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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. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  2. GRB 260401A: Fermi GBM Final Real-time Localization
  3. EP260329b: Mondy and Assy-Turgen optical upper limits
  4. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  5. EP260321a :Xinglong optical observations
  6. EP260327a: Xinglong optical upper limit
  7. EP260329b: GOTO detection of optical counterpart
  8. GRB 260330B: SVOM/VT optical upper limits
  9. Konus-Wind detection of GRB 260320A
  10. Konus-Wind detection of GRB 260316B (duplicate submission)
  11. Konus-Wind detection of GRB 260316B
  12. GRB 260321A: SVOM/ECLAIRs refined analysis
  13. EP260329b: J-band upper limits with WINTER
  14. EP260329a: J-band upper limit with WINTER
  15. GRB 260330A: Glowbug gamma-ray detection
  16. GRB 260310A: VLA Multi-frequency Radio Observations
  17. Fermi GBM Sub-Threshold Detection of GRB 260330B
  18. GRB 260330B: LCO optical upper limits
  19. GRB 260330B: SVOM detection of a burst
  20. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  21. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  22. EP260329a: COLIBRÍ optical upper limit
  23. EP260329a: EP-FXT follow up observation
  24. EP260329a: NOT optical counterpart candidate
  25. GRB 260330A: Fermi GBM Final Real-time Localization
  26. EP260329b: Global MASTER-Net observations report
  27. Fermi trigger No 796485221: Global MASTER-Net observations report
  28. GRB 260327A: Insight-HXMT/HE detection
  29. EP260329b: Optical follow-up with Kinder observations
  30. EP 260329b: COLIBRÍ optical observations
  31. EP260329a: Optical upper limit with Kinder observations
  32. EP260329b: LCO optical observations of the counterpart
  33. GRB 260326A: Insight-HXMT/HE detection
  34. EP260329b: Einstein Probe detection of an X-ray transient
  35. EP260329a: Einstein Probe detection of an X-ray transient
  36. EP-WXT trigger 01709259209: TRT optical counterpart detection
  37. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  38. GRID detection of GRB 260326A
  39. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  40. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  41. EP260327a: SVOM/VT optical upper limits
  42. SMA Detection of GRB 260310A / AT 2026fgk
  43. GRB 260307B: ATCA Radio Upper Limits
  44. EP260327a: WINTER J-band upper limit
  45. EP260327a: COLIBRÍ optical upper limits
  46. GRB 260327A: AstroSat CZTI detection of a long burst
  47. EP260327a: Gemini-North optical upper limits
  48. EP260324a: GROWTH-India Telescope optical observation
  49. EP260327a: Global MASTER-Net observations report
  50. EP260327a: Einstein Probe detection of an X-ray transient
  51. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  52. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  53. The EP-WXT trigger 01709259173 is likely a flaring star
  54. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  55. IPN triangulation of GRB 260320A
  56. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  57. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  58. GRB 260326A: Fermi GBM Detection
  59. EP260321a: JinShan near-infrared observations
  60. GRB 260325A: Fermi GBM Final Localization
  61. GRB 260326A: Fermi GBM Final Real-time Localization
  62. EP260321a: Upper limits from a neutrino search with IceCube
  63. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  64. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  65. IPN triangulation of GRB 260316B
  66. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  67. GRID detection of GRB 260320A
  68. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  69. EP260321a: Gemini-South confirmation of a supernova
  70. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  71. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  72. GRB 260310A: LBT optical observations
  73. EP260321A: Mondy optical observations
  74. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  75. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  76. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  77. The EP-WXT trigger 01709259112 is likely a flaring star
  78. Fermi GRB 260323A: Global MASTER-Net observations report
  79. GRB 260323A: Fermi GBM Final Real-time Localization
  80. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  81. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  82. GRB 260322A: Fermi GBM Final Localization
  83. GRB 260320A: Glowbug gamma-ray detection
  84. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  85. EP260321a: COLIBRÍ further optical observations and brightening
  86. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  87. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  88. EP260214b: ATCA 6 GHz detection
  89. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  90. GRB 260321A: EP-FXT follow-up observation
  91. The EP-WXT trigger 01709259045 is likely a flaring star
  92. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  93. EP260321a: GOTO detection of blue variable source
  94. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  95. EP260321a: further Kinder optical observations
  96. GRB 260321A: SVOM/VT optical upper limits
  97. EP260321a: Las Cumbres upper limit
  98. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  99. GRB 260320A: Insight-HXMT/HE detection
  100. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission

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