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تسجيل مستخدم جديدDIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. VI. Variables in the Central Part of M33
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The DIRECT project aims to determine direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. We present the results of the first large-scale CCD-based search for variables in M33. We have observed two fields located in the central region of M33 for a total of 95 nights on the F. L. Whipple Observatory 1.2-m telescope and 36 nights on the Michigan-Dartmouth-MIT 1.3-m telescope. We have found a total of 544 variables, including 251 Cepheids and 47 eclipsing binaries. The catalog of variables is available online, along with finding charts and BVI light curve data (consisting of 8.2x10^4 individual measurements). The complete set of CCD frames is available upon request.
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The DIRECT project aims to determine direct distances to two important galaxies in the cosmological distance ladder -- M31 and M33 -- using detached eclipsing binaries (DEBs) and Cepheids. The search for these variables requires time-series photometr
y of large areas of the target galaxies and yields magnitudes and positions for tens of thousands of stellar objects, which may be of use to the astronomical community at large. During the first phase of the project, between September 1996 and October 1997, we were awarded 95 nights on the F. L. Whipple Observatory 1.2 m telescope and 36 nights on the Michigan-Dartmouth-MIT 1.3 m telescope to search for DEBs and Cepheids in the M31 and M33 galaxies. This paper, the first in our series of stellar catalogs, lists the positions, three-color photometry, and variability indices of 57,581 stars with 14.4 < V < 23.6 in the central part of M33. The catalog is available from our FTP site at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/star_catalog/M33ABC/
The fundamental properties of detached eclipsing binary stars can be measured very accurately, which could make them important objects for constraining the treatment of convection in theoretical stellar models. However, only four or five pieces of in
formation can be found for the average system, which is not enough. We discuss studies of more interesting and useful objects: eclipsing binaries in clusters and eclipsing binaries with pulsating components.
Accurate stellar parameters of stars in open clusters can help constrain models of stellar structure and evolution. Here we wish to determine the age and metallicity content of the open cluster NGC 2506. To this end we investigated three detached ecl
ipsing binaries (DEBs; V2032, V4, and V5) for which we determined their masses and radii, as well as four red giant branch stars for which we determined their effective temperatures, surface gravities, and metallicities. Three of the stars in the DEBs have masses close to the cluster turn-off mass, allowing for extremely precise age determination. Comparing the values for the masses and radii of the binaries to BaSTI isochrones we estimated a cluster age of $2.01 pm 0.10$ Gyr. This does depend on the models used in the comparison, where we have found that the inclusion of convective core-overshooting is necessary to properly model the cluster. From red giant branch stars we determined values for the effective temperatures, the surface gravities, and the metallicities. From these we find a cluster metallicity of $-0.36 pm 0.10$ dex. Using this value and the values for the effective temperatures we determine the reddening to be E$(b - y) = 0.057 pm 0.004$ mag. Furthermore, we derived the distance to the cluster from Gaia parallaxes and found $3.101 pm 0.017$ kpc, and we have performed a radial velocity membership determination for stars in the field of the cluster. Finally, we report on the detection of oscillation signals in $gamma$ Dor and $delta$ Scuti members in data from the TESS mission, including the possible detection of solar-like oscillations in two of the red giants.
Detached eclipsing binaries are remarkable systems to provide accurate fundamental stellar parameters. The fundamental stellar parameters and the metallicity values of stellar systems are needed to deeply understand the stellar evolution and formatio
n. In this study, we focus on the detailed spectroscopic and photometric studies of three detached eclipsing binary systems, V372,And, V2080,Cyg, and CF,Lyn to obtain their accurate stellar, atmospheric parameters,and chemical compositions. An analysis of light and radial velocity curves was carried out to derive the orbital and stellar parameters. The disentangled spectra of component stars were obtained for the spectroscopic analysis. Final teff, logg, $xi$, vsini, parameters and the element abundances of component stars were derived by using the spectrum synthesis method. The fundamental stellar parameters were determined with a high certainty for V372,And, V2080,Cyg ($sim$$1-2$%) and with an accuracy for CF,Lyn ($sim$$2-6$%). The evolutionary status of the systems was examined and their ages were obtained. It was found that the component stars of V2080,Cyg have similar iron abundance which is slightly lower than solar iron abundance. Additionally, we showed that the primary component of CF,Lyn exhibits a non-spherical shape with its 80% Roche lobe filling factor. It could be estimated that CF,Lyn will start its first Roche overflow in the next 0.02,Gyr.
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n-Devinney (WD) code, and the absolute physical and orbital parameters of these binaries were derived. The masses of both components of ASASSN-V J063123.82+192341.9 were found to be $M_1 = 1.088 pm 0.016$ and $M_2 = 0.883 pm 0.016 M_{odot}$; and those of ASAS J011416+0426.4 were determined to be $M_1 = 0.934 pm 0.046$ and $M_2 = 0.754 pm 0.043 M_{odot}$; those of MW Aur were derived to be $M_1 = 2.052 pm 0.196$ and $M_2 = 1.939 pm 0.193 M_{odot}$. At last, the evolutionary status of these detached binaries was discussed based on their absolute parameters and the theoretical stellar models. Keywords: Stars: binaries: eclipsing $-$ stars: fundamental parameters$-$ stars: evolution $-$ stars: individual: ASASSN-V J063123.82+192341.9, ASAS J011416+0426.4 and MW Aur
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