17,819 research outputs found
Synthetic horizontal branch morphology for different metallicities and ages under tidally enhanced stellar wind
It is believed that, except for metallicity, some other parameters are needed
to explain the horizontal branch (HB) morphology of globular clusters (GCs).
Furthermore, these parameters are considered to be correlated with the mass
loss of the red giant branch (RGB) stars. In our previous work, we proposed
that tidally enhanced stellar wind during binary evolution may affect the HB
morphology by enhancing the mass loss of the red giant primary. As a further
study, we now investigate the effects of metallicity and age on HB morphology
by considering tidally enhanced stellar winds during binary evolution. We
incorporated the tidally enhanced-stellar-wind model into Eggleton's stellar
evolution code to study the binary evolution. To study the effects of
metallicity and age on our final results, we conducted two sets of model
calculations: (i) for a fixed age, we used three metallicities, namely
Z=0.0001, 0.001, and 0.02. (ii) For a fixed metallicity, Z=0.001, we used five
ages in our model calculations: 14, 13, 12, 10, and 7 Gyr. We found that HB
morphology of GCs becomes bluer with decreasing metallicity, and old GCs
present bluer HB morphology than young ones. These results are consistent with
previous work. Although the envelope-mass distributions of zero-age HB stars
produced by tidally enhanced stellar wind are similar for different
metallicities, the synthetic HB under tidally enhanced stellar wind for Z=0.02
presented a distinct gap between red and blue HB. However, this feature was not
seen clearly in the synthetic HB for Z=0.001 and 0.0001. We also found that
higher binary fractions may make HB morphology become bluer, and we discussed
the results with recent observations.Comment: 16 pages, 6 figures, 3 tables, accepted for publication in Astronomy
& Astrophysic
On 2D Viscoelasticity with Small Strain
An exact two-dimensional rotation-strain model describing the motion of
Hookean incompressible viscoelastic materials is constructed by the polar
decomposition of the deformation tensor. The global existence of classical
solutions is proved under the smallness assumptions only on the size of initial
strain tensor. The proof of global existence utilizes the weak dissipative
mechanism of motion, which is revealed by passing the partial dissipation to
the whole system.Comment: Different contributions of strain and rotation of the deformation are
studied for viscoelastic fluids of Oldroyd-B type in 2
A blowup criterion for ideal viscoelastic flow
We establish an analog of the Beale-Kato-Majda criterion for singularities of
smooth solutions of the system of PDE arising in the Oldroyd model for ideal
viscoelastic flow
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