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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"

20383 results found.

  1. EP260329a: NOT optical counterpart candidate
  2. EP260329b: Optical follow-up with Kinder observations
  3. EP 260329b: COLIBRÍ optical observations
  4. EP260329a: Optical upper limit with Kinder observations
  5. EP260329b: LCO optical observations of the counterpart
  6. EP260329b: Einstein Probe detection of an X-ray transient
  7. EP260329a: Einstein Probe detection of an X-ray transient
  8. EP-WXT trigger 01709259209: TRT optical counterpart detection
  9. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  10. GRID detection of GRB 260326A
  11. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  12. EP260327a: SVOM/VT optical upper limits
  13. EP260327a: WINTER J-band upper limit
  14. EP260327a: COLIBRÍ optical upper limits
  15. GRB 260327A: AstroSat CZTI detection of a long burst
  16. EP260327a: Gemini-North optical upper limits
  17. EP260324a: GROWTH-India Telescope optical observation
  18. EP260327a: Einstein Probe detection of an X-ray transient
  19. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  20. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  21. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  22. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  23. EP260321a: JinShan near-infrared observations
  24. EP260321a: Upper limits from a neutrino search with IceCube
  25. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  26. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  27. GRID detection of GRB 260320A
  28. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  29. EP260321a: COLIBRÍ further optical observations and brightening
  30. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  31. EP260214b: ATCA 6 GHz detection
  32. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  33. The EP-WXT trigger 01709259045 is likely a flaring star
  34. EP260321a: GOTO detection of blue variable source
  35. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  36. EP260321a: further Kinder optical observations
  37. GRB 260321A: SVOM/VT optical upper limits
  38. EP260321a: Las Cumbres upper limit
  39. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  41. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  42. EP260321a: SVOM/VT optical upper limit
  43. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  44. EP260321a: Einstein Probe detection of an X-ray transient
  45. GRB 260310A / AT 2026fgk: KAIT optical observations
  46. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  47. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  48. GRB 260318A: SVOM/GRM observation
  49. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  50. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  51. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  52. GRB 260310A / AT 2026fgk: radio detection with the VLA
  53. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  54. GRB 260310A / AT2026fgk: LCO optical observations
  55. GRB 260316B: SVOM/GRM observation
  56. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  57. EP260316a: COLIBRÍ faint optical counterpart candidate
  58. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  59. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  60. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  61. EP260316a: Xinglong optical upper limit
  62. EP260316a: optical upper limit with Kinder observations
  63. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  64. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  65. IceCube-260315A: COLIBRÍ optical observations
  66. EP260314a: Xinglong optical upper limit
  67. EP260314a: optical upper limit with Kinder observations
  68. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  69. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  70. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  71. GRB 260310A / AT 2026fgk: iTelescope optical observations
  72. EP260314a: COLIBRÍ optical upper limit
  73. GRID detection of GRB 260312B
  74. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP260314a: SVOM/VT optical candidate
  76. EP260314a: Einstein Probe detection of an X-ray transient
  77. GRB 260310A / AT2026fgk: SAO RAS optical observations
  78. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  79. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  80. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  81. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  82. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  83. GRB 260312B: AstroSat CZTI detection
  84. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  85. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  86. GRB 260310A: potential optical counterpart
  87. Fermi GRB 260311B: Global MASTER-Net observations report
  88. GRB 260131A/B: radio detection with the VLA
  89. EP260302a: MeerKAT radio counterpart
  90. GRB 260308A: SVOM/GRM observation of a short GRB
  91. EP260306a: Mondy optical upper limit
  92. GRB 260307B: SVOM/ECLAIRs refined analysis
  93. GRB 260208A: radio detection with the VLA
  94. GRB 260307B: Mephisto optical upper limits
  95. GRB 260307B: possible NOT optical counterpart
  96. GRB 260307B: SVOM/VT upper limit with X band data analysis
  97. GRB260307B: GROWTH-India Telescope optical upper limit
  98. GRB 260307B: SVOM/VT optical candidate
  99. GRB 260307B: SVOM/C-GFT upper limit
  100. GRB 260307B: SVOM detection of a burst

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