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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"

45713 results found.

  1. GRB 260330B: LCO optical upper limits
  2. GRB 260330B: SVOM detection of a burst
  3. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  4. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  5. EP260329a: COLIBRÍ optical upper limit
  6. EP260329a: EP-FXT follow up observation
  7. EP260329a: NOT optical counterpart candidate
  8. GRB 260330A: Fermi GBM Final Real-time Localization
  9. EP260329b: Global MASTER-Net observations report
  10. Fermi trigger No 796485221: Global MASTER-Net observations report
  11. GRB 260327A: Insight-HXMT/HE detection
  12. EP260329b: Optical follow-up with Kinder observations
  13. EP 260329b: COLIBRÍ optical observations
  14. EP260329a: Optical upper limit with Kinder observations
  15. EP260329b: LCO optical observations of the counterpart
  16. GRB 260326A: Insight-HXMT/HE detection
  17. EP260329b: Einstein Probe detection of an X-ray transient
  18. EP260329a: Einstein Probe detection of an X-ray transient
  19. EP-WXT trigger 01709259209: TRT optical counterpart detection
  20. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  21. GRID detection of GRB 260326A
  22. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  23. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  24. EP260327a: SVOM/VT optical upper limits
  25. SMA Detection of GRB 260310A / AT 2026fgk
  26. GRB 260307B: ATCA Radio Upper Limits
  27. EP260327a: WINTER J-band upper limit
  28. EP260327a: COLIBRÍ optical upper limits
  29. GRB 260327A: AstroSat CZTI detection of a long burst
  30. EP260327a: Gemini-North optical upper limits
  31. EP260324a: GROWTH-India Telescope optical observation
  32. EP260327a: Global MASTER-Net observations report
  33. EP260327a: Einstein Probe detection of an X-ray transient
  34. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  35. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  36. The EP-WXT trigger 01709259173 is likely a flaring star
  37. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  38. IPN triangulation of GRB 260320A
  39. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  40. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  41. GRB 260326A: Fermi GBM Detection
  42. EP260321a: JinShan near-infrared observations
  43. GRB 260325A: Fermi GBM Final Localization
  44. GRB 260326A: Fermi GBM Final Real-time Localization
  45. EP260321a: Upper limits from a neutrino search with IceCube
  46. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  47. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  48. IPN triangulation of GRB 260316B
  49. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  50. GRID detection of GRB 260320A
  51. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  52. EP260321a: Gemini-South confirmation of a supernova
  53. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  54. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  55. GRB 260310A: LBT optical observations
  56. EP260321A: Mondy optical observations
  57. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  58. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  59. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  60. The EP-WXT trigger 01709259112 is likely a flaring star
  61. Fermi GRB 260323A: Global MASTER-Net observations report
  62. GRB 260323A: Fermi GBM Final Real-time Localization
  63. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  64. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  65. GRB 260322A: Fermi GBM Final Localization
  66. GRB 260320A: Glowbug gamma-ray detection
  67. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  68. EP260321a: COLIBRÍ further optical observations and brightening
  69. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  70. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  71. EP260214b: ATCA 6 GHz detection
  72. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  73. GRB 260321A: EP-FXT follow-up observation
  74. The EP-WXT trigger 01709259045 is likely a flaring star
  75. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  76. EP260321a: GOTO detection of blue variable source
  77. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  78. EP260321a: further Kinder optical observations
  79. GRB 260321A: SVOM/VT optical upper limits
  80. EP260321a: Las Cumbres upper limit
  81. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. GRB 260320A: Insight-HXMT/HE detection
  83. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  84. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  85. EP260321a: SVOM/VT optical upper limit
  86. GRB 260310A: continued optical observation at Mondy
  87. Fermi GBM Sub-Threshold Detection of GRB 260321A
  88. GRB 260321A: SVOM detection of a burst
  89. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  90. EP260321a: Global MASTER-Net observations report
  91. EP260321a: Einstein Probe detection of an X-ray transient
  92. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  93. GRB 260318A: Glowbug gamma-ray detection
  94. GRB 260310A / AT 2026fgk: KAIT optical observations
  95. GRB 260320A: NuSTAR detection of prompt emission
  96. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  97. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  98. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  99. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  100. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening

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