Issue |
A&A
Volume 376, Number 2, September II 2001
|
|
---|---|---|
Page(s) | 497 - 517 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20010954 | |
Published online | 15 September 2001 |
Time-resolved spectral analysis of the pulsating helium star V652 Her *
1
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
2
School of Physical Sciences, Queen's University Belfast, Belfast BT7 9NN, Northern Ireland
Corresponding author: C. S. Jeffery, csj@star.arm.ac.uk
Received:
19
January
2001
Accepted:
27
June
2001
A series of 59 moderate-resolution high signal-to-noise spectra of the
pulsating helium star V652 Her covering 1.06 pulsation cycles was
obtained with the William Herschel Telescope.
These have been supplemented by archival ultraviolet and
visual spectrophotometry and used to make a time-dependent
study of the properties of V652 Her throughout the pulsation cycle. This
study includes the following features:
the most precise radial velocity curve for V652 Her measured so far,
new software for the automatic measurement of effective
temperature, surface gravity and projected rotation velocities from
moderate-resolution spectra,
self-consistent high-precision measurements of effective temperature
and surface gravity around the pulsation cycle,
a demonstration of excessive line-broadening at minimum radius and
evidence for a pulsation-driven shock front,
a new method for the direct measurement of the radius of a pulsating
star using radial velocity and surface gravity measurements alone,
new software for the automatic measurement of chemical
abundances and microturbulent velocity,
updated chemical abundances for V652 Her compared with
previous work ([CITE]),
a reanalysis of the total flux variations (cf. [CITE]) in
good agreement with previous work,
and revised measurements of the stellar mass and radius which are similar
to recent results for another pulsating helium star, BX Cir.
Masses measured without reference to the ultraviolet fluxes
turn out to be unphysically low (). The best estimate
for the dimensions of V652 Her averaged over the pulsation cycle is given by:
and
(ionization equilibrium),
(total flux method),
,
,
and
kpc.
Two significant problems were encountered. The line-blanketed
hydrogen-deficient model atmospheres used yield
effective temperatures from the optical spectrum (ionization equilibrium)
and visual and UV photometry (bolometric flux) that are inconsistent.
Secondly, the IUE spectra are poorly distributed in phase and have low
signal-to-noise. These problems may introduce systematic errors of up to
.
Key words: stars: fundamental parameters / stars: abundances / stars: individual: V652 Her / stars: oscillations / techniques: spectroscopic
© ESO, 2001
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