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of Cepheid Properties

SB2 Cepheids
Classical Cepheids
Type II Cepheids

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Scientific projects

Cepheids in Double-lined Binary Systems

Masses of classical Cepheids of 3 to 11 M⊙ are predicted by theory but those measured clump between 3.6 to 5 M⊙. As a result, their mass-luminosity relation is poorly constrained, impeding our understanding of basic stellar physics and the Leavitt Law. All Cepheid masses come from the analysis of 11 binary systems, including only 5 double-lined and well-suited for accurate dynamical mass determination. We started a project to analyze a new, numerous group of Cepheids in double-lined binary (SB2) systems to provide mass determinations in a wide mass interval and study their evolution.
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Classical Cepheids in Eclipsing Binary Systems

The analysis of classical Cepheids in eclipsing binary systems give as opportunity to learn about the physical parameters of these very important objects, which are crucial for our understanding of the theory of evolution and theory of pulsation, and are ones of the most important distance indicators. The candidates for such systems were started to be found since 1999, when microlensing surveys started to observe the nearby galaxies, Large and Small Magellanic Clouds. Yet none of these candidates was confirmed until 2010, when we published our first results on the classical Cepheid OGLE-LMC-CEP-0227 in the eclipsing binary system in the LMC. Our project started a few years earlier with the spectroscopic observations needed to confirm that the Cepheid is a component of this binary and to characterize the system. Until now we have confirmed 4 other systems with a classical Cepheid being one of the components, including one system composed of two Cepheids. I'm leading this project since 2013.
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Type II Cepheids in Eclipsing Binary Systems

The presence of type II Cepheids in eclipsing binaries give us the same opportunity for studying the physics and evolution of these stars in unprecedented detail. Although not as famous as classical Cepheids, type II Cepheids are also being used as distance indicators, and sometimes are indispensable, as classical Cepheids (being young stars) are not present in all types of galaxies and stellar systems. Their evolution is also more mysterious and our understanding of their origin, structure and pulsations is more limited. The results for the first candidate for such a system were published in 2017, but it appeared that it may be a slightly different object with the mass somewhere in between that of classical and type II Cepheids. The first system containg a genuine type II Cepheid was eventually analyzed and published in 2018. First results were also obtained for three other systems of similar kind. I'm leading this project from the beginning, when it started in 2015.
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Binary Systems in the Milky Way

This project is focused on the analysis of eclipsing and non-eclipsing binary systems in the Solar neighbourhood and in the Milky Way in general. The main goals are to obtain very precise and accurate parameters of the stars to challenge the evolution theory and to measure distances and calibrate distance determination methods for stars of different types.
more information will be provided in the future