We present the optical spectroscopic study based on 41 spectra of 4 Her and 32 spectra of 88 Her, obtained over a period of 6 months. We estimate the rotational velocity of these stars from He{\sc i} lines in the blue spectral region (4000--4500 \AA). We find that these stars are likely to be rotating at a fractional critical rotation of ∼ 0.80. We measure the average Ip/Ic ratio to quantify the strength of the Hα line and obtain 1.63 for 4 Her and 2.06 for 88 Her. The radius of the Hα emission region is estimated to be Rd/R∗∼ 5.0, assuming a Keplerian disk. These stars are thus found to be fast rotators with relatively small Hα emission region. We detect V/R variation of Hα spectral line during the observed period. We re-estimate the periods for both the stars and obtain two periods of ∼ 46 days and its harmonic of 23.095 days for 4 Her and ∼ 86 days for 88 Her. As these two are shell stars with binaries and have low Hα 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.
@article{arxiv.1602.02933,
title = {Spectroscopic study of Be-shell stars: 4 Her and 88 Her},
author = {Bhat S Shruthi and K T Paul and Subramaniam Annapurni and Mathew Blesson},
journal= {arXiv preprint arXiv:1602.02933},
year = {2016}
}