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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"

41585 results found.

  1. EP260321a: JinShan near-infrared observations
  2. GRB 260325A: Fermi GBM Final Localization
  3. GRB 260326A: Fermi GBM Final Real-time Localization
  4. EP260321a: Upper limits from a neutrino search with IceCube
  5. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  6. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  7. IPN triangulation of GRB 260316B
  8. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  9. GRID detection of GRB 260320A
  10. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  11. EP260321a: Gemini-South confirmation of a supernova
  12. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  13. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  14. GRB 260310A: LBT optical observations
  15. EP260321A: Mondy optical observations
  16. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  17. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  18. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  19. The EP-WXT trigger 01709259112 is likely a flaring star
  20. Fermi GRB 260323A: Global MASTER-Net observations report
  21. GRB 260323A: Fermi GBM Final Real-time Localization
  22. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  23. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  24. GRB 260322A: Fermi GBM Final Localization
  25. GRB 260320A: Glowbug gamma-ray detection
  26. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  27. EP260321a: COLIBRÍ further optical observations and brightening
  28. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  29. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  30. EP260214b: ATCA 6 GHz detection
  31. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  32. GRB 260321A: EP-FXT follow-up observation
  33. The EP-WXT trigger 01709259045 is likely a flaring star
  34. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  35. EP260321a: GOTO detection of blue variable source
  36. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  37. EP260321a: further Kinder optical observations
  38. GRB 260321A: SVOM/VT optical upper limits
  39. EP260321a: Las Cumbres upper limit
  40. GRB 260320A: Insight-HXMT/HE detection
  41. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  42. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  43. EP260321a: SVOM/VT optical upper limit
  44. GRB 260310A: continued optical observation at Mondy
  45. Fermi GBM Sub-Threshold Detection of GRB 260321A
  46. GRB 260321A: SVOM detection of a burst
  47. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  48. EP260321a: Global MASTER-Net observations report
  49. EP260321a: Einstein Probe detection of an X-ray transient
  50. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  51. GRB 260318A: Glowbug gamma-ray detection
  52. GRB 260310A / AT 2026fgk: KAIT optical observations
  53. GRB 260320A: NuSTAR detection of prompt emission
  54. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  55. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  56. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  57. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  58. GRB 260310A/AT2026fgk: LBT near-infrared observations
  59. NOEMA Detection of GRB 260310A / AT 2026fgk
  60. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  61. GRB 260318A: SVOM/GRM observation
  62. The EP-WXT trigger 01709258989 is likely a flaring star
  63. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  64. GRB 260318A: GECAM-B observation
  65. Fermi GRB 260318A: Global MASTER-Net observations report
  66. GRB 260318A: Fermi GBM Final Real-time Localization
  67. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  68. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  69. GRB 260310A / AT 2026fgk: radio detection with the VLA
  70. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  71. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  72. GRB 260317A: Fermi GBM Final Localization
  73. GRB 260316B: GECAM-B observation
  74. GRB 260316B: SVOM/GRM observation
  75. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  76. EP260316a: COLIBRÍ faint optical counterpart candidate
  77. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  78. GRB 260316B: AstroSat CZTI detection
  79. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  80. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  81. EP260316a: Xinglong optical upper limit
  82. GRB 260316B: Fermi GBM Final Real-time Localization
  83. EP260316a: optical upper limit with Kinder observations
  84. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  85. GRB 260314A: Glowbug gamma-ray detection
  86. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  87. IceCube-260315A: COLIBRÍ optical observations
  88. EP260314a: Xinglong optical upper limit
  89. EP260314a: optical upper limit with Kinder observations
  90. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  91. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  92. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  93. EP260314a: COLIBRÍ optical upper limit
  94. GRID detection of GRB 260312B
  95. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  96. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  97. EP260314a: BOOTES-6/DPR optical upper limits at early times
  98. EP260314a: Global MASTER-Net observations report
  99. EP260314a: SVOM/VT optical candidate
  100. Fermi trigger No 795185313: Global MASTER-Net observations report

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