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  • 1
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    An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent (2013)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2013-03-08
    Beschreibung: In the era of precision cosmology, it is essential to determine the Hubble constant to an accuracy of three per cent or better. At present, its uncertainty is dominated by the uncertainty in the distance to the Large Magellanic Cloud (LMC), which, being our second-closest galaxy, serves as the best anchor point for the cosmic distance scale. Observations of eclipsing binaries offer a unique opportunity to measure stellar parameters and distances precisely and accurately. The eclipsing-binary method was previously applied to the LMC, but the accuracy of the distance results was lessened by the need to model the bright, early-type systems used in those studies. Here we report determinations of the distances to eight long-period, late-type eclipsing systems in the LMC, composed of cool, giant stars. For these systems, we can accurately measure both the linear and the angular sizes of their components and avoid the most important problems related to the hot, early-type systems. The LMC distance that we derive from these systems (49.97 +/- 0.19 (statistical) +/- 1.11 (systematic) kiloparsecs) is accurate to 2.2 per cent and provides a firm base for a 3-per-cent determination of the Hubble constant, with prospects for improvement to 2 per cent in the future.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pietrzynski, G -- Graczyk, D -- Gieren, W -- Thompson, I B -- Pilecki, B -- Udalski, A -- Soszynski, I -- Kozlowski, S -- Konorski, P -- Suchomska, K -- Bono, G -- Moroni, P G Prada -- Villanova, S -- Nardetto, N -- Bresolin, F -- Kudritzki, R P -- Storm, J -- Gallenne, A -- Smolec, R -- Minniti, D -- Kubiak, M -- Szymanski, M K -- Poleski, R -- Wyrzykowski, L -- Ulaczyk, K -- Pietrukowicz, P -- Gorski, M -- Karczmarek, P -- England -- Nature. 2013 Mar 7;495(7439):76-9. doi: 10.1038/nature11878.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Universidad de Concepcion, Departamento de Astronomia, Casilla 160-C, Concepcion, Chile. pietrzyn@astrouw.edu.pl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23467166" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
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    The Araucaria Project: accurate stellar parameters and distance to evolved eclipsing binary ASAS J180057-2333.8 in Sagittarius Arm (2015)
    Oxford University Press
    Details
    Publikationsdatum: 2015-05-31
    Beschreibung: We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V -band and I -band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5–3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R 1 = 52.12 ± 1.38 and R 2 = 67.63 ± 1.40 R and their masses are M 1 = 4.914 ± 0.021 and M 2 = 4.875 ± 0.021 M . The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius–Carina arm. The Galactic rotational velocity of the star is s = 258 ± 26 km s –1 assuming 0 = 238 km s –1 . A comparison with PARSEC isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the mesa star code.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    Pulsation models for the 0.26 M{odot} star mimicking RR Lyrae pulsator. Model survey for the new class of variable stars (2013)
    Oxford University Press
    Details
    Publikationsdatum: 2013-01-03
    Beschreibung: We present non-linear hydrodynamic pulsation models for OGLE-BLG-RRLYR-02792 – a 0.26 M pulsator, component of the eclipsing binary system, analysed recently by Pietrzynski et al. The star’s light and radial velocity curves mimic that of classical RR Lyrae stars, except for the bump in the middle of the ascending branch of the radial velocity curve. We show that the bump is caused by the 2:1 resonance between the fundamental mode and the second overtone – the same mechanism that causes the Hertzsprung bump progression in classical Cepheids. The models allow us to constrain the parameters of the star, in particular to estimate its absolute luminosity (33 L ) and effective temperature (6970 K, close to the blue edge of the instability strip). We conduct a model survey for the new class of low-mass pulsators similar to OGLE-BLG-RRLYR-02792 – products of evolution in the binary systems. We compute a grid of models with masses corresponding to half (or less) of the typical mass of RR Lyrae variable, 0.20 ≤ M ≤ 0.30 M , and discuss the properties of the resulting light and radial velocity curves. Resonant bump progression is clear and may be used to distinguish such stars from classical RR Lyrae stars. We present the Fourier decomposition parameters for the modelled light and radial velocity curves. The expected values of the 31 Fourier phase for the light curves differ significantly from that observed in RR Lyrae stars, which is another discriminant of the new class.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
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    The Araucaria Project: accurate stellar parameters and distance to evolved eclipsing binary ASAS J180057-2333.8 in Sagittarius Arm (2015)
    Oxford University Press
    Details
    Publikationsdatum: 2015-06-12
    Beschreibung: We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V -band and I -band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5–3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R 1 = 52.12 ± 1.38 and R 2 = 67.63 ± 1.40 R and their masses are M 1 = 4.914 ± 0.021 and M 2 = 4.875 ± 0.021 M . The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius–Carina arm. The Galactic rotational velocity of the star is s = 258 ± 26 km s –1 assuming 0 = 238 km s –1 . A comparison with parsec isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the mesa star code.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Einschränkungen Verfügbarkeit
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    PAPER CURRENT
  • 5
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    Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - VIII. The totally eclipsing double-giant system HD 187669 (2015)
    Oxford University Press
    Details
    Publikationsdatum: 2015-02-26
    Beschreibung: We present the first full orbital and physical analysis of HD 187669, recognized by the All-Sky Automated Survey (ASAS) as the eclipsing binary ASAS J195222-3233.7. We combined multi-band photometry from the ASAS and SuperWASP public archives and 0.41-m PROMPT robotic telescopes with our high-precision radial velocities from the HARPS spectrograph. Two different approaches were used for the analysis: (1) fitting to all data simultaneously with the WD code and (2) analysing each light curve (with jktebop ) and radial velocities separately and combining the partial results at the end. This system also shows a total primary (deeper) eclipse, lasting for about 6 d. A spectrum obtained during this eclipse was used to perform atmospheric analysis with the moog and sme codes to constrain the physical parameters of the secondary. We found that ASAS J195222-3233.7 is a double-lined spectroscopic binary composed of two evolved, late-type giants, with masses of M 1  = 1.504 ± 0.004 and M 2  = 1.505 ± 0.004 M , and radii of R 1  = 11.33 ± 0.28 and R 2  = 22.62 ± 0.50 R . It is slightly less metal abundant than the Sun, and has a P  = 88.39 d orbit. Its properties are well reproduced by a 2.38-Gyr isochrone, and thanks to the metallicity estimation from the totality spectrum and high precision of the masses, it was possible to constrain the age down to 0.1 Gyr. It is the first so evolved Galactic eclipsing binary measured with such good accuracy, and as such it is a unique benchmark for studying the late stages of stellar evolution.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Einschränkungen Verfügbarkeit
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