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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28254 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: MAXI/GSC detection
  5. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  6. GRB 260401A: Fermi GBM Final Real-time Localization
  7. EP260329b: Mondy and Assy-Turgen optical upper limits
  8. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  9. EP260321a :Xinglong optical observations
  10. EP260327a: Xinglong optical upper limit
  11. GRB 260330B: SVOM/VT optical upper limits
  12. Konus-Wind detection of GRB 260320A
  13. GRB 260321A: SVOM/ECLAIRs refined analysis
  14. EP260329b: J-band upper limits with WINTER
  15. EP260329a: J-band upper limit with WINTER
  16. GRB 260330A: Glowbug gamma-ray detection
  17. Fermi GBM Sub-Threshold Detection of GRB 260330B
  18. GRB 260330B: LCO optical upper limits
  19. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  20. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  21. EP260329a: COLIBRÍ optical upper limit
  22. EP260329a: EP-FXT follow up observation
  23. EP260329a: NOT optical counterpart candidate
  24. EP260329b: Global MASTER-Net observations report
  25. Fermi trigger No 796485221: Global MASTER-Net observations report
  26. GRB 260327A: Insight-HXMT/HE detection
  27. EP260329b: Optical follow-up with Kinder observations
  28. EP 260329b: COLIBRÍ optical observations
  29. EP260329a: Optical upper limit with Kinder observations
  30. EP260329b: LCO optical observations of the counterpart
  31. GRB 260326A: Insight-HXMT/HE detection
  32. EP260329b: Einstein Probe detection of an X-ray transient
  33. EP260329a: Einstein Probe detection of an X-ray transient
  34. EP-WXT trigger 01709259209: TRT optical counterpart detection
  35. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  36. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  37. EP260327a: SVOM/VT optical upper limits
  38. EP260327a: WINTER J-band upper limit
  39. EP260327a: COLIBRÍ optical upper limits
  40. EP260327a: Gemini-North optical upper limits
  41. EP260324a: GROWTH-India Telescope optical observation
  42. EP260327a: Global MASTER-Net observations report
  43. EP260327a: Einstein Probe detection of an X-ray transient
  44. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  45. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  46. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  47. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  48. GRB 260326A: Fermi GBM Detection
  49. EP260321a: JinShan near-infrared observations
  50. EP260321a: Upper limits from a neutrino search with IceCube
  51. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  52. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  53. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  54. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  55. Fermi GRB 260323A: Global MASTER-Net observations report
  56. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  57. GRB 260320A: Glowbug gamma-ray detection
  58. EP260321a: COLIBRÍ further optical observations and brightening
  59. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  60. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  61. GRB 260321A: EP-FXT follow-up observation
  62. EP260321a: GOTO detection of blue variable source
  63. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  64. EP260321a: further Kinder optical observations
  65. GRB 260321A: SVOM/VT optical upper limits
  66. EP260321a: Las Cumbres upper limit
  67. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  69. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  70. EP260321a: SVOM/VT optical upper limit
  71. Fermi GBM Sub-Threshold Detection of GRB 260321A
  72. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  73. EP260321a: Global MASTER-Net observations report
  74. EP260321a: Einstein Probe detection of an X-ray transient
  75. GRB 260318A: Glowbug gamma-ray detection
  76. GRB 260310A / AT 2026fgk: KAIT optical observations
  77. GRB 260320A: NuSTAR detection of prompt emission
  78. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  79. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  80. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  81. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  82. GRB 260318A: SVOM/GRM observation
  83. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  84. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  85. Fermi GRB 260318A: Global MASTER-Net observations report
  86. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  87. GRB 260310A / AT 2026fgk: radio detection with the VLA
  88. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  89. GRB 260310A / AT2026fgk: LCO optical observations
  90. GRB 260316B: SVOM/GRM observation
  91. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  92. EP260316a: COLIBRÍ faint optical counterpart candidate
  93. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  94. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  95. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  96. EP260316a: Xinglong optical upper limit
  97. EP260316a: optical upper limit with Kinder observations
  98. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  99. GRB 260314A: Glowbug gamma-ray detection
  100. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up

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