Topic
White dwarf
About: White dwarf is a research topic. Over the lifetime, 15004 publications have been published within this topic receiving 430597 citations. The topic is also known as: degenerate dwarf.
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TL;DR: In this article, a carbon-oxygen white dwarf (C+O WD) is originated from an asymptotic giant branch star with a C+O core but from a red giant star having a helium core of ~0.8-2.0 M☉.
Abstract: We have found a new evolutionary path to Type Ia supernovae (SNe Ia) that has been overlooked in previous work. In this scenario, a carbon-oxygen white dwarf (C+O WD) is originated not from an asymptotic giant branch star with a C+O core but from a red giant star with a helium core of ~0.8-2.0 M☉. The helium star, which is formed after the first common envelope evolution, evolves to form a C+O WD of ~0.8-1.1 M☉, transferring a part of the helium envelope onto the secondary main-sequence star. This new evolutionary path, together with the optically thick wind from mass-accreting white dwarf, provides a much wider channel to SNe Ia than previous scenarios. A part of the progenitor systems are identified as luminous supersoft X-ray sources or recurrent novae such as U Sco, which are characterized by the accretion of helium-rich matter. The white dwarf accretes hydrogen-rich, helium-enhanced matter from a lobe-filling, slightly evolved companion at a critical rate and blows excess matter into the wind. The white dwarf grows in mass to the Chandrasekhar mass limit and explodes as an SN Ia. A theoretical estimate indicates that this channel contributes a considerable part of the inferred rate of SNe Ia in our Galaxy, i.e., the rate is about 10 times larger than the previous theoretical estimates for white dwarfs with slightly evolved companions.
286 citations
TL;DR: A survey of the central region of Tycho's supernova remnant, around the position of the explosion, finds a type G0–G2 star, similar to the authors' Sun in surface temperature and luminosity (but lower surface gravity), which appears to be the surviving companion of the supernova.
Abstract: The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion1,2,3. Unless the companion star is another white dwarf (in which case it should be destroyed by the mass-transfer process itself), it should survive and show distinguishing properties. Tycho's supernova4,5 is one of only two type Ia supernovae observed in our Galaxy, and so provides an opportunity to address observationally the identification of the surviving companion. Here we report a survey of the central region of its remnant, around the position of the explosion, which excludes red giants as the mass donor of the exploding white dwarf. We found a type G0–G2 star, similar to our Sun in surface temperature and luminosity (but lower surface gravity), moving at more than three times the mean velocity of the stars at that distance, which appears to be the surviving companion of the supernova.
285 citations
TL;DR: An infrared object located about 120 AU from the white dwarf GD165 has been discovered in this paper, which is the coolest (2100 K) dwarf star ever reported and, according to some theoretical models, it should be a substellar brown dwarf with a mass between 0.06 and 0.08 solar mass.
Abstract: An infrared object located about 120 AU from the white dwarf GD165 has been discovered. With the exception of the possible brown dwarf companion to Giclas 29-38 reported last year, the companion to GD165 is the coolest (2100 K) dwarf star ever reported and, according to some theoretical models, it should be a substellar brown dwarf with a mass between 0.06 and 0.08 solar mass. These results, together with newly discovered low-mass stellar companions to white dwarfs, change the investigation of very low-mass stars from the study of a few chance objects to that of a statistical distribution. In particular, it appears that very low-mass stars and perhaps even brown dwarfs could be quite common in the Galaxy.
285 citations
01 Jan 1975
TL;DR: The necessary incidence of mass loss from stars in advanced stages of evolution was recognized many years ago as mentioned in this paper, and it was recognized that stars with masses above 1.4m cannot stabilize themselves after exhaustion of the various sources of nuclear fuel and will finally collapse, releasing an enormous amount of energy in a supernova explosion.
Abstract: The necessary incidence of mass loss from stars in advanced stages of evolution was recognized many years ago. Stars with masses above the white-dwarf limit m = 1.4m⊙ cannot stabilize themselves after exhaustion of the various sources of nuclear fuel and will finally collapse, releasing an enormous amount of energy in a supernova explosion. Supernova rates, however, seem to be considerably lower than death rates of stars in the mass range above 1.4 m ⊙. On the other hand, the occurrence of nonbinary white dwarfs in the Hyades shows that stars with m ≈ 2.5 m ⊙ have succeeded in losing a large portion of their original masses during some phase of evolution. Furthermore, most field white dwarfs seem to have masses in the range 0.4 to 0.8m ⊙, whereas their parent stars must have had masses of more than one solar mass.
282 citations
TL;DR: In this paper, the authors constructed a chemical evolution model for all stable elements from C (A = 12) to U (A=238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources.
Abstract: To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C (A=12) to U (A=238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M>30M_\odot can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M~20-50M_\odot. The contribution to GCE from super asymptotic giant branch (AGB) stars (with M~8-10M_\odot at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements, Sr, Y, and Zr, are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ~3% of 25-50 M_\odot hypernovae are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with galactic archaeology surveys.
282 citations