English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The progenitors of Type IIP supernovae have an apparent upper limit to theirinitial masses of about 20 solar masses, suggesting that the most massive redsupergiants evolve to warmer temperatures before their terminal explosion. Butvery few post-red supergiants are known. We have identified a small group ofluminous stars in M31 and M33 that are candidates for post-red supergiantevolution. These stars have A -- F-type supergiant absorption line spectra andstrong hydrogen emission. Their spectra are also distinguished by the Ca IItriplet and [Ca II] doublet in emission formed in a low density circumstellarenvironment. They all have significant near- and mid-infrared excess radiationdue to free-free emission and thermal emission from dust. We estimate theamount of mass they have shed and discuss their wind parameters and mass lossrates which range from a few times$ 10^-6 to 10^-4 solar masses/yr. On an HRDiagram, these stars will overlap the region of the LBVs at maximum light,however the warm hypergiants are not LBVs. Their non-spherical winds are notoptically thick and they have not exhibited any significant variability. Wesuggest, however, that the warm hypergiants may be the progenitors of the "lessluminous" LBVs such as R71 and even SN1987A.

Luminous and Variable Stars in M31 and M33. I. The Warm Hypergiants and Post-Red Supergiant Evolution