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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"

23652 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
  5. GRB 260321A: SVOM/ECLAIRs refined analysis
  6. Fermi GBM Sub-Threshold Detection of GRB 260330B
  7. GRB 260330B: LCO optical upper limits
  8. GRB 260330B: SVOM detection of a burst
  9. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  10. EP260329a: EP-FXT follow up observation
  11. EP260329a: NOT optical counterpart candidate
  12. GRB 260330A: Fermi GBM Final Real-time Localization
  13. EP260329b: Global MASTER-Net observations report
  14. Fermi trigger No 796485221: Global MASTER-Net observations report
  15. EP260329a: Optical upper limit with Kinder observations
  16. EP-WXT trigger 01709259209: TRT optical counterpart detection
  17. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260327a: SVOM/VT optical upper limits
  19. GRB 260307B: ATCA Radio Upper Limits
  20. EP260327a: WINTER J-band upper limit
  21. EP260327a: Gemini-North optical upper limits
  22. EP260324a: GROWTH-India Telescope optical observation
  23. EP260327a: Global MASTER-Net observations report
  24. The EP-WXT trigger 01709259173 is likely a flaring star
  25. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  26. IPN triangulation of GRB 260320A
  27. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  28. GRB 260326A: Fermi GBM Detection
  29. EP260321a: JinShan near-infrared observations
  30. GRB 260325A: Fermi GBM Final Localization
  31. GRB 260326A: Fermi GBM Final Real-time Localization
  32. EP260321a: Upper limits from a neutrino search with IceCube
  33. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  34. IPN triangulation of GRB 260316B
  35. EP260321a: Gemini-South confirmation of a supernova
  36. GRB 260310A: LBT optical observations
  37. EP260321A: Mondy optical observations
  38. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  39. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  40. The EP-WXT trigger 01709259112 is likely a flaring star
  41. Fermi GRB 260323A: Global MASTER-Net observations report
  42. GRB 260323A: Fermi GBM Final Real-time Localization
  43. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  44. GRB 260322A: Fermi GBM Final Localization
  45. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  46. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  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: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  51. GRB 260321A: SVOM/VT optical upper limits
  52. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  53. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  54. EP260321a: SVOM/VT optical upper limit
  55. Fermi GBM Sub-Threshold Detection of GRB 260321A
  56. GRB 260321A: SVOM detection of a burst
  57. EP260321a: Global MASTER-Net observations report
  58. GRB 260320A: NuSTAR detection of prompt emission
  59. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  60. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  61. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  62. GRB 260318A: SVOM/GRM observation
  63. The EP-WXT trigger 01709258989 is likely a flaring star
  64. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  65. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  66. Fermi GRB 260318A: Global MASTER-Net observations report
  67. GRB 260318A: Fermi GBM Final Real-time Localization
  68. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  69. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  70. GRB 260310A / AT2026fgk: LCO optical observations
  71. GRB 260317A: Fermi GBM Final Localization
  72. GRB 260316B: SVOM/GRM observation
  73. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  74. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  75. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  76. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  77. EP260316a: Xinglong optical upper limit
  78. GRB 260316B: Fermi GBM Final Real-time Localization
  79. EP260316a: optical upper limit with Kinder observations
  80. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  81. GRB 260314A: Glowbug gamma-ray detection
  82. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  83. EP260314a: Xinglong optical upper limit
  84. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  85. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  86. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  87. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  88. EP260314a: Global MASTER-Net observations report
  89. EP260314a: SVOM/VT optical candidate
  90. Fermi trigger No 795185313: Global MASTER-Net observations report
  91. IceCube Alert 260315A: Global MASTER-Net observations report
  92. GRB 260310A / AT2026fgk: TNG NIR detection
  93. Fermi GRB 260314A: Global MASTER-Net observations report
  94. Fermi GRB 260313A: Global MASTER-Net observations report
  95. GRB 260314A: Fermi GBM Final Real-time Localization
  96. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  97. GRB 260313A: A Correction to the Fermi GBM Final Localization
  98. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  99. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  100. GRB 260313A: Fermi GBM Final Real-time Localization

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