Spectroscopic study of Be-shell stars: 4 Her and 88 Her

Title

Spectroscopic study of Be-shell stars: 4 Her and 88 Her

Creator

Bhat S.S.; Paul K.T.; Subramaniam A.; Mathew B.

Description

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 . 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 H? line and obtain 1.63 for 4 Her and 2.06 for 88 Her. The radius of the H? 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 H? emission region. We detect V/R variation of the H? 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 H? 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. 2016 National Astronomical Observatories, Chinese Academy of Sciences and IOP Publishing Ltd.

Source

Research in Astronomy and Astrophysics, Vol-16, No. 5

Date

2016-01-01

Publisher

Institute of Physics Publishing

Subject

emission-line, Be - circumstellar matter - stars; individual (4 Her, 88 Her) - stars; rotation- techniques; spectroscopic; stars

Coverage

Bhat S.S., Department of Physics, Christ University, Bangalore, 560029, India; Paul K.T., Department of Physics, Christ University, Bangalore, 560029, India; Subramaniam A., Indian Institute of Astrophysics, II Block Kormangala, Bangalore, 560034, India; Mathew B., Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai, 400005, India

Rights

All Open Access; Green Open Access

Relation

ISSN: 16744527

Format

Online

Language

English

Type

Article

Identifier

https://doi.org/10.1088/1674-4527/16/5/076

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