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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"

32685 results found.

  1. GRB 260330B: SVOM/VT optical upper limits
  2. Konus-Wind detection of GRB 260320A
  3. Konus-Wind detection of GRB 260316B (duplicate submission)
  4. Konus-Wind detection of GRB 260316B
  5. GRB 260321A: SVOM/ECLAIRs refined analysis
  6. EP260329b: J-band upper limits with WINTER
  7. EP260329a: J-band upper limit with WINTER
  8. GRB 260330A: Glowbug gamma-ray detection
  9. GRB 260310A: VLA Multi-frequency Radio Observations
  10. Fermi GBM Sub-Threshold Detection of GRB 260330B
  11. GRB 260330B: LCO optical upper limits
  12. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  13. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  14. EP260329a: COLIBRÍ optical upper limit
  15. EP260329a: EP-FXT follow up observation
  16. EP260329a: NOT optical counterpart candidate
  17. EP260329b: Global MASTER-Net observations report
  18. GRB 260327A: Insight-HXMT/HE detection
  19. EP260329b: Optical follow-up with Kinder observations
  20. EP 260329b: COLIBRÍ optical observations
  21. EP260329a: Optical upper limit with Kinder observations
  22. EP260329b: LCO optical observations of the counterpart
  23. GRB 260326A: Insight-HXMT/HE detection
  24. EP260329b: Einstein Probe detection of an X-ray transient
  25. EP-WXT trigger 01709259209: TRT optical counterpart detection
  26. GRID detection of GRB 260326A
  27. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  28. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  29. EP260327a: SVOM/VT optical upper limits
  30. SMA Detection of GRB 260310A / AT 2026fgk
  31. GRB 260307B: ATCA Radio Upper Limits
  32. EP260327a: WINTER J-band upper limit
  33. EP260327a: COLIBRÍ optical upper limits
  34. EP260327a: Gemini-North optical upper limits
  35. EP260324a: GROWTH-India Telescope optical observation
  36. EP260327a: Global MASTER-Net observations report
  37. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  38. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  39. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  40. IPN triangulation of GRB 260320A
  41. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  42. GRB 260326A: Fermi GBM Detection
  43. EP260321a: JinShan near-infrared observations
  44. EP260321a: Upper limits from a neutrino search with IceCube
  45. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  46. IPN triangulation of GRB 260316B
  47. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  48. GRID detection of GRB 260320A
  49. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  50. EP260321a: Gemini-South confirmation of a supernova
  51. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  52. GRB 260310A: LBT optical observations
  53. EP260321A: Mondy optical observations
  54. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  55. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  56. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  57. Fermi GRB 260323A: Global MASTER-Net observations report
  58. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  59. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  60. GRB 260320A: Glowbug gamma-ray detection
  61. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  62. EP260321a: COLIBRÍ further optical observations and brightening
  63. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  64. EP260214b: ATCA 6 GHz detection
  65. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  66. GRB 260321A: EP-FXT follow-up observation
  67. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  68. EP260321a: GOTO detection of blue variable source
  69. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  70. EP260321a: further Kinder optical observations
  71. GRB 260321A: SVOM/VT optical upper limits
  72. EP260321a: Las Cumbres upper limit
  73. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. GRB 260320A: Insight-HXMT/HE detection
  75. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  76. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  77. EP260321a: SVOM/VT optical upper limit
  78. GRB 260310A: continued optical observation at Mondy
  79. Fermi GBM Sub-Threshold Detection of GRB 260321A
  80. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  81. EP260321a: Global MASTER-Net observations report
  82. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  83. GRB 260318A: Glowbug gamma-ray detection
  84. GRB 260310A / AT 2026fgk: KAIT optical observations
  85. GRB 260320A: NuSTAR detection of prompt emission
  86. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  87. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  88. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  89. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  90. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  91. GRB 260310A/AT2026fgk: LBT near-infrared observations
  92. NOEMA Detection of GRB 260310A / AT 2026fgk
  93. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  94. GRB 260318A: SVOM/GRM observation
  95. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  96. GRB 260318A: GECAM-B observation
  97. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  98. Fermi GRB 260318A: Global MASTER-Net observations report
  99. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  100. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB

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