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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. The EP-WXT trigger 01709259173 is likely a flaring star
  2. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  3. IPN triangulation of GRB 260320A
  4. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  5. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  6. GRB 260326A: Fermi GBM Detection
  7. EP260321a: JinShan near-infrared observations
  8. GRB 260325A: Fermi GBM Final Localization
  9. GRB 260326A: Fermi GBM Final Real-time Localization
  10. EP260321a: Upper limits from a neutrino search with IceCube
  11. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  12. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  13. IPN triangulation of GRB 260316B
  14. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  15. GRID detection of GRB 260320A
  16. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  17. EP260321a: Gemini-South confirmation of a supernova
  18. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  19. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  20. GRB 260310A: LBT optical observations
  21. EP260321A: Mondy optical observations
  22. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  23. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  24. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  25. The EP-WXT trigger 01709259112 is likely a flaring star
  26. Fermi GRB 260323A: Global MASTER-Net observations report
  27. GRB 260323A: Fermi GBM Final Real-time Localization
  28. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  29. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  30. GRB 260322A: Fermi GBM Final Localization
  31. GRB 260320A: Glowbug gamma-ray detection
  32. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  33. EP260321a: COLIBRÍ further optical observations and brightening
  34. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  35. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  36. EP260214b: ATCA 6 GHz detection
  37. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  38. GRB 260321A: EP-FXT follow-up observation
  39. The EP-WXT trigger 01709259045 is likely a flaring star
  40. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  41. EP260321a: GOTO detection of blue variable source
  42. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  43. EP260321a: further Kinder optical observations
  44. GRB 260321A: SVOM/VT optical upper limits
  45. EP260321a: Las Cumbres upper limit
  46. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. GRB 260320A: Insight-HXMT/HE detection
  48. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  49. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  50. EP260321a: SVOM/VT optical upper limit
  51. GRB 260310A: continued optical observation at Mondy
  52. Fermi GBM Sub-Threshold Detection of GRB 260321A
  53. GRB 260321A: SVOM detection of a burst
  54. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  55. EP260321a: Global MASTER-Net observations report
  56. EP260321a: Einstein Probe detection of an X-ray transient
  57. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  58. GRB 260318A: Glowbug gamma-ray detection
  59. GRB 260310A / AT 2026fgk: KAIT optical observations
  60. GRB 260320A: NuSTAR detection of prompt emission
  61. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  62. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  63. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  64. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  65. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  66. GRB 260310A/AT2026fgk: LBT near-infrared observations
  67. NOEMA Detection of GRB 260310A / AT 2026fgk
  68. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  69. GRB 260318A: SVOM/GRM observation
  70. The EP-WXT trigger 01709258989 is likely a flaring star
  71. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  72. GRB 260318A: GECAM-B observation
  73. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  74. Fermi GRB 260318A: Global MASTER-Net observations report
  75. GRB 260318A: Fermi GBM Final Real-time Localization
  76. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  77. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  78. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  79. GRB 260310A / AT 2026fgk: radio detection with the VLA
  80. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  81. GRB 260310A / AT2026fgk: LCO optical observations
  82. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  83. GRB 260317A: Fermi GBM Final Localization
  84. GRB 260316B: GECAM-B observation
  85. GRB 260316B: SVOM/GRM observation
  86. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  87. EP260316a: COLIBRÍ faint optical counterpart candidate
  88. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  89. GRB 260316B: AstroSat CZTI detection
  90. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  91. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  92. EP260316a: Xinglong optical upper limit
  93. GRB 260316B: Fermi GBM Final Real-time Localization
  94. EP260316a: optical upper limit with Kinder observations
  95. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  96. GRB 260314A: Glowbug gamma-ray detection
  97. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  98. IceCube-260315A: COLIBRÍ optical observations
  99. EP260314a: Xinglong optical upper limit
  100. EP260314a: optical upper limit with Kinder observations

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