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1

The 1985 Superoutburst of U Geminorum. Modulation of the Superhump Amplitude

Smak J. I.

Acta Astronomica

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2006

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Vol. 56, No. 4

365--371

EN

The superhump amplitude was modulated with phase of the beat period. The highest amplitudes (2Amax≈0.4 mag) occurred when the superhump maximum coincided with the orbital phases φorb≈0.15 and 0.65, while the lowest (2Amin≈0.2 mag) - with φorb≈0.40 and 0.90. The directions defined by those two pairs of orbital phases appear to be parallel and perpendicular to the direction of the stream.

2

On the Mass Ratio of TU Men

Smak J. I.

Acta Astronomica

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2006

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Vol. 56, No. 3

277--282

EN

Radial velocities of TU Men measured from peaks of the emission lines are re-analyzed within the three-body approximation. The resulting crude estimate of the mass ratio is q=M₂/M₁=0.5±0.2. Using the mass of the secondary estimated from the M₂-P relation we obtain an independent lower limit q>0.41±0.08. These estimates exclude the possibility of superhumps being due to the tidal instability involving the 3:1 resonance which requires qcrit=0.25. The common belief that q_crit could be as high as q=0.33 is critically re-examined. It is shown that the results of numerical simulations, which form the basis of this belief, do not apply to situations encountered in the case of the observed superhumps.

3

Dwarf Nova Outbursts. IV. Absolute Magnitudes at Maximum

Smak J. I.

Acta Astronomica

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2000

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Vol. 50, No. 3

399--404

EN

Absolute visual magnitudes and bolometric luminosities at maximum, calculated from models of dwarf nova outbursts, are practically identical with those corresponding to the steady-state accretion at the critical mass transfer rate. This is due to the fact that the temperature distribution in the inner parts of the disk, which contribute most of the global flux, matches closely the standard, steady-state distribution. The theoretical MV(max)=f(M1,P) relations reproduce, on the average, quite well the observed MV vs. P relation. Observational data appear insufficient, however, to confirm the predicted dependence on M1.

4

Dwarf Nova Outbursts. I. The UV Delay

Smak J. I.

Acta Astronomica

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1998

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Vol. 48, No. 4

677--693

EN

Models of dwarf nova outbursts are calculated for a range of relevant parameters: the masses of the components which determine the orbital period and the radius of the disk, the mass transfer rate, and the viscosity parameter α. The visual (λ 5500 Å) and ultraviolet (λ 1200 Å) light curves are calculated using black body and Kurucz fluxes. The resulting UV delays show strong dependence on model parameters and, in particular, confirm the existence of a dichotomy between Type A and Type B outbursts. The model predicted UV delays agree quite well with observations, with the "best-fit" for αhot between 0.1 and 0.2. Earlier, negative conclusions and the controversy around the "problem of UV delay" resulted primarily from incorrect outer boundary conditions and other model simplifications.