Pre-Supernova Outbursts via Wave Heating in Massive Stars II: Hydrogen-poor Stars

Pre-supernova (SN) outbursts from massive stars may be driven by hydrodynamical wave energy emerging from the core of the progenitor star during late nuclear burning phases. Here, we examine the effects of wave heating in stars containing little or no hydrogen, i.e., progenitors of type IIb/Ib SNe. Because there is no massive hydrogen envelope, wave energy is thermalized near the stellar surface where the overlying atmospheric mass is small but the optical depth is large. Wave energy can thus unbind this material, driving an optically thick, super-Eddington wind. Using 1D hydodynamic MESA simulations of $\sim \! 5 \, M_\odot$ He stars, we find that wave heating can drive pre-SN outbursts composed of a dense wind whose mass loss rate can exceed $\sim \! 0.1 \, M_\odot/{\rm yr}$. The wind terminal velocities are a few $100 \, {\rm km}/{\rm s}$, and outburst luminosities can reach $\sim \! 10^6 \, L_\odot$. Wave-driven outbursts may be linked with observed or inferred pre-SN outbursts of type Ibn/transitional/transformational SNe, and pre-SN wave-driven mass loss is a good candidate to produce these types of SNe. However, we also show that non-linear wave breaking in the core of the star may prevent such outbursts in stars with thick convective helium-burning shells. Hence, only a limited subset of SN progenitors are likely to experience wave-driven pre-SN outbursts.Comment: Accepted to MNRA

The current state of E-commerce in Jordan: Applicability and future prospects

This study aimed at determining the current state of e-commerce in Jordan, as well as its future prospects. The research population consisted of all Jordanian industrial, service and/or trade companies that have a registered website. The population size was 712 companies. A total of 118 questionnaires were distributed to randomly selected companies and 95 were returned. Cronbach alpha measure was used to test the reliability of the organizational questionnaire and was calculated to be 0.80 reflecting stability and consistency of the scale and indicating the goodness of the measure. Other statistical tests were used to test the research hypotheses such as One-Sample t-test, Independent-Samples t-test, One-Way ANOVA, Chi-Square and Bivariate Correlations (Pearson). The research indicated that Jordan has adequate and efficient e-commerce requirements in general, but there is no suitable and appropriate Community Culture in order to reach E-commerce Readiness Stage. Some recommendations are then made based on research findings