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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"

32692 results found.

  1. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  2. GRB 260401A: MAXI/GSC detection
  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. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  20. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  21. EP260329a: COLIBRÍ optical upper limit
  22. EP260329a: EP-FXT follow up observation
  23. EP260329a: NOT optical counterpart candidate
  24. EP260329b: Global MASTER-Net observations report
  25. GRB 260327A: Insight-HXMT/HE detection
  26. EP260329b: Optical follow-up with Kinder observations
  27. EP 260329b: COLIBRÍ optical observations
  28. EP260329a: Optical upper limit with Kinder observations
  29. EP260329b: LCO optical observations of the counterpart
  30. GRB 260326A: Insight-HXMT/HE detection
  31. EP260329b: Einstein Probe detection of an X-ray transient
  32. EP-WXT trigger 01709259209: TRT optical counterpart detection
  33. GRID detection of GRB 260326A
  34. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  35. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260327a: SVOM/VT optical upper limits
  37. SMA Detection of GRB 260310A / AT 2026fgk
  38. GRB 260307B: ATCA Radio Upper Limits
  39. EP260327a: WINTER J-band upper limit
  40. EP260327a: COLIBRÍ optical upper limits
  41. EP260327a: Gemini-North optical upper limits
  42. EP260324a: GROWTH-India Telescope optical observation
  43. EP260327a: Global MASTER-Net observations report
  44. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  45. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  46. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  47. IPN triangulation of GRB 260320A
  48. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  49. GRB 260326A: Fermi GBM Detection
  50. EP260321a: JinShan near-infrared observations
  51. EP260321a: Upper limits from a neutrino search with IceCube
  52. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  53. IPN triangulation of GRB 260316B
  54. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  55. GRID detection of GRB 260320A
  56. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  57. EP260321a: Gemini-South confirmation of a supernova
  58. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  59. GRB 260310A: LBT optical observations
  60. EP260321A: Mondy optical observations
  61. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  62. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  63. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  64. Fermi GRB 260323A: Global MASTER-Net observations report
  65. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  66. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  67. GRB 260320A: Glowbug gamma-ray detection
  68. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  69. EP260321a: COLIBRÍ further optical observations and brightening
  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. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  75. EP260321a: GOTO detection of blue variable source
  76. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  77. EP260321a: further Kinder optical observations
  78. GRB 260321A: SVOM/VT optical upper limits
  79. EP260321a: Las Cumbres upper limit
  80. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. GRB 260320A: Insight-HXMT/HE detection
  82. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  83. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  84. EP260321a: SVOM/VT optical upper limit
  85. GRB 260310A: continued optical observation at Mondy
  86. Fermi GBM Sub-Threshold Detection of GRB 260321A
  87. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  88. EP260321a: Global MASTER-Net observations report
  89. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  90. GRB 260318A: Glowbug gamma-ray detection
  91. GRB 260310A / AT 2026fgk: KAIT optical observations
  92. GRB 260320A: NuSTAR detection of prompt emission
  93. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  94. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  95. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  96. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  97. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  98. GRB 260310A/AT2026fgk: LBT near-infrared observations
  99. NOEMA Detection of GRB 260310A / AT 2026fgk
  100. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7

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