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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"

32686 results found.

  1. EP260329b: GOTO detection of optical counterpart
  2. GRB 260330B: SVOM/VT optical upper limits
  3. Konus-Wind detection of GRB 260320A
  4. Konus-Wind detection of GRB 260316B (duplicate submission)
  5. Konus-Wind detection of GRB 260316B
  6. GRB 260321A: SVOM/ECLAIRs refined analysis
  7. EP260329b: J-band upper limits with WINTER
  8. EP260329a: J-band upper limit with WINTER
  9. GRB 260330A: Glowbug gamma-ray detection
  10. GRB 260310A: VLA Multi-frequency Radio Observations
  11. Fermi GBM Sub-Threshold Detection of GRB 260330B
  12. GRB 260330B: LCO optical upper limits
  13. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  14. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  15. EP260329a: COLIBRÍ optical upper limit
  16. EP260329a: EP-FXT follow up observation
  17. EP260329a: NOT optical counterpart candidate
  18. EP260329b: Global MASTER-Net observations report
  19. GRB 260327A: Insight-HXMT/HE detection
  20. EP260329b: Optical follow-up with Kinder observations
  21. EP 260329b: COLIBRÍ optical observations
  22. EP260329a: Optical upper limit with Kinder observations
  23. EP260329b: LCO optical observations of the counterpart
  24. GRB 260326A: Insight-HXMT/HE detection
  25. EP260329b: Einstein Probe detection of an X-ray transient
  26. EP-WXT trigger 01709259209: TRT optical counterpart detection
  27. GRID detection of GRB 260326A
  28. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  29. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. EP260327a: SVOM/VT optical upper limits
  31. SMA Detection of GRB 260310A / AT 2026fgk
  32. GRB 260307B: ATCA Radio Upper Limits
  33. EP260327a: WINTER J-band upper limit
  34. EP260327a: COLIBRÍ optical upper limits
  35. EP260327a: Gemini-North optical upper limits
  36. EP260324a: GROWTH-India Telescope optical observation
  37. EP260327a: Global MASTER-Net observations report
  38. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  39. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  40. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  41. IPN triangulation of GRB 260320A
  42. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  43. GRB 260326A: Fermi GBM Detection
  44. EP260321a: JinShan near-infrared observations
  45. EP260321a: Upper limits from a neutrino search with IceCube
  46. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  47. IPN triangulation of GRB 260316B
  48. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  49. GRID detection of GRB 260320A
  50. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  51. EP260321a: Gemini-South confirmation of a supernova
  52. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  53. GRB 260310A: LBT optical observations
  54. EP260321A: Mondy optical observations
  55. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  56. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  57. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  58. Fermi GRB 260323A: Global MASTER-Net observations report
  59. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  60. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  61. GRB 260320A: Glowbug gamma-ray detection
  62. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  63. EP260321a: COLIBRÍ further optical observations and brightening
  64. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  65. EP260214b: ATCA 6 GHz detection
  66. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  67. GRB 260321A: EP-FXT follow-up observation
  68. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  69. EP260321a: GOTO detection of blue variable source
  70. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  71. EP260321a: further Kinder optical observations
  72. GRB 260321A: SVOM/VT optical upper limits
  73. EP260321a: Las Cumbres upper limit
  74. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. GRB 260320A: Insight-HXMT/HE detection
  76. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  77. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  78. EP260321a: SVOM/VT optical upper limit
  79. GRB 260310A: continued optical observation at Mondy
  80. Fermi GBM Sub-Threshold Detection of GRB 260321A
  81. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  82. EP260321a: Global MASTER-Net observations report
  83. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  84. GRB 260318A: Glowbug gamma-ray detection
  85. GRB 260310A / AT 2026fgk: KAIT optical observations
  86. GRB 260320A: NuSTAR detection of prompt emission
  87. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  88. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  89. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  90. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  91. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  92. GRB 260310A/AT2026fgk: LBT near-infrared observations
  93. NOEMA Detection of GRB 260310A / AT 2026fgk
  94. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  95. GRB 260318A: SVOM/GRM observation
  96. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  97. GRB 260318A: GECAM-B observation
  98. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  99. Fermi GRB 260318A: Global MASTER-Net observations report
  100. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility

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