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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"

24359 results found.

  1. GRB 260401A: Fermi GBM Observation
  2. GRB 260401A: NuSTAR detection of prompt emission
  3. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  5. GRB 260401A: Fermi GBM Final Real-time Localization
  6. EP260321a :Xinglong optical observations
  7. EP260327a: Xinglong optical upper limit
  8. EP260329b: GOTO detection of optical counterpart
  9. GRB 260330B: SVOM/VT optical upper limits
  10. Konus-Wind detection of GRB 260320A
  11. Konus-Wind detection of GRB 260316B
  12. GRB 260321A: SVOM/ECLAIRs refined analysis
  13. Fermi GBM Sub-Threshold Detection of GRB 260330B
  14. GRB 260330B: LCO optical upper limits
  15. GRB 260330B: SVOM detection of a burst
  16. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  17. EP260329a: EP-FXT follow up observation
  18. EP260329a: NOT optical counterpart candidate
  19. GRB 260330A: Fermi GBM Final Real-time Localization
  20. EP260329b: Global MASTER-Net observations report
  21. Fermi trigger No 796485221: Global MASTER-Net observations report
  22. EP260329a: Optical upper limit with Kinder observations
  23. EP-WXT trigger 01709259209: TRT optical counterpart detection
  24. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  25. EP260327a: SVOM/VT optical upper limits
  26. GRB 260307B: ATCA Radio Upper Limits
  27. EP260327a: WINTER J-band upper limit
  28. EP260327a: Gemini-North optical upper limits
  29. EP260324a: GROWTH-India Telescope optical observation
  30. EP260327a: Global MASTER-Net observations report
  31. The EP-WXT trigger 01709259173 is likely a flaring star
  32. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  33. IPN triangulation of GRB 260320A
  34. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  35. GRB 260326A: Fermi GBM Detection
  36. EP260321a: JinShan near-infrared observations
  37. GRB 260325A: Fermi GBM Final Localization
  38. GRB 260326A: Fermi GBM Final Real-time Localization
  39. EP260321a: Upper limits from a neutrino search with IceCube
  40. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  41. IPN triangulation of GRB 260316B
  42. EP260321a: Gemini-South confirmation of a supernova
  43. GRB 260310A: LBT optical observations
  44. EP260321A: Mondy optical observations
  45. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  46. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  47. The EP-WXT trigger 01709259112 is likely a flaring star
  48. Fermi GRB 260323A: Global MASTER-Net observations report
  49. GRB 260323A: Fermi GBM Final Real-time Localization
  50. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  51. GRB 260322A: Fermi GBM Final Localization
  52. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  53. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  54. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  55. GRB 260321A: EP-FXT follow-up observation
  56. The EP-WXT trigger 01709259045 is likely a flaring star
  57. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  58. GRB 260321A: SVOM/VT optical upper limits
  59. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  60. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  61. EP260321a: SVOM/VT optical upper limit
  62. Fermi GBM Sub-Threshold Detection of GRB 260321A
  63. GRB 260321A: SVOM detection of a burst
  64. EP260321a: Global MASTER-Net observations report
  65. GRB 260320A: NuSTAR detection of prompt emission
  66. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  67. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  68. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  69. GRB 260318A: SVOM/GRM observation
  70. The EP-WXT trigger 01709258989 is likely a flaring star
  71. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  72. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  73. Fermi GRB 260318A: Global MASTER-Net observations report
  74. GRB 260318A: Fermi GBM Final Real-time Localization
  75. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  76. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  77. GRB 260310A / AT2026fgk: LCO optical observations
  78. GRB 260317A: Fermi GBM Final Localization
  79. GRB 260316B: SVOM/GRM observation
  80. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  81. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  82. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  83. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  84. EP260316a: Xinglong optical upper limit
  85. GRB 260316B: Fermi GBM Final Real-time Localization
  86. EP260316a: optical upper limit with Kinder observations
  87. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  88. GRB 260314A: Glowbug gamma-ray detection
  89. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  90. EP260314a: Xinglong optical upper limit
  91. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  92. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  93. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  94. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  95. EP260314a: Global MASTER-Net observations report
  96. EP260314a: SVOM/VT optical candidate
  97. Fermi trigger No 795185313: Global MASTER-Net observations report
  98. IceCube Alert 260315A: Global MASTER-Net observations report
  99. GRB 260310A / AT2026fgk: TNG NIR detection
  100. Fermi GRB 260314A: Global MASTER-Net observations report

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