M-type Mira models with a moderate deviation from solar metallicity (2x and 0.5 x) have been computed and compared to solar-metallicity models. Selected effects of abundance changes on pulsation properties, atmospheric stratifications, spectral features (colours) and surface brightness distributions are discussed.

Narrow-band classification photometry, on a six-color system that measures near-infrared bands of TiO and CN, has been obtained for a set of red supergiants in the Small Magellanic Cloud. To investigate the effects of metallicity on the band-strength indices, comparisons are made to supergiants in the LMC and the Galaxy. Two new variable stars are reported.

About 25% of variable asymptotic giant branch stars in the LMC have light curves that are modulated by a long secondary period of length ~ 1–4 yr. Solar-vicinity analogs of these stars show radial velocity curves that are asymmetric and of small amplitude (~3–5km s−1). Possible explanations for the photometric and radial velocity variations include: eccentric motion of an orbiting companion of mass ~0.1 M⊙; radial and nonradial pulsation; rotation of an ellipsoidal-shaped red giant; episodic dust ejection; and star spot cycles. We find that there are severe difficulties with each of these models. Thus, the long secondary periods are the only unexplained type of large-amplitude stellar variability known at this time.

We present the results of two multi-wavelength studies of the angular diameters of the Mira-like stars ο Cet, W Hya and R Leo. The MAPPIT experiment was able to deliver diameters of these stars over a continuous wavelength region from 0.65 – 1 micron, while the Keck aperture-masking experiment was able to deliver diameters between 1.2 and 3.5 microns. Strong size variations with wavelength were recorded for all stars, and we discuss the implications for model atmospheres of these stars, and speculate on the necessity of including dust scattering in radiative transfer calculations.

More than 4000 stars observed in both MOA and DENIS projects showing periodic or quasi-periodic light curves are studied. Almost all Mira stars are located on the classical period-luminosity relation, and the multiplicity of the period-luminosity relation is confirmed for small-amplitude stars. The colour-magnitude diagrams based on the MOA red band, Rm, and Ks constructed for the sequences, form a single strip with small successive shifts.

We have studied variations of physical parameters in the circumstellar envelopes of carbon-rich Mira variables at different pulsation phases. After comparing the ISO/SWS spectra of these stars with spectral energy distributions calculated from models, we could find the best-fitted parameters for the physical state of the dust envelope at each phase. The variations of the parameters effective temperature, fraction of SiC grains, mass-loss rates, and inner radius of shell, are found to have nearly the same trend as that of the light curve. The other parameters grain size, optical depth, radius of central star and dust temperature at the inner boundary of envelope, are inversely varying to the light curve.

Spectroscopy and variability studies of red stars in the Bar of the LMC enable the stars to be classed as spectral type M, S or C and as variables of class L, SR or Mira. The results are compared with data for Magellanic Cloud star clusters and for the galactic field. The number of S stars relative to carbon stars is generally high in comparison to theoretical expectation.

Low-resolution (0.6 nm) spectra of 24 RV Tauri stars in the LMC shows that most are of intermediate Preston type, hence intermediate metal deficiency. Two belong to Preston’s class B, with enhanced CH and CN. Higher resolution spectra of the carbon star MACHO 47.2496.8 show that the 12C/13C ratio is high and that the Ball lines at 455.4 and 493.4 nm are enhanced. This suggests that the star has undergone the third dredge-up of helium-burning products on the thermally-pulsing AGB and is now in a post-AGB stage of evolution. JHK photometry from the 2MASS catalogue confirms and extends earlier findings that only moderate infrared excesses occur among this sample of RV Tauri stars.

We describe several aspects of the variability of bright pulsating red giant (PRG) stars, with emphasis on the determination of pulsation modes and pulsation masses by using observed multiperiodicity and pulsation constants (Q- values). Our studies of bright PRGs provide a model for the analysis and interpretation of the thousands of PRGs being discovered in surveys of Local Group galaxies.

We present the results of contemporaneous photometric and spectroscopic monitoring of 20 post-AGB stars from Mt John University Observatory. Photometric measures were carried out using Johnson BV and Cousins RI filters, and the radial velocity measurements were acquired using spectra from an echelle spectrograph. Our programme spanned five years and the stars covered a range of spectral types from B to K in order to investigate the behaviour of post-AGB stars as they evolve away from the AGB. A number of stars proved to be variable in ways incompatible with post-AGB models and are reclassified. Periodicities are presented for a number of stars. Photometrically, HD 70379 was found to be pulsating in two modes with periods of 85 and 97 d. The radial velocities also varied, with the peak amplitude occurring when the photometry was also changing most. AI CMi presented three different types of spectra associated with photometric brightness, with varying strengths of narrow emission lines and molecular bandheads. The Hα profiles in almost all of the stars show evidence of emission which varies on time scales of days to months. The Na D line profiles are generally complex showing between 4 and 7 components due to both circumstellar and interstellar material.

A brief rationale for the use of a period test statistic based on the periodogram is given. Results of its application to 380 Mira datasets are summarised.

We report on the progress of the program to study eclipsing binaries (EBs) in the Local Group galaxies. The primary goals of the program are to determine accurate distances and physical properties of the stars, and to probe the structure and evolution of the host galaxies. In particular, the distance to the Large Magellanic Cloud (LMC) is critically important because this nearby galaxy is used to calibrate most of the important cosmic distance indicators such as Cepheid and RR Lyr variables. Over the last several years, we have demonstrated that the distance of the LMC can be reliably measured using selected eclipsing binaries. The combined analyses of the UV/optical spectrophotometry, radial velocities, and light curves yield the stars’ physical properties (mass, radius, Teff, luminosity, metal abundance) and accurate (2–3%) distances. So far, the physical properties and distances of four LMC EBs have been completed and give a distance to the centroid of the LMC of 48.3 ± 1.6 kpc. Several additional EBs in the LMC and the Small Magellanic Cloud have been observed and are being analyzed. Also several LMC EBs have been observed with FUSE (92 – 119 nm) to further refine values of Teff and interstellar absorption. As an extension of these studies, 19–20th mag EBs in M31 are being observed photometrically and spectroscopically. The results of this extragalactic EB program are discussed along with plans to use EBs to study the host galaxy structure.

Eclipsing binary systems potentially allow the direct and precise determination of the important properties of their component stars. An eclipsing binary containing a Cepheid variable which is also a double-lined spectroscopic binary would allow, for the first time, the direct measurement of the absolute luminosity and mass of the Cepheid. The MACHO Project LMC database contains five systems whose light curves show variations due to both eclipses and pulsation but only one has been clearly identified as an intermediate-mass, Population I object. This object, MACHO 81.8997.87 (= OGLELMC_SC16 119952) is a 2.035-d overtone Cepheid in an 800.4-d binary system with an M-type companion. Here we present the results of the analysis of the light curve of this system, the implications for its evolutionary history and discuss the prospects for future observations.

S Mus is the Cepheid with the hottest known companion. As a benefit, the large ultraviolet flux made it the only Cepheid companion for which the velocity amplitude could be measured with the echelle mode of the HST GHRS. Unfortunately, the high temperature is difficult to constrain at wavelengths longer than 1200 Å because of the degeneracy between temperature and reddening. We have now obtained a FUSE spectrum in order to determine the temperature of the companion better. We have identified two regions which are temperature sensitive near 16 000 K, but are relatively unaffected by H2 absorption (940 Å, and the Ly β wings). By comparing S Mus B with other FUSE spectra, we have determined a temperature of 17 000 K. The resultant Cepheid mass is 6.0 ± 0.4 M⊙

There are now four dwarf novae known with white dwarf primaries that show large amplitude non-radial oscillations of the kind seen in ZZ Cet stars. We compare the properties of these stars and point out that by the end of the Sloan Digital Sky Survey more than 30 should be known.

The analysis of radial velocities (RVs) of the Be star ο Cas from 27 high S/N spectra allowed us to revive the binary nature of this star, first suggested by Abt & Levy (1978, “AL”), but later refuted by several authors. The period search in our RV data based on measurements of Hα emission and He I λ6678 Å absorption profiles detected a dominant peak close to the 1033-d period found by AL. The resulting curves are very smooth. The rms error of the solution for the emission RVs is nearly 5 times lower than the scatter of the solution by AL. If the RV variations are due to orbital motion, then ο Cas turns out to be a challenging system with an unseen secondary component with mass comparable to, or even more massive than the primary.

Superhumps – quasi-periodic oscillations at periods a few percent different than the orbital periods – have been observed in several dozen binary systems of various types. It is well-accepted now that they are caused by the precession of the accretion disc. New findings on TV Col, TX Col and V4742 Sgr are presented. These cataclysmic variables (CVs) have exceptional precessing periods that cast strong doubt on the predictions of the Tidal Disc Instability model.

20 Leo is a spectroscopic triple system composed of 3 very similar stars, one of which seems to be a δ Sct star. Observations at high spectral and high time resolution have been obtained at the Observatoire de Haute Provence with the ELODIE spectrograph on the 1.9-m telescope. The spectra were taken during 7 nights in 2003 January and cover the whole optical domain from 3900 to 6800 Å. We used a Fourier transform technique recently developed by P. Hadrava to disentangle the combined spectrum. Application of the method allows the derivation of radial velocities at all orbital phases (even at phases of complete blending), as well as individual spectra for each component. From these computations we deduced more accurate individual radial velocities and improved orbital parameters describing the motion of the inner binary. Model atmospheres were used to analyze each individual spectrum and determine stellar fundamental parameters of the three components such as effective temperature, surface gravity and projected rotation velocity.

We present new photometric results of the Algol-type semidetached eclipsing binary AB Per which was recently discovered to have a Delta Scuti pulsating component.

High-resolution spectroscopic observations have been made of a number of southern binary Cepheids to determine their dynamical masses. The stars are part of a long-term programme to observe southern variable stars for which a valuable long-term database has been obtained. The most recent radial velocities have a precision of ~300ms−1, allowing the detection of velocity differences of ~l kms−1 with confidence. Masses were determined for three systems: the 9-day Cepheid S Mus (6.0±0.4M⊙), the double-mode Cepheid Y Car (4.5±1.8M⊙) and the 5-day Cepheid V350Sgr (6.0±0.9M⊙). For five Cepheids (YZCar, AX Cir, V636 Sco, W Sgr and T Mon) new or improved orbital solutions were found. Line level effects have been observed in several species of lines. Most Cepheids were observed to show the same progression of line level effects. Using non-linear radiative hydrodynamical models, we have compared the results of these models with our observations. These have shown that AX Cir and YZ Car have the following properties: L = 2050 L⊙, M = 4.8 M), Teff = 5900 K and L = 9350 L∩, M = 7.7M∩, Teff = 5590 K. Our models show no strong Shockwaves being produced. Good agreement was found between the observed and modelled spectral lines Fe I 5576Å, Si II 6347Å, Ba II 5853Å and Ca II 8542Å.