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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"

28089 results found.

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

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