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تسجيل مستخدم جديدOn the Progenitors of Local Group Novae. II. The Red Giant Nova Rate of M31
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In our preceding paper, Liverpool Telescope data of M31 novae in eruption were used to facilitate a search for their progenitor systems within archival Hubble Space Telescope (HST) data, with the aim of detecting systems with red giant secondaries (RG-novae) or luminous accretion disks. From an input catalog of 38 spectroscopically confirmed novae with archival quiescent observations, likely progenitors were recovered for eleven systems. Here we present the results of the subsequent statistical analysis of the original survey, including possible biases associated with the survey and the M31 nova population in general. As part of this analysis we examine the distribution of optical decline times (t(2)) of M31 novae, how the likely bulge and disk nova distributions compare, and how the M31 t(2) distribution compares to that of the Milky Way. Using a detailed Monte Carlo simulation, we determine that 30 (+13/-10) percent of all M31 nova eruptions can be attributed to RG-nova systems, and at the 99 percent confidence level, >10 percent of all M31 novae are RG-novae. This is the first estimate of a RG-nova rate of an entire galaxy. Our results also imply that RG-novae in M31 are more likely to be associated with the M31 disk population than the bulge, indeed the results are consistent with all RG-novae residing in the disk. If this result is confirmed in other galaxies, it suggests any Type Ia supernovae that originate from RG-nova systems are more likely to be associated with younger populations, and may be rare in old stellar populations, such as early-type galaxies.
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We report the results of a survey of M31 novae in quiescence. This is the first catalog of extragalactic systems in quiescence to be published, and contains data for 38 spectroscopically confirmed novae from 2006 to 2012. We used Liverpool Telescope
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Mass loss is an important activity for red supergiants (RSGs) which can influence their evolution and final fate. Previous estimations of mass loss rates (MLRs) of RSGs exhibit significant dispersion due to the difference in method and the incomplete
ness of sample. With the improved quality and depth of the surveys including the UKIRT/WFCAM observation in near infrared, LGGS and PS1 in optical, a rather complete sample of RSGs is identified in M31 and M33 according to their brightness and colors. For about 2000 objects in either galaxy from this ever largest sample, the MLR is derived by fitting the observational optical-to-mid infrared spectral energy distribution (SED) with the DUSTY code of a 1-D dust radiative transfer model. The average MLR of RSGs is found to be around $2.0times10^{-5}{text{M}_odot}/text{yr}$ with a gas-to-dust ratio of 100, which yields a total contribution to the interstellar dust by RSGs of about $1.1times10^{-3}{text{M}_odot}/text{yr}$ in M31 and $6.0 times10^{-4}{text{M}_odot}/text{yr}$ in M33, a non-negligible source in comparison with evolved low-mass stars. The MLRs are divided into three types by the dust properties, i.e. amorphous silicate, amorphous carbon and optically thin, and the relations of MLR with stellar parameters, infrared flux and colors are discussed and compared with previous works for the silicate and carbon dust group respectively.
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