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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"

17591 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. GRB 260330B: SVOM detection of a burst
  7. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  8. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  9. EP260329a: COLIBRÍ optical upper limit
  10. EP260329a: EP-FXT follow up observation
  11. EP260329a: NOT optical counterpart candidate
  12. EP260329b: Optical follow-up with Kinder observations
  13. EP 260329b: COLIBRÍ optical observations
  14. EP260329a: Optical upper limit with Kinder observations
  15. EP260329b: LCO optical observations of the counterpart
  16. EP260329b: Einstein Probe detection of an X-ray transient
  17. EP260329a: Einstein Probe detection of an X-ray transient
  18. EP-WXT trigger 01709259209: TRT optical counterpart detection
  19. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  20. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  21. EP260327a: SVOM/VT optical 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. The EP-WXT trigger 01709259173 is likely a flaring star
  29. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  30. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  31. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  32. EP260321a: JinShan near-infrared observations
  33. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  34. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  35. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  36. The EP-WXT trigger 01709259112 is likely a flaring star
  37. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  38. EP260321a: COLIBRÍ further optical observations and brightening
  39. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  40. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  41. GRB 260321A: EP-FXT follow-up observation
  42. The EP-WXT trigger 01709259045 is likely a flaring star
  43. EP260321a: GOTO detection of blue variable source
  44. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  45. EP260321a: further Kinder optical observations
  46. GRB 260321A: SVOM/VT optical upper limits
  47. EP260321a: Las Cumbres upper limit
  48. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  49. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  50. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  51. EP260321a: SVOM/VT optical upper limit
  52. GRB 260310A: continued optical observation at Mondy
  53. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  54. EP260321a: Einstein Probe detection of an X-ray transient
  55. GRB 260310A / AT 2026fgk: KAIT optical observations
  56. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  57. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  58. GRB 260318A: SVOM/GRM observation
  59. The EP-WXT trigger 01709258989 is likely a flaring star
  60. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  61. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  62. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  63. GRB 260310A / AT 2026fgk: radio detection with the VLA
  64. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  65. GRB 260310A / AT2026fgk: LCO optical observations
  66. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  67. GRB 260316B: SVOM/GRM observation
  68. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  69. EP260316a: COLIBRÍ faint optical counterpart candidate
  70. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  71. EP260316a: Xinglong optical upper limit
  72. EP260316a: optical upper limit with Kinder observations
  73. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  74. IceCube-260315A: COLIBRÍ optical observations
  75. EP260314a: Xinglong optical upper limit
  76. EP260314a: optical upper limit with Kinder observations
  77. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  78. GRB 260310A / AT 2026fgk: iTelescope optical observations
  79. EP260314a: COLIBRÍ optical upper limit
  80. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260314a: SVOM/VT optical candidate
  82. EP260314a: Einstein Probe detection of an X-ray transient
  83. GRB 260310A / AT2026fgk: SAO RAS optical observations
  84. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  85. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  86. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  87. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  88. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  89. GRB 260310A / AT 2026fgk: COLIBRÍ optical 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 260208A: radio detection with the VLA
  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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