RV Tauri Stars Research Articles

Two-color photographic photometry of variables in the globular cluster M28

Visual magnitudes have been measured for 20 variables on 32 plates of M28. These have been combined with previously published as well as newly determined blue magnitudes in order to obtain colors for the variables. Blue and visual light curves are presented for 15 of the the variables, including one W Virginis star V4, one RV Tauri star V17, one field Mira variable V7, nine cluster RR Lyrae stars, and three field RR Lyrae stars. It is shown that V14, previously thought to be a c type RR Lyrae star, is to the red of the instability strip. The visual light curve of V9 suggests that the star may be a member of a binary or a very close optical double. Possible evidence for differential reddening in the vicinity of M28 is presented. The bimodal distribution of the periods of the RR Lyrae stars in M28 may indicate a spread in metallicity among the RR Lyrae variables. 16 refs.

Polarimetric and photometric study of the RV Tauri star AR Puppis

Les resultats de la polarimetrie UBVRI et de la photometrie BV de l'etoile AR Pup de type RV Tauri sont presentes et discutes

The nature of RV Tauri variables. II- Properties of the peculiar F stars

Basic atmospheric parameters for six RV Tauri variables are considered. The Fe/H abundance ratios for the stars are found to be between -1 and - 1.7, inclusively. Stars of the Preston (1962) type B and C subclasses do not appear segregated by metallicity. In comparison to the cooler Preston type A stars, types B and C are shown to be more metal poor by a factor of 10, on average. The results are consistent with the theory that RV Tau type B and C variables are a direct evolutionary analog to the cluster type II Cepheids.

The nature of RV Tauri variables. I - Spectrophotometric atlas of selected field stars

The nature of RV Tauri variables. I - Spectrophotometric atlas of selected field stars

A Study of Period Doubling in a One-Zone Pulsating Stellar Model

AbstractA simple one-zone model for nonlinear stellar pulsations is outlined and applied to the study of period doubling observed in some W Virginis and RV Tauri stars. The model reveals a number of period doubling bifurcations as the parameters are varied, similar to those found by Buchler & Kovacs in their series of hydrodynamic models. In the vicinity of a stable limit cycle, despite its large number of degrees of freedom, the model develops an essentially one-dimensional Poincaré’s return map, determining the modulation of the amplitude. The analysis of these maps confirmed that period doubling has its origin in a strong nonlinear increase of total energy losses per period as radial amplitude, δr/r, increases. An additional study of nearly periodic hydrodynamic models with P > 15 days, calculated including radiative transfer effects, shows that the rate of energy dissipation per period by shocks in the atmospheres increases rapidly with δr/r, whereas the excitation rate, δo, remains rather stable. This permitted us to construct an analytic return map for maxima of the total kinetic energy which clearly demonstrates the mechanism of successive period doubling as δo, the sole bifurcation parameter, grows monotonically.

IRAS Infrared Fluxes of RV Tauri Stars

Data resulting from the IRAS survey relating to the stars of the RV Tauri class have been examined. Of a total of 78 objects definitely assigned to this class in the 4th edition of the GCVS, 33 are to be found in the Point-Source Catalogue, and for six of these spectral data are available in the low-resolution Spectral Atlas (to 22.6 μm published by the IRAS Science Team (A & A Suppl. 65, 607, 1986). In the latter the pronounced difference in infrared emission between the carbon-rich star AC Her and most other RV Tauri stars, first noted by Gehrz in 1972, is striking, taking the form of a very marked continuation of that star's emission to at least 22 μm.

Spectroscopic and Polarimetric Observations of AC Her and UU Her

We present preliminary results obtained between March and August of 1987 of a two-year spectropolarimetric study of 10 RV Tauri stars. The observations were made at the University of Wisconsin's Pine Bluff Observatory using the 36 inch cassegrain telescope with a Lyot polarimeter. The spectral resolution of the instrument was 6 A and covered the range between 4350 A and 7500 A. The polarimetry covered the same wavelength range but is binned in four broad bands at 4828 A, 5361 A, 6025 A, and 6877 A.

Another Look at the RV Tauri Period-Luminosity Relation

The Period-Luminosity (P-L) relation for the RV Tauri variables (DuPuy 1973) contradicts those of other variables in the instability strip as it predicts lower luminosity at longer pulsational periods. It is based primarily upon three globular cluster variables. DuPuy determined secular and statistical parallaxes from 23 field variables, defining a simple P-L relation with a slightly negative slope.

The long-term behavior of the population II Cepheid V1 in the globular cluster Messier 12

Observations made over an interval of 73 yr have been used to study the period changes of the W Virginis star in M12. They show that the period has undergone a series of abrupt changes, both increasing and decreasing, instead of a smooth change as predicted by evolutionary theory. This result is compared with period changes of W Virginis and RV Tauri stars in other galactic globular clusters, and it is found that the long-term behavior of the periods of most of these stars is similar to that of the variable in M12. However, two stars, V42 in M5 and V1 in Omega Centauri, may be in their final blueward evolutionary phase. 45 references.

Photometric and Polarimetric Observations of the RV Tauri Star AR Puppis

RV Tauri stars are variable yellow supergiants and they display anomalous excesses in infrared radiation indicating the presence of cool and extended dust thermospheres, presumbly formed from the matter ejected by them (Gehrz 1972). AR Pup, recognised as a member of RV Tauri stars, shows strong CH and CN bands in the optical spectrum and is considered to be carbon-rich (Lloyd Evans 1974). During a programme of broad band polarimetric observations of carbon variables, AR Pup was found to exhibit a large and highly time-dependent linear polarisation (Raveendran & Kameswara Rao 1987).During the period from 1987 January 20 to April 6, AR Pup was observed on 33 nights through standard B and V filters with the 34-cm reflector of the Vainu Bappu Observatory, Kavalur. We also obtained UBVRI polarimetry of AR Pup with the PRL - Polarimeter (Deshpande et al. 1985) attached to the 102-cm reflector on six nights during the same period. Present observations clearly indicate that the large time dependent variations in polarisation, both in the amount and wavelength dependence, observed at earlier epochs by us were not isolated events but were segments of a continuous variation which is cyclic and related to the light curve.

Balmer Emission Profiles in Radially Pulsating Stars: The Case of the Double Hα Emission

We present new high resolution profiles of Ha emissions in radially pulsating stars (RR Lyrae, W Virginis, RV Tauri, Mira stars and Classical Cepheids). Depending on phase, these profiles can show an apparent absorption within the emission close to the Hα laboratory wavelength. The origin of this feature is discussed in the framework : (a) of a composite of a single emission and a deep photospheric absorption (RR Lyrae, W Virginis and RV Tauri stars); (b) of a true absorption caused by cool hydrogen above the shock wave producing the emission; (c) of a geometric model in which the absorption is a lack of emission. Recent observations (Hα profiles of Mira stars S Car and T Cen), which show that the absorption dip is below the continuum level, are in favour of the true absorption model.

Optical and infrared observations of RV Tauri stars

Optical and infrared observations of RV Tauri stars

Slow variability and circumstellar shells of red variable stars

Infrared photometry shows that while all RV Tauri stars have circumstellar dust shells, the RVb stars with slow cyclic variations in mean light as well as the 30–100 day variations common to all RV stars have more hot dust close to the star (Lloyd Evans 1985). Many M giant stars which are variables of semiregular type also show long-period variations in the mean light (O'Connell 1933; Payne-Gaposchkin 1954), with a roughly constant ratio between the two periods. Payne-Gaposchkin (1954) found P2/P1 ~9.4 for red variables of type M and P2/P1 ~19.4 for stars of type F-K, most of which are FV Tauri stars. Re-analysis using the more extensive data available now indicates P2/P1 ~10 for the M giants and P2/P1 ~15 for the FV Tauri stars. The nature of the long-period variability is unknown (Wood 1975).

Optical/infrared observations of RV Tauri stars

Optical/infrared observations of RV Tauri stars obtained at SAAO have allowed the natures of the dust shells around stars with infrared excess to be investigated. The data suggest that dust formation occurs sporadically and that some stars have multiple shells. There is no photometrically discernible difference between carbon- and oxygen-rich stars or their dust shells. There is some evidence that stars with higher metallicity have more dust.

Pulsation masses and luminosities for the double mode RV Tauri star UU Her and the 89 Her star HD 161796

Pulsation masses and luminosities for the double mode RV Tauri star UU Her and the 89 Her star HD 161796

RV Tauri stars as post-asymptotic giant branch objects

RV Tau stars are rare, luminous pulsators of spectral types F, G, and K. Analysis of the IRAS data shows that the mass-loss rates from RV Tau stars have apparently significantly decreased during the past 500 yr. It seems likely that these stars have just evolved from the phase of rapid mass loss, characteristic of the last stages of the asymptotic giant branch (AGB). The birthrate of RV Tau stars in the solar neighborhood is about a tenth of the birthrate of all planetary nebulae, and this is consistent with the view that we are witnessing the subset of stars undergoing post-AGB evolution that are low mass and at least in some cases of low metallicity.

Circumstellar material and the light variations of RV Tauri stars

Photometrie IR dans le systeme JHKL de 35 etoiles de type RV Tauri ou relies. Ces etoiles montrent un exces IR indiquant la presence de poussiere circumstellaire avec une temperature d'environ 900 K

The 2200 A circumstellar dust absorption feature in the spectra of three bright RV Tauri stars

view Abstract Citations (17) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The 2200 A circumstellar dust absorption feature in the spectra of three bright RV Tauri stars. Baird, S. R. ; Cardelli, J. A. Abstract IUE observations of the 2200 A absorption feature of circumstellar dust were made of the three RV Tauri stars AC Her, U Mon, and R Sct. U Mon was found to have a dust shell with a much lower column density at 2200 A than R Sct and possibly AC Her, requiring U Mon to have a much more extended dust shell than R Sct to account for its greater infrared excess. AC Her and R Sct were observed twice, at different phases of their cycles, and no major change in the 2200 A absorption feature with phase was detected. Such a change would have supported the idea that the slight polarization of these stars' visual light is caused by the circumstellar dust. Publication: The Astrophysical Journal Pub Date: March 1985 DOI: 10.1086/163026 Bibcode: 1985ApJ...290..689B Keywords: Absorption Spectra; Cosmic Dust; Stellar Envelopes; Stellar Spectra; Supergiant Stars; Ultraviolet Absorption; Variable Stars; Interstellar Extinction; Iue; Particle Density (Concentration); Polarization Characteristics; Stellar Luminosity; Stellar Spectrophotometry; Astrophysics full text sources ADS | data products SIMBAD (3) MAST (1) INES (1)

The Chemical Composition of Cool Stars: II - The Hydrogen Deficient Stars

AbstractThe chemical composition of the R Coronae Borealis and cool hydrogen deficient carbon stars is reviewed. Similarities and differences between these stars and the hot He stars are noted. Proposed origins for the hydrogen deficient stars are sketched. Recent claims that normal (spectral type N) cool carbon stars are hydrogen deficient are shown to be unfounded. Attention is drawn to the curious case of pop. II variables (RV Tauri, W Virginis, and RR Lyrae stars) whose atmospheres show striking deficiencies of heavy elements and may be hydrogen deficient.

EMISSION LINES IN THE SPECTRA OF THE RV TAURIS STARS U MONOCEROTIS AND AC HERCULIS.

ABSTRACT Strong metallic emission lines have been observed in the spectra of the RV Tauri stars U Mon and AC Her near recent light minima. While these two variables differ in a number of significant respects, the metallic emission spectra are quite similar, resembling the emission that was previously reported as present in the spectrum of R Sct at a deep minimum. The data appear to support Baird's shock-wave model for the spectral behavior of RV Tauri stars.