scholarly journals The ESO supernovae type Ia progenitor survey (SPY)

2020 ◽  
Vol 638 ◽  
pp. A131 ◽  
Author(s):  
R. Napiwotzki ◽  
C. A. Karl ◽  
T. Lisker ◽  
S. Catalán ◽  
H. Drechsel ◽  
...  
Keyword(s):  
Radial Velocity ◽  
White Dwarfs ◽  
Binary Systems ◽  
Detection Efficiency ◽  
Close Binary ◽  
The Galaxy ◽  
Type Ia ◽  
Low Mass ◽  
Kinematic Studies ◽  
Ia Supernovae

Close double degenerate binaries are one of the favoured progenitor channels for type Ia supernovae, but it is unclear how many suitable systems there are in the Galaxy. We report results of a large radial velocity survey for double degenerate (DD) binaries using the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY – SPY). Exposures taken at different epochs are checked for radial velocity shifts indicating close binary systems. We observed 689 targets classified as DA white dwarfs (displaying hydrogen-rich atmospheres), of which 46 were found to possess a cool companion. We measured radial velocities (RV) of the remaining 643 DA white dwarfs. We managed to secure observations at two or more epochs for 625 targets, supplemented by eleven objects meeting our selection criteria from literature. The data reduction and analysis methods applied to the survey data are described in detail. The sample contains 39 double degenerate binaries, only four of which were previously known. Twenty are double-lined systems, in which features from both components are visible, the other 19 are single-lined binaries. We provide absolute RVs transformed to the heliocentric system suitable for kinematic studies. Our sample is large enough to sub-divide by mass: 16 out of 44 low mass targets (≤0.45 M⊙) are detected as DDs, while just 23 of the remaining 567 targets with multiple spectra and mass > 0.45 M⊙ are double. The detected fraction amongst the low mass objects (36.4 ± 7.3%) is significantly higher than for the higher-mass, carbon-oxygen core dominated part of the sample (3.9 ± 0.8%), but it is much lower than expected from the detection efficiency for companion masses of 0.05 M⊙ or higher and a 100% binary fraction. This suggests either companion stars of with a mass below 0.05 M⊙ or some of the low mass white dwarfs are single.

scholarly journals SNIa, white dwarfs and the variation of the gravitational constant

2009 ◽  
Vol 5 (H15) ◽  
pp. 311-311
Author(s):  
J. Isern ◽  
E. Garcia–Berro ◽  
P. Lorén–Aguilar
Keyword(s):  
Secular Variation ◽  
White Dwarfs ◽  
Binary Systems ◽  
Gravitational Constant ◽  
Critical Role ◽  
Close Binary ◽  
Evolutionary Stage ◽  
Total Binding Energy ◽  
The Galaxy ◽  
Type Ia

AbstractThe critical role that the gravitational constant, G, plays in the Theory of General Relativity and the possibility, introduced by theories that unify gravity with other interactions, that G could vary in time and space have bursted the interest in detecting such variations or, at least, to bound them as tightly as possible.White dwarfs represent the last evolutionary stage of stars with masses smaller than 10 ± 2 M⊙. Since their mechanical structure is sustained by the pressure of degenerate electrons, they do not radiate nuclear energy and their evolution is just a simple gravothermal cooling process. On the other hand, white dwarfs in close binary systems can accrete matter from the companion, experiencing nova outbursts, or in some cases they can also reach Chandrasekhar's mass and explode as a Type Ia supernova (SNIa). Since the cooling of single white dwarfs and the properties of SNIa strongly depend on the precise value of G and on its possible secular variation, white dwarfs can be used to constrain such hypothetical variations.When white dwarfs are cool enough, their luminosity is entirely of gravothermal origin. Any variation of G modifies the energy balance of their interiors and, consequently, also modifies their luminosity. Formally, the influence of a secular variation of G can be expressed as L=-Ḃ+Ω(Ġ/G) where B=U+Ω is the total binding energy, U is the total internal energy and Ω is the gravitational energy. Thus, if Ġ ≠ 0 the luminosity is modified and the characteristic cooling time is different from that obtained in the case in which Ġ = 0. Detecting such variations can be done using the luminosity function of white dwarfs, which is defined as the number of white dwarfs of a given luminosity per unit of magnitude interval. It increases monotonically with the magnitude and displays a sharp cut-off due to the finite age of the Galaxy. The position of this cut-off is sensitive to the age of the Galaxy and to the value of Ġ and, thus, it can be used to obtain a bound. White dwarfs also display g-mode pulsations driven by the κ-mechanism and the period of pulsation experiences a secular drift of Ṗ/P ≃ -aṪ/T + bṘ/R, where a and b are model-dependent constants of the order of unity. Since both Ṫ and Ṙ depend on Ġ, the measure of Ṗ can also provide useful constraints.Type Ia supernovae are thought to be the result of the thermonuclear explosion of a carbon-oxygen white dwarf with a mass near Chandrasekhar's limit in a close binary system. The peak luminosity of SNIa is proportional to the mass of nickel synthesized which can be considered as a fixed fraction of the mass of the exploding star, MNi ∝ MCh = (ħc)3/2/mpG3/2. Therefore the properties of this peak with redshift can be used to test the variation of G with cosmic ages.Although the bounds obtained in these ways have been currently superseeded by other more accurate methods, when the ongoing surveys searching for SNIa and white dwarfs will be completed, the expected bounds will be as tight as ~ 10−13 yr−1.

scholarly journals Effects of Rotation on Helium Accreting White Dwarf

2004 ◽  
Vol 215 ◽  
pp. 571-572 ◽  
Author(s):  
S.-C. Yoon ◽  
N. Langer
Keyword(s):  
Angular Momentum ◽  
White Dwarf ◽  
Spherical Symmetry ◽  
Binary Systems ◽  
Close Binary ◽  
Type Ia Supernovae ◽  
Classical Studies ◽  
Type Ia ◽  
Effects Of Rotation ◽  
Ia Supernovae

Classical studies of accreting white dwarfs have assumed spherical symmetry. However, it is believed that in close binary systems the transfered matter carries angular momentum to spin up the accreting star. Here, we present preliminary results of CO white dwarf models which accrete helium rich matter with effects of rotation considered, in the context of the Sub-Chandrasekhar mass scenario for Type Ia supernovae.

scholarly journals Neutron Star Formation in Theoretical Supernovae — Low Mass Stars and White Dwarfs —

1987 ◽  
Vol 125 ◽  
pp. 281-303
Author(s):  
Ken'ichi Nomoto
Keyword(s):  
Neutron Stars ◽  
White Dwarfs ◽  
Binary Systems ◽  
Crab Nebula ◽  
Close Binary ◽  
Low Mass Stars ◽  
Supernova Explosions ◽  
Low Mass ◽  
Strongly Degenerate ◽  
The Crab Nebula

The presupernova evolution of stars that form semi-degenerate or strongly degenerate O+Ne+Mg cores is discussed. For the 10–13 M⊙ stars, behavior of off-center neon flashes is crucial. The 8–10 M⊙ stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these low mass progenitors are compared with the Crab nebula. We also examine the conditions for which neutron stars form from accretion-induced collapse of white dwarfs in close binary systems.

scholarly journals Evolution of Rotating White Dwarfs in Close Binaries and Diversity of Type Ia Supernovae

2003 ◽  
Vol 208 ◽  
pp. 459-460
Author(s):  
Tatsuhiro Uenishi ◽  
Ken'ichi Nomoto ◽  
Izumi Hachisu
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
White Dwarf ◽  
Binary Systems ◽  
Close Binary ◽  
Close Binaries ◽  
Type Ia Supernovae ◽  
Rapid Rotation ◽  
Type Ia ◽  
Ia Supernovae

Type Ia supernovae are very good, but not perfect, standard candles, because their observed brightness shows a little diversity. The origin of this dibersity needs to be understood for the application to cosmology.In close binary systems, a white dwarf must be rotating faster and faster as it gains angular momentum from the accretion disk. Its rapid rotation affects its final mass and strucure just before a supernova expolosion. Brightness of supernovae can be changed if mass of their progenitors have some diversity.

scholarly journals Type Ia supernovae and the formation of single low-mass white dwarfs

2008 ◽  
Vol 493 (3) ◽  
pp. 1081-1091 ◽  
Author(s):  
S. Justham ◽  
C. Wolf ◽  
Ph. Podsiadlowski ◽  
Zh. Han
Keyword(s):  
White Dwarfs ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Low Mass ◽  
Ia Supernovae

scholarly journals The origin and pulsations of extreme helium stars

2013 ◽  
Vol 9 (S301) ◽  
pp. 297-304
Author(s):  
C. Simon Jeffery
Keyword(s):  
Hydrogen Atom ◽  
White Dwarfs ◽  
Recent Progress ◽  
Surface Composition ◽  
Evolutionary Origin ◽  
Type Ia Supernovae ◽  
Helium Stars ◽  
The Galaxy ◽  
Type Ia ◽  
Ia Supernovae

AbstractStars consume hydrogen in their interiors but, generally speaking, their surfaces continue to contain some 70% hydrogen (by mass) throughout their lives. Nevertheless, many types of star can be found with hydrogen-deficient surfaces, in some cases with as little as one hydrogen atom in 10 000. Amongst these, the luminous B- and A-type extreme helium stars are genuinely rare; only ~15 are known within a very substantial volume of the Galaxy.Evidence from surface composition suggests a connection to the cooler R CrB variables and some of the hotter helium-rich subdwarf O stars. Arguments currently favour an origin in the merger of two white dwarfs; thus there are also connections with AM CVn variables and Type Ia supernovae. Pulsations in many extreme helium stars provide an opportune window into their interiors. These pulsations have unusual properties, some being “strange” modes, and others being driven by Z-bump opacities. They have the potential to deliver distance-independent masses and to provide a unique view of pulsation physics.We review the evolutionary origin and pulsations of these stars, and introduce recent progress and continuing challenges.

scholarly journals Correlation of the rate of Type Ia supernovae with the parent galaxy properties: Light and shadows

2019 ◽  
Vol 625 ◽  
pp. A113 ◽  
Author(s):  
L. Greggio ◽  
E. Cappellaro
Keyword(s):  
Binary Systems ◽  
Cosmological Parameters ◽  
Stellar Populations ◽  
Star Formation History ◽  
Close Binary ◽  
Type Ia Supernovae ◽  
Wide Range ◽  
Type Ia ◽  
Ia Supernovae ◽  
Parent Galaxy

Context. The identification of the progenitors of Type Ia supernovae (SNIa) is extremely important in several astrophysical contexts, ranging from stellar evolution in close binary systems to evaluating cosmological parameters. Determining the distribution of the delay times (DTD) of SNIa progenitors can shed light on their nature. The DTD can be constrained by analysing the correlation between the SNIa rate and those properties of the parent galaxy which trace the average age of their stellar populations. Aims. We investigate the diagnostic capabilities of this correlation by examining its systematics with the various parameters at play: simple stellar population models, the adopted description for the star formation history (SFH) in galaxies, and the way in which the masses of the galaxies are evaluated. Methods. We computed models for the diagnostic correlations for a variety of input ingredients and for a few astrophysically motivated DTD laws appropriate for a wide range of possibilities for the SNIa progenitors. The models are compared to the results of three independent observational surveys. Results. The scaling of the SNIa rate with the properties of the parent galaxy is sensitive to all input ingredients mentioned above. This is a severe limitation on the possibility to discriminate alternative DTDs. In addition, current surveys show some discrepancies for the reddest and bluest galaxies, likely because of limited statistics and the inhomogeneity of the observations. For galaxies with intermediate colours the rates are in agreement, leading to a robust determination of the productivity of SNIa from stellar populations of ≃0.8 events per 1000 M⊙. Conclusions. Large stastistics of SNIa events along with accurate measurements of the SFH in the galaxies are required to derive firm constraints on the DTD. The LSST will achieve these results by providing a homogeneous, unbiased, and vast database on both SNIa and galaxies.

scholarly journals Close Binary White Dwarfs and Supernovae la

2004 ◽  
Vol 194 ◽  
pp. 113-116
Author(s):  
R. Napiwotzki ◽  
C. Karl ◽  
G. Nelemans ◽  
L. Yungelson ◽  
N. Christlieb ◽  
...  
Keyword(s):  
Radial Velocity ◽  
White Dwarf ◽  
White Dwarfs ◽  
Close Binary ◽  
Current Status ◽  
Large Sample ◽  
Observational Test ◽  
Type Ia ◽  
Binary Evolution

AbstractWe report on the current status of radial velocity surveys for white dwarf binaries (double degenerates DDs) including SPY (ESO Supernovae la progenitor survey) recently carried out at the VLT. A large sample of DD will allow us to put strong constraints on the phases of close binary evolution of the progenitor systems and to perform an observational test of the DD scenario for Supernovae of type Ia.

Type IA Supernovae and Chemical Evolution of Galaxies

2002 ◽  
Vol 187 ◽  
pp. 33-46
Author(s):  
K. Nomoto ◽  
C. Kobayashi ◽  
H. Umeda
Keyword(s):  
Chemical Evolution ◽  
White Dwarfs ◽  
Binary Systems ◽  
Cosmological Parameters ◽  
Type Ia Supernovae ◽  
Exact Nature ◽  
Type Ia ◽  
Low Metallicity ◽  
Strong Winds ◽  
Ia Supernovae

The cosmic/galactic chemical evolutions have been modeled with the early metal enrichment by Type II supernovae (SNe II) and the delayed enrichment of Fe by Type Ia supernovae (SNe Ia). However, the exact nature of SN Ia progenitors have been obscure. Here we present the currently most plausible scenario of the progenitor binary systems of SNe Ia. This scenario involves strong winds from accreting white dwarfs, which introduces important metallicity effects, namely, low-metallicity inhibition of SNe Ia. Resultant predictions for the Galactic/cosmic chemical evolution and the cosmic SNe Ia rate are presented. Another importance of identifying the SN Ia progenitors lies in the use of SNe Ia as a “standard candle” to determine cosmological parameters. To examine whether the “evolution” of SNe Ia with redshift and metallicity is significant, we discuss how the metallicity affects the properties of the C+O white dwarfs such as the C/O ratio, and find the metallicity dependence is rather weak.

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