The evolution of Red Supergiant mass-loss rates

The fate of massive stars with initial masses >8M$_\odot$ depends largely on the mass-loss rate (\mdot ) in the end stages of their lives. Red supergiants (RSGs) are the direct progenitors to Type II-P core collapse supernovae (SN), but there is uncertainty regarding the scale and impact of any mass-loss during this phase. Here we used near and mid-IR photometry and the radiative transfer code DUSTY to determine luminosity and \mdot\ values for the RSGs in two Galactic clusters (NGC 7419 and $\chi$ Per) where the RSGs are all of similar initial mass ($M_{\rm initial}$$\sim$16M$_\odot$), allowing us to study how \mdot\ changes with time along an evolutionary sequence. We find a clear, tight correlation between luminosity and \mdot\ suggesting the scatter seen in studies of field stars is caused by stars of similar luminosity being of different initial masses. From our results we estimate how much mass a 16M$_\odot$ star would lose during the RSG phase, finding a star of this mass would lose a total of 0.61$^{+0.92}_{-0.31}$M$_\odot$. This is much less than expected for \mdot\ prescriptions currently used in evolutionary models

Star forming regions of the southern galaxy

A catalog of southern dust cloud properties is being compiled to aid in the planning and analysis of radio spectral line surveys in the southern hemisphere. Ultimately, images of dust temperature and column density will be produced. For the interim, a list of the 60 and 100 micron fluxes was prepared for the cores and adjacent backgrounds of 65 prominent dust clouds. Dust temperatures and column densities were derived

The 'red supergiant problem': the upper luminosity boundary of Type II supernova progenitors

By comparing the properties of red supergiant (RSG) supernova (SN) progenitors to those of field RSGs, it has been claimed that there is an absence of progenitors with luminosities L above log (L/L⊙) > 5.2. This is in tension with the empirical upper luminosity limit of RSGs at log (L/L⊙) = 5.5, a result known as the ‘RSG problem’. This has been interpreted as an evidence for an upper mass threshold for the formation of black holes. In this paper, we compare the observed luminosities of RSG SN progenitors with the observed RSG L-distribution in the Magellanic Clouds. Our results indicate that the absence of bright SN II-P/L progenitors in this sample can be explained at least in part by the steepness of the L-distribution and a small sample size, and that the statistical significance of the RSG problem is between 1σ and 2σ . Secondly, we model the luminosity distribution of II-P/L progenitors as a simple power law with an upper and lower cut-off, and find an upper luminosity limit of log(Lhi/L⊙)=5.20+0.17−0.11 (68 per cent confidence), though this increases to ∼5.3 if one fixes the power-law slope to be that expected from theoretical arguments. Again, the results point to the significance of the RSG problem being within ∼2σ. Under the assumption that all progenitors are the result of single-star evolution, this corresponds to an upper mass limit for the parent distribution of Mhi=19.2M⊙⁠, ±1.3M⊙(systematic)⁠, +4.5−2.3M⊙ (random; 68 per cent confidence limits)

The evolution of red supergiants to supernovae

With red supergiants (RSGs) predicted to end their lives as Type IIP core collapse supernova (CCSN), their behaviour before explosion needs to be fully understood. Mass loss rates govern RSG evolution towards SN and have strong implications on the appearance of the resulting explosion. To study how the mass-loss rates change with the evolution of the star, we have measured the amount of circumstellar material around 19 RSGs in a coeval cluster. Our study has shown that mass loss rates ramp up throughout the lifetime of an RSG, with more evolved stars having mass loss rates a factor of 40 higher than early stage RSGs. Interestingly, we have also found evidence for an increase in circumstellar extinction throughout the RSG lifetime, meaning the most evolved stars are most severely affected. We find that, were the most evolved RSGs in NGC2100 to go SN, this extra extinction would cause the progenitor's initial mass to be underestimated by up to 9M$_\odot$

The Initial Masses of the Red Supergiant Progenitors to Type-II Supernovae

There are a growing number of nearby SNe for which the progenitor star is detected in archival pre-explosion imaging. From these images it is possible to measure the progenitor's brightness a few years before explosion, and ultimately estimate its initial mass. Previous work has shown that II-P and II-L supernovae (SNe) have Red Supergiant (RSG) progenitors, and that the range of initial masses for these progenitors seems to be limited to $<$17M$_\odot$. This is in contrast with the cutoff of 25-30M$_\odot$ predicted by evolutionary models, a result which is termed the 'Red Supergiant Problem'. Here we investigate one particular source of systematic error present in converting pre-explosion photometry into an initial mass, that of the bolometric correction (BC) used to convert a single-band flux into a bolometric luminosity. We show, using star clusters, that RSGs evolve to later spectral types as they approach SN, which in turn causes the BC to become larger. Failure to account for this results in a systematic underestimate of a star's luminosity, and hence its initial mass. Using our empirically motivated BCs we reappraise the II-P and II-L SNe that have their progenitors detected in pre-explosion imaging. Fitting an initial mass function to these updated masses results in an increased upper mass cutoff of $M_{\rm hi}$=$19.0^{+2.5}_{-1.3}$M$_\odot$, with a 95% upper confidence limit of $<$27M$_\odot$. Accounting for finite sample size effects and systematic uncertainties in the mass-luminosity relationship raises the cutoff to $M_{\rm hi}$=25M$_\odot$ ($<$33M$_\odot$, 95% confidence). We therefore conclude that there is currently no strong evidence for `missing' high mass progenitors to core-collapse SNe

Effects of image and advertising efficiency on customer loyalty and antecedents of loyalty: turkish banks sample

The present study examines the relationships between image, advertising efficiency, customer satisfaction, customer expectation, perceived quality, perceived value, customer complaint and customer loyalty. These variables are increasingly recognised as being sources of competitive advantage. However, little empirical research has been conducted to examine these variables simultaneously and their relationships with post-purchase behaviour especially service organizations like banks. The present study was therefore designed to develop an understanding of the relationships between these variables and their influence on loyalty. An integrative model was developed and tested by using data collected from the customers of Turkish banks. The results reveal that bank image and advertising efficiency influence customer loyalty and antecedents of loyalty significantly

Sequestration of G3BP coupled with efficient translation inhibits stress granules in Semliki Forest virus infection

Dynamic, mRNA-containing stress granules (SGs) form in the cytoplasm of cells under environmental stresses, including viral infection. Many viruses appear to employ mechanisms to disrupt the formation of SGs on their mRNAs, suggesting that they represent a cellular defense against infection. Here, we report that early in Semliki Forest virus infection, the C-terminal domain of the viral nonstructural protein 3 (nsP3) forms a complex with Ras-GAP SH3-domain–binding protein (G3BP) and sequesters it into viral RNA replication complexes in a manner that inhibits the formation of SGs on viral mRNAs. A viral mutant carrying a C-terminal truncation of nsP3 induces more persistent SGs and is attenuated for propagation in cell culture. Of importance, we also show that the efficient translation of viral mRNAs containing a translation enhancer sequence also contributes to the disassembly of SGs in infected cells. Furthermore, we show that the nsP3/G3BP interaction also blocks SGs induced by other stresses than virus infection. This is one of few described viral mechanisms for SG disruption and underlines the role of SGs in antiviral defense

Effects of image and advertising efficiency on customer loyalty and antecedents of loyalty: turkish banks sample

The present study examines the relationships between image, advertising efficiency, customer satisfaction, customer expectation, perceived quality, perceived value, customer complaint and customer loyalty. These variables are increasingly recognised as being sources of competitive advantage. However, little empirical research has been conducted to examine these variables simultaneously and their relationships with post-purchase behaviour especially service organizations like banks. The present study was therefore designed to develop an understanding of the relationships between these variables and their influence on loyalty. An integrative model was developed and tested by using data collected from the customers of Turkish banks. The results reveal that bank image and advertising efficiency influence customer loyalty and antecedents of loyalty significantly