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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"

27028 results found.

  1. GRB 260327A: Insight-HXMT/HE detection
  2. EP260329b: Optical follow-up with Kinder observations
  3. EP 260329b: COLIBRÍ optical observations
  4. EP260329a: Optical upper limit with Kinder observations
  5. EP260329b: LCO optical observations of the counterpart
  6. GRB 260326A: Insight-HXMT/HE detection
  7. EP260329b: Einstein Probe detection of an X-ray transient
  8. EP260329a: Einstein Probe detection of an X-ray transient
  9. EP-WXT trigger 01709259209: TRT optical counterpart detection
  10. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  11. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  12. EP260327a: SVOM/VT optical upper limits
  13. EP260327a: WINTER J-band upper limit
  14. EP260327a: COLIBRÍ optical upper limits
  15. EP260327a: Gemini-North optical upper limits
  16. EP260324a: GROWTH-India Telescope optical observation
  17. EP260327a: Global MASTER-Net observations report
  18. EP260327a: Einstein Probe detection of an X-ray transient
  19. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  20. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  21. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  22. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  23. GRB 260326A: Fermi GBM Detection
  24. EP260321a: JinShan near-infrared observations
  25. EP260321a: Upper limits from a neutrino search with IceCube
  26. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  27. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  28. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  29. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  30. Fermi GRB 260323A: Global MASTER-Net observations report
  31. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  32. GRB 260320A: Glowbug gamma-ray detection
  33. EP260321a: COLIBRÍ further optical observations and brightening
  34. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  35. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  36. GRB 260321A: EP-FXT follow-up observation
  37. EP260321a: GOTO detection of blue variable source
  38. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  39. EP260321a: further Kinder optical observations
  40. GRB 260321A: SVOM/VT optical upper limits
  41. EP260321a: Las Cumbres upper limit
  42. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  44. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  45. EP260321a: SVOM/VT optical upper limit
  46. Fermi GBM Sub-Threshold Detection of GRB 260321A
  47. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  48. EP260321a: Global MASTER-Net observations report
  49. EP260321a: Einstein Probe detection of an X-ray transient
  50. GRB 260318A: Glowbug gamma-ray detection
  51. GRB 260310A / AT 2026fgk: KAIT optical observations
  52. GRB 260320A: NuSTAR detection of prompt emission
  53. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  54. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  55. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  56. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  57. GRB 260318A: SVOM/GRM observation
  58. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  59. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  60. Fermi GRB 260318A: Global MASTER-Net observations report
  61. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  62. GRB 260310A / AT 2026fgk: radio detection with the VLA
  63. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  64. GRB 260310A / AT2026fgk: LCO optical observations
  65. GRB 260316B: SVOM/GRM observation
  66. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  67. EP260316a: COLIBRÍ faint optical counterpart candidate
  68. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  69. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  70. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  71. EP260316a: Xinglong optical upper limit
  72. EP260316a: optical upper limit with Kinder observations
  73. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  74. GRB 260314A: Glowbug gamma-ray detection
  75. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  76. IceCube-260315A: COLIBRÍ optical observations
  77. EP260314a: Xinglong optical upper limit
  78. EP260314a: optical upper limit with Kinder observations
  79. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  80. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  81. GRB 260310A / AT 2026fgk: iTelescope optical observations
  82. EP260314a: COLIBRÍ optical upper limit
  83. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP260314a: Global MASTER-Net observations report
  85. EP260314a: SVOM/VT optical candidate
  86. Fermi trigger No 795185313: Global MASTER-Net observations report
  87. IceCube Alert 260315A: Global MASTER-Net observations report
  88. EP260314a: Einstein Probe detection of an X-ray transient
  89. GRB 260310A / AT2026fgk: SAO RAS optical observations
  90. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  91. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  92. Fermi GRB 260314A: Global MASTER-Net observations report
  93. Fermi GRB 260313A: Global MASTER-Net observations report
  94. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  95. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  96. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  97. GRB 260312B: AstroSat CZTI detection
  98. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  99. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  100. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations

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