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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"

21263 results found.

  1. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  2. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  3. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  4. EP260321a: COLIBRÍ further optical observations and brightening
  5. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  6. EP260214b: ATCA 6 GHz detection
  7. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  8. EP260321a: GOTO detection of blue variable source
  9. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  10. EP260321a: further Kinder optical observations
  11. GRB 260321A: SVOM/VT optical upper limits
  12. EP260321a: Las Cumbres upper limit
  13. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  15. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  16. EP260321a: SVOM/VT optical upper limit
  17. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  18. EP260321a: Einstein Probe detection of an X-ray transient
  19. GRB 260310A / AT 2026fgk: KAIT optical observations
  20. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  21. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  22. GRB 260318A: SVOM/GRM observation
  23. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  24. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  25. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  26. GRB 260310A / AT 2026fgk: radio detection with the VLA
  27. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  28. GRB 260310A / AT2026fgk: LCO optical observations
  29. GRB 260316B: SVOM/GRM observation
  30. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  31. EP260316a: COLIBRÍ faint optical counterpart candidate
  32. GRB 260316B: AstroSat CZTI detection
  33. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  34. EP260316a: Xinglong optical upper limit
  35. EP260316a: optical upper limit with Kinder observations
  36. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  37. IceCube-260315A: COLIBRÍ optical observations
  38. EP260314a: Xinglong optical upper limit
  39. EP260314a: optical upper limit with Kinder observations
  40. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  41. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  42. GRB 260310A / AT 2026fgk: iTelescope optical observations
  43. EP260314a: COLIBRÍ optical upper limit
  44. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP260314a: SVOM/VT optical candidate
  46. EP260314a: Einstein Probe detection of an X-ray transient
  47. GRB 260310A / AT2026fgk: SAO RAS optical observations
  48. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  49. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  50. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  51. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  52. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  53. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  54. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  55. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  56. GRB 260310A: Fermi GBM Observation
  57. GRB 260310A: potential optical counterpart
  58. GRB 260131A/B: radio detection with the VLA
  59. EP260302a: MeerKAT radio counterpart
  60. GRB 260308A: SVOM/GRM observation of a short GRB
  61. EP260306a: Mondy optical upper limit
  62. GRB 260307B: SVOM/ECLAIRs refined analysis
  63. GRB 260208A: radio detection with the VLA
  64. GRB 260307B: Mephisto optical upper limits
  65. GRB 260307B: possible NOT optical counterpart
  66. GRB 260307B: SVOM/VT upper limit with X band data analysis
  67. GRB260307B: GROWTH-India Telescope optical upper limit
  68. GRB 260307B: SVOM/VT optical candidate
  69. GRB 260307B: SVOM/C-GFT upper limit
  70. GRB 260307B: SVOM detection of a burst
  71. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 260207A: TESS Detection and Possible VLA Counterpart
  73. EP260302a: SVOM/VT optical observation
  74. EP260306a: SVOM/VT optical observation
  75. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  76. EP260306a: Einstein Probe detection of an X-ray transient
  77. GRB 260303A: 1.3m DFOT optical upper limit
  78. GRB 260303A: SVOM/ECLAIRs refined analysis
  79. GRB 260305A: Fermi GBM Final Real-time Localization
  80. GRB 260303B: AstroSat CZTI detection
  81. GRB 260304A: AstroSat CZTI detection of a long burst
  82. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  83. GRB 260303A: SVOM/VT optical observations
  84. GRB 260303A: J-band observations with WINTER
  85. GRB 260303B: NuSTAR detection of prompt emission
  86. GRB 260228A: SVOM/ECLAIRs refined analysis
  87. GRB 260225A: SVOM/ECLAIRs refined analysis
  88. EP260302a: analysis of the follow-up EP-FXT observation
  89. EP260302a: LCO observations
  90. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  91. GRB 260303A: SVOM detection of a burst
  92. GRB 260228A: EP-FXT follow-up observation
  93. EP260302a: Einstein Probe detection of an X-ray transient
  94. EP260227a: Mondy optical observations
  95. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. EP260227a: Mephisto optical detection
  97. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  98. EP260227a: SVOM/VT optical observation
  99. GRB 260228A: SVOM/VT optical upper limits
  100. GRB 260225D: SVOM/GRM observation

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