Neutral and ionized emission lines in the type II Cepheid W Virginis

Kovtyukh, V. V.; Wallerstein, George; Andrievsky, S. M.; Gillet, Denis; Фокин, А. Б.; Templeton, Matthew R.; Henden, A. A.

doi:10.1051/0004-6361/201015912

Cited by 17 publications

(21 citation statements)

References 11 publications

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“…Once again, they are very similar to those presented for W Vir by Lèbre & Gillet (1992, their Fig. 6) and by Kovtyukh et al (2011, their Figs. 4,8).…”

Section: Emission In Hαsupporting

confidence: 90%

“…Lèbre & Gillet (1992) used high resolution spectroscopy to follow the evolution of the emission profile of Hα through an entire cycle of W Vir and further improved the shock model. Finally, Kovtyukh et al (2011) extended this study to many metallic lines including Fe I, Fe II, Na I, and Ba II and concluded that W Vir consists in its inner part of a pulsating star with periodic shocks reaching the upper atmosphere and in its outer part of a circumstellar envelope.…”

Section: Emission In Hαmentioning

confidence: 84%

“…More recent observations by Raga et al (1989) were used to determine the H/He ratio in the atmosphere of W Vir. He I emission lines were extensively studied by both Lèbre & Gillet (1992) and Kovtyukh et al (2011). The former reported the presence of emission in the He 5875.64 Å line between phases φ = 0.827 and φ = 0.009, while the latter detected emission between φ = 0.865 and φ = 0.201 for the same line.…”

Section: Emission In Hαmentioning

confidence: 98%

“…As far as Type II Cepheids are concerned, Kovtyukh et al (2011) analysed hydrogen, helium, and metallic lines in W Vir itself. They were able to reproduce the specifics of spectral line variability in W Vir with the help of a non-linear pulsation model.…”

Section: Chemical Compositionmentioning

confidence: 99%

“…Since the Maas et al (2007) paper, only two new Type II Cepheids have been studied in detail: QQ Per by Wallerstein et al (2008) and W Vir by Kovtyukh et al (2011). After a brief description of the data in Sect.…”

Section: Introductionmentioning

confidence: 99%

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Type II Cepheids in the Milky Way disc

Lemasle

Kovtyukh

Bono

et al. 2015

A&A

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Context. A robust classification of Cepheids into their different sub-classes and, in particular, between classical and Type II Cepheids, is necessary to properly calibrate the period-luminosity relations and for populations studies in the Galactic disc. Type II Cepheids are, however, very diverse, and classifications based either on intrinsic (period, light curve) or external parameters (e.g., [Fe/H], |z|) do not provide a unique classification. Aims. We want to ascertain the classification of two Cepheids, HQ Car and DD Vel, that are sometimes classified as classical Cepheids and sometimes as Type II Cepheids. Methods. To achieve this goal, we examine both their chemical composition and the presence of specific features in their spectra. Results. We find emission features in the Hα and in the 5875.64 Å He I lines that are typical of W Vir stars. The [Na/Fe] (or [Na/Zn]) abundances are typical of thick-disc stars, while BL Her stars are Na-overabundant ([Na/Fe] > +0.5 dex). Finally, the two Cepheids show a possible (HQ Car) or probable (DD Vel) signature of mild dust-gas separation that is usually observed only in long-period type II Cepheids and RV Tau stars. Conclusions. These findings clearly indicate that HQ Car and DD Vel are both Type II Cepheids from the W Vir sub-class. Several studies have reported an increase in the Cepheids' abundance dispersion towards the outer (thin) disc. A detailed inspection of the Cepheid classification, in particular for those located in the outer disc, will indicate whether this feature is real or simply an artefact of the inclusion of type II Cepheids belonging to the thick disc in the current samples.

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“…Once again, they are very similar to those presented for W Vir by Lèbre & Gillet (1992, their Fig. 6) and by Kovtyukh et al (2011, their Figs. 4,8).…”

Section: Emission In Hαsupporting

confidence: 90%

Section: Emission In Hαmentioning

confidence: 84%

Section: Emission In Hαmentioning

confidence: 98%

Section: Chemical Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Type II Cepheids in the Milky Way disc

Lemasle

Kovtyukh

Bono

et al. 2015

A&A

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First detection of helium emissions in RR Lyrae

Gillet

Fabas

Lèbre

2013

A&A

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Context. During the past 100 years, helium emission lines have never been observed in RR Lyrae stars, especially in RRab-type ones where strong shock waves are nevertheless present in their atmosphere. Only recently have the observation of He I emission lines in 10 RRab stars and the detection of very weak He II emission in 3 of them been reported. All these stars are Blazhko stars, while helium emission has never been detected in non-Blazhko stars. Aims. We investigate the physical origin of the presence (or absence) of helium emission in the spectra of RR Lyrae stars, using a recent explanation of the Blazhko effect based on the interplay between two shocks occurring during each pulsation cycle. Methods. From high-resolution spectra collected with ESPaDOnS at CFHT, we report for the first time the observation of He I emission lines in the brightest RR Lyrae star of the sky, RR Lyr. Our observation was done just after a Blazhko maximum. We have also very likely detected He II emission. Results. The presence of He I and He II emission lines is directly connected to the shock intensity. Helium emissions only occur during the strongest amplitude phase of Blazhko stars in which an amplification mechanism of the shock intensity arises. This kind of hypersonic shock has not yet been reported in non-Blazhko stars because in this picture the intensity of their shocks is not amplified. Conclusions. The occurrence of helium emission is a direct consequence of the Blazhko effect. The greater the Blazhko amplitude, the greater the shock intensity, and therefore emission lines of helium increase. Considering the spectroscopic features observed (or not) in the RR Lyrae stars, we can define three hydrodynamic regimes: (a) the supersonic regime in which only hydrogen emissions are visible such as in non-Blazhko stars; (b) the weak hypersonic regime where the He I emission lines are also observed; and (c) the strong hypersonic regime with the additional observation of He II emission lines. These two last regimes only occur in Blazhko stars.

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Broad-band spectroscopy of the ongoing large eruption of the luminous blue variable R71

Mehner

Baade

Rivinius

et al. 2013

A&A

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Aims. The luminous blue variable (LBV) R71 is currently undergoing an eruption, which differs photometrically and spectroscopically from its last outburst in the 1970s. Valuable information on the physics of LBV eruptions can be gained by analyzing the spectral evolution during this eruption and by comparing R71's present appearance to its previous outburst and its quiescent state.Methods. An ongoing monitoring program with VLT/X-shooter will secure key spectral data ranging from visual to near- show H i and Fe ii P Cyg profiles, which were present during its last outburst in the 1970s and which are normally observed during LBV outbursts. Low-excitation forbidden emission lines and Fe i P Cyg-like profiles from a slowly expanding nebula became apparent in late 2012. These lines originate likely in the rarefied region above the pseudo-photosphere up to 13 AU from the star. Conclusions. The rise in R71's visual magnitude and the low apparent temperature of its pseudo-photosphere during the current eruption are unprecedented for this star. R71 most likely increased its bolometric luminosity by ΔM bol = 0.4-1.3 mag compared to its quiescent state. The very low temperature of its pseudo-photosphere implies a very high-mass loss rate on the order ofṀ R71,2012 ∼ 5 × 10 −4 M yr −1 compared toṀ quiescence ∼ 3 × 10 −7 M yr −1 . The apparent radius increased by a factor of 5 to about 500 R . No fastmoving material indicative of an explosion is observed. The changes in R71's photometry and spectrum are thus likely consequences of a tremendously increased wind density, which led to the formation of a pseudo-photosphere.

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Neutral and ionized emission lines in the type II Cepheid W Virginis

Cited by 17 publications

References 11 publications

Type II Cepheids in the Milky Way disc

Type II Cepheids in the Milky Way disc

First detection of helium emissions in RR Lyrae

Broad-band spectroscopy of the ongoing large eruption of the luminous blue variable R71

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