(Press-News.org) Type Ia supernovae (SNe Ia) play an important role as cosmological distance indicators and have been used successfully to determine cosmological parameters, which resulted in the discovery of the accelerating expansion of the Universe. However, the exact nature of SN Ia progenitors is still not well understood. There is a popular theory that SNe Ia originate from runaway thermonuclear events in carbon–oxygen white dwarves (CO WD) in binary systems. The CO WD accretes material from its companion. When the CO WD increases its mass above the maximum stable mass, it will explode.
Based on the nature of the companions of the mass accreting WDs, two competing scenarios have been proposed, namely, the double-degenerate (DD) channel and the single degenerate (SD) channel. Using the SD framework, Meng & Yang (2010) developed a comprehensive model of SNe Ia, including the WD + main sequence (MS) and WD + red giant channels. In the model, the mass-striping effects of optically thick wind and the effects of the thermally unstable disks were included. A model by Hachisu et al, which details how WDs accrete hydrogen-rich material from their companions, was applied to calculate the WD mass growth. Based on the model, Meng & Yang (2010) derived the Galactic birth rate of SNe Ia, which is comparable with that from observations. In this paper, Meng & Yang build on ideas from their earlier paper, Meng and Yang (2010). The purpose of this paper is to present the final parameter space and confirm that the model describes the potential progenitors systems of SNe Ia.
In this paper, researchers show the initial and final state of the progenitor systems of SNe Ia in an orbital-period–secondary-mass plane for the four cases, namely Case Wind, Case Calm, Case Nova, and Case DNova. In Case Wind, the exploding SNe Ia might be observed like SN 2006X, which shows a variable Na-1D line in its spectra and the others may be normal SNe Ia. Before a supernova explosion, Case Wind may be observed as quasi-regular transient supersoft X-ray sources (SSS) such as V Sagittae. Case Calm might be observed as a persistent SSS and Case Nova as recurrent novae and Case DNova as dwarf nova with recurrent novae.
In the paper also show that the properties of SSS (RX J0513) can be explained by a WD + MS system experiencing stable mass transfer and/or optically thick wind. Its location in the orbital-period–secondary-mass plane can be explained by both the Case Wind and Case Calm models.
Researchers also present the positions of three recurrent novae: U Sco, V394 CrA, and CI Aql. Based on their position in the orbital-period–secondary-mass plane, researchers predict that U Sco and V394 CrA are very likely progenitor candidates for SNe Ia. However, CI Aql is also a possible progenitor of SNe Ia, but is less likely. Further observation is still necessary to confirm their companion masses to judge their final fates.
After an SN Ia explosion, the companion star would survive. The supernova ejecta may collide with envelope and strip some hydrogen-rich material from the surface of the companion. The stripped-off hydrogen-rich material may manifest as a narrow hydrogen emission or absorption lines in the spectra of advanced SNe Ia. The amount of the stripped-off material determines whether the narrow hydrogen line can be observed. Analytic study and numerical simulations showed that the lower limit on the quantity of stripped-off material that can be observed is 0.035 solar mass. However, this scenario has not been verified by observations. The use of a reasonable companion structure when simulating the interaction between the supernova ejecta and the companion might be a key factor in overcoming the contradictions between observations and theory. The results in this paper will help to provide constraints on the companion structure, and will guide the study of the interaction between supernova ejecta and companions.
INFORMATION:
The author is currently with the School of Physics and Chemistry at Henan Polytechnic University.
This work was supported by the Natural Science Foundation of China under grant no. 10963001 and the Project of Fundamental and Frontier Research of Henan Province under grant no. 102300410223
Reference: Meng X, Yang W. A Comprehensive Progenitor Model for SNe Ia. Astrophys J, 2010, 710: 1310--1323
The initial and final state of SNe Ia from the single degenerate model
2010-12-04
ELSE PRESS RELEASES FROM THIS DATE:
The race against age
2010-12-04
Impairments to health and physical performance are not primarily a result of aging but of unfavorable lifestyle habits and lack of exercise. This is the position taken by Dieter Leyk and his coauthors in the new issue of Deutsches Ärzteblatt International (Dtsch Arztebl Int 2010; 107[46]: 809).
Sporty elderly people have a life expectancy that is almost 4 years higher and are often faster than younger athletes.
In their study, the sports scientists analyzed the stamina of more than 600 000 marathon and half marathon runners and asked participants about their ...
Soya beans could hold clue to treating fatal childhood disease
2010-12-04
Scientists from The University of Manchester say a naturally occurring chemical found in soy could prove to be an effective new treatment for a fatal genetic disease that affects children.
Dr Brian Bigger, from the University's MPS Stem Cell Research Laboratory, found that genistein – derived from soya beans and licensed in the US as an osteoporosis drug – had a dramatic effect on mice suffering from the human childhood disease Sanfilippo.
"Sanfilippo is an untreatable mucopolysaccharide (MPS) disease affecting one in 89,000 children in the United Kingdom," said Dr ...
Smoking may thin the brain
2010-12-04
Philadelphia, PA, 2 December 2010 - Many brain imaging studies have reported that tobacco smoking is associated with large-scale and wide-spread structural brain abnormalities.
The cerebral cortex is a specific area of the brain responsible for many important higher-order functions, including language, information processing, and memory. Reduced cortical thickness has been associated with normal aging, reduced intelligence, and impaired cognition.
However, prior research had not described the impact of smoking upon cortical thickness.
A new study, published in ...
Low-status leaders are ignored
2010-12-04
People who are deemed social misfits or "losers" aren't effective leaders, even if they are crusading for a cause that would benefit a larger group, according to new research from Rice University, the University of Texas and Universitat de Valencia.
The study's authors observed the contributions of 80 participants in a repeated public-goods game and found that players were more likely to mimic the actions of a leader they perceived as a high-status individual; they ignored leaders perceived as low-status and, when they had a chance, punished them for trying to lead. ...
Do our bodies' bacteria play matchmaker?
2010-12-04
Tel Aviv ― Could the bacteria that we carry in our bodies decide who we marry? According to a new study from Tel Aviv University, the answer lies in the gut of a small fruit fly.
Prof. Eugene Rosenberg, Prof. Daniel Segel and doctoral student Gil Sharon of Tel Aviv University's Department of Molecular Microbiology and Biotechnology recently demonstrated that the symbiotic bacteria inside a fruit fly greatly influence its choice of mates.
The research was done in cooperation with Prof. John Ringo of the University of Maine, and was recently published in the Proceedings ...
Widely used arthritis pill protects against skin cancer
2010-12-04
A widely-used arthritis drug reduces the incidence of non-melanoma skin cancers – the most common cancers in humans – according to a study published this week in the Journal of the National Cancer Institute. The COX-2 inhibitor celecoxib (brand name Celebrex), which is currently approved for the treatment of osteoarthritis, rheumatoid arthritis and acute pain in adults led to a 62 percent reduction in non-melanoma skin cancers, which includes basal cell carcinomas and squamous cell carcinomas.
Celecoxib, a prescription-strength nonsteroidal anti-inflammatory drug (NSAID), ...
Kicking the habit: Study suggests that quitting smoking improves mood
2010-12-04
PROVIDENCE, R.I. [Brown University] — Quitting smoking is certainly healthy for the body, but doctors and scientists haven't been sure whether quitting makes people happier, especially since conventional wisdom says many smokers use cigarettes to ease anxiety and depression. In a new study, researchers tracked the symptoms of depression in people who were trying to quit and found that they were never happier than when they were being successful, for however long that was.
Based on their results, the authors of the article published online Nov. 24 in the journal Nicotine ...
Set of specific interventions rapidly improves hospital safety 'culture'
2010-12-04
A prescribed set of hospital-wide patient-safety programs can lead to rapid improvements in the "culture of safety" even in a large, complex, academic medical center, according to a new study by safety experts at Johns Hopkins.
"It doesn't take decades or tons of money to get from a culture that says 'mistakes are inevitable' to a belief that harm is entirely preventable," says Peter Pronovost, M.D., Ph.D., a professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine and leader of the study published online in the journal ...
Relationship-strengthening class improves life for new families
2010-12-04
Expectant parents who completed a brief relationship-strengthening class around the time their child was born showed lasting effects on each family member's well being and on the family's overall relationships, according to a recent Penn State study.
The team, led by Mark Feinberg, senior research associate in Penn State's Prevention Research Center for the Promotion of Human Development, analyzed the effects of the Family Foundations program for three years after a child was born.
The Family Foundations program, offered in several Pennsylvania locations as part of ...
Lower occurrence of atopic dermatitis in children thanks to farm animals and cats
2010-12-04
Atopic dermatitis (also known as atopic eczema) is a chronic and extremely painful inflammation of the skin that frequently occurs in early childhood, generally already in infancy. Up to 20 percent of all children in industrialized countries are affected, making it one of the most common childhood skin diseases.
The need to better understand this disease is all the greater considering the intense suffering it causes in small children. Atopic dermatitis is, however, an allergic condition and all allergic reactions result from complex interactions of genetic and environmental ...