Luminosities and infrared excess in Type II and anomalous Cepheids in the Large and Small Magellanic Clouds

Abstract

(abridged) Type II and anomalous Cepheids (ACs) are useful distance indicators when there are too few classical Cepheids or when RR Lyrae stars are too faint. We study the sample of 335 Type II and ACs in the Small and Large MCls detected in OGLE-III data.The SEDs are constructed and fitted with a dust radiative transfer model, thereby leading to a determination of luminosity and effective temperature.In addition, a subsample of targets is investigated for possible binarity by looking for the light-time travel effect (LITE). Hertzsprung-Russell diagrams (HRD) are constructed and compared to evolutionary tracks and theoretical instability strips (ISs). In agreement with previous suggestions, the BL Her subclass can be explained by the evolution of $\sim$0.5-0.6~\msol\ stars evolving off the ZAHB and the ACs can be explained by the evolution of $\sim$1.1-2.3~\msol\ stars. The evolution of the W Vir subclass is not clear. A relation to binarity might be at the origin of the W Vir stars, which has already been explicitly suggested for the peculiar W Vir stars. For $\sim 60\%$ of the RV Tau and $\sim 10\%$ of the W Vir objects an infrared excess is detected from the SED fitting. A recent result is confirmed that stars exist with luminosities below that predicted from single-star evolution, which show a clear infrared excess, and the shape of the excess suggests a connection to binary evolution. The investigation of the LITE effect revealed 20 systems that appear to show periodic variations and may be new binaries, although this study requires follow-up. About 40 stars show significant period changes.

A&A accepted

References in corpus (22)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• Clustering of Local Group distances: publication bias or correlated measurements? I. The Large Magellanic Cloud
• Clustering of Local Group distances: publication bias or correlated measurements? III. The Small Magellanic Cloud
• RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system
• Optically visible post-AGB/RGB stars and young stellar objects in the Small Magellanic Cloud: candidate selection, spectral energy distributions and spectroscopic examination
• A newly discovered stellar type: dusty post-red giant branch stars in the Magellanic Clouds
• The panchromatic view of the Magellanic Clouds from Classical Cepheids. I. Distance, Reddening and Geometry of the Large Magellanic Cloud disk
• The VMC Survey. XIII. Type II Cepheids in the Large Magellanic Cloud
• Variable stars in Local Group Galaxies - II. Sculptor dSph
• Accelerated post-AGB evolution, initial-final mass relations, and the star-formation history of the Galactic bulge
• New RR Lyrae variables in binary systems
• The occurrence of Binary Evolution Pulsators in the classical instability strip of RR Lyrae and Cepheid variables
• Survey of non-linear hydrodynamic models of type-II Cepheids
• Synthetic properties of bright metal-poor variables. II. BL Her stars
• The evolved circumbinary disk of AC Her: a radiative transfer, interferometric and mineralogical study
• Synthetic properties of bright metal-poor variables. I. "Anomalous" Cepheids
• AGB nucleosynthesis in the Large Magellanic Cloud. Detailed abundance analysis of the RV Tauri star MACHO47.2496.8
• First detection of photospheric depletion in the LMC
• First observations of W Virginis stars with K2: detection of period doubling
• Multicolor photometry of the Type II Cepheid prototype W Virginis
• Chaos in hydrodynamic BL Herculis models

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• Old-Aged Stellar Population Distance Indicators
• TESS observations of Cepheid stars: first light results
• The period-luminosity and period-radius relations of Type II and anomalous Cepheids
• High-precision distance measurements with classical pulsating stars
• Evolutionary and pulsation properties of Type II Cepheids
• Studying bright variable stars with the Multi-site All-Sky CAmeRA (MASCARA)
• Analysing the spectral energy distributions of Galactic classical Cepheids
• Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution
• The evolutionary nature of RV Tauri stars in the SMC and LMC
• A theoretical framework of BL Her stars. I. Effect of metallicity and convection parameters on period-luminosity and period-radius relations
• An absolute calibration of the near-infrared Period-Luminosity Relations of Type II Cepheids in the Milky Way and in the Large Magellanic Cloud
• Variable star classification with a Multiple-Input Neural Network
• The stellar photosphere-hydrogen ionization front interaction in Classical Pulsators: a theoretical explanation for observed period-colour relations
• Physical properties of galactic RV Tauri stars from Gaia DR2 data
• OGLE-GAL-ACEP-091 -- The First Known Multi-Mode Anomalous Cepheid
• Type II and anomalous Cepheids in the Kepler K2 mission