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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"

5513 results found.

  1. GRB 260330B: SVOM detection of a burst
  2. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  3. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  4. EP260329a: COLIBRÍ optical upper limit
  5. EP260329a: EP-FXT follow up observation
  6. GRB 260330A: Fermi GBM Final Real-time Localization
  7. EP260329b: Global MASTER-Net observations report
  8. Fermi trigger No 796485221: Global MASTER-Net observations report
  9. GRB 260327A: Insight-HXMT/HE detection
  10. EP 260329b: COLIBRÍ optical observations
  11. EP260329a: Optical upper limit with Kinder observations
  12. EP260329b: LCO optical observations of the counterpart
  13. GRB 260326A: Insight-HXMT/HE detection
  14. EP260329b: Einstein Probe detection of an X-ray transient
  15. EP260329a: Einstein Probe detection of an X-ray transient
  16. EP-WXT trigger 01709259209: TRT optical counterpart detection
  17. GRID detection of GRB 260326A
  18. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  19. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  20. EP260327a: SVOM/VT optical upper limits
  21. EP260327a: WINTER J-band upper limit
  22. EP260327a: COLIBRÍ optical upper limits
  23. GRB 260327A: AstroSat CZTI detection of a long burst
  24. EP260327a: Gemini-North optical upper limits
  25. EP260324a: GROWTH-India Telescope optical observation
  26. EP260327a: Global MASTER-Net observations report
  27. EP260327a: Einstein Probe detection of an X-ray transient
  28. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  29. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  30. The EP-WXT trigger 01709259173 is likely a flaring star
  31. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  32. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  33. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  34. EP260321a: JinShan near-infrared observations
  35. EP260321a: Upper limits from a neutrino search with IceCube
  36. GRID detection of GRB 260320A
  37. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  38. GRB 260310A: LBT optical observations
  39. EP260321A: Mondy optical observations
  40. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  41. The EP-WXT trigger 01709259112 is likely a flaring star
  42. Fermi GRB 260323A: Global MASTER-Net observations report
  43. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  44. GRB 260320A: Glowbug gamma-ray detection
  45. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  46. EP260321a: COLIBRÍ further optical observations and brightening
  47. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  48. GRB 260321A: EP-FXT follow-up observation
  49. The EP-WXT trigger 01709259045 is likely a flaring star
  50. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  51. EP260321a: GOTO detection of blue variable source
  52. GRB 260321A: SVOM/VT optical upper limits
  53. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. GRB 260320A: Insight-HXMT/HE detection
  55. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  56. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  57. EP260321a: SVOM/VT optical upper limit
  58. GRB 260310A: continued optical observation at Mondy
  59. Fermi GBM Sub-Threshold Detection of GRB 260321A
  60. GRB 260321A: SVOM detection of a burst
  61. EP260321a: Global MASTER-Net observations report
  62. EP260321a: Einstein Probe detection of an X-ray transient
  63. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  64. GRB 260318A: Glowbug gamma-ray detection
  65. GRB 260320A: NuSTAR detection of prompt emission
  66. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  67. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  68. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  69. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  70. GRB 260310A/AT2026fgk: LBT near-infrared observations
  71. GRB 260318A: SVOM/GRM observation
  72. The EP-WXT trigger 01709258989 is likely a flaring star
  73. GRB 260318A: GECAM-B observation
  74. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  75. Fermi GRB 260318A: Global MASTER-Net observations report
  76. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  77. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  78. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  79. GRB 260310A / AT2026fgk: LCO optical observations
  80. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  81. GRB 260316B: GECAM-B observation
  82. GRB 260316B: SVOM/GRM observation
  83. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  84. EP260316a: COLIBRÍ faint optical counterpart candidate
  85. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  86. GRB 260316B: AstroSat CZTI detection
  87. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  88. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  89. EP260316a: Xinglong optical upper limit
  90. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  91. GRB 260314A: Glowbug gamma-ray detection
  92. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  93. IceCube-260315A: COLIBRÍ optical observations
  94. EP260314a: Xinglong optical upper limit
  95. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  96. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  97. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  98. GRB 260310A / AT 2026fgk: iTelescope optical observations
  99. EP260314a: COLIBRÍ optical upper limit
  100. GRID detection of GRB 260312B

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