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

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