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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"

28081 results found.

  1. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  2. EP260321a: Global MASTER-Net observations report
  3. EP260321a: Einstein Probe detection of an X-ray transient
  4. GRB 260318A: Glowbug gamma-ray detection
  5. GRB 260310A / AT 2026fgk: KAIT optical observations
  6. GRB 260320A: NuSTAR detection of prompt emission
  7. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  8. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  9. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  10. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  11. GRB 260318A: SVOM/GRM observation
  12. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  13. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  14. Fermi GRB 260318A: Global MASTER-Net observations report
  15. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  16. GRB 260310A / AT 2026fgk: radio detection with the VLA
  17. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  18. GRB 260310A / AT2026fgk: LCO optical observations
  19. GRB 260316B: SVOM/GRM observation
  20. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  21. EP260316a: COLIBRÍ faint optical counterpart candidate
  22. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  23. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  24. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  25. EP260316a: Xinglong optical upper limit
  26. EP260316a: optical upper limit with Kinder observations
  27. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  28. GRB 260314A: Glowbug gamma-ray detection
  29. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  30. IceCube-260315A: COLIBRÍ optical observations
  31. EP260314a: Xinglong optical upper limit
  32. EP260314a: optical upper limit with Kinder observations
  33. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  34. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  35. GRB 260310A / AT 2026fgk: iTelescope optical observations
  36. EP260314a: COLIBRÍ optical upper limit
  37. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  38. EP260314a: Global MASTER-Net observations report
  39. EP260314a: SVOM/VT optical candidate
  40. Fermi trigger No 795185313: Global MASTER-Net observations report
  41. IceCube Alert 260315A: Global MASTER-Net observations report
  42. EP260314a: Einstein Probe detection of an X-ray transient
  43. GRB 260310A / AT2026fgk: SAO RAS optical observations
  44. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  45. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  46. Fermi GRB 260314A: Global MASTER-Net observations report
  47. Fermi GRB 260313A: Global MASTER-Net observations report
  48. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  49. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  50. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  51. GRB 260312B: AstroSat CZTI detection
  52. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  53. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  54. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  55. GRB 260312B: Glowbug gamma-ray detection
  56. GRB 260310A: Fermi GBM Observation
  57. GRB 260310A: potential optical counterpart
  58. Fermi GRB 260312B: Global MASTER-Net observations report
  59. Fermi GRB 260311B: Global MASTER-Net observations report
  60. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  61. GRB 260131A/B: radio detection with the VLA
  62. EP260302a: MeerKAT radio counterpart
  63. GRB 260308A: SVOM/GRM observation of a short GRB
  64. EP260306a: Mondy optical upper limit
  65. Fermi GRB 260310B: Global MASTER-Net observations report
  66. Fermi GRB 260310A: Global MASTER-Net observations report
  67. GRB 260208A: radio detection with the VLA
  68. GRB 260307A: Glowbug gamma-ray detection
  69. Fermi GBM Sub-Threshold Detection of GRB 260307B
  70. GRB 260307B: Mephisto optical upper limits
  71. GRB 260307B: possible NOT optical counterpart
  72. GRB 260307B: SVOM/VT upper limit with X band data analysis
  73. Fermi GRB 260307A: Global MASTER-Net observations report
  74. GRB260307B: GROWTH-India Telescope optical upper limit
  75. GRB 260307B: SVOM/VT optical candidate
  76. GRB 260307B: SVOM/C-GFT upper limit
  77. GRB 260307B: SVOM detection of a burst
  78. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 260207A: TESS Detection and Possible VLA Counterpart
  80. EP260302a: SVOM/VT optical observation
  81. EP260306a: Gemini-North redshift z = 4.773
  82. EP260306a: SVOM/VT optical observation
  83. EP260302a: Gemini-South redshift z = 1.535
  84. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  85. EP260306a: Einstein Probe detection of an X-ray transient
  86. EP260302a: Optical afterglow rebrightening
  87. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  88. GRB 260303A: 1.3m DFOT optical upper limit
  89. Fermi GRB 260305A: Global MASTER-Net observations report
  90. GRB 260303B: AstroSat CZTI detection
  91. GRB 260303A: SVOM/VT optical observations
  92. GRB 260303A: J-band observations with WINTER
  93. GRB 260303B: NuSTAR detection of prompt emission
  94. EP260302a: Global MASTER-Net observations report
  95. Fermi GRB 260303B: Global MASTER-Net observations report
  96. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  97. EP260302a: analysis of the follow-up EP-FXT observation
  98. EP260302a: LCO observations
  99. EP260302a: BOOTES-7 optical counterpart detection at early times
  100. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate

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