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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"

21572 results found.

  1. EP260321a: further Kinder optical observations
  2. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  4. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  5. EP260321a: SVOM/VT optical upper limit
  6. GRB 260310A: continued optical observation at Mondy
  7. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  8. EP260321a: Global MASTER-Net observations report
  9. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  10. GRB 260310A / AT 2026fgk: KAIT optical observations
  11. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  12. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  13. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  14. GRB 260310A/AT2026fgk: LBT near-infrared observations
  15. NOEMA Detection of GRB 260310A / AT 2026fgk
  16. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  17. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  18. Fermi GRB 260318A: Global MASTER-Net observations report
  19. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  20. GRB 260310A / AT 2026fgk: radio detection with the VLA
  21. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  22. GRB 260310A / AT2026fgk: LCO optical observations
  23. EP260316a: COLIBRÍ faint optical counterpart candidate
  24. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  25. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP260316a: optical upper limit with Kinder observations
  27. IceCube-260315A: COLIBRÍ optical observations
  28. EP260314a: optical upper limit with Kinder observations
  29. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  30. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  31. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  32. GRB 260310A / AT 2026fgk: iTelescope optical observations
  33. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  34. EP260314a: Global MASTER-Net observations report
  35. Fermi trigger No 795185313: Global MASTER-Net observations report
  36. IceCube Alert 260315A: Global MASTER-Net observations report
  37. GRB 260310A / AT2026fgk: SAO RAS optical observations
  38. GRB 260310A/AT2026fgk: radio detection at 15GHz
  39. GRB 260310A / AT2026fgk: TNG NIR detection
  40. GRB 260310A / AT2026fgk: OASDG optical observations
  41. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  42. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  43. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  44. Fermi GRB 260314A: Global MASTER-Net observations report
  45. Fermi GRB 260313A: Global MASTER-Net observations report
  46. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  47. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  48. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  49. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  50. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  51. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  52. GRB260310A / AT2026fgk: P200 Spectroscopy
  53. GRB 260310A: potential optical counterpart
  54. Fermi GRB 260312B: Global MASTER-Net observations report
  55. Fermi GRB 260311B: Global MASTER-Net observations report
  56. GRB 260131A/B: radio detection with the VLA
  57. EP260302a: MeerKAT radio counterpart
  58. Fermi GRB 260310B: Global MASTER-Net observations report
  59. Fermi GRB 260310A: Global MASTER-Net observations report
  60. GRB 260307B: SVOM/ECLAIRs refined analysis
  61. GRB 260208A: radio detection with the VLA
  62. GRB 260307B: possible NOT optical counterpart
  63. GRB 260307B: SVOM/VT upper limit with X band data analysis
  64. Fermi GRB 260307A: Global MASTER-Net observations report
  65. GRB260307B: GROWTH-India Telescope optical upper limit
  66. GRB 260307B: SVOM/C-GFT upper limit
  67. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  68. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 260207A: TESS Detection and Possible VLA Counterpart
  70. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  71. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  72. GRB 260303A: 1.3m DFOT optical upper limit
  73. EP260214b: ATCA 6 GHz observations
  74. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  75. GRB 260303A: SVOM/ECLAIRs refined analysis
  76. Fermi GRB 260305A: Global MASTER-Net observations report
  77. GRB 260303A: SVOM/VT optical observations
  78. GRB 260303A: J-band observations with WINTER
  79. EP260302a: Global MASTER-Net observations report
  80. Fermi GRB 260303B: Global MASTER-Net observations report
  81. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  82. GRB 260228A: SVOM/ECLAIRs refined analysis
  83. GRB 260225A: SVOM/ECLAIRs refined analysis
  84. EP260227a: Gemini-South optical observations
  85. EP260302a: LCO observations
  86. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  87. EP260227a: Mondy optical observations
  88. EP260227a: Mephisto optical detection
  89. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  90. EP260227a: further LCO observations
  91. EP260227A: 3.6m DOT optical afterglow detection
  92. EP260227a: FTW optical and NIR observations
  93. EP260227a: Liverpool Telescope optical observations
  94. EP260227a: LCOGT Optical Observations
  95. GRB 260226A: Asiago r-band upper limit
  96. EP260227a: Thai National Telescope observations
  97. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  98. EP260227a: Liverpool Telescope observations
  99. EP260227a: COLIBRÍ optical observations
  100. EP260227a: NOT optical observations

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