SOUSA: the Swift Optical/Ultraviolet Supernova Archive

This paper studies the motion of an infinitesimal mass in the framework of Robe’s circular restricted three-body problem in two cases; the first case is when the hydrostatic equilibrium figure of the first primary is an oblate spheroid, the shape of the second primary is considered as an oblate spheroid with oblateness coefficients up to the second zonal harmonic, while the first primary is a Roche ellipsoid in the second case and the full buoyancy of the fluid is taken into account. In case one; it is observed that there are two axial libration points on the line joining the centres of the primaries, points on the circle within the first primary are also libration points under certain conditions. It is further found that the first axial point is stable, while the second one is conditionally stable, and the circular points are unstable. It is found in case two that there is exist only one libration point (0,0,0) this point is stable.     

An application of the tensor virial theorem to hole + vortex + bulge systems

The tensor virial theorem for subsystems is formulated for three-component systems and further effort is devoted to a special case where the inner subsystems and the central region of the outer one are homogeneous, the last surrounded by an isothermal homeoid. The virial equations are explicitly written under the additional restrictions: (i) similar and similarly placed inner subsystems, and (ii) spherical outer subsystem. An application is made to hole + vortex + bulge systems, in the limit of flattened inner subsystems, which implies three virial equations in three unknowns. Using the Faber-Jackson relation, $R_{\text{e}}\propto {\sigma }_0^2$, the standard $M_{\text{H}}$-${\sigma }_0$ form $(M_{\text{H}}\propto {\sigma }_0^4)$ is deduced from qualitative considerations. The projected bulge velocity dispersion to projected vortex velocity ratio, $\eta =({\sigma }_{\text{B}}{)}_{33}/\{[(v_{\text{V}}{)}_{\mathit{qq}}{]}^2+[({\sigma }_{\text{V}}{)}_{\mathit{qq}}{]}^2{\}}^{1/2}$, as a function of the fractional radius, $y_{\text{BV}}=R_{\text{B}}/R_{\text{V}}$, and the fractional masses, $m_{\text{BH}}=M_{\text{B}}/M_{\text{H}}$ and $m_{\text{BV}}=M_{\text{B}}/M_{\text{V}}$, is studied in the range of interest, $0?m_{\text{VH}}=M_{\text{V}}/M_{\text{H}}?5$ [Escala, A., 2006. ApJ, 648, L13] and $229?m_{\text{BH}}?795$ [Marconi, A., Hunt, L.H., 2003. ApJ 589, L21], consistent with observations. The related curves appear to be similar to Maxwell velocity distributions, which implies a fixed value of $\eta$ below the maximum corresponds to two different configurations: a compact bulge on the left of the maximum, and an extended bulge on the right. All curves lie very close one to the other on the left of the maximum, and parallel one to the other on the right. On the other hand, fixed $m_{\text{BH}}$ or $m_{\text{BV}}$, and $y_{\text{BV}}$, are found to imply more massive bulges passing from bottom to top along a vertical line on the $(\mathsf{O}{y}_{\text{BV}}\eta )$ plane, and vice versa. The model is applied to NGC 4374 and NGC 4486, taking the fractional mass,$m_{\text{BH}}$, and the fractional radius, $y_{\text{BV}}$, as unknowns, and the bulge mass is inferred from the knowledge of the hole mass, and compared with results from different methods. In presence of a massive vortex $(m_{\text{VH}}=5)$, the hole mass has to be reduced by a factor 2–3 with respect to the case of a massless vortex, to get the fit. Finally, the assumptions of homogeneous inner bulge and isotropic stress tensor are discussed.     

New orbital solutions and absolute elements of the eclipsing binary TV Cet

We present new differential, four-color photoelectric photometry for the eclipsing binary TV Cet. UBVR light curves and radial velocities published previously are solved simultaneously using the Wilson–Devinney computer program. Our solutions indicate that TV Cet includes a third light contribution with 2.3% in U, 1.9% in B, 1.3% in V and 1.6% in R. The masses of the component stars are $1.34\pm 0.05$ and $1.23\pm 0.05M\odot$, while the radii are $1.47\pm 0.02$ and $1.21\pm 0.01R\odot$ for the primary and secondary components, respectively. Using new absolute properties and our previous results from period analysis, we calculated the observational and theoretical internal structure constants to be ${\overline{k}}_{2\text{,}\mathit{obs}}=-1.66$ and ${\overline{k}}_{2\text{,}\mathit{theo}}=-2.25$, respectively. Taking into account the third light contribution from the Wilson–Devinney solution and properties of the third body orbit from period analysis, the mass of the third body is obtained as $0.56M\odot$, corresponding to the inclination value $i_3=20°$. Evolutionary status of the component stars is also studied. We present the position of the stars in an H–R diagram for solar compositions.     

Planetary formation from charged bodies

The suggestion of Sarvajna that a charged body which has been ejected from the Sun can be captured in orbit because of electromagnetic effects is reinvestigated. It is concluded that the charged assumed by Sarvajna is too high by many orders of magnitude. An alternative scheme is proposed in which the charge requirement is much more realistic and it is shown that this scheme is feasible.     

Orbital period analysis of eclipsing post-novae T Aurigae: Evidence of magnetic braking and an unseen companion

Four new CCD times of light minimum of T Aurigae are presented. The orbital period variation is analyzed by means of the standard O–C technique. The new times of light minimum indicate that a ～24 yr sine-like period variation superimposed on a secular orbital period decrease is obviously seen in the O–C diagram. However, the orbital period should increase because of mass transfer between components. In order to solve this apparent paradox, three possibilities including magnetic braking mechanism, which plays an important role in angular moment loss of binary, are proposed. The mass loss rate $\dot{M}={10}^{-10.4}{M}_{\odot }{\text{yr}}^{-1}$ is derived by assuming that the Alfvén radius of secondary is the same as that of the sun (i.e. $R_A?15R_{\odot }$). Using the observational relationship of ${\dot{M}}_{\mathit{mb}}-P_{\mathit{orb}}(h)$ (McDermott and Taam, 1989, Rappaport et al., 1983), the Alfvén radius of secondary is estimated as $R_A?1.9R_{\odot }$, which only requires a weak magnetic field in secondary. Since the brightness variations of T Aurigae caused by Applegate’s mechanism need large energy beyond the total radiant energy in the time interval of 24 yr, the third body light travel-time effect is the most likely explanation for the 24-yr variation. The third body may be a brown-dwarf star in case of the high orbital inclination.     

Absolute parameters of the newly-identified contact binary star IS Canis Major

This paper presents the results of the first high-resolution spectroscopic observations of the Southern W UMa type system IS CMa. Spectroscopic observations of the system were made at Mt. John University Observatory using a HERCULES fibre-fed échelle spectrograph in September 2007. The first radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The resulting orbital elements of IS CMa are: $a_1\sin i=0.0041\pm 0.0001$ AU, $a_2\sin i=0.0135\pm 0.0001$ AU, $M_1{\sin }^{3}i=1.48\pm 0.01{\mathrm{M}}_{\odot }$, and $M_2{\sin }^{3}i=0.44\pm 0.01{\mathrm{M}}_{\odot }$. The components were found to be in synchronous rotation taking into account the disentangled ${\mathrm{H}}_{\delta }$ line profiles of both components of the system. The Hipparcos light curve was solved by means of the Wilson–Devinney method supplemented with a Monte Carlo type algorithm. The radial velocity curve solutions including the proximity effects give the mass ratio of the system as 0.297 ± 0.001. The combination of the Hipparcos light and radial velocity curve solutions give the following absolute parameters of the components: $M_1=1.68\pm 0.04{\mathrm{M}}_{\odot }\text{,}{\mathrm{M}}_2=0.50\pm 0.02{\mathrm{M}}_{\odot }\text{,}{R}_1=2.00\pm 0.02{\mathrm{R}}_{\odot }\text{,}{R}_2=1.18\pm 0.03R_{\odot }\text{,}{L}_1=7.65\pm 0.60$ ${\mathrm{L}}_{\odot }$ and $L_2=1.99\pm 0.80{\mathrm{L}}_{\odot }$. The distance to IS CMa was calculated as $87\pm 5$ pc using the distance modulus with corrections for interstellar extinction. The position of the components of IS CMa in the HR diagram are also discussed: the system seems to have an age of 1.6 Gyr.     

Time-dependent heating of the solar corona

The problem of how the corona is heated is of central importance in solar physics research. Here it is assumed that the heating occurs in a regular time-dependent manner and the response of the plasma is investigated. If the magnetic field is strong then the dynamics reduces to a one-dimensional problem along the field. In addition if the radiative time in the corona is much longer than the sound travel time then the plasma evolvesisobarically. The frequency with which heat is deposited in the corona is investigated and it is shown that there is a critical frequency above which a hot corona can be maintained and below which the plasma temperature cools to chromospheric values. An evaluation of the isobaric assumption to the solar corona and the implications of time-dependent heating upon the forthcoming SOHO observations are also presented.     

On axisymmetric hydromagnetic equilibria

The physical characteristics of possible axisymmetric equilibria are examined on the basis of the integrals of hydromagnetic equations. It is shown for nearly spherical configurations that a surface differential rotation is possible only in the absence of a meridional circulation with either purely toroidal or purely poloidal magnetic field. In the presence of a meridional circulation, it is shown that no surface rotation or constant rotation is possible if the magnetic field is purely toroidal, and that no rotation is possible if the magnetic field is purely poloidal. A brief discussion is given on the possible solutions including the case of stellar winds with force-free magnetic fields.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Constraints on the tidal dissipation factor of a main sequence star: The case of OGLE-TR-56b

The planet OGLE-TR-56b is the extrasolar giant planet closest to its host star. This planet and its star exchange extreme tidal forces. This leads to a reduction of the planetary orbit and a spin-up of the stellar rotation. The tidal migration rate depends crucially on the ratio of the tidal dissipation factor $Q_{*}$ and the stellar love number $k_{2{,}^{*}}$of the star, which is only poorly known and estimates range within $5\times 10^5<(Q_{*}/k_{2^{*}})<10^{10}$. For values greater than $Q_{*}/k_{2^{*}}>1.5\times 10^9$no observable influence by tidal forces on the planet's orbit within the lifetime for the star can be found. A lower limit for the possible values of the parameter $Q_{*}/k_{2^{*}}$for the G-type star OGLE-TR-56 was found by studying the evolution of possible tidal interaction into the future and in the past. This study demonstrates that on the basis of conservative model assumptions, a considerable but unrealistic spin-up of the star can be expected if $Q_{*}/k_{2^{*}}<2\times 10^7$, which is not in agreement with observed stellar rotation periods. From a statistical analysis based on a Monte-Carlo tidal evolution simulation, the $Q_{*}/k_{2^{*}}$ parameter can be constrained to the range $2\times 10^7<Q_{*}/k_{2^{*}}<1.5\times 10^9$ if the system shall evolve significantly and realistically by tidal forces.     

Studies in the application of recurrence relations to special perturbation methods

Using the rectangular equations of motion for the restricted three-body problem a comparison is made of the Encke and Cowell methods of integration. Each set of differential equations is integrated using Taylor series expansions where the coefficients of the powers of time are determined by recurrence relationships. It is shown that for fairly highly eccentric orbits in which the perturbing force is less than one thousandth of the two-body force the Encke method achieves a considerable saving in machine time. This is also true for almost circular orbits when low or moderate accuracy is required. When very high accuracy is required, however, the Cowell method is faster unless the perturbing force is less than 10^–6 of the two-body force. There is little difference in the accuracy of the two methods, the Cowell method being slightly more accurate when a low or moderate accuracy criterion is imposed.     

Magnetohydrodynamic simulations of gamma-ray burst jets: Beyond the progenitor star

Achromatic breaks in afterglow light curves of gamma-ray bursts (GRBs) arise naturally if the product of the jet’s Lorentz factor $\gamma$ and opening angle ${\Theta }_j$ satisfies $\gamma {\Theta }_j?1$ at the onset of the afterglow phase, i.e., soon after the conclusion of the prompt emission. Magnetohydrodynamic (MHD) simulations of collimated GRB jets generally give $\gamma {\Theta }_j?1$, suggesting that MHD models may be inconsistent with jet breaks. We work within the collapsar paradigm and use axisymmetric relativistic MHD simulations to explore the effect of a finite stellar envelope on the structure of the jet. Our idealized models treat the jet–envelope interface as a collimating rigid wall, which opens up outside the star to mimic loss of collimation. We find that the onset of deconfinement causes a burst of acceleration accompanied by a slight increase in the opening angle. In our fiducial model with a stellar radius equal to ${10}^{4.5}$ times that of the central compact object, the jet achieves an asymptotic Lorentz factor $\gamma ～500$ far outside the star and an asymptotic opening angle ${\Theta }_j?0.04\text{rad}?2°$, giving $\gamma {\Theta }_j～20$. These values are consistent with observations of typical long-duration GRBs, and explain the occurrence of jet breaks. We provide approximate analytic solutions that describe the numerical results well.     

Time-dependent interaction of granules with magnetic flux tubes

The time-dependent interaction of the granulation velocity field with a magnetic flux tube is investigated here. It is seen that when a magnetic field line is displaced normal to itself so as to simulate thebuffeting action of granules, a flow of gas is initiated along the field. By choosing a lateral velocity field which is consistent with observations of granules, it is found that the resulting gas motion is a downward flow with a velocity compatible with the observed downflow in isolated photospheric flux tubes. It is therefore proposed that the observed photospheric downflow is a manifestation of the interaction of granules with flux tubes.     

太阳光谱望远镜鬼线强度测量方法及初步结果

介绍了云台太阳光谱望远镜光栅鬼线强度测量方法。给出了２ 级光谱罗兰鬼线强度的初步测量结果, 为母线强度的０ ．０４９ ％ 。结果表明光栅的质量优良, 鬼线对光谱测量的影响非常小, 一般情况下在光谱资料处理中可以不必考虑鬼线强度的改正     

First comprehensive study of W-type W UMa eclipsing binary V1036 Her

CCD photometry of the eclipsing binary system V1036 Her was performed using Johnson V filter in Dr. Mojtahedi Observatory of the University of Birjand during July-August 2017 and July 2018. Moreover, the spectroscopy of the system was carried out by TRES during April 2018. A mass ratio of $3.07\left(27\right)$is obtained and an initial effective temperature of 5500 was suggested. For the first time, the relative and absolute parameters of the system are determined by analyzing the light curve and radial velocity data. The results indicate that V1036 Her is a W-subtype W UMa system with a degree of overcontact of 22%. The analysis of the period change shows that the period of the system changes with the rate of $\dot{P}=2.23\left(4\right)\times {10}^{-7}\text{day}/\text{year}$. With the assumption of the system mass conservation, a mass transfer rate from the primary to the secondary component of ${\dot{m}}_1=1.00\left(3\right)\times {10}^{-7}{M}_{\odot }/\mathit{year}$ is probable. Additionally, a periodic behavior with a period of about 10 years is observed in the O-C curve, which predicts the possibility of a third body with a minimum mass of $0.14\left(1\right)M_{\odot }$.