Abstract:
We present an optical spectroscopic study based on 41 spectr
a of 4 Her and 32 spectra of 88 Her,
obtained over a period of 6 months. We estimate the rotationa
l velocity of these stars from He
I
lines in the
blue spectral region (4000–4500
̊
A). We find that these stars are likely to be rotating at a fract
ional critical
rotation of
∼
0.80. We measure the average
I
p
/I
c
ratio to quantify the strength of the H
α
line and obtain
1.63 for 4 Her and 2.06 for 88 Her. The radius of the H
α
emission region is estimated to be
R
d
/R
∗
∼
5.0,
assuming a Keplerian disk. These stars are thus found to be fa
st rotators with a relatively small H
α
emission
region. We detect
V/R
variation of the H
α
spectral line during the observed period. We re-estimate th
e
periods for both stars and obtain a period of
∼
46 d and its harmonic of 23.095 d for 4 Her, and a period of
∼
86 d for 88 Her. As these two cases are shell stars with binarie
s and have low H
α
EW with the emission
region closer to the central star, the
V/R
variation and a change in period may be an effect of the binary
on
the circumstellar disk.
