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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"

21319 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. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  4. GRB 260310A / AT 2026fgk: KAIT optical observations
  5. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  6. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  7. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  8. GRB 260310A/AT2026fgk: LBT near-infrared observations
  9. NOEMA Detection of GRB 260310A / AT 2026fgk
  10. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  11. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  12. Fermi GRB 260318A: Global MASTER-Net observations report
  13. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  14. GRB 260310A / AT 2026fgk: radio detection with the VLA
  15. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  16. GRB 260310A / AT2026fgk: LCO optical observations
  17. EP260316a: COLIBRÍ faint optical counterpart candidate
  18. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  19. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  20. EP260316a: optical upper limit with Kinder observations
  21. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  22. IceCube-260315A: COLIBRÍ optical observations
  23. EP260314a: optical upper limit with Kinder observations
  24. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  25. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  26. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  27. GRB 260310A / AT 2026fgk: iTelescope optical observations
  28. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  29. EP260314a: Global MASTER-Net observations report
  30. Fermi trigger No 795185313: Global MASTER-Net observations report
  31. IceCube Alert 260315A: Global MASTER-Net observations report
  32. GRB 260310A / AT2026fgk: SAO RAS optical observations
  33. GRB 260310A/AT2026fgk: radio detection at 15GHz
  34. GRB 260310A / AT2026fgk: OASDG optical observations
  35. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  36. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  37. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  38. Fermi GRB 260314A: Global MASTER-Net observations report
  39. Fermi GRB 260313A: Global MASTER-Net observations report
  40. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  41. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  42. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  43. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  44. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  45. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  46. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  47. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  48. GRB260310A / AT2026fgk: P200 Spectroscopy
  49. GRB 260310A: potential optical counterpart
  50. Fermi GRB 260312B: Global MASTER-Net observations report
  51. Fermi GRB 260311B: Global MASTER-Net observations report
  52. GRB 260131A/B: radio detection with the VLA
  53. EP260302a: MeerKAT radio counterpart
  54. EP260306a: Mondy optical upper limit
  55. Fermi GRB 260310B: Global MASTER-Net observations report
  56. Fermi GRB 260310A: Global MASTER-Net observations report
  57. GRB 260307B: SVOM/ECLAIRs refined analysis
  58. GRB 260208A: radio detection with the VLA
  59. Fermi GBM Sub-Threshold Detection of GRB 260307B
  60. GRB 260307B: possible NOT optical counterpart
  61. GRB 260307B: SVOM/VT upper limit with X band data analysis
  62. Fermi GRB 260307A: Global MASTER-Net observations report
  63. GRB260307B: GROWTH-India Telescope optical upper limit
  64. GRB 260307B: SVOM/C-GFT upper limit
  65. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  66. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 260207A: TESS Detection and Possible VLA Counterpart
  68. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  69. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  70. GRB 260303A: 1.3m DFOT optical upper limit
  71. EP260214b: ATCA 6 GHz observations
  72. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  73. GRB 260303A: SVOM/ECLAIRs refined analysis
  74. Fermi GRB 260305A: Global MASTER-Net observations report
  75. GRB 260303A: SVOM/VT optical observations
  76. GRB 260303A: J-band observations with WINTER
  77. EP260302a: Global MASTER-Net observations report
  78. Fermi GRB 260303B: Global MASTER-Net observations report
  79. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  80. GRB 260228A: SVOM/ECLAIRs refined analysis
  81. GRB 260225A: SVOM/ECLAIRs refined analysis
  82. EP260227a: Gemini-South optical observations
  83. EP260302a: LCO observations
  84. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  85. EP260227a: Mondy optical observations
  86. EP260227a: Mephisto optical detection
  87. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  88. EP260227a: further LCO observations
  89. EP260227A: 3.6m DOT optical afterglow detection
  90. EP260227a: FTW optical and NIR observations
  91. EP260227a: Liverpool Telescope optical observations
  92. EP260227a: LCOGT Optical Observations
  93. GRB 260226A: Asiago r-band upper limit
  94. EP260227a: Thai National Telescope observations
  95. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  96. EP260227a: Liverpool Telescope observations
  97. EP260227a: COLIBRÍ optical observations
  98. EP260227a: NOT optical observations
  99. GRB 260225A: SVOM/VT optical continued observations and upper limit
  100. EP260227a: Global MASTER-Net observations report

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