ﻻ يوجد ملخص باللغة العربية
We report mid- to far-infrared imaging and photomety from 7 to 37 microns with SOFIA/FORCAST and 2 micron adaptive optics imaging with LBTI/LMIRCam of a large sample of red supergiants (RSGs) in four Galactic clusters; RSGC1, RSGC2=Stephenson 2, RSGC3, and NGC 7419. The red supergiants in these clusters cover their expected range in luminosity and initial mass from approximately 9 to more than 25 Solar masses. The population includes examples of very late-type RSGs such as MY Cep which may be near the end of the RSG stage, high mass losing maser sources, yellow hypergiants and post-RSG candidates. Many of the stars and almost all of the most luminous have spectral energy distributions (SEDs) with extended infrared excess radiation at the longest wavelengths. To best model their SEDs we use DUSTY with a variable radial density distribution function to estimate their mass loss rates. Our mass loss rate -- luminosity relation for 42 RSGs basically follows the classical de Jager curve, but at luminosities below 10^5 Solar luminosities we find a significant population of red supergiants with mass loss rate below the de Jager relation. At luminosities above 10^5 Solar luminosities there is a rapid transition to higher mass loss rates that approximates and overlaps the de Jager curve. We recommend that instead of using a linear relation or single curve, the empirical mass loss rate -- luminosity relation is better represented by a broad band. Interestingly, the transition to much higher mass loss rates at about 10^5 Lsun corresponds approximately to an initial mass of 18 --20 Msun which is close to the upper limit for RSGs becoming Type II SNe.
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
We aim to investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metalliticies and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor
The post main-sequence evolution of massive stars is very sensitive to many parameters of the stellar models. Key parameters are the mixing processes, the metallicity, the mass-loss rate and the effect of a close companion. We study how the red super
Using the PACS and SPIRE spectrometers on-board the Herschel Space Observatory, we obtained spectra of two red supergiants (RSGs) in the Large Magellanic Cloud (LMC). Multiple rotational CO emission lines (J=6-5 to 15-14) and 15 H2O lines were detect
The mass-loss rates of red supergiant stars (RSGs) are poorly constrained by direct measurements, and yet the subsequent evolution of these stars depends critically on how much mass is lost during the RSG phase. In 2012 the Geneva evolutionary group