The effect of mass loss on the ? Cephei instability strip

1980 ◽  
Vol 70 (2) ◽  
pp. 441-445
Author(s):  
C. Chiosi
Keyword(s):  
Mass Loss ◽  
Instability Strip

scholarly journals Enhanced mass-loss rate evolution of stars with ≳18 M⊙ and missing optically observed type II core-collapse supernovae

2020 ◽  
Vol 494 (4) ◽  
pp. 5230-5238
Author(s):  
Roni Anna Gofman ◽  
Naomi Gluck ◽  
Noam Soker
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Core Collapse ◽  
Type Ii ◽  
Instability Strip ◽  
Stellar Envelope ◽  
Explosion Mechanism ◽  
Hydrogen Mass

ABSTRACT We evolve stellar models with zero-age main-sequence (ZAMS) mass of MZAMS ≳ 18 M⊙ under the assumption that they experience an enhanced mass-loss rate when crossing the instability strip at high luminosities and conclude that most of them end as type Ibc supernovae (SNe Ibc) or dust-obscured SNe II. We explore what level of enhanced mass-loss rate during the instability strip would be necessary to explain the ‘red supergiant problem’. This problem refers to the dearth of observed core-collapse supernovae progenitors with MZAMS ≳ 18 M⊙. Namely, we examine what enhanced mass-loss rate could make it possible for all these stars actually to explode as core-collapse supernovae (CCSNe). We find that the mass-loss rate should increase by a factor of at least about 10. We reach this conclusion by analysing the hydrogen mass in the stellar envelope and the optical depth of the dusty wind at the explosion, and crudely estimate that under our assumptions only about a fifth of these stars explode as unobscured SNe II and SNe IIb. About 10–15 per cent end as obscured SNe II that are infrared-bright but visibly very faint, and the rest, about 65–70 per cent, end as SNe Ibc. However, the statistical uncertainties are still too significant to decide whether many stars with MZAMS ≳ 18 M⊙ do not explode as expected in the neutrino driven explosion mechanism, or whether all of them explode as CCSNe, as expected by the jittering jets explosion mechanism.

scholarly journals Cepheid Evolution with Pulsationally-Driven Mass Loss

1989 ◽  
Vol 111 ◽  
pp. 252-252 ◽  
Author(s):  
Wendee M. Brunish ◽  
Lee Anne Willson
Keyword(s):  
Mass Loss ◽  
Instability Strip

AbstractWe have studied the effects of a pulsationally-driven wind on Cepheid evolution. Mass loss due to the wind, which occurs only when the star is crossing the Cepheid instability strip, is a function of luminosity and radius. We have investigated the evolution of 4, 5, 6, 7 and 8 M⊙ stars using the updated 12C(α,γ) 16O rates.

scholarly journals Pulsation Period Change & Classical Cepheids: Probing the Details of Stellar Evolution

2014 ◽  
Vol 9 (S307) ◽  
pp. 224-225
Author(s):  
Hilding R. Neilson ◽  
Alexandra C. Bisol ◽  
Ed Guinan ◽  
Scott Engle
Keyword(s):  
Mass Loss ◽  
Real Time ◽  
Stellar Evolution ◽  
Stellar Mass ◽  
Period Change ◽  
Pulsation Period ◽  
Instability Strip ◽  
Loss Mechanism ◽  
Stellar Pulsation ◽  
Classical Cepheids

AbstractMeasurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 M⊙ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instability strip.

scholarly journals A SEARCH FOR MASS LOSS ON THE CEPHEID INSTABILITY STRIP USING H i 21 cm LINE OBSERVATIONS

2016 ◽  
Vol 152 (6) ◽  
pp. 200 ◽  
Author(s):  
L. D. Matthews ◽  
M. Marengo ◽  
N. R. Evans
Keyword(s):  
Mass Loss ◽  
Instability Strip

scholarly journals Mass-Loss During the RR Lyrae Phase of the HB: Mass Dispersion on the HB and RR Lyrae Period Changes

1993 ◽  
Vol 139 ◽  
pp. 312-312
Author(s):  
Rebecca A. Koopmann ◽  
Young-Wook Lee ◽  
Pierre Demarque ◽  
Jamie M. Howard
Keyword(s):  
Mass Loss ◽  
Horizontal Branch ◽  
Constant Mass ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Mass Dispersion ◽  
Low Mass ◽  
Lyrae Stars ◽  
Loss Rates

Horizontal branch (HB) models were evolved using the Yale stellar evolution code, YREC, to test the possibility that mass loss during the RR Lyrae phase is able to produce the observed color (mass) dispersion on the HB (Willson and Bowen 1984) and the anomalous period changes in RR Lyrae stars (Laskarides 1974). Models of total mass 0.64, 0.66, 0.68, 0.70, and 0.72 M⊙ (YMS = 0.23, Z = 0.001) were evolved with constant mass loss rates of 0, 10-10, and 10-9 M⊙ yr-1. Mass loss was assumed to occur only in the RR Lyrae phase, and the instability strip was defined by 3.800 < log Teff < 3.875.HB stars which lose mass evolve further to the blue. Low mass loss rates do not affect the shape of the tracks significantly. Stars, which without mass loss could not become blue HB stars, were able to emerge from the instability strip on the blue side.

scholarly journals Updated theoretical period–age and period–age–colour relations for Galactic Classical Cepheids: an application to the Gaia DR2 sample

2020 ◽  
Vol 496 (4) ◽  
pp. 5039-5051
Author(s):  
Giulia De Somma ◽  
Marcella Marconi ◽  
Santi Cassisi ◽  
Vincenzo Ripepi ◽  
Silvio Leccia ◽  
...  
Keyword(s):  
Mass Loss ◽  
Age Distribution ◽  
Theoretical Framework ◽  
Distribution Analysis ◽  
Chemical Abundance ◽  
Instability Strip ◽  
Abundance Pattern ◽  
The Core ◽  
Classical Cepheids ◽  
The Impact

ABSTRACT Updated evolutionary and pulsational model predictions are combined in order to interpret the properties of Galactic Classical Cepheids in the Gaia Data Release 2. In particular, the location of the instability strip boundaries and the analytical relations connecting pulsation periods to the intrinsic stellar parameters are combined with evolutionary tracks to derive reliable and accurate period–age and the first theoretical period–age–colour relations in the Gaia bands for a solar chemical abundance pattern (Z = 0.02, Y = 0.28). The adopted theoretical framework takes into account possible variations in the mass–luminosity relation for the core helium-burning stage as due to changes in the core convective overshooting and/or mass-loss efficiency, as well as the impact on the instability strip boundaries due to different assumptions for superadiabatic convection efficiency. The inferred period–age and period–age–colour relations are applied to a selected sample of both fundamental and first overtone Gaia Cepheids, and individual ages for the various adopted theoretical scenarios are derived. The retrieved age distributions confirm that a variation in the efficiency of superadiabatic convection in the pulsational model computations has a negligible effect, whereas a brighter mass–luminosity relation, as produced by mild overshooting, rotation, or mass-loss, implies significantly older age predictions. Moreover, older Cepheids are found at larger Galactocentric distances, while first overtone Cepheids are found to be systematically older than the fundamental ones. The comparison with independent age distribution analysis in literature supports the predictive capability of current theoretical framework.

scholarly journals Pulsations of Proto-Giant-Planets

1993 ◽  
Vol 139 ◽  
pp. 284-284
Author(s):  
G. Wuchterl
Keyword(s):  
Mass Loss ◽  
Nonlinear Oscillations ◽  
Critical Mass ◽  
Giant Planets ◽  
Quasi Equilibrium ◽  
Planetary Formation ◽  
Instability Strip ◽  
The Earth ◽  
Relative Luminosity ◽  
Two Phases

AbstractNonlinear oscillations of proto-giant-planets have been found in recent numerical calculations relevant to planetary formation. Pulsations are excited in two phases of the protoplanetary evolution, (a) In an ‘instability strip’ at core masses of typically 0.2M⊙ (M⊕ is the earth mass). Perturbations grow into the nonlinear domain and saturate into perodic variations with relative luminosity-amplitudes of 0.2m (b) At the so called critical mass (typically at Mcore ≈ 15M⊕). There the pulsations drive a strong mass loss. A large portion of the envelope is ejected. Then the mass loss fades and the envelope settles into a new quasi-equilibrium. This remnant — a post nucleated instability protoplanet — has a compact envelope and is in core and envelope mass similar to Uranus and Neptune.

The Case for Surface Helium Enhancement in Cepheids

1979 ◽  
Vol 46 ◽  
pp. 318-321
Author(s):  
Arthur N. Cox
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Evolution Theory ◽  
Instability Strip ◽  
Long Period ◽  
Homogeneous Models ◽  
Red Giant ◽  
Triple Mode ◽  
Standing Problem

Cepheid masses obtained from pulsation theory are almost always less than those derived from observed luminosities and the no-mass-loss stellar evolution theory mass-luminosity relation. This may indicate mass loss in the red giant region. However, evolution theory indicates that more than ten percent mass loss will prevent the blue loops that move most of the stars into the Cepheid pulsation instability strip. The mass anomaly problem is about thirty percent for the long period (&gt; 15 days) Cepheids with observed Baade-Wesselink method radii and for those with bumps in their light and velocity curves (5.5 - 13 day periods). Chemically homogeneous models produce the correct bump phases only with lower than evolution theory masses. The mass anomaly is a factor of three or four for the double mode Cepheids and AC Andromedae, the only triple mode Cepheid. The long standing problem is to reconcile the differing masses obtained from evolution and pulsation theories.

scholarly journals New Evidence for Mass Loss in Classical Cepheids

1985 ◽  
Vol 82 ◽  
pp. 63-66
Author(s):  
M. J. Stift
Keyword(s):  
Mass Loss ◽  
Physical Parameters ◽  
Complete Sample ◽  
Instability Strip ◽  
Classical Cepheids ◽  
The Masses ◽  
New Evidence ◽  
Significant Mass Loss ◽  
Possible Cause ◽  
Significant Mass

The question of apparent mass anomalies in classical cepheids was first brought up by Christy (1968) and Stobie (1969), but 15 years later there is still no definite picture concerning the reality and the possible cause of these mass anomalies. The masses obtained from application of standard evolutionary theory were always sensibly larger than the masses derived from pulsation theory using both linear and nonlinear codes. Since for various reasons few people have accepted the idea that mass loss could play an important role in cepheids a number of elaborate scenarios have been proposed to account for the mass discrepancies. Among these are helium enriched outer layers and tangled magnetic fields. It is difficult, however, to see how significant mass loss can be avoided during the evolution of the more massive cepheids. In fact, practically all supergiants lose mass over the whole HR diagram, a process frequently manifesting itself in photometric microvariability. Little hope can be placed in attempts to solve the problem by means of improved determinations of the physical parameters of cepheids; intrinsic colours, luminosities, radii, effective temperatures, and the width of the instability strip have been disputed for years with no definite results yet. Only independent observational evidence will make it possible to confirm - or reject - the mass anomalies. On account of the large number observed and because of the fairly complete sample they represent, the cepheids in the LMC, SMC and in our Galaxy are best suited for this kind of investigation.

scholarly journals Classical Cepheids: Period Changes and Mass Loss

1985 ◽  
Vol 82 ◽  
pp. 67-70
Author(s):  
H. Deasy
Keyword(s):  
Mass Loss ◽  
Secular Variation ◽  
Separate Study ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Classical Cepheids ◽  
Random Fluctuations ◽  
Lyrae Stars

The period is an ideal parameter for monitoring minute changes in the structure of a star passing through the instability strip, as it can be measured with an accuracy of up to one part per million. The view of Parenago (1956) that only abrupt period changes occur in cepheids is no longer prevalent, and it is generally accepted that random period changes are superposed on the secular variation due to evolution. One possible mechanism for the random fluctuations in period or phase is convection or semiconvection, which Sweigert & Renzini (1979) showed could account for the period changes of RR Lyrae stars. Other mechanisms include the influence of binary companions and mass loss. The latter mechanism forms the basis for a separate study involving the use of IUE spectra to search for evidence of matter being ejected from cepheids.

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