A Full-Amplitude Nonlinear Model for RR Lyr: Pulsations, Shock Waves and Hα Peculiarities

AbstractThe shock phenomena and Hα formation in the atmosphere of RR Lyrae are investigated by means of numerical simulations. The full-amplitude hydrodynamical model is generated, adopting M = 0.578M⊙, L = 62L⊙, Teff = 7175K and Population II composition. The Hα profiles are obtained by solution of the non-LTE line transfer problem for the multilevel hydrogen atom. In the course of pulsations an extended (about 16 static scales) low-density atmosphere is produced with nearly exponential density decrease. Two shocks, propagating outwards, are successively generated during one period. The shock amplitude reaches 140 km/s. No mass loss has been found. These results confirm the earlier results of S. Hill (1972). The main shock develops very high, at mass depths near 0.001 g per area, whereas computations for W Vir yield 100. An analysis of the Fe I and Ti II lines shows that this difference is sufficient to explain the lack of metallic line-doubling in RR Lyrae stars. The bump on the light curve is due to a weak shock, propagating below the photosphere, which is generated with the early shock at the stage of expansion at the H-recombination front. The central intensities, Dopplerian shifts, amplitudes and phases of splitting of the computed Hα profiles agree well with the observed values (Gillet & Crowe 1988). The lack of strong emission also fits the observations, resulting from strong scattering processes near the shock. The predicted Lyman lines show strong emission, reaching maximum at the maximum light.

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Physical parameters for RR Lyrae stars in the sdss filter system

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312021230 ◽

2012 ◽

Vol 8 (S289) ◽

pp. 126-129 ◽

Cited By ~ 1

Author(s):

Márcio Catelan ◽

Gabriel I. Torrealba ◽

Claudio Cáceres ◽

Horace A. Smith ◽

Nathan De Lee ◽

...

Keyword(s):

Physical Parameters ◽

Photometric System ◽

Rr Lyrae Stars ◽

Filter System ◽

Rr Lyrae ◽

Wide Range ◽

Lyrae Stars ◽

Very High

AbstractWe present a calibration of the metallicity and physical parameters (temperature, luminosity, gravity, mass, radius) for RR Lyrae stars using the ugrizsdss photometric system. Our work is based on calculations of synthetic horizontal branches (HBs), fully taking into account evolutionary effects for a wide range in metallicities and HB morphologies. We provide analytical fits that are able to provide all quantities mentioned with very high (internal) precision, based solely on mean sdss magnitudes and colors.

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Spectroscopic and photometric time series of the bright RRc star T Sex

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3452 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2554-2563

Author(s):

József M Benkő ◽

Ádám Sódor ◽

András Pál

Keyword(s):

Time Series ◽

Weak Shock ◽

Characteristic Line ◽

Interstellar Space ◽

Data Sets ◽

Pulsation Frequency ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Lyrae Stars ◽

Different Sources

ABSTRACT We present spectroscopic time series observations on one of the brightest northern RRc stars, namely T Sex. Additionally, we also analysed extended photometric data sets, particularly the recent observations of the TESS space telescope. The main findings of our studies are as follows: T Sex, unlike all RRc stars whose space photometry has been analysed, shows only the 0.5fx frequency as an additional pulsation frequency. With this, T Sex may be the first represent of such rare RRc stars found from space photometry. The spectroscopic data show a periodic distortion of the H α line with the pulsation phase. This phenomenon has not been reported for any RR Lyrae stars. The characteristic line distortion is probably caused by the turbulent convection, which resulted in higher macroturbulent velocity for T Sex than that for typical RRab stars. Line doubling of the Na D line was observed between the 0.37 and 0.80 pulsation phases. The explanation of this phenomenon is that the two absorption components originate from different sources. The redder component comes from the pulsating atmosphere of the star, while the bluer one comes from the interstellar space. At phase 0.438, we detected emission on the Na D line, which may indicate a weak shock wave.

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The Unusual Period Distribution of the RR Lyrae Variables in NGC 5897

International Astronomical Union Colloquium ◽

10.1017/s0252921100011957 ◽

1989 ◽

Vol 111 ◽

pp. 287-287

Author(s):

Amelia Wehlau

Keyword(s):

Light Curves ◽

Instability Strip ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Period Distribution ◽

Unusual Distribution ◽

Photoelectric Observations ◽

Lyrae Stars ◽

Branch Star ◽

Central Concentration

AbstractAttention is called to the rather unusual distribution of the periods of the RR Lyrae variables in NGC 5897, a metal-poor halo globular cluster with a very low central concentration. Of the seven RR Lyrae stars known in the cluster, three have periods between 0.797 and 0.856 day and two have periods of 0.45 and 0.42 day. The other two have periods of 0.34 and 0.35 day with much lower amplitudes of variation. Due to the lack of crowding in this cluster photoelectric observations and Fourier decompositions of the resulting light curves should be possible for at least six of the RR Lyrae variables. In addition, the cluster appears to contain a non-variable horizontal branch star, SK 120, lying within the instability strip. As this is the only well documented case of such a star, photoelectric observations of this star would also be desirable.

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General Properties of the Two Groups of Globular Clusters and Their Variable Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900010743 ◽

1975 ◽

Vol 67 ◽

pp. 541-543

Author(s):

A. V. Mironov ◽

N. N. Samus'

Keyword(s):

Chemical Composition ◽

Globular Clusters ◽

Variable Stars ◽

Rr Lyrae Stars ◽

General Properties ◽

Rr Lyrae ◽

Lyrae Stars

The dependences of the numbers of variable stars in globular clusters on the chemical composition are studied. For given metallicity the numbers of RR Lyrae stars reduced to some definite total number of stars in the cluster are different for the two groups of globular clusters introduced by Mironov.

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