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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"

28054 results found.

  1. GRB 260402A: SVOM detection of a burst
  2. Fermi GRB 260401A: Global MASTER-Net observations report
  3. GRB 260401A: Fermi GBM Observation
  4. GRB 260401A: NuSTAR detection of prompt emission
  5. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260401A: MAXI/GSC detection
  7. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  8. GRB 260401A: Fermi GBM Final Real-time Localization
  9. EP260329b: Mondy and Assy-Turgen optical upper limits
  10. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  11. EP260321a :Xinglong optical observations
  12. EP260327a: Xinglong optical upper limit
  13. GRB 260330B: SVOM/VT optical upper limits
  14. Konus-Wind detection of GRB 260320A
  15. GRB 260321A: SVOM/ECLAIRs refined analysis
  16. EP260329b: J-band upper limits with WINTER
  17. EP260329a: J-band upper limit with WINTER
  18. GRB 260330A: Glowbug gamma-ray detection
  19. Fermi GBM Sub-Threshold Detection of GRB 260330B
  20. GRB 260330B: LCO optical upper limits
  21. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  22. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  23. EP260329a: COLIBRÍ optical upper limit
  24. EP260329a: EP-FXT follow up observation
  25. EP260329a: NOT optical counterpart candidate
  26. EP260329b: Global MASTER-Net observations report
  27. Fermi trigger No 796485221: Global MASTER-Net observations report
  28. GRB 260327A: Insight-HXMT/HE detection
  29. EP260329b: Optical follow-up with Kinder observations
  30. EP 260329b: COLIBRÍ optical observations
  31. EP260329a: Optical upper limit with Kinder observations
  32. EP260329b: LCO optical observations of the counterpart
  33. GRB 260326A: Insight-HXMT/HE detection
  34. EP260329b: Einstein Probe detection of an X-ray transient
  35. EP260329a: Einstein Probe detection of an X-ray transient
  36. EP-WXT trigger 01709259209: TRT optical counterpart detection
  37. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  38. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. EP260327a: SVOM/VT optical upper limits
  40. EP260327a: WINTER J-band upper limit
  41. EP260327a: COLIBRÍ optical upper limits
  42. EP260327a: Gemini-North optical upper limits
  43. EP260324a: GROWTH-India Telescope optical observation
  44. EP260327a: Global MASTER-Net observations report
  45. EP260327a: Einstein Probe detection of an X-ray transient
  46. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  47. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  48. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  49. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  50. GRB 260326A: Fermi GBM Detection
  51. EP260321a: JinShan near-infrared observations
  52. EP260321a: Upper limits from a neutrino search with IceCube
  53. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  54. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  55. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  56. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  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 260320A: Glowbug gamma-ray detection
  60. EP260321a: COLIBRÍ further optical observations and brightening
  61. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  62. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  63. GRB 260321A: EP-FXT follow-up observation
  64. EP260321a: GOTO detection of blue variable source
  65. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  66. EP260321a: further Kinder optical observations
  67. GRB 260321A: SVOM/VT optical upper limits
  68. EP260321a: Las Cumbres upper limit
  69. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  71. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  72. EP260321a: SVOM/VT optical upper limit
  73. Fermi GBM Sub-Threshold Detection of GRB 260321A
  74. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  75. EP260321a: Global MASTER-Net observations report
  76. EP260321a: Einstein Probe detection of an X-ray transient
  77. GRB 260318A: Glowbug gamma-ray detection
  78. GRB 260310A / AT 2026fgk: KAIT optical observations
  79. GRB 260320A: NuSTAR detection of prompt emission
  80. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  81. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  82. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  83. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  84. GRB 260318A: SVOM/GRM observation
  85. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  86. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  87. Fermi GRB 260318A: Global MASTER-Net observations report
  88. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  89. GRB 260310A / AT 2026fgk: radio detection with the VLA
  90. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  91. GRB 260310A / AT2026fgk: LCO optical observations
  92. GRB 260316B: SVOM/GRM observation
  93. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  94. EP260316a: COLIBRÍ faint optical counterpart candidate
  95. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  96. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  97. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  98. EP260316a: Xinglong optical upper limit
  99. EP260316a: optical upper limit with Kinder observations
  100. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection

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