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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"

21793 results found.

  1. GRB 260310A / AT 2026fgk: iTelescope optical observations
  2. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP260314a: Global MASTER-Net observations report
  4. Fermi trigger No 795185313: Global MASTER-Net observations report
  5. IceCube Alert 260315A: Global MASTER-Net observations report
  6. GRB 260310A / AT2026fgk: SAO RAS optical observations
  7. GRB 260310A/AT2026fgk: radio detection at 15GHz
  8. GRB 260310A / AT2026fgk: OASDG optical observations
  9. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  10. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  11. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  12. Fermi GRB 260314A: Global MASTER-Net observations report
  13. Fermi GRB 260313A: Global MASTER-Net observations report
  14. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  15. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  16. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  17. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  18. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  19. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  20. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  21. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  22. GRB260310A / AT2026fgk: P200 Spectroscopy
  23. GRB 260310A: potential optical counterpart
  24. Fermi GRB 260312B: Global MASTER-Net observations report
  25. Fermi GRB 260311B: Global MASTER-Net observations report
  26. GRB 260131A/B: radio detection with the VLA
  27. EP260302a: MeerKAT radio counterpart
  28. EP260306a: Mondy optical upper limit
  29. Fermi GRB 260310B: Global MASTER-Net observations report
  30. Fermi GRB 260310A: Global MASTER-Net observations report
  31. GRB 260307B: SVOM/ECLAIRs refined analysis
  32. GRB 260208A: radio detection with the VLA
  33. Fermi GBM Sub-Threshold Detection of GRB 260307B
  34. GRB 260307B: possible NOT optical counterpart
  35. GRB 260307B: SVOM/VT upper limit with X band data analysis
  36. Fermi GRB 260307A: Global MASTER-Net observations report
  37. GRB260307B: GROWTH-India Telescope optical upper limit
  38. GRB 260307B: SVOM/C-GFT upper limit
  39. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  40. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 260207A: TESS Detection and Possible VLA Counterpart
  42. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  43. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  44. GRB 260303A: 1.3m DFOT optical upper limit
  45. EP260214b: ATCA 6 GHz observations
  46. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  47. GRB 260303A: SVOM/ECLAIRs refined analysis
  48. Fermi GRB 260305A: Global MASTER-Net observations report
  49. GRB 260303A: SVOM/VT optical observations
  50. GRB 260303A: J-band observations with WINTER
  51. EP260302a: Global MASTER-Net observations report
  52. Fermi GRB 260303B: Global MASTER-Net observations report
  53. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  54. GRB 260228A: SVOM/ECLAIRs refined analysis
  55. GRB 260225A: SVOM/ECLAIRs refined analysis
  56. EP260227a: Gemini-South optical observations
  57. EP260302a: LCO observations
  58. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  59. EP260227a: Mondy optical observations
  60. EP260227a: Mephisto optical detection
  61. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  62. EP260227a: further LCO observations
  63. EP260227A: 3.6m DOT optical afterglow detection
  64. EP260227a: FTW optical and NIR observations
  65. EP260227a: Liverpool Telescope optical observations
  66. EP260227a: LCOGT Optical Observations
  67. GRB 260226A: Asiago r-band upper limit
  68. EP260227a: Thai National Telescope observations
  69. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  70. EP260227a: Liverpool Telescope observations
  71. EP260227a: COLIBRÍ optical observations
  72. EP260227a: NOT optical observations
  73. GRB 260225A: SVOM/VT optical continued observations and upper limit
  74. EP260227a: Global MASTER-Net observations report
  75. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  76. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  77. EP260214a: VLT/FORS2 optical observations
  78. GRB 260225A: WINTER J-band upper limit
  79. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  80. GRB 260226A : GROWTH-India Telescope optical observations
  81. GRB 260226A: LAST optical upper limit
  82. LAT GRB260226.44: Global MASTER-Net observations report
  83. Fermi GRB 260226A: Global MASTER-Net observations report
  84. EP260214a: VLA 6 GHz detection
  85. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  86. EP260126a: VLA 6 GHz detection
  87. GRB 260225A: SVOM detection of a burst
  88. EP260224a: Einstein Probe detection of an X-ray transient
  89. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  90. sb26021801: SVOM/C-GFT upper limit
  91. EP260223a: Einstein Probe detection of an X-ray transient
  92. GRB 260223A: COLIBRÍ further optical observations and a brightening
  93. EP260221a: Optical upper limit with Kinder observations
  94. GRB 260223A: COLIBRÍ optical observations
  95. GRB 260223A: DDOTI Optical Candidate
  96. Fermi GRB 260223A: Global MASTER-Net observations report
  97. EP260221a: COLIBRÍ optical counterpart candidate
  98. EP260221a: Global MASTER-Net observations report
  99. Fermi GRB 260221B: Global MASTER-Net observations report
  100. Fermi GRB 260221A: Global MASTER-Net observations report

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