1992 UBV observations of UV piscium and light curve analysis

Jassur, D. M. Z.; Kermani, M. H.

doi:10.1007/bf00657858

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…Zeilik et al (1981Zeilik et al ( , 1982 also noted a large asymmetry of the secondary eclipse, which was confirmed later by observations of Jassur & Kermani (1993. Han & Kim (1988) found a depression at phase 0.3-0.4, and Ibanoglu (1987) detected variations in the depth of the primary minimum up to 0.09 mag in blue light, while there was no variation in yellow light.…”

Section: Introductionsupporting

confidence: 50%

“…Vivekananda Rao & Sarma (1981 established the migration of the distortion wave along the light curve, and Han et al (1984) found that it is toward decreasing orbital phase with a period of 5 yr. Oliver (1974) noted that the amplitude of the distortion wave increased at longer wavelengths, whereas Sadik (1979) and Han et al (1984) noted the opposite dependence and concluded that the hotter component is more responsible for the distortion wave. Jassur & Kermani (1994) found that UV Psc has central eclipses and that the color of the system is 0.1 mag redder during the primary eclipse and 0.05 mag bluer during the secondary eclipse. Hence, the primary eclipse is a transit.…”

Section: Introductionmentioning

confidence: 98%

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Spectroscopic and Photometric Observations of the Short-Period RS CVn-Type Star UV Piscium

et al. 2005

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High-resolution spectroscopic observations around the H line and long-term BVRI photometry of the eclipsing short-period RS CVn star UV Psc are presented. The simultaneous solution of our radial velocity curves and light curves yields the following values for the global parameters of the components:The measured rotational broadening of the spectral lines corresponds to equatorial velocities V 1 ¼ 68:3 and V 2 ¼ 53:3 km s À1 . Our spectral data reveal high activity of the two stellar components and very fast variability of the H line in the center of the primary eclipse. Modeling our photometric data shows trends in the starspot behavior. The trend toward active longitude belts can have occasional exceptions. The observed secular luminosity decrease in 1999 may signal the onset of a new magnetic activity cycle.

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Section: Introductionsupporting

confidence: 50%

Section: Introductionmentioning

confidence: 98%

Spectroscopic and Photometric Observations of the Short-Period RS CVn-Type Star UV Piscium

et al. 2005

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“…Another concern about RS CVn stars is the possible distortion of light curves due to starspots, which could bias the derivation of their fundamental stellar parameters. Jassur & Kermani (1994) suggested the presence of cool spots on the surface of the primary component, but according to Popper (1997, and references therein), this should not affect the value of the quantities used in this paper. The period has been recently revised by Sowell et al (2001) who didn't find any evidence for a cyclic modulation or period change.…”

Section: Introductionmentioning

confidence: 93%

Disentangling discrepancies between stellar evolution theory and sub-solar mass stars

Lastennet

Fernandes

Valls–Gabaud

et al. 2003

A&A

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Abstract. Serious discrepancies have recently been observed between predictions of stellar evolution models in the 0.7-1.1 M mass range and accurately measured properties of binary stars with components in this mass range. We study one of these objects, the eclipsing binary UV Piscium, which is particularly interesting because Popper (1997) derived age estimates for each component that differed by more than a factor of two. In an attempt to solve this significant discrepancy (a difference in age of 11 Gyr), we compute a large grid of stellar evolution models with the CESAM code for each component. By fixing the masses to their accurately determined values (relative error smaller than 1% for both stars), we consider a wide range of possible metallicities Z (0.01 to 0.05), and helium content Y (0.25 to 0.34) uncorrelated to Z. In addition, the mixing length parameter α MLT is left as another free parameter. We obtain a best fit in the T eff -radius diagram for a common chemical composition (Z, Y) = (0.012, 0.31), but a different MLT parameter α MLT,A = 0.95 ± 0.12(statistical)+0.30(systematic) and α MLT,B = 0.65 ± 0.07(stat)+0.10(syst). The apparent age discrepancy found by Popper (1997) disappears with this solution, the components being coeval to within 1%. This suggests that fixing α MLT to its solar value (∼1.6), a common hypothesis assumed in most stellar evolutionary models, may not be correct. Secondly, since α MLT is smaller for the less massive component, this suggests that the α MLT parameter may decrease with stellar mass, showing yet another shortcoming of the mixing length theory to explain stellar convection. This trend needs further confirmation with other binary stars with accurate data.

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“…Note that light fluctuations take place in the UV Psc system outside eclipses, whereas photometric parameters of the minima are very similar (see, for example Han & Kim 1988). This behaviour can be a consequence of variable mass flow, although to explain it Jassur & Kermani (1994) suggested the presence of cool spots on the surface of the primary component. Our data are insufficient to distinguish between these mechanisms.…”

Section: Comments On Rs Cvn-type Starsmentioning

confidence: 99%

Polarimetry of evolved stars

Yudin

Evans²

2002

A&A

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Abstract. We present broadband optical polarimetry of 3 RS CVn stars and 3 Mira variables, including the symbiotic star R Aqr, which contains a Mira component. Polarimetric variability has been studied on timescales from hours to years. Our programme objects at the time of our observations showed different forms of P (λ) dependence, P ∝ ∼ λ −4 for most of the RS CVn-type stars, and P ∝ ∼ λ −2 for the RS CVn-type star UV Psc and the Mira Ceti-type variables, and a significant increase of polarization to the red for the Mira R Cet. Combining our data with previously published data, we conclude that most of RS CVn-type and Mira Ceti-type objects show evidence of large polarimetric variability at wavelengths shorter than 0.5 µm, whereas the level of polarization is more stable in the red. This behaviour is consistent with episodic mass ejection and formation of small dust particles in the circumstellar environment. Although all targets showed polarimetric variability on different time scales, only for IM Peg might these variations be possibly linked with the photometric period.

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1992 UBV observations of UV piscium and light curve analysis

Cited by 4 publications

References 5 publications

Spectroscopic and Photometric Observations of the Short-Period RS CVn-Type Star UV Piscium

Spectroscopic and Photometric Observations of the Short-Period RS CVn-Type Star UV Piscium

Disentangling discrepancies between stellar evolution theory and sub-solar mass stars

Polarimetry of evolved stars

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