scholarly journals Carbon Depletion in Case B Mass Transfer Algol-Type Binaries

1992 ◽  
Vol 151 ◽  
pp. 355-358
Author(s):  
Tae S. Yoon ◽  
Kent Honeycutt
Keyword(s):  
Mass Transfer ◽  
Mass Loss ◽  
Similar Type ◽  
Single Star ◽  
Star Models ◽  
Promising Tool ◽  
Carbon Abundance ◽  
Processed Material ◽  
C And N ◽  
Larger Sample

The surface carbon abundances of Algol secondaries are known to be low compared to field stars of similar type. The C and N anomalies of these G and K subgiants are undoubtedly due to the exposure of CN cycle processed material as mass transfer removes the outer layers of the star. Therefore the carbon abundance is a promising tool for helping fix the evolutionary state of Algols, particularly the amount of mass which has been lost from the secondary. We report here the carbon abundance of 12 Algol secondaries as deduced from the g-band in spectra obtained during photometric totality. We compare the abundances to those from models of single stars of appropriate age and mass. The values of log ∊(C) for this sample fall 0.25–0.75 dex below field G and K giants, and 1.25–1.75 dex above “stripped” single star models. This larger sample supports the conclusions of Parthasarthy et al. regarding mixing and mass loss, which they deduced from a smaller sample of carbon abundances.

scholarly journals Hydrogen-Poor Binary Stars

1985 ◽  
Vol 87 ◽  
pp. 230-243 ◽  
Author(s):  
Mirek J. Plavec
Keyword(s):  
Mass Transfer ◽  
Mass Loss ◽  
Binary Stars ◽  
Large Scale ◽  
Hydrogen Burning ◽  
Complex Process ◽  
Processed Material ◽  
Helium Stars ◽  
Two Stages

AbstractHydrogen-poor and helium-rich stars are easy to produce in interacting binaries. Thus they should be found among Population I binaries, in which a large-scale mass transfer has occurred between the components (possibly associated with mass loss from the system). For in such cases, those layers are now on the surface of the “loser” (and, most likely, also on the surface of the “gainer”) that were subject to hydrogen burning and the associated mixing of processed material. Helium overabundance in these objects will be accompanied by an overabundance of nitrogen and underabundance of carbon, as a result of the CNO process. All the Algol-like semidetached binaries should be mild helium stars; so far this has been demonstrated only in β Lyrae, for the He/H ratio is not extreme in such cases. Extreme helium stars require a more complex process, with two stages of mass transfer and/or loss (“case BB”); υ Sagittarii and KS Persei seem to be good examples of this process. The optically invisible components of these two stars seem to have been detected with the IUE. Good model atmospheres do not exist yet, so caution must be exercised in interpreting the UV data.

scholarly journals Equatorial mass loss from Be stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 640-641
Author(s):  
Cyril Georgy ◽  
Sylvia Ekström ◽  
Anahí Granada ◽  
Georges Meynet
Keyword(s):  
Mass Loss ◽  
Be Stars ◽  
Rotating Stars ◽  
Single Star ◽  
Star Models ◽  
Total Mass Loss ◽  
Rotation Phase ◽  
Rotating Star ◽  
Mechanical Mass ◽  
Fast Rotating

AbstractBe stars are thought to be fast rotating stars surrounded by an equatorial disc. The formation, structure and evolution of the disc are still not well understood. In the frame of single star models, it is expected that the surface of an initially fast rotating star can reach its keplerian velocity (critical velocity). The Geneva stellar evolution code has been recently improved, in order to obtain some estimates of the total mass loss and of the mechanical mass loss rates in the equatorial disc during the whole critical rotation phase. We present here the first results of the computation of a grid of fast rotating B stars evolving towards the Be phase, and discuss the first estimates we obtained.

scholarly journals The effects of surface fossil magnetic fields on massive star evolution: III. The case of τ Sco

2021 ◽  
Author(s):  
Z Keszthelyi ◽  
G Meynet ◽  
F Martins ◽  
A de Koter ◽  
A David-Uraz
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Massive Star ◽  
Slow Rotation ◽  
Single Star ◽  
Surface Magnetic Field ◽  
Fundamental Parameters ◽  
Chemical Enrichment ◽  
Star Models ◽  
Nitrogen Excess

Abstract τ Sco, a well-studied magnetic B-type star in the Uτer Sco association, has a number of surprising characteristics. It rotates very slowly and shows nitrogen excess. Its surface magnetic field is much more complex than a purely dipolar configuration which is unusual for a magnetic massive star. We employ the cmfgen radiative transfer code to determine the fundamental parameters and surface CNO and helium abundances. Then, we employ mesa and genec stellar evolution models accounting for the effects of surface magnetic fields. To reconcile τ Sco’s properties with single-star models, an increase is necessary in the efficiency of rotational mixing by a factor of 3 to 10 and in the efficiency of magnetic braking by a factor of 10. The spin down could be explained by assuming a magnetic field decay scenario. However, the simultaneous chemical enrichment challenges the single-star scenario. Previous works indeed suggested a stellar merger origin for τ Sco. However, the merger scenario also faces similar challenges as our magnetic single-star models to explain τ Sco’s simultaneous slow rotation and nitrogen excess. In conclusion, the single-star channel seems less likely and versatile to explain these discrepancies, while the merger scenario and other potential binary-evolution channels still require further assessment as to whether they may self-consistently explain the observables of τ Sco.

scholarly journals Evolution of O stars and the WR connection

1979 ◽  
Vol 83 ◽  
pp. 431-445 ◽  
Author(s):  
Peter S. Conti
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
High Luminosity ◽  
Loss Mechanism ◽  
Evolutionary Scenario ◽  
Processed Material ◽  
Dominant Process ◽  
Highly Evolved ◽  
Loss Rates ◽  
Enriched Composition

The stellar wind mass loss rates of at least some single Of type stars appear to be sufficient to remove much if not all of the hydrogen-rich envelope such that nuclear processed material is observed at the surface. This highly evolved state can then be naturally associated with classic Population I WR stars that have properties of high luminosity for their mass, helium enriched composition, and nitrogen or carbon enhanced abundances. If stellar wind mass loss is the dominant process involved in this evolutionary scenario, then stars with properties intermediate between Of and WR types should exist. The stellar parameters of luminosity, temperature, mass and composition are briefly reviewed for both types. All late WN stars so far observed are relatively luminous like Of stars, and also contain hydrogen. All early WN stars, and WC stars, are relatively faint and contain little or no hydrogen. The late WN stars seem to have the intermediate properties required if a stellar wind is the dominant mass loss mechanism that transforms an Of star to a WR type.

scholarly journals A New Concept of Stirred Multiphase Reactor Using a Stationary Catalytic Foam

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 117 ◽  
Author(s):  
Nassima Benamara ◽  
Didier Assoua ◽  
Louis Jaffeux ◽  
Laurent Vanoye ◽  
Florica Simescu-Lazar ◽  
...  
Keyword(s):  
Mass Transfer ◽  
High Mass ◽  
Hydrogenation Rate ◽  
Transfer Rates ◽  
Promising Tool ◽  
Intrinsic Kinetics ◽  
Stirred Reactor ◽  
Al2o3 Catalyst ◽  
Absorption Of Hydrogen

Developing new stirred gas–liquid–solid reactors with high mass transfer capabilities is still a challenge. In this publication, we present a new concept of multiphase reactor using a stationary catalytic foam and a gas-inducing impeller. The gas–liquid (GL) and liquid–solid (LS) mass transfer rates in this reactor were compared to a stirred reactor with basket filled with beads. Batch absorption of hydrogen and measurement of α-methylstyrene hydrogenation rate on Pd/Al2O3 catalyst were used to evaluate kGLaGL coefficients and kLS coefficients, respectively. With similar LS transfer rates to the basket-reactor and much higher GL transfer rates, the new reactor reveals a very promising tool for intrinsic kinetics investigations.

Microbial biomass and activity in the humus layer following burning: short-term effects of two different fires

1993 ◽  
Vol 23 (7) ◽  
pp. 1275-1285 ◽  
Author(s):  
Janna Pietikäinen ◽  
Hannu Fritze
Keyword(s):  
Microbial Community ◽  
Microbial Biomass ◽  
Soil Respiration ◽  
Mass Loss ◽  
Forest Fire ◽  
Prescribed Burning ◽  
Microbial Biomass C ◽  
Soil Microbial ◽  
Fungal Hyphae ◽  
C And N

During a 3-year study, soil microbial biomass C and N, length of the fungal hyphae, soil respiration, and the percent mass loss of needle litter were recorded in coniferous forest soil humus layers following a prescribed burning (PB) treatment or a forest fire simulation (FF) treatment (five plots per treatment). Unburned humus from adjacent plots served as controls (PC and FC, respectively). Prescribed burning was more intensive than the forest fire, and this was reflected in all the measurements taken. The amounts of microbial biomass C and N, length of fungal hyphae, and soil respiration in the PB area did not recover to their controls levels, whereas unchanged microbial biomass N and recovery of the length of the fungal hyphae to control levels were observed in the FF area. The mean microbial C/N ratio was approximately 7 in all the areas, which reflected the C/N ratio of the soil microbial community. Deviation from this mean value, as observed during the first three samplings from the PB area (3, 18, and 35 days after fire treatment), suggested a change in the composition of the microbial community. Of the two treated areas, the decrease in soil respiration (laboratory measurements) was much more pronounced in the PB area. However, when the humus samples from both areas were adjusted to 60% water holding capacity, no differences in respiration capacity were observed. The drier humus, due to higher soil temperatures, of the PB area is a likely explanation for the low soil respiration. Lower soil respiration was not reflected in lower litter decomposition rates of the PB area, since there was a significantly higher needle litter mass loss during the first year in the PB area followed by a decline to the control level during the second year. Consistently higher mass losses were recorded in the FC area than in the FF area.

Mass Loss and Mass Transfer in Algols

1980 ◽  
pp. 207-210
Author(s):  
G. Giuricin ◽  
F. Mardirossian ◽  
M. Mezzetti
Keyword(s):  
Mass Transfer ◽  
Mass Loss

scholarly journals Mass Loss and Shell Masses of Close Binary Stars

1987 ◽  
Vol 93 ◽  
pp. 675-679
Author(s):  
V.G. Karetnikov
Keyword(s):  
Mass Transfer ◽  
Mass Loss ◽  
Binary Stars ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Close Binary ◽  
Time Interval ◽  
Close Binary Stars

AbstractFrom the values of period changes for 6 close binary stars the mass transfer rate was calculated. Comparing these values Mt with the values of shell masses Msh, the expressionwas derived. The analysis of this expression points out the initial character of the outflow of matter, and one may determine the time interval of the substitution of the shell matter. So one may conclude that for a certain mass transfer rate, a certain amount of matter accumulates in the nearby regions of the system.

scholarly journals Secular Mass Loss from Cataclysmic Variables

1977 ◽  
Vol 42 ◽  
pp. 365-370
Author(s):  
Józef Smak
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Chemical Composition ◽  
Mass Loss ◽  
Cataclysmic Variables ◽  
Dynamical Evolution ◽  
Good Insight ◽  
Physical Mechanisms ◽  
Cataclysmic Binaries ◽  
Insight Into

The mass loss from cataclysmic binaries seems an important and worth studying phenomenon for a number of reasons. It is probably enough to mention only two of them:(a) Whenever we can directly observe the ejected material, determine its amount and the rate of mass loss, as well as its chemical composition (this being the case of the expanding envelopes of novae), we are getting a good insight into the basic physical mechanisms responsible for the observed phenomena.(b) The mass loss (together with the mass transfer) and the loss of the orbital angular momentum are related directly to the dynamical evolution of a binary system and - indirectly - to the evolution of its components.

scholarly journals SN 2018hti: a nearby superluminous supernova discovered in a metal-poor galaxy

2020 ◽  
Vol 497 (1) ◽  
pp. 318-335 ◽  
Author(s):  
W L Lin ◽  
X F Wang ◽  
W X Li ◽  
J J Zhang ◽  
J Mo ◽  
...  
Keyword(s):  
Formation Rate ◽  
Host Galaxy ◽  
Type I ◽  
Single Star ◽  
Maximum Brightness ◽  
Star Evolution ◽  
Low Metallicity ◽  
Rotating Star ◽  
Larger Sample ◽  
Luminosity Evolution

ABSTRACT SN 2018hti is a Type I superluminous supernova (SLSN I) with an absolute g-band magnitude of −22.2 at maximum brightness, discovered by the Asteroid Terrestrial-impact Last Alert System in a metal-poor galaxy at a redshift of 0.0612. We present extensive photometric and spectroscopic observations of this supernova, covering the phases from ∼−35 d to more than  +340 d from the r-band maximum. Combining our BVgri-band photometry with Swift UVOT optical/ultraviolet photometry, we calculated the peak luminosity as ∼3.5 × 1044 erg s−1. Modelling the observed light curve reveals that the luminosity evolution of SN 2018hti can be produced by an ejecta mass of 5.8 M⊙ and a magnetar with a magnetic field of B = 1.8 × 1013 G having an initial spin period of P0 = 1.8 ms. Based on such a magnetar-powered scenario and a larger sample, a correlation between the spin of the magnetar and the kinetic energy of the ejecta can be inferred for most SLSNe I, suggesting a self-consistent scenario. Like for other SLSNe I, the host galaxy of SN 2018hti is found to be relatively faint (Mg = −17.75 mag) and of low metallicity (Z = 0.3 Z⊙), with a star formation rate of 0.3 M⊙ yr−1. According to simulation results of single-star evolution, SN 2018hti could originate from a massive, metal-poor star with a zero-age main sequence (ZAMS) mass of 25–40 M⊙, or from a less massive rotating star with MZAMS ≈ 16–25 M⊙. For the case of a binary system, its progenitor could also be a star with $M_\mathrm{ZAMS} \gtrsim 25\, \mathrm{ M}_\odot$.

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