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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 260402A: SVOM/MXT candidate X-ray afterglow
  2. GRB 260402A: SVOM detection of a burst
  3. Fermi GRB 260401A: Global MASTER-Net observations report
  4. GRB 260401A: Fermi GBM Observation
  5. GRB 260401A: NuSTAR detection of prompt emission
  6. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260401A: MAXI/GSC detection
  8. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  9. GRB 260401A: Fermi GBM Final Real-time Localization
  10. EP260329b: Mondy and Assy-Turgen optical upper limits
  11. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  12. EP260321a :Xinglong optical observations
  13. EP260327a: Xinglong optical upper limit
  14. EP260329b: GOTO detection of optical counterpart
  15. GRB 260330B: SVOM/VT optical upper limits
  16. Konus-Wind detection of GRB 260320A
  17. Konus-Wind detection of GRB 260316B (duplicate submission)
  18. Konus-Wind detection of GRB 260316B
  19. GRB 260321A: SVOM/ECLAIRs refined analysis
  20. EP260329b: J-band upper limits with WINTER
  21. EP260329a: J-band upper limit with WINTER
  22. GRB 260330A: Glowbug gamma-ray detection
  23. GRB 260310A: VLA Multi-frequency Radio Observations
  24. Fermi GBM Sub-Threshold Detection of GRB 260330B
  25. GRB 260330B: LCO optical upper limits
  26. GRB 260330B: SVOM detection of a burst
  27. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  28. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  29. EP260329a: COLIBRÍ optical upper limit
  30. EP260329a: EP-FXT follow up observation
  31. EP260329a: NOT optical counterpart candidate
  32. GRB 260330A: Fermi GBM Final Real-time Localization
  33. EP260329b: Global MASTER-Net observations report
  34. Fermi trigger No 796485221: Global MASTER-Net observations report
  35. GRB 260327A: Insight-HXMT/HE detection
  36. EP260329b: Optical follow-up with Kinder observations
  37. EP 260329b: COLIBRÍ optical observations
  38. EP260329a: Optical upper limit with Kinder observations
  39. EP260329b: LCO optical observations of the counterpart
  40. GRB 260326A: Insight-HXMT/HE detection
  41. EP260329b: Einstein Probe detection of an X-ray transient
  42. EP260329a: Einstein Probe detection of an X-ray transient
  43. EP-WXT trigger 01709259209: TRT optical counterpart detection
  44. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  45. GRID detection of GRB 260326A
  46. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  47. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  48. EP260327a: SVOM/VT optical upper limits
  49. SMA Detection of GRB 260310A / AT 2026fgk
  50. GRB 260307B: ATCA Radio Upper Limits
  51. EP260327a: WINTER J-band upper limit
  52. EP260327a: COLIBRÍ optical upper limits
  53. GRB 260327A: AstroSat CZTI detection of a long burst
  54. EP260327a: Gemini-North optical upper limits
  55. EP260324a: GROWTH-India Telescope optical observation
  56. EP260327a: Global MASTER-Net observations report
  57. EP260327a: Einstein Probe detection of an X-ray transient
  58. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  59. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  60. The EP-WXT trigger 01709259173 is likely a flaring star
  61. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  62. IPN triangulation of GRB 260320A
  63. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  64. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  65. GRB 260326A: Fermi GBM Detection
  66. EP260321a: JinShan near-infrared observations
  67. GRB 260325A: Fermi GBM Final Localization
  68. GRB 260326A: Fermi GBM Final Real-time Localization
  69. EP260321a: Upper limits from a neutrino search with IceCube
  70. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  71. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  72. IPN triangulation of GRB 260316B
  73. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  74. GRID detection of GRB 260320A
  75. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  76. EP260321a: Gemini-South confirmation of a supernova
  77. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  78. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  79. GRB 260310A: LBT optical observations
  80. EP260321A: Mondy optical observations
  81. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  82. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  83. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  84. The EP-WXT trigger 01709259112 is likely a flaring star
  85. Fermi GRB 260323A: Global MASTER-Net observations report
  86. GRB 260323A: Fermi GBM Final Real-time Localization
  87. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  88. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  89. GRB 260322A: Fermi GBM Final Localization
  90. GRB 260320A: Glowbug gamma-ray detection
  91. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  92. EP260321a: COLIBRÍ further optical observations and brightening
  93. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  94. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  95. EP260214b: ATCA 6 GHz detection
  96. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  97. GRB 260321A: EP-FXT follow-up observation
  98. The EP-WXT trigger 01709259045 is likely a flaring star
  99. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  100. EP260321a: GOTO detection of blue variable source

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