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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"

19550 results found.

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

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