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SUMMARY:HST-1 knot: Results from quad-frequency observations of the M87 Je
 t
DTSTART;VALUE=DATE-TIME:20240903T144500Z
DTEND;VALUE=DATE-TIME:20240903T150000Z
DTSTAMP;VALUE=DATE-TIME:20260514T114954Z
UID:indico-contribution-54@cern.ch
DESCRIPTION:Speakers: Mr. NIKONOV\, Aleksei (MPI für Radioastronomie)\nHS
 T-1 is a knot in the conical kiloparsec-scale M87 jet\, observed for the\n
 first time by the Hubble Space Telescope. In the images\, it is the first\
 nthe resolved feature near the jet's "core" on the arcsecond scale. HST-1 
 showed superluminal speeds up to 6c and significant flaring activity in op
 tical and across all bands from radio to X-rays and even gamma-rays. Throu
 gh the perspective of VLBI\, the M87 jet exhibits a parabolic geometry\, h
 inting at the significant role of HST-1 in the jet's collimation and evolu
 tion. However\, due to its distance from the jet base and consequently\, t
 he smearing effects limiting the field of view for VLBI\, HST-1 remains a\
 nchallenging feature to study in detail\, resulting in a lack of high-reso
 lution VLBI data and spectral information. \n\nIn this talk\, I will prese
 nt our attempt to mitigate the problems introduced\nabove using quad-frequ
 ency observations of HST-1 at 2\, 5\, 8\, and 15 GHz with\nthe VLBA and th
 e EVN arrays. By utilizing these four frequencies\, we have constructed a 
 spectral index map of the knot and notably\, a turnover frequency map for 
 the first\ntime.\n\nThe spectral index maps reveal a uniform structure wit
 h a steep spectrum slope of approximately -0.7\, suggesting that HST-1 is 
 likely part of an optically thin jet rather than a standing shock. The tur
 nover frequency maps have also allowed us to estimate a magnetic field str
 ength of the order of milliGauss.\n\nhttps://events.mpifr-bonn.mpg.de/indi
 co/event/371/session/9/contribution/54
LOCATION:CJD Bonn Castell
URL:https://events.mpifr-bonn.mpg.de/indico/event/371/session/9/contributi
 on/54
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