scholarly journals Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio

2018 ◽  
Vol 481 (4) ◽  
pp. 5660-5674 ◽  
Author(s):  
A Dervişoğlu ◽  
K Pavlovski ◽  
H Lehmann ◽  
J Southworth ◽  
D Bewsher
Keyword(s):  
Mass Transfer ◽  
Abundance Ratio ◽  
Surface Carbon ◽  
Nitrogen Abundance ◽  
Algol System

scholarly journals Carbon-loud SDSS BOSS type II quasars at z > 2: high-density gas or secondary production of carbon?

2020 ◽  
Vol 495 (4) ◽  
pp. 4707-4746
Author(s):  
M Silva ◽  
A Humphrey ◽  
P Lagos ◽  
S G Morais
Keyword(s):  
Abundance Ratio ◽  
Systematic Difference ◽  
Sloan Digital Sky Survey ◽  
Type Ii ◽  
Narrow Line ◽  
Chemical Abundances ◽  
Gas Density ◽  
Chemical Enrichment ◽  
Order Of Magnitude ◽  
Nitrogen Abundance

ABSTRACT We study the ultraviolet (UV) emission-line ratios of a sample of 145 type II quasars (QSO2s) from Sloan Digital Sky Survey iii Baryon Oscillation Spectroscopic Survey, and compare against a grid of active galactic nucleus (AGN) photoionization models with a range in gas density, gas chemical abundances, and ionization parameter. Most of the quasars are ‘carbon-loud’, with C  iv/He ii ratios that are unusually high for the narrow-line region, implying higher than expected gas density (>106 cm−3) and/or significantly supersolar-relative carbon abundance. We also find that solar or supersolar nitrogen abundance and metallicity are required in the majority of our sample, with potentially significant variation between objects. Compared to radio galaxies at similar redshifts (HzRGs; z > 2), the QSO2s are offset to higher N  v/He ii, C  iv/He ii, and C iii]/He ii, suggesting systematically higher gas density and/or systematically higher C and N abundances. We find no evidence for a systematic difference in the N/C abundance ratio between the two types of objects. Scatter in the N  iv]/C  iv ratio implies a significant scatter in the N/C abundance ratio among the QSO2s and HzRGs, consistent with differences in the chemical enrichment histories between objects. Interestingly, we find that adopting secondary behaviour for both N and C alleviates the long-standing ‘N  iv] problem’. A subset of the QSO2s and HzRGs also appear to be ‘silicon-loud’, with Si iii] relative fluxes suggesting Si/C and Si/O are an order of magnitude above their solar values. Finally, we propose new UV-line criteria to select genuine QSO2s with low-density narrow-line regions.

scholarly journals The Carbon and Nitrogen Abundance Ratio in the Broad Line Region of Tidal Disruption Events

2017 ◽  
Vol 846 (2) ◽  
pp. 150 ◽  
Author(s):  
Chenwei Yang ◽  
Tinggui Wang ◽  
Gary J. Ferland ◽  
Liming Dou ◽  
Hongyan Zhou ◽  
...  
Keyword(s):  
Abundance Ratio ◽  
Broad Line ◽  
Tidal Disruption ◽  
Carbon And Nitrogen ◽  
Broad Line Region ◽  
Line Region ◽  
Nitrogen Abundance

scholarly journals Nitrogen abundance in the Blue Compact Dwarf galaxies from SDSS

2015 ◽  
Vol 5 (1) ◽  
pp. 39-42
Author(s):  
K. Vovk
Keyword(s):  
Emission Line ◽  
Dwarf Galaxies ◽  
Direct Method ◽  
Hii Regions ◽  
Abundance Ratio ◽  
Sloan Digital Sky Survey ◽  
Nitrogen Enrichment ◽  
Element Abundances ◽  
Sky Survey ◽  
Nitrogen Abundance

We examined all of the galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) to select those with a detected OIII λ4363 emission line, which allows to derive electron temperatures in HII regions and element abundances by the direct method. We selected two sub-samples of galaxies: one with detected WR features in their spectra, and the other with the nebular HeII λ4686 emission line. We confirm the increase of the N/O abundance ratio with decrease of the equivalent width EW(Hβ) of the Hβ emission line. This result is explained by gradual nitrogen enrichment of the interstellar medium by ejecta from massive stars in the most recent starburst episode.

scholarly journals Evidence of a Tidal-disruption Event in GSN 069 from the Abnormal Carbon and Nitrogen Abundance Ratio

2021 ◽  
Vol 920 (1) ◽  
pp. L25
Author(s):  
Zhenfeng Sheng ◽  
Tinggui Wang ◽  
Gary Ferland ◽  
Xinwen Shu ◽  
Chenwei Yang ◽  
...  
Keyword(s):  
Abundance Ratio ◽  
Tidal Disruption ◽  
Carbon And Nitrogen ◽  
Nitrogen Abundance ◽  
Disruption Event

scholarly journals The Relation of Algols and W Serpentis Stars

1989 ◽  
Vol 107 ◽  
pp. 191-203
Author(s):  
R. E. Wilson
Keyword(s):  
Mass Transfer ◽  
Mass Transfer Rate ◽  
Type System ◽  
Type Systems ◽  
Morphological Type ◽  
Light Curves ◽  
Close Binary ◽  
Rapid Phase ◽  
Hydrogen Burning ◽  
Algol System

AbstractEvidence on the issues of whether the W Serpentis stars are a coherent class, and how they may interface with the Algol systems, is reviewed, with emphasis on the idea that they are semi-detached systems in the latter part of the rapid phase of mass transfer, with optically and geometrically thick disks of transferred gas around the (now) more massive star. We are interested in what will be seen when the gas clears away, and mainly examine the idea that it will be an Algol-type system. More particularly, consideration is given to centrifugally limited accretion as a mechanism to build up a substantial disk, and the presumed evolutionary sequence is from a W Ser to a rapidly rotating Algol to a normal Algol system. Systems such as V367 Cyg and RW Tau fit into this scheme only with difficulty. Because it is extremely difficult to measure the rotation of some W Ser (mass) primaries, it is natural to look at the rotation statistics of Algols to test this idea. The badly behaved light curves and spectroscopy of some Algols (eg. U Cep, RZ Set) may be attributable to the double contact condition, and the ramifications of this possibility are discussed. If so, the rotation statistics of Algols should show two spikes, corresponding to the two special conditions into which a system should be driven by tidal braking and centrifugally limited spin-up. Present rotation statistics do show these spikes. Algols should flip between these states fairly quickly, depending on the mass transfer rate. Thus, to the extent that the meager statistics can be accepted as meaningful, the new (fourth) morphological type of close binary (double contact) has attained demonstrable reality. The rotation statistics are presented in terms of a particular rotation parameter, R, which is zero for synchronism and unity for the centrifugal limit. Future work should develop rotation statistics to see if the rotational lobe-filling (R=l) spike persists. It should also look into whether W Ser primaries are on the hydrogen burning main sequence, or in general what they are. We also need more light curves of W Ser type systems, high resolution line profiles for the (mass) primaries (with particular attention to the W Ser-Algol transition cases), and spectroscopy of low inclination W Serpentis systems, such as KX And.

Calculation of Gas Carburizing Kinetics from Carbon Concentration Profiles based on Direct Flux Integration

2007 ◽  
Vol 266 ◽  
pp. 171-180 ◽  
Author(s):  
Olga Karabelchtchikova ◽  
Richard D. Sisson
Keyword(s):  
Mass Transfer ◽  
Weight Gain ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Carbon Concentration ◽  
Concentration Profiles ◽  
Surface Carbon ◽  
Average Mass ◽  
Gas Carburizing ◽  
Carbon Diffusivity

Initiated by the need of industry for gas carburizing process control and optimization, this paper focuses on understanding the effect of the time, temperature and carbon potential on the mass transfer coefficient and carbon diffusivity in Austenite. A method for direct flux integration has previously been proposed to calculate these kinetic parameters from the experimental carbon concentration profiles. AISI 8620 steel discs were gas carburized at different levels of atmosphere carburizing potential for selected austenizing temperatures. Analyses of the carburized parts included experimental measurement of weight gain, surface carbon concentration and carbon concentration profiles. The time-dependent weight gain and surface carbon content measurements allowed calculation of the time average mass transfer coefficient, while carbon concentration profiles were used to calculate the concentration dependent carbon diffusivity for selected process parameters. Excellent agreement was found between the calculated mass transfer coefficient and carbon diffusivity values and those reported in the literature. The calculated values served as input in the previously developed carburizing model validating the predicted results by comparison with the experimental concentration profiles.

scholarly journals The 12C/13C Ratio as a Tracer of the Evolution of Post Common Envelope Systems and Cataclysmic Variables

1996 ◽  
Vol 158 ◽  
pp. 457-458
Author(s):  
M. J. Sarna ◽  
P. B. Marks ◽  
R. C. Smith
Keyword(s):  
Mass Transfer ◽  
Cataclysmic Variables ◽  
Abundance Ratio ◽  
Roche Lobe ◽  
Mass Star ◽  
Convective Envelope ◽  
Dwarf Stars ◽  
Common Envelope ◽  
Secondary Star ◽  
Nova Outbursts

To provide a direct test of common envelope (CE) evolution which can be easily confirmed by observations, we (Sarna et al. 1995) recently modelled the change in the abundance ratio of 12C/13C on the surface of the lower mass star of a binary during the CE phase. The model is based on the fact that it is probable that the dwarf star accretes material during the CE phase. Since, during the CE phase, the dwarf secondary effectively exists within the atmosphere/envelope of the giant or supergiant primary, the accreted material has the abundances/composition of a giant/supergiant star. The 12C/13C ratio is known to decrease from approximately 90 in dwarf stars (in which the 13CO band at 2.3448 microns is barely visible) to approximately 10 in giants (in which the 13CO band at 2.3448 microns is fairly prominent). Hence, by measuring the 12C/13C ratio in post common envelope binaries (PCEBs) and comparing it to our models we would be able not only to confirm the CE theory but also to determine the amount of mass accreted during the CE phase and hence the initial mass of the dwarf component prior to the CE phase. We also propose an evolutionary scenario in which PCEBs with secondary component mass near 1.0 M⊙ start semi-detached evolution almost immediately after the CE phase. The progenitor system is a wide binary consisting of a 3 M⊙ primary with a 1.0 M⊙ secondary star. The primary evolves to fill its Roche lobe when it has a 0.6 M⊙ C–O core, with two shell burning regions. Such a star has a thick convective envelope, mass transfer is dynamically unstable and a common envelope forms. After the CE phase we are left with a close detached binary consisting of the primary’s core (0.6 M⊙) and the secondary (1.0 M⊙) main sequence star. Shortly afterwards the secondary fills its Roche lobe and mass transfer occurs (Sarna, Marks & Smith 1995). The system now evolves as a semi-detached binary (CV), transferring material to the white dwarf which undergoes nova outbursts. Figs. 1 and 2 show the isotopic ratios of 12C/13C and 16O/17O during the semi-detached evolution. In Fig. 1 the secondary did not accrete any material during CE evolution whilst in Fig. 2 the secondary accreted 0.2M⊙ during the CE stage.

scholarly journals Two Centuries of Study of Algol Systems

1989 ◽  
Vol 107 ◽  
pp. 1-8
Author(s):  
Alan H. Batten
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Circumstellar Matter ◽  
Second Century ◽  
Light Curves ◽  
Eclipsing Binary ◽  
The Galaxy ◽  
Algol System ◽  
Binary Hypothesis ◽  
Theoretical Developments

AbstractThe periodicity of the light variation of Algol, discovered just over 200 years ago, may be regarded as the beginning of the study of eclipsing binary systems, especially those of the Algol type. Such studies, however, gained no real momentum until Vogel, 100 years ago, demonstrated by spectroscopy that the binary hypothesis of Algol’s light changes is, in its essentials, correct. Three elements were needed to give us our modern notions of evolution by mass-transfer, namely: (i) results of combined analysis of light-curves and velocity-curves, (ii) evidence of circumstellar matter within binary systems and (iii) the notion that at least one component of an Algol system was near the limit of dynamical stability. All three entered the literature within about a decade, approximately halfway through the second century of eclipsing-binary studies; but it is the computational and instrumental developments of the last 25 years that have made real progress possible. We still lack commensurate theoretical developments, and the whole question of the contribution of Algol systems to the development of the Galaxy has barely been considered.

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