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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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 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. EP260321a: Upper limits from a neutrino search with IceCube
  6. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  7. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  8. IPN triangulation of GRB 260316B
  9. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  10. GRID detection of GRB 260320A
  11. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  12. EP260321a: Gemini-South confirmation of a supernova
  13. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  14. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  15. GRB 260310A: LBT optical observations
  16. EP260321A: Mondy optical observations
  17. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  18. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  19. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  20. The EP-WXT trigger 01709259112 is likely a flaring star
  21. Fermi GRB 260323A: Global MASTER-Net observations report
  22. GRB 260323A: Fermi GBM Final Real-time Localization
  23. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  24. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  25. GRB 260322A: Fermi GBM Final Localization
  26. GRB 260320A: Glowbug gamma-ray detection
  27. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  28. EP260321a: COLIBRÍ further optical observations and brightening
  29. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  30. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  31. EP260214b: ATCA 6 GHz detection
  32. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  33. GRB 260321A: EP-FXT follow-up observation
  34. The EP-WXT trigger 01709259045 is likely a flaring star
  35. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  36. EP260321a: GOTO detection of blue variable source
  37. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  38. EP260321a: further Kinder optical observations
  39. GRB 260321A: SVOM/VT optical upper limits
  40. EP260321a: Las Cumbres upper limit
  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: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  50. EP260321a: Global MASTER-Net observations report
  51. EP260321a: Einstein Probe detection of an X-ray transient
  52. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  53. GRB 260318A: Glowbug gamma-ray detection
  54. GRB 260310A / AT 2026fgk: KAIT optical observations
  55. GRB 260320A: NuSTAR detection of prompt emission
  56. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  57. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  58. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  59. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  60. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  61. GRB 260310A/AT2026fgk: LBT near-infrared observations
  62. NOEMA Detection of GRB 260310A / AT 2026fgk
  63. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  64. GRB 260318A: SVOM/GRM observation
  65. The EP-WXT trigger 01709258989 is likely a flaring star
  66. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  67. GRB 260318A: GECAM-B observation
  68. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  69. Fermi GRB 260318A: Global MASTER-Net observations report
  70. GRB 260318A: Fermi GBM Final Real-time Localization
  71. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  72. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  73. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  74. GRB 260310A / AT 2026fgk: radio detection with the VLA
  75. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  76. GRB 260310A / AT2026fgk: LCO optical observations
  77. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  78. GRB 260317A: Fermi GBM Final Localization
  79. GRB 260316B: GECAM-B observation
  80. GRB 260316B: SVOM/GRM observation
  81. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  82. EP260316a: COLIBRÍ faint optical counterpart candidate
  83. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  84. GRB 260316B: AstroSat CZTI detection
  85. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  86. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  87. EP260316a: Xinglong optical upper limit
  88. GRB 260316B: Fermi GBM Final Real-time Localization
  89. EP260316a: optical upper limit with Kinder observations
  90. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  91. GRB 260314A: Glowbug gamma-ray detection
  92. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  93. IceCube-260315A: COLIBRÍ optical observations
  94. EP260314a: Xinglong optical upper limit
  95. EP260314a: optical upper limit with Kinder observations
  96. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  97. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  98. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  99. GRB 260310A / AT 2026fgk: iTelescope optical observations
  100. EP260314a: COLIBRÍ optical upper limit

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