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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"

32502 results found.

  1. GRB 260401A: GECAM-B observation
  2. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  3. GRB 260402A: Kilonova-Catcher optical upper limit
  4. GRB 260402A: MASTER optical observations
  5. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  7. Fermi GRB 260401A: Global MASTER-Net observations report
  8. GRB 260401A: Fermi GBM Observation
  9. GRB 260401A: NuSTAR detection of prompt emission
  10. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  11. GRB 260401A: MAXI/GSC detection
  12. EP260329b: Mondy and Assy-Turgen optical upper limits
  13. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  14. EP260321a :Xinglong optical observations
  15. EP260327a: Xinglong optical upper limit
  16. EP260329b: GOTO detection of optical counterpart
  17. GRB 260330B: SVOM/VT optical upper limits
  18. Konus-Wind detection of GRB 260320A
  19. Konus-Wind detection of GRB 260316B (duplicate submission)
  20. Konus-Wind detection of GRB 260316B
  21. GRB 260321A: SVOM/ECLAIRs refined analysis
  22. EP260329b: J-band upper limits with WINTER
  23. EP260329a: J-band upper limit with WINTER
  24. GRB 260330A: Glowbug gamma-ray detection
  25. GRB 260310A: VLA Multi-frequency Radio Observations
  26. Fermi GBM Sub-Threshold Detection of GRB 260330B
  27. GRB 260330B: LCO optical upper limits
  28. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  29. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  30. EP260329a: COLIBRÍ optical upper limit
  31. EP260329a: EP-FXT follow up observation
  32. EP260329a: NOT optical counterpart candidate
  33. EP260329b: Global MASTER-Net observations report
  34. GRB 260327A: Insight-HXMT/HE detection
  35. EP260329b: Optical follow-up with Kinder observations
  36. EP 260329b: COLIBRÍ optical observations
  37. EP260329a: Optical upper limit with Kinder observations
  38. EP260329b: LCO optical observations of the counterpart
  39. GRB 260326A: Insight-HXMT/HE detection
  40. EP260329b: Einstein Probe detection of an X-ray transient
  41. EP-WXT trigger 01709259209: TRT optical counterpart detection
  42. GRID detection of GRB 260326A
  43. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  44. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  45. EP260327a: SVOM/VT optical upper limits
  46. SMA Detection of GRB 260310A / AT 2026fgk
  47. GRB 260307B: ATCA Radio Upper Limits
  48. EP260327a: WINTER J-band upper limit
  49. EP260327a: COLIBRÍ optical upper limits
  50. EP260327a: Gemini-North optical upper limits
  51. EP260324a: GROWTH-India Telescope optical observation
  52. EP260327a: Global MASTER-Net observations report
  53. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  54. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  55. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  56. IPN triangulation of GRB 260320A
  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. EP260321a: Upper limits from a neutrino search with IceCube
  61. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  62. IPN triangulation of GRB 260316B
  63. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  64. GRID detection of GRB 260320A
  65. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  66. EP260321a: Gemini-South confirmation of a supernova
  67. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  68. GRB 260310A: LBT optical observations
  69. EP260321A: Mondy optical observations
  70. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  71. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  72. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  73. Fermi GRB 260323A: Global MASTER-Net observations report
  74. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  75. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  76. GRB 260320A: Glowbug gamma-ray detection
  77. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  78. EP260321a: COLIBRÍ further optical observations and brightening
  79. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  80. EP260214b: ATCA 6 GHz detection
  81. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  82. GRB 260321A: EP-FXT follow-up observation
  83. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  84. EP260321a: GOTO detection of blue variable source
  85. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  86. EP260321a: further Kinder optical observations
  87. GRB 260321A: SVOM/VT optical upper limits
  88. EP260321a: Las Cumbres upper limit
  89. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 260320A: Insight-HXMT/HE detection
  91. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  92. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  93. EP260321a: SVOM/VT optical upper limit
  94. GRB 260310A: continued optical observation at Mondy
  95. Fermi GBM Sub-Threshold Detection of GRB 260321A
  96. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  97. EP260321a: Global MASTER-Net observations report
  98. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  99. GRB 260318A: Glowbug gamma-ray detection
  100. GRB 260310A / AT 2026fgk: KAIT optical observations

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