By assuming an aspherical stellar wind with an equatorial disc from a red giant, we investigate the production of Type Ia supernovae (SNe Ia) via a symbiotic channel. We estimate that the Galactic birthrate of SNe Ia via the symbiotic channel is between 1.03 × 10−3 and 2.27 × 10−5 yr−1, while the delay time of SNe Ia has a wide range from ∼0.07 to 5 Gyr. The results are greatly affected by the outflow velocity and mass‐loss rate of the equatorial disc. Using our model, we discuss the progenitors of SN 2002ic and SN 2006X.
The material that is ejected in a common-envelope (CE) phase in a close binary system provides an ideal environment for dust formation. By constructing a simple toy model to describe the evolution of the density and the temperature of CE ejecta and using the AGBDUST code to model dust formation, we show that dust can form efficiently in this environment. The actual dust masses produced in the CE ejecta depend strongly on their temperature and density evolution. We estimate the total dust masses produced by CE evolution by means of a population synthesis code and show that, compared to dust production in AGB stars, the dust produced in CE ejecta may be quite significant and could even dominate under certain circumstances.
Symbiotic X‐ray binaries (SyXBs) comprise a rare class of low‐mass X‐ray binaries. We study the Galactic SyXBs, which we consider as detached binaries composed of low‐mass giants and wind‐fed neutron star (NS) companions, by simulation of the interaction of a magnetized NS with its environment and utilizing a population synthesis code. We focus mainly on the parameters that influence the observational appearance of an SyXB: the donor wind velocity (vw) and the angular momentum distribution in the shell of matter settling on to an NS. We estimate the birthrate of SyXBs as ∼4.1 × 10−5 to ∼6.6 × 10−6 yr−1 and their number in the Galaxy as ∼100–1000. The assumed stellar wind velocity from cool giants is the input parameter that influences the model SyXB population most. Among known SyXBs or candidate systems, 4U 1954+31 and IGR J16358−4724 in which the NSs have very long spin periods may host quasi‐spherically accreting NSs. GX 1+4 has a peculiar long‐term spin behaviour and it may also be a quasi‐spherical wind‐accreting source. We cannot identify whether there are wind‐fed accretion discs in 4U 1700+24, Sct X‐1, IRXS J180431.1−273932 and 2XMM J174016.0−290337.
We use the Modules for Experiments in Stellar Astrophysics (MESA) code to calculate the yields of Li 7 in the ejecta of classical novae, occurring on the surface of carbon-oxygen (CO) and oxygen-neon-magnesium (ONeMg)
As the evolutionary link between the radio millisecond pulsars (MSPs) and the low mass X-ray binaries or intermediate mass X-ray binaries, the millisecond X-ray pulsars (MSXPs) are important objects in testing theories of pulsar formation and evolution. In general, neutron stars in MSXPs can form via core collapse supernova (CC channel) of massive stars or accretion induced collapse (AIC channel) of an accreting ONeMg WD whose mass reaches the Chandrasekhar limit. Here, in addition to CC and AIC channels we also consider another channel, i.e., evolution induced collapse (EIC channel) of a helium star with mass between 1.4 and 2.5M ⊙ . Using a population synthesis code, we have studied MSXPs arising from three different evolutionary channels. We find that the Galactic birthrates of transient MSXPs and persistent MSXPs are about 0.7-1.4 × 10 −4 yr −1 . Our population synthesis calculations have shown that about 50%-90% of the MSXPs have undergone CC channel, about 10%-40% of them have undergone EIC channel, and the MSXPs via AIC channel are the least.
We have carried out a study of the chemical abundances of 1 H, 4 He, 12 C, 13 C, 14 N, 15 N, 16 O, 17 O, 20 Ne, and 22 Ne in symbiotic stars (SSs) by means of a population synthesis code. We find that the ratios of the number of O-rich SSs to that of C-rich SSs in our simulations are between 3.4 and 24.1, depending on the third dredge-up efficiency k and the terminal velocity of the stellar wind v(1). The fraction of SSs with extrinsic C-rich cool giants in C-rich cool giants ranges from 2.1% to 22.7%, depending on k, the common envelope algorithm, and the mass-loss rate. Compared with the observations, the distributions of the relative abundances of 12 C/ 13 C vs. [C/H] of the cool giants in SSs suggest that thermohaline mixing in low-mass stars may exist. The distributions of the relative abundances of C/N vs. O/N, Ne/O vs. N/O, and He/H vs. N/O in the symbiotic nebulae indicate that it is quite common for the nebular chemical abundances in SSs to be modified by the ejected materials from the hot components. Helium overabundance in some symbiotic nebulae may be relevant to a helium layer on the surfaces of white dwarf accretors.
The origin of dust grains in the interstellar medium is still open problem. Nicholls et al. (2013) found the presence of a significant amount of dust around V1309 Sco which maybe originate from the merger of a contact binary. We investigate the origin of dust around V1309 Sco, and suggest that these dust grains are efficiently produced in the binary-merger ejecta. By means of AGBDUST code, we estimate that ∼ 5.2 × 10 −4 M ⊙ of dust grains are produced, and their radii are ∼ 10 −5 cm. These dust grains mainly are composed of silicate and iron grains. Because the mass of the binary-merger ejecta is very small, the contribution of dust produced by binarymerger ejecta to the overall dust production in the interstellar medium is negligible. However, it is the most important that the discovery of a significant amount of dust around V1309 Sco offers a direct support for the idea-common-envelope ejecta provides an ideal environment for dust formation and growth. Therefore, we confirm that common-envelope ejecta can be important source of cosmic dust.
Using the Modules for Experiments in Stellar Astrophysics code, we investigate the influences of irradiation on ultra-compact X-ray binary (UCXB) evolution. Although the persistent UCXBs have short orbital periods which result in high irradiation flux, the irradiation hardly affects the evolution of persistent sources because the WDs in these binaries have large masses which lead to very low irradiation depth. The irradiation has a significant effect on the transient sources during outburst phase. At the beginning of the outburst, high X-ray luminosity produces high radiation flux, which results in the significant expansion of WD. Then, the irradiation triggers high masstransfer rates, which can last several days for the transient sources with WDs whose masses are larger than ∼ 0.015M ⊙ or several hundred years for these sources with WDs whose masses are less than ∼ 0.012M ⊙ . The observed three persistent UCXBs, XTE J0929-314, 4U 1916-05 and SWIFT J1756.9-2508, may belong to the latter.
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