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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"

24162 results found.

  1. GRB 260402A: MASTER optical observations
  2. GRB 260402A: SVOM detection of a burst
  3. Fermi GRB 260401A: Global MASTER-Net observations report
  4. GRB 260401A: Fermi GBM Observation
  5. GRB 260401A: NuSTAR detection of prompt emission
  6. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  8. GRB 260401A: Fermi GBM Final Real-time Localization
  9. EP260321a :Xinglong optical observations
  10. EP260327a: Xinglong optical upper limit
  11. EP260329b: GOTO detection of optical counterpart
  12. GRB 260330B: SVOM/VT optical upper limits
  13. Konus-Wind detection of GRB 260320A
  14. Konus-Wind detection of GRB 260316B
  15. GRB 260321A: SVOM/ECLAIRs refined analysis
  16. Fermi GBM Sub-Threshold Detection of GRB 260330B
  17. GRB 260330B: LCO optical upper limits
  18. GRB 260330B: SVOM detection of a burst
  19. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  20. EP260329a: EP-FXT follow up observation
  21. EP260329a: NOT optical counterpart candidate
  22. GRB 260330A: Fermi GBM Final Real-time Localization
  23. EP260329b: Global MASTER-Net observations report
  24. Fermi trigger No 796485221: Global MASTER-Net observations report
  25. EP260329a: Optical upper limit with Kinder observations
  26. EP-WXT trigger 01709259209: TRT optical counterpart detection
  27. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  28. EP260327a: SVOM/VT optical upper limits
  29. GRB 260307B: ATCA Radio Upper Limits
  30. EP260327a: WINTER J-band upper limit
  31. EP260327a: Gemini-North optical upper limits
  32. EP260324a: GROWTH-India Telescope optical observation
  33. EP260327a: Global MASTER-Net observations report
  34. The EP-WXT trigger 01709259173 is likely a flaring star
  35. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  36. IPN triangulation of GRB 260320A
  37. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  38. GRB 260326A: Fermi GBM Detection
  39. EP260321a: JinShan near-infrared observations
  40. GRB 260325A: Fermi GBM Final Localization
  41. GRB 260326A: Fermi GBM Final Real-time Localization
  42. EP260321a: Upper limits from a neutrino search with IceCube
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  44. IPN triangulation of GRB 260316B
  45. EP260321a: Gemini-South confirmation of a supernova
  46. GRB 260310A: LBT optical observations
  47. EP260321A: Mondy optical observations
  48. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  49. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  50. The EP-WXT trigger 01709259112 is likely a flaring star
  51. Fermi GRB 260323A: Global MASTER-Net observations report
  52. GRB 260323A: Fermi GBM Final Real-time Localization
  53. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  54. GRB 260322A: Fermi GBM Final Localization
  55. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  56. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  57. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  58. GRB 260321A: EP-FXT follow-up observation
  59. The EP-WXT trigger 01709259045 is likely a flaring star
  60. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  61. GRB 260321A: SVOM/VT optical upper limits
  62. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  63. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  64. EP260321a: SVOM/VT optical upper limit
  65. Fermi GBM Sub-Threshold Detection of GRB 260321A
  66. GRB 260321A: SVOM detection of a burst
  67. EP260321a: Global MASTER-Net observations report
  68. GRB 260320A: NuSTAR detection of prompt emission
  69. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  70. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  71. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  72. GRB 260318A: SVOM/GRM observation
  73. The EP-WXT trigger 01709258989 is likely a flaring star
  74. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  75. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  76. Fermi GRB 260318A: Global MASTER-Net observations report
  77. GRB 260318A: Fermi GBM Final Real-time Localization
  78. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  79. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  80. GRB 260310A / AT2026fgk: LCO optical observations
  81. GRB 260317A: Fermi GBM Final Localization
  82. GRB 260316B: SVOM/GRM observation
  83. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  84. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  85. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  86. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  87. EP260316a: Xinglong optical upper limit
  88. GRB 260316B: Fermi GBM Final Real-time Localization
  89. EP260316a: optical upper limit with Kinder observations
  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. EP260314a: Xinglong optical upper limit
  94. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  95. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  96. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  97. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP260314a: Global MASTER-Net observations report
  99. EP260314a: SVOM/VT optical candidate
  100. Fermi trigger No 795185313: Global MASTER-Net observations report

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