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1

Does the A-type Metallic-Line Star IW Persei Have Non-Uniform Chemical Anomaly on the Surface?

Takeda Y.

Acta Astronomica

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2023

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Vol. 73, No. 1

35--55

EN

IW Per, a single-lined spectroscopic binary with a short period of 0.92 d, is known to be a A-type metallic-line (Am) star showing anomalous line strengths of specific elements. It was previously reported that its equivalent widths of CaII 3934, SrII 4215, and ScII 4320 lines (important key lines characterizing the Am anomaly) show cyclic variations in accordance with the rotation phase, implying that the chemical peculiarities on the surface are not uniform but of rather patchy distribution. However, no attempts of reconfirmation have been done so far. In order to check the validity of this finding, ten high-dispersion spectra of IW Per covering different phases were analyzed for these lines by using the spectrum-fitting technique to determine the abundances of Ca, Sr, and Sc and the corresponding equivalent widths. It turned out, however, that no firm evidence of such phase-dependent line-strength variations could be found, suggesting that significant chemical inhomogeneity on the surface of IW Per is unlikely to exist, at least during the period of our observations (2010 December). Meanwhile, the abundances of O, Si, Ca, Ba, and Fe resulting from the 6130-6180 Å region corroborate that IW Per is a distinct Am star (though the degree of peculiarity differs from element to element) despite that its rotational velocity (≈100 km/s) is near to the limit of Am phenomenon.

2

GT Ursae Majoris AB - a Possible Quadruple System

Dimitrov W., Tomov T., Kamiński K., Polińska M., Iliev I., Kamińska M. K.

Acta Astronomica

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2018

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Vol. 68, No. 2

141--158

EN

We present the first spectroscopic study of an eclipsing system GT UMa. Our spectra show that the main visual component A is a triple-lined star, which consists of a close eclipsing pair and a farther third component. Radial velocity measurements show evidence of reflex motion. We used Hipparcos and our own R-band light curves for the analysis. These results enabled us to calculate absolute parameters of the eclipsing binary system: 1.37 M⊙ and 1.31 M⊙ and corresponding radii 2.11 R⊙ and 1.63 R⊙. Both eclipsing components are evolved. The orbital period of the eclipsing subsystem is 1.2 d and the semi-major axis - 6.5 R⊙. The wide orbit has low radial velocity amplitude and its parameters are difficult to determine. We obtained a preliminary solution which must be confirmed with future observations. The preliminary period of the wide orbit is 394 d and the lower limit for the semi-major axis - 174 R⊙ (0.81 a.u.). We estimated the mass of the third body to about 1.1 M⊙. Additionally, we investigated the visual companion B. We obtained spectra of this star and measured the radial velocity which is very close to the one of the component A. The proper motions and the parallax are also similar. These are strong arguments that component B is gravitationally bound with the main triple system A.

3

The Clusters AgeS Experiment (CASE). VI. Analysis of Two Detached Eclipsing Binaries in the Globular Cluster M55

Kaluzny J., Thompson I. B., Dotter A., Rozyczka M., Pych W., Rucinski S. M., Burley G. S.

Acta Astronomica

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2014

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Vol. 64, No. 1

11--26

EN

We present an analysis of the detached eclipsing binaries V44 and V54 belonging to the globular cluster M55. For V54 we obtain the following absolute parameters: Mp=0.726±0.015 Msun, Rp=1.006± 0.009 Rsun, Lp=1.38±0.07 Lsun for the primary, and Ms=0.555± 0.008 Msun, Rs=0.528±0.005 Rsun, Ls=0.16±0.01 Lsun for the secondary. The age and apparent distance modulus of V54 are estimated at 13.3-14.7 Gyr and 13.94±0.05 mag, respectively. This derived age is substantially larger than ages we have derived from the analysis of binary systems in 47 Tuc and M4. The secondary of V44 is so weak in the optical domain that only mass function and relative parameters are obtained for the components of this system. However, there is a good chance that the velocity curve of the secondary could be derived from near-IR spectra. As the primary of V44 is more evolved than that of V54, such data would impose much tighter limits on the age and distance of M55.

4

The Clusters AgeS Experiment (CASE). Analysis of the Detached Eclipsing Binary V15 in the Metal-Rich Open Cluster NGC 6253

Rozyczka M., Kaluzny J., Thompson I. B., Dotter A., Pych W., Narloch W.

Acta Astronomica

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2014

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Vol. 64, No. 3

233--246

EN

We present the first detailed analysis of the detached eclipsing binary V15 in the super-metal rich open cluster NGC 6253. We obtain the following absolute parameters: Mp=1.303±0.006 MSun, Rp=1.71±0.03 RSun, Lp=2.98±0.10 LSun for the primary, and Ms=1.225±0.006 MSun, Rs=1.44±0.02 RSun, Ls=2.13±0.06 LSun for the secondary. Based on Dartmouth isochrones, the age of NGC 6253 is estimated to be 3.80-4.25 Gyr from the mass-radius diagram and 3.9-4.6 Gyr from color-magnitude diagram fitting. Both of these estimates are significantly higher than those reported so far. The derived apparent distance modulus of 11.65 mag agrees well with the range of 10.9-12.2 mag derived by other authors; however our estimated reddening (0.113 mag) is lower than the lowest published value (0.15 mag). We confirm earlier observations that model atmospheres are not accurate enough to account for the whole CMD of the cluster, with the largest discrepancies appearing on the subgiant and giant branches. Although age estimation from the mass-radius diagram is a relatively safe, distance- and reddening-independent procedure, our results should be verified by photometric and spectroscopic observations of additional detached eclipsing binaries which we have discovered, at least two of which are proper-motion members of NGC 6253.

5

Rotation of δ Scuti Stars in the Open Clusters NGC 1817 and NGC 7062

Molenda-Żakowicz J., Arentoft T., Frandsen S., Grundahl F.

Acta Astronomica

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2009

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Vol. 59, No. 1

69--88

EN

We report results of spectroscopic and photometric observations of ten δ Sct stars and one eclipsing binary in the open cluster NGC 1817, and of ten δ Sct stars and two other variables in the open cluster NGC 7062. For all targets in NGC 1817 and for three targets in NGC 7062 the radial velocity and projected rotational velocity are determined. For all stars the effective temperature and surface gravity is measured. Two δ Sct stars, NGC 1817 -V1 and NGC 7062 -V1, and the eclipsing binary, NGC 1817 -V18, are discovered to be single-lined spectroscopic binaries. The eclipsing binary δ Sct star NGC 1817 -V4 is discovered to be a double-lined spectroscopic binary. All δ Sct stars which we observed spectroscopically are found to be moderate or fast rotators.

6

Spectroscopic Study of Candidates for Kepler Asteroseismic Targets - Solar-Like Stars

Molenda-Żakowicz J., Frasca A., Latham D. W.

Acta Astronomica

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2008

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Vol. 58, No. 4

419--431

EN

We report spectroscopic observations of 23 candidates for Kepler asteroseismic targets and 10 other stars in the Kepler field. For all these stars, we derive the radial velocities, effective temperature, surface gravity, metallicity, the projected rotational velocity, and estimate the MK type. HIP 97513 and HIP 92132 are classified as suspected new single-lined spectroscopic binaries. For 28 stars, the radial velocity is measured for the first time.

7

Spectroscopic Study of Kepler Asteroseismic Targets

Molenda-Żakowicz J., Frasca A., Latham D. W., Jerzykiewicz M.

Acta Astronomica

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2007

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Vol. 57, No. 4

301--321

EN

Reported are spectroscopic observations of 15 candidates for Kepler primary asteroseismic targets and 14 other stars in the Kepler field, carried out at three observatories. For all these stars, the radial velocities, effective temperature, surface gravity, metallicity, and the projected rotational velocity are derived from two separate sets of data by means of two independent methods. In addition, MK type is estimated from one of these sets of data. Three stars, HIP 94335, HIP 94734, and HIP 94743, are found to have variable radial-velocity. For HIP 94335=FL Lyr, a well-known Algol-type eclipsing variable and a double-lined spectroscopic binary, the orbital elements computed from our data agree closely with those of Popper et al. For HIP 94734 and HIP 94743=V2077 Cyg, which we discover to be single-lined systems, orbital elements are derived. In addition, from our value of the orbital period and the Hipparcos epoch photometry, HIP 94743 is demonstrated to be a detached eclipsing binary.

8

The Distance to Pleiades

Paczyński B.

Acta Astronomica

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2003

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Vol. 56, No. 2

209--211

EN

The distance to Pleiades remains controversial. There is a simple way to resolve the dispute definitely by measuring the distance to one of its brightest members, Atlas, which is an astrometric and spectroscopic binary.

9

The Distance to the Magellanic Clouds

Paczyński B.

Acta Astronomica

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2001

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Vol. 51, No. 2

81--89

EN

The distance to the LMC and SMC is a subject of controversy, with the difference between the extreme values in distance moduli exceeding 0.5 mag. While currently the best calibrated method is based on red clump giants, and the near future improvement is most likely to come from detached eclipsing binaries, the ultimate goal is to have a purely geometrical determination. The best prospect will be to use relatively wide binary stars, for which spectroscopic orbits will be obtained with large ground based telescopes, and astrometric orbits will be obtained either with SIM, or with future ground based interferometers. A preliminary list of 25 candidate systems is presented. It is based on OGLE catalogs of BVI photometry.

10

Hα Observations of SS Cyg at Quiescence and Outburst

Marchev D., Kjurkchieva D., Ogłoza W.

Acta Astronomica

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1999

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Vol. 49, No. 4

585--598

EN

Observations of Hα line of SS Cyg at quiescence and outburst are presented. The corresponding radial velocity curve is sinusoidal with semiamplitude K1=91±3.5 km/s. The width and intensity of the Hα line during quiescence are slightly variable. Its profile shape changes quite irregular but does not show the typical double-peaked structure of an accretion disk. The small peaks at the profile cores form S-wave with half-orbital period. The Hα profiles of SS Cyg at outburst consist of central emission core superposed on wide shallow absorption base. The intensity of the emission core is almost the same as that of the emission line in quiescence. The double-peaked shape of the profile is not well pronounced during the outburst too. On the base of the parameters of the Hα profile we estimate that the condition for the existence of an accretion disk during quiescence is not fulfilled. Such a structure can exist in outburst but it cannot be a dominant source of the Hα emission. Taking into account similarity of SS Cyg and the polar AM Her we conclude that the Balmer emission of SS Cyg originates mostly from the polar caps.

11

Orbital Solutions for Three RS CVn Systems: WY Cnc, SV Cam and XY UMa

Pojmański G.

Acta Astronomica

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1998

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Vol. 48, No. 4

711--727

EN

Near IR spectroscopic observations of WY Cnc, SV Cam and XY UMa binary systems of RS CVn type are presented. Systemic velocity and radial velocity semi-amplitudes of primary components in each system are derived using cross-correlation between cleaned spectra and G2 noiseless templates. Secondary semi amplitudes are determined from the primary subtracted spectra using the cross-correlation function maps and direct cross-correlation. Masses of the stars are derived and system properties briefly discussed. Primary components in all three systems seem to be more massive than was earlier deduced from their spectral classification. Regarding stellar masses, SV Cam should be classified as F5V+K0V pair. Observations of XY UMa fully confirm results obtained previously using a method for detecting faint secondaries in the low signal-to-noise spectra.