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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"

27359 results found.

  1. Fermi GRB 260401A: Global MASTER-Net observations report
  2. GRB 260401A: Fermi GBM Observation
  3. GRB 260401A: NuSTAR detection of prompt emission
  4. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260401A: MAXI/GSC detection
  6. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  7. GRB 260401A: Fermi GBM Final Real-time Localization
  8. EP260329b: Mondy and Assy-Turgen optical upper limits
  9. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  10. EP260321a :Xinglong optical observations
  11. EP260327a: Xinglong optical upper limit
  12. GRB 260330B: SVOM/VT optical upper limits
  13. Konus-Wind detection of GRB 260320A
  14. GRB 260321A: SVOM/ECLAIRs refined analysis
  15. EP260329b: J-band upper limits with WINTER
  16. EP260329a: J-band upper limit with WINTER
  17. GRB 260330A: Glowbug gamma-ray detection
  18. Fermi GBM Sub-Threshold Detection of GRB 260330B
  19. GRB 260330B: LCO optical upper limits
  20. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  21. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  22. EP260329a: COLIBRÍ optical upper limit
  23. EP260329a: EP-FXT follow up observation
  24. EP260329a: NOT optical counterpart candidate
  25. EP260329b: Global MASTER-Net observations report
  26. Fermi trigger No 796485221: Global MASTER-Net observations report
  27. GRB 260327A: Insight-HXMT/HE detection
  28. EP260329b: Optical follow-up with Kinder observations
  29. EP 260329b: COLIBRÍ optical observations
  30. EP260329a: Optical upper limit with Kinder observations
  31. EP260329b: LCO optical observations of the counterpart
  32. GRB 260326A: Insight-HXMT/HE detection
  33. EP260329b: Einstein Probe detection of an X-ray transient
  34. EP260329a: Einstein Probe detection of an X-ray transient
  35. EP-WXT trigger 01709259209: TRT optical counterpart detection
  36. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  37. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260327a: SVOM/VT optical upper limits
  39. EP260327a: WINTER J-band upper limit
  40. EP260327a: COLIBRÍ optical upper limits
  41. EP260327a: Gemini-North optical upper limits
  42. EP260324a: GROWTH-India Telescope optical observation
  43. EP260327a: Global MASTER-Net observations report
  44. EP260327a: Einstein Probe detection of an X-ray transient
  45. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  46. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  47. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  48. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  49. GRB 260326A: Fermi GBM Detection
  50. EP260321a: JinShan near-infrared observations
  51. EP260321a: Upper limits from a neutrino search with IceCube
  52. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  53. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  54. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  55. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  56. Fermi GRB 260323A: Global MASTER-Net observations report
  57. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  58. GRB 260320A: Glowbug gamma-ray detection
  59. EP260321a: COLIBRÍ further optical observations and brightening
  60. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  61. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  62. GRB 260321A: EP-FXT follow-up observation
  63. EP260321a: GOTO detection of blue variable source
  64. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  65. EP260321a: further Kinder optical observations
  66. GRB 260321A: SVOM/VT optical upper limits
  67. EP260321a: Las Cumbres upper limit
  68. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  70. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  71. EP260321a: SVOM/VT optical upper limit
  72. Fermi GBM Sub-Threshold Detection of GRB 260321A
  73. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  74. EP260321a: Global MASTER-Net observations report
  75. EP260321a: Einstein Probe detection of an X-ray transient
  76. GRB 260318A: Glowbug gamma-ray detection
  77. GRB 260310A / AT 2026fgk: KAIT optical observations
  78. GRB 260320A: NuSTAR detection of prompt emission
  79. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  80. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  81. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  82. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  83. GRB 260318A: SVOM/GRM observation
  84. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  85. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  86. Fermi GRB 260318A: Global MASTER-Net observations report
  87. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  88. GRB 260310A / AT 2026fgk: radio detection with the VLA
  89. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  90. GRB 260310A / AT2026fgk: LCO optical observations
  91. GRB 260316B: SVOM/GRM observation
  92. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  93. EP260316a: COLIBRÍ faint optical counterpart candidate
  94. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  95. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  96. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  97. EP260316a: Xinglong optical upper limit
  98. EP260316a: optical upper limit with Kinder observations
  99. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  100. GRB 260314A: Glowbug gamma-ray detection

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