Search results for: J. Smak

Items from 1 to 20 out of 44 results

article

AM CVn - System Parameters and Gravitational Waves

J. Smak

Acta Astronomica > 2023 > Vol. 73, No. 3 > 227--232

System parameters of AM CVn are re-determined: M₁=0.86±0.18 M_☉, M₂=0.103±0.0022 M_☉, A=1.508±0.100×10¹⁰ cm, and i=69±3°. The secondary component of the system is a semi-degenerate helium star loosing mass at a rate M=4.93±1.65×10^-9 M_☉/yr. The accretion disk is sufficiently hot to avoid thermal instability. The orbital light curve recovered from observations made in 1962 shows minimum shifted to phase...

article

On the Orbital Period and Models of V Sge

J. Smak

Acta Astronomica > 2022 > Vol. 72, No. 1 > 21--29

The orbital period of V Sge is decreasing at a rate which increased from dP/dt=-(4.11±0.33)×10^-10 in 1962 to -(5.44±0.61)× 10^-10 in 2022. This implies that the mass transfer from the secondary component is accelerating. From the evidence based on the orbital period variations, combined with estimates of the mass loss from the system based on radio observations, it follows that (1) the mass transfer...

article

On the Periods and Nature of Superhumps

J. Smak

Acta Astronomica > 2020 > Vol. 70, No. 4 > 317--321

It is commonly accepted that the periods of superhumps can be satisfactorily explained within a model involving apsidal motion of the accretion disk provided the frequency of the apsidal motion in addition to the dynamical term includes also the pressure effects. Using a larger sample of systems with reliable mass ratios it is shown, however, that this view is not true and the model requires further...

article

On the Critical Mass Ratio for the 3:1 Resonance in Accretion Disks

J. Smak

Acta Astronomica > 2020 > Vol. 70, No. 4 > 313--315

The 3:1 resonance between the orbital frequency of the binary system and the orbital frequency of the outer parts of the disk can occur only in systems with mass ratio smaller than certain critical value. It is shown that q_crit=0.22, i.e. smaller than obtained earlier by other authors (q_crit=0.25-0.39). This implies that the tidal-resonance model fails to explain superhumps in systems with orbital...

article

RW Tri - its Negative Superhumps and System Parameters

J. Smak

Acta Astronomica > 2019 > Vol. 69, No. 1 > 79--85

Negative superhumps are detected in the light curves of RW Tri observed in September 1994 and November/December 1957. New system parameters, obtained using K₂ and V_2,rotsin i and q (estimated from P_nSH), are M₁=0.60±0.20 M☉, M₂=0.48±0.15 M☉, A=1.13±0.09×1011 cm and i=72°.5±2°.5.

article

DW UMa and the Irradiation Modulated Mass Transfer Model for Superhumps

J. Smak

Acta Astronomica > 2017 > Vol. 67, No. 3 > 273--280

The light curves of the permanent superhumper DW UMa are analyzed in order to determine the amplitudes of its superhumps, A_SH, and the amplitudes of the periodic light variations with the beat period - the irradiation amplitudes - A_irr. The resulting values of A_SHand A_irr, together with other values from the literature, turn out to be correlated thereby confirming the irradiation modulated mass transfer...

article

On the Light Curves of AM CVn

J. Smak

Acta Astronomica > 2017 > Vol. 67, No. 1 > 63--69

Light curves of AM CVn are analyzed by decomposing them into their Fourier components. The amplitudes of the fundamental mode and overtones of the three components: the superhumps, the negative superhumps and the orbital variations, are found to be variable. This implies that variations in the shape of the observed light curve of AM CVn are not only due to the interference between those components,...

article

Superhumps and their Evolution during Superoutbursts

J. Smak

Acta Astronomica > 2016 > Vol. 66, No. 1 > 75--83

Light curves of superhumps and their evolution during superoutbursts are analyzed by decomposing them into their Fourier components, including the fundamental mode and the first three overtones. The amplitudes of the fundamental mode are found to decrease significantly during superoutburst while those of the overtones remain practically constant. The phases of maxima of the fundamental mode increase...

article

TT Ari and its Quasi-Periodic Oscillations

J. Smak

Acta Astronomica > 2014 > Vol. 64, No. 2 > 167--175

Quasi-periodic oscillation (QPO) of TT Ari are transient, short-lived phenomena. They appear and disappear and their periods and amplitudes vary on a time scale as short as 1 hour. Consequently the periodograms covering longer intervals of time are generally meaningless.

article

High-k ZrO2 dielectric thin films on GaAs semiconductor with reduced regrowth of native oxides by atomic layer deposition

R.B. Konda, C. White, J. Smak, R. Mundle, more

Chemical Physics Letters > 2013 > 583 > Complete > 74-79

GaAs surfaces were self-cleaned through fast pulsing of the Trimethylaluminum (TMA) precursor by reducing and restraining the regrowth of native oxides using the atomic layer deposition (ALD). The thermal conversion of As–O in to Ga–O reduction was evaluated by the X-ray photoelectron spectroscopy. Metal oxide semiconductor (MOS) capacitor was using ZrO ₂ as high-k gate dielectric on n-GaAs...

article

Seasonal differences in cytokine expression in the skin of Shetland ponies suffering from insect bite hypersensitivity

C. Meulenbroeks, N.M.A. van der Meide, D.M.W. Zaiss, M.M. Sloet van Oldruitenborgh-Oosterbaan, more

Veterinary Immunology and Immunopathology > 2013 > 151 > 1-2 > 147-156

Insect bite hypersensitivity (IBH) in horses is a seasonal, IgE-mediated, pruritic skin disorder primarily caused by Culicoides spp.We hypothesize that a mixed Th2/Th1-type immune status, off season, alters into Th2-dominated immune reactivity in the skin of IBH-affected ponies in the IBH season.To study these immune response patterns Culicoides-specific IgE levels, skin histopathology and cytokine...

article

On the Nature of Superhumps

J. Smak

Acta Astronomica > 2013 > Vol. 63, No. 3 > 369--377

Further evidence is presented supporting the alternative interpretation of superhumps as being due to irradiation modulated periodically variable mass transfer rate. NZ Boo, HT Cas and PU UMa are added to the sample of high inclination dwarf novae showing - during their superoutbursts - modulation of the observed brightness of the disk with beat period. Simple model calculations confirm earlier hypothesis...

article

Fifty Years of TT Arietis

J. Smak

Acta Astronomica > 2013 > Vol. 63, No. 4 > 453--463

Results of photometric observations of the permanent negative superhumper TT Ari in 1961/62 and 1966 are presented. Together with data from the literature they are used to discuss the negative superhump amplitudes A_nSH and the amplitudes A_beat of the modulation with the beat period P_beat. Both amplitudes are shown to vary considerably from one season to another. Three correlations are found: (1) between...

article

On the Periods of Negative Superhumps and the Nature of Superhumps

J. Smak

Acta Astronomica > 2013 > Vol. 63, No. 1 > 109--114

Osaki and Kato interpreted variations of the negative superhump periods, discovered by them in dwarf nova V1504 Cyg, as evidence in favor of the thermal-tidal instability model for superoutbursts. It is shown that their interpretation was incorrect. The observational evidence is recalled showing that superoutbursts are due to the enhanced mass transfer rate.

article

Stream Overflow in Z Cha and OY Car during Quiescence

J. Smak

Acta Astronomica > 2012 > Vol. 62, No. 2 > 213--217

Eclipses of the hot spot in Z Cha and OY Car observed by many authors during their quiescence are re-analyzed. Distances of the spot from the center of the disk rs are determined from phases of ingress and egress. In the case of several eclipses of Z Cha and nearly all eclipses of OY Car it is found that r_s(egress)<r_s(ingress). This is interpreted as being due to the effects of stream overflow...

article

Direct Evidence for Modulated Irradiation of Secondary Components in Dwarf Novae during Superoutbursts

J. Smak

Acta Astronomica > 2011 > Vol. 61, No. 1 > 59--69

Contribution from the irradiated secondary component is detected in the light curves of five dwarf novae observed during superoutbursts. Their superhump light curves show that irradiation is modulated with the superhump phase. This strengthens the new interpretation of superhumps as being due to the irradiation controlled mass transfer rate resulting in modulated dissipation of the kinetic energy...

article

On the Mass Transfer Rate in SS Cyg

J. Smak

Acta Astronomica > 2010 > Vol. 60, No. 1 > 83--89

The mass transfer rate in SS Cyg at quiescence, estimated from the observed luminosity of the hot spot, is log M_tr=16.8±0.3. This is safely below the critical mass transfer rates of log M_crit=18.1 (corresponding to log T_crit⁰=3.88) or log M_crit=17.2 (corresponding to the "revised" value of log T_crit⁰=3.65). The mass transfer rate during outbursts is strongly enhanced.

article

Superhumps and their Amplitudes

J. Smak

Acta Astronomica > 2010 > Vol. 60, No. 4 > 357--371

Superhump amplitudes observed in dwarf novae during their superoutbursts depend on orbital inclination: the maximum amplitudes in systems with low inclinations are A₀≈0.25 mag, while at higher inclinations they increase from A₀≈0.3 mag to A₀≈0.6 mag. The mean maximum superhump amplitudes normalized to the average luminosity of the disk are: <A_n>=0.34±0.02 mag in low inclination systems and...

article

On the Origin of Tilted Disks and Negative Superhumps

J. Smak

Acta Astronomica > 2009 > Vol. 59, No. 4 > 419--430

The origin of tilted disks in cataclysmic variables is explained in terms of a model involving the stream-disk interactions. Tilted, precessing disk causes periodically variable asymmetry in the irradiation of the two hemispheres of the secondary component, resulting in variable vertical component of the velocity of the stream. The following stream-disk interactions provide additional vertical acceleration...

article

On the Amplitudes of Superhumps

J. Smak

Acta Astronomica > 2009 > Vol. 59, No. 1 > 103--107

Amplitudes of bolometric light curves produced by 2D and 3D SPH simulations are used to determine the corresponding visual amplitudes. They turn out to be ≈10 times lower than typical amplitudes of superhumps. This means a major failure of the tidal model of superhumps.

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Search results for: J. Smak

AM CVn - System Parameters and Gravitational Waves

On the Orbital Period and Models of V Sge

On the Periods and Nature of Superhumps

On the Critical Mass Ratio for the 3:1 Resonance in Accretion Disks

RW Tri - its Negative Superhumps and System Parameters

DW UMa and the Irradiation Modulated Mass Transfer Model for Superhumps

On the Light Curves of AM CVn

Superhumps and their Evolution during Superoutbursts

TT Ari and its Quasi-Periodic Oscillations

High-k ZrO2 dielectric thin films on GaAs semiconductor with reduced regrowth of native oxides by atomic layer deposition

Seasonal differences in cytokine expression in the skin of Shetland ponies suffering from insect bite hypersensitivity

On the Nature of Superhumps

Fifty Years of TT Arietis

On the Periods of Negative Superhumps and the Nature of Superhumps

Stream Overflow in Z Cha and OY Car during Quiescence

Direct Evidence for Modulated Irradiation of Secondary Components in Dwarf Novae during Superoutbursts

On the Mass Transfer Rate in SS Cyg

Superhumps and their Amplitudes

On the Origin of Tilted Disks and Negative Superhumps

On the Amplitudes of Superhumps

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