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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"

23417 results found.

  1. EP260329b: GOTO detection of optical counterpart
  2. GRB 260330B: SVOM/VT optical upper limits
  3. GRB 260321A: SVOM/ECLAIRs refined analysis
  4. EP260329b: J-band upper limits with WINTER
  5. EP260329a: J-band upper limit with WINTER
  6. GRB 260330A: Glowbug gamma-ray detection
  7. GRB 260310A: VLA Multi-frequency Radio Observations
  8. GRB 260330B: LCO optical upper limits
  9. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  10. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  11. EP260329a: COLIBRÍ optical upper limit
  12. EP260329a: EP-FXT follow up observation
  13. EP260329a: NOT optical counterpart candidate
  14. EP260329b: Optical follow-up with Kinder observations
  15. EP 260329b: COLIBRÍ optical observations
  16. EP260329a: Optical upper limit with Kinder observations
  17. EP260329b: LCO optical observations of the counterpart
  18. EP260329b: Einstein Probe detection of an X-ray transient
  19. EP260329a: Einstein Probe detection of an X-ray transient
  20. EP-WXT trigger 01709259209: TRT optical counterpart detection
  21. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  22. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260327a: SVOM/VT optical upper limits
  24. GRB 260307B: ATCA Radio Upper Limits
  25. EP260327a: WINTER J-band upper limit
  26. EP260327a: COLIBRÍ optical upper limits
  27. GRB 260327A: AstroSat CZTI detection of a long burst
  28. EP260327a: Gemini-North optical upper limits
  29. EP260324a: GROWTH-India Telescope optical observation
  30. EP260327a: Einstein Probe detection of an X-ray transient
  31. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  32. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  33. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  34. IPN triangulation of GRB 260320A
  35. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  36. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  37. EP260321a: JinShan near-infrared observations
  38. EP260321a: Upper limits from a neutrino search with IceCube
  39. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  40. IPN triangulation of GRB 260316B
  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. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  44. GRB 260320A: Glowbug gamma-ray detection
  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. EP260321a: GOTO detection of blue variable source
  49. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  50. EP260321a: further Kinder optical observations
  51. GRB 260321A: SVOM/VT optical upper limits
  52. EP260321a: Las Cumbres upper limit
  53. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  55. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  56. EP260321a: SVOM/VT optical upper limit
  57. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  58. EP260321a: Einstein Probe detection of an X-ray transient
  59. GRB 260318A: Glowbug gamma-ray detection
  60. GRB 260310A / AT 2026fgk: KAIT optical observations
  61. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  62. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  63. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  64. GRB 260318A: SVOM/GRM observation
  65. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  66. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  67. GRB 260310A / AT 2026fgk: radio detection with the VLA
  68. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  69. GRB 260310A / AT2026fgk: LCO optical observations
  70. GRB 260316B: SVOM/GRM observation
  71. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  72. EP260316a: COLIBRÍ faint optical counterpart candidate
  73. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP260316a: Xinglong optical upper limit
  75. EP260316a: optical upper limit with Kinder observations
  76. GRB 260314A: Glowbug gamma-ray detection
  77. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  78. IceCube-260315A: COLIBRÍ optical observations
  79. EP260314a: Xinglong optical upper limit
  80. EP260314a: optical upper limit with Kinder observations
  81. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  82. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  83. GRB 260310A / AT 2026fgk: iTelescope optical observations
  84. EP260314a: COLIBRÍ optical upper limit
  85. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP260314a: SVOM/VT optical candidate
  87. EP260314a: Einstein Probe detection of an X-ray transient
  88. GRB 260310A / AT2026fgk: SAO RAS optical observations
  89. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  90. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  91. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  92. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  93. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  94. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  95. GRB 260310A: NOT optical polarimetry
  96. GRB 260312B: AstroSat CZTI detection
  97. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  98. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  99. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  100. GRB 260312B: Glowbug gamma-ray detection

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