While most white dwarfs are assumed to harbor carbon or carbon/oxygen cores, we have no observational evidence for such an assumption. Three objects in our study, GD 140, EG 50, and Procyon B have radii that are much smaller than predicted by their observed masses. One interpretation of this result is the presence of an iron core
--TESTING THE WHITE DWARF MASS-RADIUS RELATION WITH HIPPARCOS (http://iopscience.iop.org/article/10.1086/305238/pdf)
On the contrary, for the cases of the other considered objects,
they fall clearly below the standard composition sequences,
indicating a denser interior. If we assume GD 140
and Procyon B to have an iron core, we find that they fall on
a sequence of a Teff compatible with the observed value. Nevertheless,
the EG 50 mean radius is smaller than predicted for an iron core object for the observed Teff. Thus, on the basis of
the current observational eterminations for EG 50, this WD
seems to be even denser than an iron WD.
Accordingly,
if observations are confirmed to be accurate enough,
we should seriously consider some physical process capable to
produce an iron core for such low mass objects
--Mass - radius relations for white dwarf stars of different internal
compositions (http://arxiv.org/pdf/astro-ph/9909499v1.pdf)
All SNe Iax for which we have late-time spectra
have calcium interior to iron. This is the opposite
of what is seen in SNe Ia
--TYPE Iax SUPERNOVAE: A NEW CLASS OF STELLAR EXPLOSION (http://arxiv.org/pdf/1212.2209v2.pdf)
至少鐵核白矮星還是爭論,尤其對這四個候選人:40 Eri B, EG 50, Procyon B, GD 140; 如果是假設是存在的,是否有可能續命呢?
而所謂Iax型超新星,其特殊之處在於其亮度比Ia型超新星要小很多,因此又被稱為subluminous (亮度較暗的) Ia超新星(NASA"s Hubble Finds Supernova Star System Linked to Potential "Zombie Star");除此之外還有許多難以解釋的地方(雖然Ia型超新星的爆發機制也尚無定論)。比較有趣的是先於問題中提到的這篇13年的觀測文章,在12年的時候就有篇數值模擬文章(Failed-detonation Supernovae,下圖是該數值模擬的的可視化)預言了這類超新星的存在;而文章作者之一是我的前老闆…