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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"

15556 results found.

  1. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  2. EP260321a: GOTO detection of blue variable source
  3. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  4. EP260321a: further Kinder optical observations
  5. GRB 260321A: SVOM/VT optical upper limits
  6. EP260321a: Las Cumbres upper limit
  7. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  9. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  10. EP260321a: SVOM/VT optical upper limit
  11. GRB 260310A: continued optical observation at Mondy
  12. GRB 260321A: SVOM detection of a burst
  13. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  14. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  15. GRB 260310A / AT 2026fgk: KAIT optical observations
  16. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  17. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  18. GRB 260318A: SVOM/GRM observation
  19. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  20. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  21. GRB 260310A / AT 2026fgk: radio detection with the VLA
  22. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  23. GRB 260310A / AT2026fgk: LCO optical observations
  24. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  25. GRB 260316B: SVOM/GRM observation
  26. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  27. EP260316a: COLIBRÍ faint optical counterpart candidate
  28. EP260316a: Xinglong optical upper limit
  29. EP260316a: optical upper limit with Kinder observations
  30. IceCube-260315A: COLIBRÍ optical observations
  31. EP260314a: Xinglong optical upper limit
  32. EP260314a: optical upper limit with Kinder observations
  33. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  34. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  35. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  36. GRB 260310A / AT 2026fgk: iTelescope optical observations
  37. EP260314a: COLIBRÍ optical upper limit
  38. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  39. EP260314a: BOOTES-6/DPR optical upper limits at early times
  40. EP260314a: SVOM/VT optical candidate
  41. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  42. GRB 260310A / AT2026fgk: SAO RAS optical observations
  43. GRB 260310A / AT2026fgk: TNG NIR detection
  44. GRB 260310A / AT2026fgk: OASDG optical observations
  45. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  46. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  47. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  48. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  49. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  50. GRB 260310A: NOT optical polarimetry
  51. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  52. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  53. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  54. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  55. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  56. GRB260310A / AT2026fgk: P200 Spectroscopy
  57. GRB 260310A: Fermi GBM Observation
  58. GRB 260310A: potential optical counterpart
  59. GRB 260131A/B: radio detection with the VLA
  60. GRB 260308A: SVOM/GRM observation of a short GRB
  61. EP260306a: Mondy optical upper limit
  62. GRB 260208A: radio detection with the VLA
  63. GRB 260307B: Mephisto optical upper limits
  64. GRB 260307B: possible NOT optical counterpart
  65. GRB260307B: GROWTH-India Telescope optical upper limit
  66. GRB 260307B: SVOM/VT optical candidate
  67. GRB 260307B: SVOM detection of a burst
  68. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  69. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  70. EP260302a: SVOM/VT optical observation
  71. EP260306a: Gemini-North redshift z = 4.773
  72. EP260306a: SVOM/VT optical observation
  73. EP260302a: Gemini-South redshift z = 1.535
  74. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  75. EP260306a: Einstein Probe detection of an X-ray transient
  76. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  77. EP260302a: Optical afterglow rebrightening
  78. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  79. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  80. GRB 260303A: 1.3m DFOT optical upper limit
  81. EP260214b: ATCA 6 GHz observations
  82. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  83. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  84. GRB 260303A: SVOM/VT optical observations
  85. GRB 260303A: J-band observations with WINTER
  86. EP260227a: Gemini-South optical observations
  87. EP260302a: LCO observations
  88. EP260302a: BOOTES-7 optical counterpart detection at early times
  89. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  90. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  91. EP260227a: Mondy optical observations
  92. GRB 260228A: CAHA 2.2m telescope optical upper limit
  93. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. EP260227a: Mephisto optical detection
  95. EP260227a: further LCO observations
  96. EP260227a: SVOM/VT optical observation
  97. GRB 260228A: SVOM/VT optical upper limits
  98. GRB 260225D: SVOM/GRM observation
  99. EP260227A: 3.6m DOT optical afterglow detection
  100. GRB 260225B: SVOM/GRM observation

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