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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"

27320 results found.

  1. EP260329a: Einstein Probe detection of an X-ray transient
  2. EP-WXT trigger 01709259209: TRT optical counterpart detection
  3. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  4. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  5. EP260327a: SVOM/VT optical upper limits
  6. EP260327a: WINTER J-band upper limit
  7. EP260327a: COLIBRÍ optical upper limits
  8. EP260327a: Gemini-North optical upper limits
  9. EP260324a: GROWTH-India Telescope optical observation
  10. EP260327a: Global MASTER-Net observations report
  11. EP260327a: Einstein Probe detection of an X-ray transient
  12. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  13. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  14. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  15. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  16. GRB 260326A: Fermi GBM Detection
  17. EP260321a: JinShan near-infrared observations
  18. EP260321a: Upper limits from a neutrino search with IceCube
  19. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  20. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  21. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  22. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  23. Fermi GRB 260323A: Global MASTER-Net observations report
  24. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  25. GRB 260320A: Glowbug gamma-ray detection
  26. EP260321a: COLIBRÍ further optical observations and brightening
  27. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  28. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  29. GRB 260321A: EP-FXT follow-up observation
  30. EP260321a: GOTO detection of blue variable source
  31. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  32. EP260321a: further Kinder optical observations
  33. GRB 260321A: SVOM/VT optical upper limits
  34. EP260321a: Las Cumbres upper limit
  35. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  36. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  37. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  38. EP260321a: SVOM/VT optical upper limit
  39. Fermi GBM Sub-Threshold Detection of GRB 260321A
  40. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  41. EP260321a: Global MASTER-Net observations report
  42. EP260321a: Einstein Probe detection of an X-ray transient
  43. GRB 260318A: Glowbug gamma-ray detection
  44. GRB 260310A / AT 2026fgk: KAIT optical observations
  45. GRB 260320A: NuSTAR detection of prompt emission
  46. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  47. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  48. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  49. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  50. GRB 260318A: SVOM/GRM observation
  51. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  52. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  53. Fermi GRB 260318A: Global MASTER-Net observations report
  54. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  55. GRB 260310A / AT 2026fgk: radio detection with the VLA
  56. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  57. GRB 260310A / AT2026fgk: LCO optical observations
  58. GRB 260316B: SVOM/GRM observation
  59. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  60. EP260316a: COLIBRÍ faint optical counterpart candidate
  61. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  62. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  63. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  64. EP260316a: Xinglong optical upper limit
  65. EP260316a: optical upper limit with Kinder observations
  66. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  67. GRB 260314A: Glowbug gamma-ray detection
  68. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  69. IceCube-260315A: COLIBRÍ optical observations
  70. EP260314a: Xinglong optical upper limit
  71. EP260314a: optical upper limit with Kinder observations
  72. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  73. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  74. GRB 260310A / AT 2026fgk: iTelescope optical observations
  75. EP260314a: COLIBRÍ optical upper limit
  76. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  77. EP260314a: Global MASTER-Net observations report
  78. EP260314a: SVOM/VT optical candidate
  79. Fermi trigger No 795185313: Global MASTER-Net observations report
  80. IceCube Alert 260315A: Global MASTER-Net observations report
  81. EP260314a: Einstein Probe detection of an X-ray transient
  82. GRB 260310A / AT2026fgk: SAO RAS optical observations
  83. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  84. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  85. Fermi GRB 260314A: Global MASTER-Net observations report
  86. Fermi GRB 260313A: Global MASTER-Net observations report
  87. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  88. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  89. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  90. GRB 260312B: AstroSat CZTI detection
  91. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  92. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  93. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  94. GRB 260312B: Glowbug gamma-ray detection
  95. GRB 260310A: Fermi GBM Observation
  96. GRB 260310A: potential optical counterpart
  97. Fermi GRB 260312B: Global MASTER-Net observations report
  98. Fermi GRB 260311B: Global MASTER-Net observations report
  99. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  100. GRB 260131A/B: radio detection with the VLA

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