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Title: Spectroscopic study of Be-shell stars : 4 Her and 88 Her
Authors: Bhat, S. S
Paul, K. T
Subramaniam, A
Mathew, B
Keywords: Stars: emission-line, Be;Circumstellar matter;Stars: individual (4 Her, 88 Her);Stars: rotation;Techniques: spectroscopic
Issue Date: May-2016
Publisher: IOP Publishing
Citation: Research in Astronomy and Astrophysics, Vol. 16, No. 05, pp. 76
Abstract: We present an 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 HeI lines in the blue spectral region (4000–4500 Å). We find that these stars are likely to be rotating at a fractional critical rotation of ~0.80. We measure the average I p/I c 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 a relatively small Hα emission region. We detect V/R variation of the Hα spectral line during the observed period. We re-estimate the 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 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.
Description: Restricted Access
ISSN: 1674-4527
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Appears in Collections:IIAP Publications

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