Speaker
Description
HST-1 is a knot in the conical kiloparsec-scale M87 jet, observed for the first time by the Hubble Space Telescope. In the images, it is the first resolved feature near the jet's "core" on the arcsecond scale. HST-1 showed superluminal speeds up to 6c and significant flaring activity in optical and across all bands from radio to X-rays and even gamma-rays. From the perspective of VLBI, the M87 jet exhibits a parabolic geometry, which indicates the significant role of HST-1 in the jet's collimation and evolution. However, due to its distance from the jet base and, consequently, the smearing effects limiting the field of view for VLBI, HST-1 remains a challenging feature to study in detail, resulting in a lack of high-resolution VLBI data and spectral information.
In this talk, I will present our attempt to mitigate the problems introduced above using quad-frequency observations of HST-1 at 2, 5, 8, and 15 GHz with the VLBA and the 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 time.
The spectral index maps reveal a uniform structure with 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 turnover frequency maps have also allowed us to estimate the magnetic field strength of the milliGauss order.
| What is your career stage? | Graduate researcher (pre PhD) |
|---|---|
| Which telescopes do you use / are you affiliated with? | VLBA, Effelsberg |
