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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"

32490 results found.

  1. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  2. EP260321a :Xinglong optical observations
  3. EP260327a: Xinglong optical upper limit
  4. EP260329b: GOTO detection of optical counterpart
  5. GRB 260330B: SVOM/VT optical upper limits
  6. Konus-Wind detection of GRB 260320A
  7. Konus-Wind detection of GRB 260316B (duplicate submission)
  8. Konus-Wind detection of GRB 260316B
  9. GRB 260321A: SVOM/ECLAIRs refined analysis
  10. EP260329b: J-band upper limits with WINTER
  11. EP260329a: J-band upper limit with WINTER
  12. GRB 260330A: Glowbug gamma-ray detection
  13. GRB 260310A: VLA Multi-frequency Radio Observations
  14. Fermi GBM Sub-Threshold Detection of GRB 260330B
  15. GRB 260330B: LCO optical upper limits
  16. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  17. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  18. EP260329a: COLIBRÍ optical upper limit
  19. EP260329a: EP-FXT follow up observation
  20. EP260329a: NOT optical counterpart candidate
  21. EP260329b: Global MASTER-Net observations report
  22. GRB 260327A: Insight-HXMT/HE detection
  23. EP260329b: Optical follow-up with Kinder observations
  24. EP 260329b: COLIBRÍ optical observations
  25. EP260329a: Optical upper limit with Kinder observations
  26. EP260329b: LCO optical observations of the counterpart
  27. GRB 260326A: Insight-HXMT/HE detection
  28. EP260329b: Einstein Probe detection of an X-ray transient
  29. EP-WXT trigger 01709259209: TRT optical counterpart detection
  30. GRID detection of GRB 260326A
  31. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  32. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260327a: SVOM/VT optical upper limits
  34. SMA Detection of GRB 260310A / AT 2026fgk
  35. GRB 260307B: ATCA Radio Upper Limits
  36. EP260327a: WINTER J-band upper limit
  37. EP260327a: COLIBRÍ optical upper limits
  38. EP260327a: Gemini-North optical upper limits
  39. EP260324a: GROWTH-India Telescope optical observation
  40. EP260327a: Global MASTER-Net observations report
  41. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  42. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  43. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  44. IPN triangulation of GRB 260320A
  45. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  46. GRB 260326A: Fermi GBM Detection
  47. EP260321a: JinShan near-infrared observations
  48. EP260321a: Upper limits from a neutrino search with IceCube
  49. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  50. IPN triangulation of GRB 260316B
  51. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  52. GRID detection of GRB 260320A
  53. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  54. EP260321a: Gemini-South confirmation of a supernova
  55. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  56. GRB 260310A: LBT optical observations
  57. EP260321A: Mondy optical observations
  58. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  59. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  60. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  61. Fermi GRB 260323A: Global MASTER-Net observations report
  62. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  63. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  64. GRB 260320A: Glowbug gamma-ray detection
  65. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  66. EP260321a: COLIBRÍ further optical observations and brightening
  67. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  68. EP260214b: ATCA 6 GHz detection
  69. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  70. GRB 260321A: EP-FXT follow-up observation
  71. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  72. EP260321a: GOTO detection of blue variable source
  73. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  74. EP260321a: further Kinder optical observations
  75. GRB 260321A: SVOM/VT optical upper limits
  76. EP260321a: Las Cumbres upper limit
  77. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  78. GRB 260320A: Insight-HXMT/HE detection
  79. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  80. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  81. EP260321a: SVOM/VT optical upper limit
  82. GRB 260310A: continued optical observation at Mondy
  83. Fermi GBM Sub-Threshold Detection of GRB 260321A
  84. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  85. EP260321a: Global MASTER-Net observations report
  86. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  87. GRB 260318A: Glowbug gamma-ray detection
  88. GRB 260310A / AT 2026fgk: KAIT optical observations
  89. GRB 260320A: NuSTAR detection of prompt emission
  90. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  91. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  92. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  93. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  94. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  95. GRB 260310A/AT2026fgk: LBT near-infrared observations
  96. NOEMA Detection of GRB 260310A / AT 2026fgk
  97. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  98. GRB 260318A: SVOM/GRM observation
  99. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  100. GRB 260318A: GECAM-B observation

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