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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"

27392 results found.

  1. EP260321a: GOTO detection of blue variable source
  2. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  3. EP260321a: further Kinder optical observations
  4. GRB 260321A: SVOM/VT optical upper limits
  5. EP260321a: Las Cumbres upper limit
  6. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  8. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  9. EP260321a: SVOM/VT optical upper limit
  10. Fermi GBM Sub-Threshold Detection of GRB 260321A
  11. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  12. EP260321a: Global MASTER-Net observations report
  13. EP260321a: Einstein Probe detection of an X-ray transient
  14. GRB 260318A: Glowbug gamma-ray detection
  15. GRB 260310A / AT 2026fgk: KAIT optical observations
  16. GRB 260320A: NuSTAR detection of prompt emission
  17. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  18. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  19. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  20. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  21. GRB 260318A: SVOM/GRM observation
  22. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  23. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  24. Fermi GRB 260318A: Global MASTER-Net observations report
  25. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  26. GRB 260310A / AT 2026fgk: radio detection with the VLA
  27. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  28. GRB 260310A / AT2026fgk: LCO optical observations
  29. GRB 260316B: SVOM/GRM observation
  30. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  31. EP260316a: COLIBRÍ faint optical counterpart candidate
  32. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  33. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  34. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  35. EP260316a: Xinglong optical upper limit
  36. EP260316a: optical upper limit with Kinder observations
  37. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  38. GRB 260314A: Glowbug gamma-ray detection
  39. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  40. IceCube-260315A: COLIBRÍ optical observations
  41. EP260314a: Xinglong optical upper limit
  42. EP260314a: optical upper limit with Kinder observations
  43. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  44. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  45. GRB 260310A / AT 2026fgk: iTelescope optical observations
  46. EP260314a: COLIBRÍ optical upper limit
  47. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  48. EP260314a: Global MASTER-Net observations report
  49. EP260314a: SVOM/VT optical candidate
  50. Fermi trigger No 795185313: Global MASTER-Net observations report
  51. IceCube Alert 260315A: Global MASTER-Net observations report
  52. EP260314a: Einstein Probe detection of an X-ray transient
  53. GRB 260310A / AT2026fgk: SAO RAS optical observations
  54. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  55. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  56. Fermi GRB 260314A: Global MASTER-Net observations report
  57. Fermi GRB 260313A: Global MASTER-Net observations report
  58. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  59. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  60. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  61. GRB 260312B: AstroSat CZTI detection
  62. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  63. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  64. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  65. GRB 260312B: Glowbug gamma-ray detection
  66. GRB 260310A: Fermi GBM Observation
  67. GRB 260310A: potential optical counterpart
  68. Fermi GRB 260312B: Global MASTER-Net observations report
  69. Fermi GRB 260311B: Global MASTER-Net observations report
  70. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  71. GRB 260131A/B: radio detection with the VLA
  72. EP260302a: MeerKAT radio counterpart
  73. GRB 260308A: SVOM/GRM observation of a short GRB
  74. EP260306a: Mondy optical upper limit
  75. Fermi GRB 260310B: Global MASTER-Net observations report
  76. Fermi GRB 260310A: Global MASTER-Net observations report
  77. GRB 260208A: radio detection with the VLA
  78. GRB 260307A: Glowbug gamma-ray detection
  79. Fermi GBM Sub-Threshold Detection of GRB 260307B
  80. GRB 260307B: Mephisto optical upper limits
  81. GRB 260307B: possible NOT optical counterpart
  82. GRB 260307B: SVOM/VT upper limit with X band data analysis
  83. Fermi GRB 260307A: Global MASTER-Net observations report
  84. GRB260307B: GROWTH-India Telescope optical upper limit
  85. GRB 260307B: SVOM/VT optical candidate
  86. GRB 260307B: SVOM/C-GFT upper limit
  87. GRB 260307B: SVOM detection of a burst
  88. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 260207A: TESS Detection and Possible VLA Counterpart
  90. EP260302a: SVOM/VT optical observation
  91. EP260306a: Gemini-North redshift z = 4.773
  92. EP260306a: SVOM/VT optical observation
  93. EP260302a: Gemini-South redshift z = 1.535
  94. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  95. EP260306a: Einstein Probe detection of an X-ray transient
  96. EP260302a: Optical afterglow rebrightening
  97. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  98. GRB 260303A: 1.3m DFOT optical upper limit
  99. Fermi GRB 260305A: Global MASTER-Net observations report
  100. GRB 260303B: AstroSat CZTI detection

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