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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: Continued brightening from Kinder follow-up of the emerging supernova candidate
  2. EP260214b: ATCA 6 GHz detection
  3. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  4. GRB 260321A: EP-FXT follow-up observation
  5. The EP-WXT trigger 01709259045 is likely a flaring star
  6. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  7. EP260321a: GOTO detection of blue variable source
  8. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  9. EP260321a: further Kinder optical observations
  10. GRB 260321A: SVOM/VT optical upper limits
  11. EP260321a: Las Cumbres upper limit
  12. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. GRB 260320A: Insight-HXMT/HE detection
  14. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  15. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  16. EP260321a: SVOM/VT optical upper limit
  17. GRB 260310A: continued optical observation at Mondy
  18. Fermi GBM Sub-Threshold Detection of GRB 260321A
  19. GRB 260321A: SVOM detection of a burst
  20. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  21. EP260321a: Global MASTER-Net observations report
  22. EP260321a: Einstein Probe detection of an X-ray transient
  23. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  24. GRB 260318A: Glowbug gamma-ray detection
  25. GRB 260310A / AT 2026fgk: KAIT optical observations
  26. GRB 260320A: NuSTAR detection of prompt emission
  27. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  28. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  29. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  30. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  31. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  32. GRB 260310A/AT2026fgk: LBT near-infrared observations
  33. NOEMA Detection of GRB 260310A / AT 2026fgk
  34. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  35. GRB 260318A: SVOM/GRM observation
  36. The EP-WXT trigger 01709258989 is likely a flaring star
  37. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  38. GRB 260318A: GECAM-B observation
  39. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  40. Fermi GRB 260318A: Global MASTER-Net observations report
  41. GRB 260318A: Fermi GBM Final Real-time Localization
  42. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  43. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  44. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  45. GRB 260310A / AT 2026fgk: radio detection with the VLA
  46. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  47. GRB 260310A / AT2026fgk: LCO optical observations
  48. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  49. GRB 260317A: Fermi GBM Final Localization
  50. GRB 260316B: GECAM-B observation
  51. GRB 260316B: SVOM/GRM observation
  52. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  53. EP260316a: COLIBRÍ faint optical counterpart candidate
  54. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  55. GRB 260316B: AstroSat CZTI detection
  56. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  57. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  58. EP260316a: Xinglong optical upper limit
  59. GRB 260316B: Fermi GBM Final Real-time Localization
  60. EP260316a: optical upper limit with Kinder observations
  61. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  62. GRB 260314A: Glowbug gamma-ray detection
  63. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  64. IceCube-260315A: COLIBRÍ optical observations
  65. EP260314a: Xinglong optical upper limit
  66. EP260314a: optical upper limit with Kinder observations
  67. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  68. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  69. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  70. GRB 260310A / AT 2026fgk: iTelescope optical observations
  71. EP260314a: COLIBRÍ optical upper limit
  72. GRID detection of GRB 260312B
  73. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  74. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP260314a: BOOTES-6/DPR optical upper limits at early times
  76. EP260314a: Global MASTER-Net observations report
  77. EP260314a: SVOM/VT optical candidate
  78. Fermi trigger No 795185313: Global MASTER-Net observations report
  79. IceCube Alert 260315A: Global MASTER-Net observations report
  80. EP260314a: Einstein Probe detection of an X-ray transient
  81. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  82. GRB 260314A: GECAM-B observation of a burst
  83. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  84. GRB 260310A / AT2026fgk: SAO RAS optical observations
  85. GRB 260310A/AT2026fgk: radio detection at 15GHz
  86. GRB 260310A / AT2026fgk: TNG NIR detection
  87. GRB 260310A / AT2026fgk: OASDG optical observations
  88. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  89. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  90. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  91. Fermi GRB 260314A: Global MASTER-Net observations report
  92. Fermi GRB 260313A: Global MASTER-Net observations report
  93. GRB 260314A: Fermi GBM Final Real-time Localization
  94. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  95. GRB 260313A: A Correction to the Fermi GBM Final Localization
  96. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  97. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  98. GRB 260310B: Insight-HXMT/HE detection
  99. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  100. GRB 260310A: NOT optical polarimetry

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