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1

A Method of Improving Standard Stellar Luminosities with Multiband Standard Bolometric Corrections

Bakış V., Eker Z.

Acta Astronomica

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2022

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Vol. 72, No. 3

195--232

EN

Standard luminosity (L) of 406 main-sequence stars with the most accurate astrophysical parameters are calculated from their absolute magnitudes and bolometric corrections at Johnson BV, and Gaia EDR3 G, GBP, GRP filters. Required multiband BC and BC-Teff relations are obtained first from the parameters of 209 Double-lined Detached Eclipsing Binaries with main-sequence components and Gaia EDR3 parallaxes. A simplified SED is formulated to give filter dependent component light contributions and interstellar dimming, which are essential in computing BC of a component, virtually at any filter. The mean standard L of a star is calculated from the mean Mbolwhich is a mathematical average of independent Mboll values predicted at different filters, while the uncertainty of L is the uncertainty propagated from the uncertainty of the mean Mbol. The mean standard L of the sample stars are compared to the corresponding L values according to the Stefan-Boltzmann law. A very high correlation (R2>0.999) is found. Comparing histogram distributions of errors shows that uncertainties associated with the mean standard L (peak at ≈2.5 per cent) are much smaller than the uncertainties of L (peak at ≈8 per cent) by the Stefan-Boltzmann law. Increasing the number of filters used in predicting the mean Mbol increases the accuracy of the standard stellar luminosity. Extinction law, color-color relations and color excess vs. color excess relations for Gaia passbands are presented for the first time for main-sequence stars.

2

On the Eclipsing Cataclysmic Variable Star HBHA 4705-03

Rutkowski A., Ak T., Marsh T. R., Eker Z.

Acta Astronomica

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2013

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Vol. 63, No. 2

225--238

EN

We present observations and analysis of a new eclipsing binary HBHA 4705-03. Using decomposition of the light curve into accretion disk and hot spot components, we estimated photometrically the mass ratio of the studied system to be q=0.62±0.07. Modeling of the system yields the following fundamental parameters: white dwarf mass M1=(0.8±0.2) Msun, secondary mass M2=(0.497±0.05) Msun, orbital radius a=1.418 Rsun, orbital inclination i=(81.°58±0.°5), accretion disk radius rd/a=0.366±0.002, and accretion rate M=(2.5±2)x1018 [g/s] (3×10-8 Msun/yr). Power spectrum analysis revealed a set of possible low-period Quasi Periodic Oscillations centered at the frequencies f1=0.00076 Hz, f2=0.00048 Hz and f3=0.00036 Hz. The system B-V=0.04 mag corresponds to a dwarf nova color during an outburst. The light curves of HBHA 4705-03 suggest that it is a nova-like variable star.

3

Dwarf Nova V1040 Centauri and Variable Stars in its Vicinity

Rutkowski A., Pietrukowicz P., Olech A., Ak T., Złoczewski K., Poleski R., Tappert C., Eker Z.

Acta Astronomica

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2011

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Vol. 61, No. 4

345--357

EN

We present the results of a photometric campaign of the dwarf nova V1040 Cen. The light curve shows two normal outbursts with recurrence time ≈40 days and amplitude ≈2.5 mag. Quiescence data show oscillations with periods in the range ≈0.1 days (2.4 h) to ≈0.5 days (12 h) of unknown origin. We measured the orbital period of V1040 Cen to be Porb=0.060458(80) days (1.451±0.002 h). Based on the MV-Porb relation we found the distance of V1040 Cen to be 137±31 pc. In this paper we also report the detection of eleven new variable stars in the field of the monitored dwarf nova.