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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"

22062 results found.

  1. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  2. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  3. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  4. GRB 260310A/AT2026fgk: LBT near-infrared observations
  5. NOEMA Detection of GRB 260310A / AT 2026fgk
  6. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  7. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  8. Fermi GRB 260318A: Global MASTER-Net observations report
  9. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  10. GRB 260310A / AT 2026fgk: radio detection with the VLA
  11. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  12. GRB 260310A / AT2026fgk: LCO optical observations
  13. EP260316a: COLIBRÍ faint optical counterpart candidate
  14. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  15. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  16. EP260316a: optical upper limit with Kinder observations
  17. IceCube-260315A: COLIBRÍ optical observations
  18. EP260314a: optical upper limit with Kinder observations
  19. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  20. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  21. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  22. GRB 260310A / AT 2026fgk: iTelescope optical observations
  23. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  24. EP260314a: Global MASTER-Net observations report
  25. Fermi trigger No 795185313: Global MASTER-Net observations report
  26. IceCube Alert 260315A: Global MASTER-Net observations report
  27. GRB 260310A / AT2026fgk: SAO RAS optical observations
  28. GRB 260310A/AT2026fgk: radio detection at 15GHz
  29. GRB 260310A / AT2026fgk: TNG NIR detection
  30. GRB 260310A / AT2026fgk: OASDG optical observations
  31. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  32. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  33. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  34. Fermi GRB 260314A: Global MASTER-Net observations report
  35. Fermi GRB 260313A: Global MASTER-Net observations report
  36. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  37. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  38. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  39. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  40. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  41. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  42. GRB260310A / AT2026fgk: P200 Spectroscopy
  43. GRB 260310A: potential optical counterpart
  44. Fermi GRB 260312B: Global MASTER-Net observations report
  45. Fermi GRB 260311B: Global MASTER-Net observations report
  46. GRB 260131A/B: radio detection with the VLA
  47. EP260302a: MeerKAT radio counterpart
  48. Fermi GRB 260310B: Global MASTER-Net observations report
  49. Fermi GRB 260310A: Global MASTER-Net observations report
  50. GRB 260307B: SVOM/ECLAIRs refined analysis
  51. GRB 260208A: radio detection with the VLA
  52. GRB 260307B: possible NOT optical counterpart
  53. GRB 260307B: SVOM/VT upper limit with X band data analysis
  54. Fermi GRB 260307A: Global MASTER-Net observations report
  55. GRB260307B: GROWTH-India Telescope optical upper limit
  56. GRB 260307B: SVOM/C-GFT upper limit
  57. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  58. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  59. GRB 260207A: TESS Detection and Possible VLA Counterpart
  60. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  61. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  62. GRB 260303A: 1.3m DFOT optical upper limit
  63. EP260214b: ATCA 6 GHz observations
  64. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  65. GRB 260303A: SVOM/ECLAIRs refined analysis
  66. Fermi GRB 260305A: Global MASTER-Net observations report
  67. GRB 260303A: SVOM/VT optical observations
  68. GRB 260303A: J-band observations with WINTER
  69. EP260302a: Global MASTER-Net observations report
  70. Fermi GRB 260303B: Global MASTER-Net observations report
  71. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  72. GRB 260228A: SVOM/ECLAIRs refined analysis
  73. GRB 260225A: SVOM/ECLAIRs refined analysis
  74. EP260227a: Gemini-South optical observations
  75. EP260302a: LCO observations
  76. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  77. EP260227a: Mondy optical observations
  78. EP260227a: Mephisto optical detection
  79. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  80. EP260227a: further LCO observations
  81. EP260227A: 3.6m DOT optical afterglow detection
  82. EP260227a: FTW optical and NIR observations
  83. EP260227a: Liverpool Telescope optical observations
  84. EP260227a: LCOGT Optical Observations
  85. GRB 260226A: Asiago r-band upper limit
  86. EP260227a: Thai National Telescope observations
  87. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  88. EP260227a: Liverpool Telescope observations
  89. EP260227a: COLIBRÍ optical observations
  90. EP260227a: NOT optical observations
  91. GRB 260225A: SVOM/VT optical continued observations and upper limit
  92. EP260227a: Global MASTER-Net observations report
  93. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  94. Konus-Wind detection of GRB 260226A
  95. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  96. EP260214a: VLT/FORS2 optical observations
  97. GRB 260225A: WINTER J-band upper limit
  98. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  99. GRB 260226A : GROWTH-India Telescope optical observations
  100. GRB 260226A: LAST optical upper limit

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