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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"

22912 results found.

  1. GRB 260330A: Glowbug gamma-ray detection
  2. GRB 260310A: VLA Multi-frequency Radio Observations
  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. GRB 260327A: AstroSat CZTI detection of a long burst
  23. EP260327a: Gemini-North optical upper limits
  24. EP260324a: GROWTH-India Telescope optical observation
  25. EP260327a: Einstein Probe detection of an X-ray transient
  26. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  27. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  28. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  29. IPN triangulation of GRB 260320A
  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. EP260321a: Upper limits from a neutrino search with IceCube
  34. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  35. IPN triangulation of GRB 260316B
  36. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  37. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  38. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  39. GRB 260320A: Glowbug gamma-ray detection
  40. EP260321a: COLIBRÍ further optical observations and brightening
  41. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  42. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  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. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  53. EP260321a: Einstein Probe detection of an X-ray transient
  54. GRB 260318A: Glowbug gamma-ray detection
  55. GRB 260310A / AT 2026fgk: KAIT optical observations
  56. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  57. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  58. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  59. GRB 260318A: SVOM/GRM observation
  60. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  61. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  62. GRB 260310A / AT 2026fgk: radio detection with the VLA
  63. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  64. GRB 260310A / AT2026fgk: LCO optical observations
  65. GRB 260316B: SVOM/GRM observation
  66. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  67. EP260316a: COLIBRÍ faint optical counterpart candidate
  68. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  69. EP260316a: Xinglong optical upper limit
  70. EP260316a: optical upper limit with Kinder observations
  71. GRB 260314A: Glowbug gamma-ray detection
  72. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  73. IceCube-260315A: COLIBRÍ optical observations
  74. EP260314a: Xinglong optical upper limit
  75. EP260314a: optical upper limit with Kinder observations
  76. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  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 / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  87. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  88. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  89. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  90. GRB 260310A: NOT optical polarimetry
  91. GRB 260312B: AstroSat CZTI detection
  92. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  93. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  94. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  95. GRB 260312B: Glowbug gamma-ray detection
  96. GRB 260310A: potential optical counterpart
  97. GRB 260312A: Swift detection of a burst
  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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