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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"

17798 results found.

  1. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  2. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  3. GRB 260402A: SVOM detection of a burst
  4. EP260329b: Mondy and Assy-Turgen optical upper limits
  5. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  6. EP260321a :Xinglong optical observations
  7. EP260327a: Xinglong optical upper limit
  8. GRB 260330B: SVOM/VT optical upper limits
  9. GRB 260321A: SVOM/ECLAIRs refined analysis
  10. EP260329b: J-band upper limits with WINTER
  11. EP260329a: J-band upper limit with WINTER
  12. GRB 260330B: LCO optical upper limits
  13. GRB 260330B: SVOM detection of a burst
  14. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  15. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  16. EP260329a: COLIBRÍ optical upper limit
  17. EP260329a: EP-FXT follow up observation
  18. EP260329a: NOT optical counterpart candidate
  19. EP260329b: Optical follow-up with Kinder observations
  20. EP 260329b: COLIBRÍ optical observations
  21. EP260329a: Optical upper limit with Kinder observations
  22. EP260329b: LCO optical observations of the counterpart
  23. EP260329b: Einstein Probe detection of an X-ray transient
  24. EP260329a: Einstein Probe detection of an X-ray transient
  25. EP-WXT trigger 01709259209: TRT optical counterpart detection
  26. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  27. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  28. EP260327a: SVOM/VT optical upper limits
  29. EP260327a: WINTER J-band upper limit
  30. EP260327a: COLIBRÍ optical upper limits
  31. EP260327a: Gemini-North optical upper limits
  32. EP260324a: GROWTH-India Telescope optical observation
  33. EP260327a: Einstein Probe detection of an X-ray transient
  34. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  35. The EP-WXT trigger 01709259173 is likely a flaring star
  36. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  37. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  38. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  39. EP260321a: JinShan near-infrared observations
  40. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  41. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  42. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  43. The EP-WXT trigger 01709259112 is likely a flaring star
  44. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  45. EP260321a: COLIBRÍ further optical observations and brightening
  46. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  47. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  48. GRB 260321A: EP-FXT follow-up observation
  49. The EP-WXT trigger 01709259045 is likely a flaring star
  50. EP260321a: GOTO detection of blue variable source
  51. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  52. EP260321a: further Kinder optical observations
  53. GRB 260321A: SVOM/VT optical upper limits
  54. EP260321a: Las Cumbres upper limit
  55. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  56. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  57. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  58. EP260321a: SVOM/VT optical upper limit
  59. GRB 260310A: continued optical observation at Mondy
  60. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  61. EP260321a: Einstein Probe detection of an X-ray transient
  62. GRB 260310A / AT 2026fgk: KAIT optical observations
  63. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  64. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  65. GRB 260318A: SVOM/GRM observation
  66. The EP-WXT trigger 01709258989 is likely a flaring star
  67. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  68. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  69. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  70. GRB 260310A / AT 2026fgk: radio detection with the VLA
  71. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  72. GRB 260310A / AT2026fgk: LCO optical observations
  73. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  74. GRB 260316B: SVOM/GRM observation
  75. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  76. EP260316a: COLIBRÍ faint optical counterpart candidate
  77. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260316a: Xinglong optical upper limit
  79. EP260316a: optical upper limit with Kinder observations
  80. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  81. IceCube-260315A: COLIBRÍ optical observations
  82. EP260314a: Xinglong optical upper limit
  83. EP260314a: optical upper limit with Kinder observations
  84. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  85. GRB 260310A / AT 2026fgk: iTelescope optical observations
  86. EP260314a: COLIBRÍ optical upper limit
  87. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  88. EP260314a: SVOM/VT optical candidate
  89. EP260314a: Einstein Probe detection of an X-ray transient
  90. GRB 260310A / AT2026fgk: SAO RAS optical observations
  91. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  92. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  93. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  94. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  95. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  96. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  97. GRB 260310A: potential optical counterpart
  98. GRB 260131A/B: radio detection with the VLA
  99. EP260302a: MeerKAT radio counterpart
  100. GRB 260308A: SVOM/GRM observation of a short GRB

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