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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"

19548 results found.

  1. EP260329b: J-band upper limits with WINTER
  2. EP260329a: J-band upper limit with WINTER
  3. GRB 260330B: LCO optical upper limits
  4. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  5. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  6. EP260329a: COLIBRÍ optical upper limit
  7. EP260329a: EP-FXT follow up observation
  8. EP260329a: NOT optical counterpart candidate
  9. EP260329b: Optical follow-up with Kinder observations
  10. EP 260329b: COLIBRÍ optical observations
  11. EP260329a: Optical upper limit with Kinder observations
  12. EP260329b: LCO optical observations of the counterpart
  13. EP260329b: Einstein Probe detection of an X-ray transient
  14. EP260329a: Einstein Probe detection of an X-ray transient
  15. EP-WXT trigger 01709259209: TRT optical counterpart detection
  16. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  17. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260327a: SVOM/VT optical upper limits
  19. GRB 260307B: ATCA Radio Upper Limits
  20. EP260327a: WINTER J-band upper limit
  21. EP260327a: COLIBRÍ optical upper limits
  22. EP260327a: Gemini-North optical upper limits
  23. EP260324a: GROWTH-India Telescope optical observation
  24. EP260327a: Einstein Probe detection of an X-ray transient
  25. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  26. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  27. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  28. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  29. EP260321a: JinShan near-infrared observations
  30. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  31. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  32. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  33. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  34. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  35. EP260321a: COLIBRÍ further optical observations and brightening
  36. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  37. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  38. EP260321a: GOTO detection of blue variable source
  39. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  40. EP260321a: further Kinder optical observations
  41. GRB 260321A: SVOM/VT optical upper limits
  42. EP260321a: Las Cumbres upper limit
  43. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  45. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  46. EP260321a: SVOM/VT optical upper limit
  47. Fermi GBM Sub-Threshold Detection of GRB 260321A
  48. GRB 260321A: SVOM detection of a burst
  49. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  50. EP260321a: Einstein Probe detection of an X-ray transient
  51. GRB 260310A / AT 2026fgk: KAIT optical observations
  52. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  53. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  54. GRB 260318A: SVOM/GRM observation
  55. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  56. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  57. GRB 260310A / AT 2026fgk: radio detection with the VLA
  58. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  59. GRB 260310A / AT2026fgk: LCO optical observations
  60. GRB 260316B: SVOM/GRM observation
  61. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  62. EP260316a: COLIBRÍ faint optical counterpart candidate
  63. GRB 260316B: AstroSat CZTI detection
  64. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  65. EP260316a: Xinglong optical upper limit
  66. EP260316a: optical upper limit with Kinder observations
  67. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  68. IceCube-260315A: COLIBRÍ optical observations
  69. EP260314a: Xinglong optical upper limit
  70. EP260314a: optical upper limit with Kinder observations
  71. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  72. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  73. GRB 260310A / AT 2026fgk: iTelescope optical observations
  74. EP260314a: COLIBRÍ optical upper limit
  75. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  76. EP260314a: SVOM/VT optical candidate
  77. EP260314a: Einstein Probe detection of an X-ray transient
  78. GRB 260310A / AT2026fgk: SAO RAS optical observations
  79. GRB 260310A/AT2026fgk: radio detection at 15GHz
  80. GRB 260310A / AT2026fgk: OASDG optical observations
  81. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  82. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  83. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  84. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  85. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  86. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  87. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  88. GRB 260310A: potential optical counterpart
  89. GRB 260131A/B: radio detection with the VLA
  90. EP260302a: MeerKAT radio counterpart
  91. GRB 260308A: SVOM/GRM observation of a short GRB
  92. EP260306a: Mondy optical upper limit
  93. GRB 260310A: AstroSat CZTI detection of a long burst
  94. GRB 260208A: radio detection with the VLA
  95. GRB 260308A: Fermi GBM Final Real-time Localization
  96. GRB 260307B: Mephisto optical upper limits
  97. GRB 260307B: possible NOT optical counterpart
  98. GRB 260307B: SVOM/VT upper limit with X band data analysis
  99. GRB260307B: GROWTH-India Telescope optical upper limit
  100. GRB 260307B: SVOM/VT optical candidate

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