314A: Glowbug gamma-ray detection
  77. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  78. IceCube-260315A: COLIBRÍ optical observations
  79. EP260314a: Xinglong optical upper limit
  80. EP260314a: optical upper limit with Kinder observations
  81. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  82. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  83. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  84. GRB 260310A / AT 2026fgk: iTelescope optical observations
  85. EP260314a: COLIBRÍ optical upper limit
  86. GRID detection of GRB 260312B
  87. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  88. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  89. EP260314a: BOOTES-6/DPR optical upper limits at early times
  90. EP260314a: Global MASTER-Net observations report
  91. EP260314a: SVOM/VT optical candidate
  92. Fermi trigger No 795185313: Global MASTER-Net observations report
  93. IceCube Alert 260315A: Global MASTER-Net observations report
  94. EP260314a: Einstein Probe detection of an X-ray transient
  95. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  96. GRB 260314A: GECAM-B observation of a burst
  97. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  98. GRB 260310A / AT2026fgk: SAO RAS optical observations
  99. GRB 260310A/AT2026fgk: radio detection at 15GHz
  100. GRB 260310A / AT2026fgk: TNG NIR detection

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