Bibcode
Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Fossati, L.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 474, Issue 3, p.3344-3360
Advertised on:
3
2018
Citations
6
Refereed citations
5
Description
We present a radial velocity analysis of 20 solar neighbourhood RR Lyrae
and three Population II Cepheid variables. We obtained high-resolution,
moderate-to-high signal-to-noise ratio spectra for most stars; these
spectra covered different pulsation phases for each star. To estimate
the gamma (centre-of-mass) velocities of the programme stars, we use two
independent methods. The first, `classic' method is based on RR Lyrae
radial velocity curve templates. The second method is based on the
analysis of absorption-line profile asymmetry to determine both
pulsational and gamma velocities. This second method is based on the
least-squares deconvolution (LSD) technique applied to analyse the line
asymmetry that occurs in the spectra. We obtain measurements of the
pulsation component of the radial velocity with an accuracy of
±3.5 km s-1. The gamma velocity was determined with an
accuracy of ±10 km s-1, even for those stars having a
small number of spectra. The main advantage of this method is the
possibility of obtaining an estimation of gamma velocity even from one
spectroscopic observation with uncertain pulsation phase. A detailed
investigation of LSD profile asymmetry shows that the projection factor
p varies as a function of the pulsation phase - this is a key parameter,
which converts observed spectral line radial velocity variations into
photospheric pulsation velocities. As a by-product of our study, we
present 41 densely spaced synthetic grids of LSD profile bisectors based
on atmospheric models of RR Lyr covering all pulsation phases.
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