Super Metal-rich Stars Research Articles

Probing the strength of radial migration via churning by using metal-rich red giant stars from APOGEE

ABSTRACT Making use of the APOGEE DR17 catalogue with high quality data for 143 509 red giant branch stars we explore the strength of different mechanisms that causes a star to radially migrate in the Milky Way stellar disc. At any position in the disc we find stars that are more metal-rich than the local interstellar medium. This is surprising and normally attributed to the migration of these stars after their formation inside their current Galactocentric radius. Such stars are prime candidates for studying the strength of different migratory processes. We specifically select two types of metal-rich stars: (i) super metal-rich stars ($\mathrm{[Fe/H]}\gt 0.2$) and (ii) stars that are more metal-rich than their local environment. For both, we explore the distribution of orbital parameters and ages as evidence of their migration history. We find that most super metal-rich stars have experienced some amount of churning as they have orbits with $R_g\gtrsim 5 \,{\rm kpc}$. Furthermore, about half of the super metal-rich stars are on non-circular orbits ($\mathrm{ecc} \gt 0.15$) and therefore also have experienced blurring. The metallicity of young stars in our sample is generally the same as the metallicity of the interstellar medium, suggesting they have not radially migrated yet. Stars with lower metallicity than the local environment have intermediate to old ages. We further find that super metal-rich stars have approximately the same age distribution at all Galactocentric radii, which suggests that radial migration is a key mechanism responsible for the chemical compositions of stellar populations in the Milky Way.

Evidence for Corotation Origin of Super-metal-rich Stars in LAMOST-Gaia: Multiple Ridges with a Similar Slope in the ϕ versus L z Plane

Super-metal-rich (SMR) stars in the solar neighborhood are thought to be born in the inner disk and come to their present location by radial migration, which is most intense at the corotation resonance (CR) of the Galactic bar. In this work, we show evidence for the CR origin of SMR stars in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and Gaia by detecting six ridges and undulations in the ϕ versus L z space coded by median V R, following a similar slope of −8 km s−1 kpc deg−1. The slope is predicted by Monario et al.'s model for CR of a large and slow Galactic bar. For the first time, we show the variation in the angular momentum with azimuths from −10° to 20° for two outer and broad undulations with negative V R around − 18 km s−1 following this slope. The wave-like pattern with large amplitude outside CR and a wide peak of the second undulation indicate that minor merger of the Sagittarius dwarf galaxy with the disk might play a role besides the significant impact of the CR of the Galactic bar.

High-α-Metal-Rich stars in the LAMOST-MRS survey and its connection with the galactic bulge

We report the detection of a large sample of high-α-metal-rich stars on the low giant branch with 2.6 < log g < 3.3 dex in the LAMOST-MRS survey. This special group corresponds to an intermediate-age population of 5 – 9 Gyr based on the [Fe/H]-[C/N] diagram and age-[C/N] calibration. A comparison group is selected to have a solar α ratio at super metallicity, which is young and has a narrow age range around 3 Gyr. Both groups have thin-disk like kinematics but the former shows slightly large velocity dispersions. The special group shows a larger extension in a vertical distance toward 1.2 kpc, a second peak at smaller Galactic radius and a larger fraction of super metal rich stars with [Fe/H] > 0.2 than the comparison group. These properties strongly indicate its connection with the outer bar/bulge region at R = 3 – 5 kpc. A tentative interpretation of this special group is that its stars were formed in the X-shaped bar/bulge region, close to its corotation radius, where radial migration is the most intense, and brings them to present locations at 9 kpc and beyond. Low eccentricities and slightly outward radial excursions of its stars are consistent with this scenario. Its kinematics (cold) and chemistry ([α/Fe] ∼ 0.1) further support the formation of the instability-driven X-shaped bar/bulge from the thin disk.

The chemodynamics of prograde and retrograde Milky Way stars

Context. The accretion history of the Milky Way is still unknown, despite the recent discovery of stellar systems that stand out in terms of their energy-angular momentum space, such as Gaia-Enceladus-Sausage. In particular, it is still unclear how these groups are linked and to what extent they are well-mixed. Aims. We investigate the similarities and differences in the properties between the prograde and retrograde (counter-rotating) stars and set those results in context by using the properties of Gaia-Enceladus-Sausage, Thamnos/Sequoia, and other suggested accreted populations. Methods. We used the stellar metallicities of the major large spectroscopic surveys (APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE, SEGUE) in combination with astrometric and photometric data from Gaia’s second data-release. We investigated the presence of radial and vertical metallicity gradients as well as the possible correlations between the azimuthal velocity, vϕ, and metallicity, [M/H], as qualitative indicators of the presence of mixed populations. Results. We find that a handful of super metal-rich stars exist on retrograde orbits at various distances from the Galactic center and the Galactic plane. We also find that the counter-rotating stars appear to be a well-mixed population, exhibiting radial and vertical metallicity gradients on the order of ∼ − 0.04 dex kpc−1 and −0.06 dex kpc−1, respectively, with little (if any) variation when different regions of the Galaxy are probed. The prograde stars show a vϕ − [M/H] relation that flattens – and, perhaps, even reverses as a function of distance from the plane. Retrograde samples selected to roughly probe Thamnos and Gaia-Enceladus-Sausage appear to be different populations yet they also appear to be quite linked, as they follow the same trend in terms of the eccentricity versus metallicity space.

Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues

We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution ($\mathcal{R} \sim 80\,000$) spectroscopic images, obtained at the Observatorio Astrof\'isico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar analogues. Within our sample, BD+60 600 is the most metal-rich star ([Fe/H]=+0.35 dex), while for HD 166991 we obtained the lowest iron abundance ([Fe/H]=$-0.53$ dex). We also computed the so-called [Ref] index for 25 of our solar analogues, and we found, that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search.

Supersolar metallicity in G0–G3 main-sequence stars with V &lt; 15

The basic stellar atmospheric parameters (effective temperature, surface gravity and global metallicity) were simultaneously determined for a sample of 233 stars, limited in magnitude ($V<15$) with spectral types between G0 and G3 and luminosity class V (main sequence). The analysis was based on spectroscopic observations collected at the Observatorio Astrof\'isico Guillermo Haro and using a set of Lick-like indices defined in the spectral range of 3800-4800 $\AA$. An extensive set of indices computed in a grid of theoretical spectra was used as a comparison tool in order to determine the photospheric parameters. The method was validated by matching the results from spectra of the asteroids Vesta and Ceres with the Sun parameters. The main results were: i) the photospheric parameters were determined for the first time for 213 objects in our sample; ii) a sample of 20 new super metal-rich stars candidates was found.

Chemical abundances and kinematics of a sample of metal-rich barium stars

We determined the atmospheric parameters and abundance pattern for a sample of metal-rich barium stars. We used high-resolution optical spectroscopy. Atmospheric parameters and abundances were determined using the local thermodynamic equilibrium atmosphere models of Kurucz and the spectral analysis code MOOG. We show that the stars have enhancement factors, [s/Fe], from 0.25 to 1.16. Their abundance pattern of the Na, Al, alpha-elements, and iron group elements as well as their kinematical properties are similar to the characteristics of the other metal-rich and super metal-rich stars already analyzed. We conclude that metal-rich barium stars do not belong to the bulge population. We also show that metal-rich barium stars are useful targets for probing the s-process enrichment in high-metallicity environments.

Metal-rich infall onto the inner disk through the interaction between bulge winds and gaseous halos

AbstractWe demonstrate for the first time that gaseous halos of disk galaxies can play a vital role in recycling metal-rich gas ejected from the bulges and thus in promoting the chemical evolution of the disks. Our numerical simulations show that metal-rich bulge winds can be accreted onto the thin disks owing to hydrodynamical interaction between the gaseous ejecta and the gaseous halos. Accordingly, we anticipate that chemical abundances of the inner disk stars are significantly influenced by the enriched winds. About ~1% of gaseous ejecta from the bulges can be accreted onto the middle disk corresponding to the sun's position. We discuss these results in the context of the origin of super metal-rich stars in the solar neighborhood as well as an observed flattening of the abundance gradient in the Galactic disk.

A new search for planet transits in NGC 6791

Context. Searching for planets in open clusters allows us to study the effects of dynamical environment on planet formation and evolution. Aims. Considering the strong dependence of planet frequency on stellar metallicity, we studied the metal rich old open cluster NGC 6791 and searched for close-in planets using the transit technique. Methods. A ten-night observational campaign was performed using the Canada-France-Hawaii Telescope (3.6 m), the San Pedro Martir telescope (2.1 m), and the Loiano telescope (1.5 m). To increase the transit detection probability we also made use of the Bruntt et al. (2003, AA (ii) a smaller planetary radius for planets orbiting super metal rich stars; or (iii) limitations in the basic assumptions. More extensive photometry with 3–4 m class telescopes is required to allow conclusive inferences about the frequency of planets in NGC 6791.

Abundances in metal-rich stars

We have derived elemental abundances of O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni as well as for a number of s-elements for 47 G and K dwarf, with [Me/H] dex. The selection of stars was based on their kinematics as well as on their photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits, the evolution around the solar orbit. A few Extreme Population I stars were included in the latter sample. The stars have -0.1 dex dex. The spectroscopic [Fe/H] correlate well with the [Me/H] derived from photometry. We find that the elemental abundances of Mg, Al, Si, Ca, Ti, Cr and Ni all follow [Fe/H]. Our data put further constraints on models of galactic chemical evolution, in particular of Cr, Mn and Co which have not previously been studied for dwarf stars with dex. The increase in [Na/Fe] and [Al/Fe] as a function of [Fe/H] found previously by Edvardsson et al. (1993a) has been confirmed for [Na/Fe]. This upturning relation, and the scatter around it, are shown not to be due to a mixture of populations with different mean distances to the galactic centre. We do not confirm the same trend for aluminium, which is somewhat surprising since both these elements are thought to be produced in the same environments in the pre-supernova stars. Nor have we been able to trace any tendency for relative abundances of O, Si, and Ti relative to Fe to vary with the stellar velocities, i.e. the stars present mean distance to the galactic centre. These results imply that there is no significant difference in the chemical evolution of the different stellar populations for stars with [Me/H] dex. We find that [O/Fe] continue to decline with increasing [Fe/H] and that oxygen and europium correlate well. However [Si/Fe] and [Ca/Fe] seem to stay constant. A real ("cosmic”) scatter in [Ti/Fe] at given [Fe/H] is suggested as well as a decreasing abundance of the s-elements relative to iron for the most metal-rich dwarf stars. We discuss our results in the context of recent models of galactic chemical evolution. In our sample we have included a few very metal rich stars, sometimes called SMR (super metal rich) stars. We find these stars to be among the most iron-rich in our sample but far from as metal-rich as indicated by their photometric metallicities. SMR stars on highly eccentric orbits, alleged to trace the evolution of the chemical evolution in the galactic Bulge, have previously been found overabundant in O, Mg and Si. We have included three such stars from the study by Barbuy & Grenon (1990). We find them to be less metal rich and the other elemental abundances remain puzzling. Detailed spectroscopic abundance analyses of K dwarf stars are rare. Our study includes 5 K dwarf stars and has revealed what appears to be a striking example of overionization. The overionization is especially prominent for Ca, Cr and Fe. The origin of this apparent overionization is not clear and we discuss different explanations in some detail.

The Most Metal-Rich Dwarf Stars in the Galactic Disk

The metal-rich dwarf stars in the solar neighbourhood have historically not attracted as much attention as the metal-poor (halo) stars which tell us about the early phases of the chemical evolution of our galaxy. The properties of metal-rich stars are highly important when we try to interpret integrated spectra from metal-rich stellar populations, such as the Bulge and elliptical galaxies. A small group of so called super metal rich stars (SMR) have played a significant role in shaping the conceptions of such populations. Famous examples are the dwarf HR1614 and the giant μ Leonis. In the review by Taylor (1996) SMR stars are discussed in great detail, in particular the reality of extremly high [Fe/H]. Taylor (1996) find that no giant stars fulfil the criteria fulr SMR-ness that he sets and only a handful of dwarf stars do, and most of them are possible candidates rather than firm detections.A few recent studies have studied known SMR candidates and stars with high [M/H] (as derived from photometry), Feltzing &amp; Gustafsson (1997), Castro et al. (1997), Gonzalez (1997), McWilliam &amp; Rich (1994), Castro et al. (1996). A first conclusion is that there are indeed quite a few stars with [Fe/H] &gt; 0.2 dex (the definition of SMR, see Taylor 1996). We will here review these studies in some detail.The combination of abundance ratios with kinematical data can detail the picture even further. For example we can study stars on highly eccentric orbits which trace the evolution in the galactic disk closer to the galctic centre. Not much is known about these stars but we did have some very intriguing observations; Barbuy &amp; Grenon (1990) (hereafter BG90) found that dwarf stars on very eccentric orbits contained much more oxygen than what was expected from standard models of galactic chemical evolution of the disk, Edvardsson et al.(1993) (hereafter E93) found large spreads and “upturns” for certain elements, Na, Si, Ti, Al, for stars with 0.0dex &lt; [Fe/H] &lt; 0.2 dex.

Evolutionary and Pulsational Constraints for Super–Metal‐rich Stars withZ= 0.04

We investigate the evolutionary behavior of stellar structures with metallicity Z = 0.04 in order to disclose theoretical expectations for both evolutionary and pulsational behaviors of super-metal-rich (SMR) objects, which are found in the solar neighborhood, in the Galactic bulge, and in elliptical galaxies. A suitable set of stellar models is presented for the given metallicity value but for two alternative assumptions about the amount of original He, namely, Y = 0.34 and Y = 0.37. Theoretical isochrones for H-burning evolutionary phases are presented for ages ranging from 18 to less than 1 Gyr. The evolutionary behavior of He-burning structures is discussed for suitable assumptions about the mass of the progenitors and the amount of mass loss. For both quoted assumptions of original He abundance, we confirm that at metal contents larger than the solar value the luminosity of the horizontal branch (HB) at the RR Lyrae gap increases as the metal content increases, a direct consequence of the expected simultaneous increase of original He. We find that, at the exhaustion of central helium, SMR stars definitely undergo the gravonuclear instabilities previously found in some He-burning structures with solar metallicity. On the basis of such an evolutionary scenario, we investigate the expected pulsational behavior of He-burning SMR stars for suitable assumptions on the pulsators' evolutionary parameters. Linear blue boundaries for pulsational instability in the fundamental and in the first-overtone modes are derived, and their dependence on stellar mass and chemical composition is investigated. Nonlinear, nonlocal, and time-dependent convective models are discussed, the modal stability is investigated for the first two modes, and the theoretical predictions about the period distribution inside the instability strip and the shape of both light and velocity curves are presented. Full-amplitude, nonlinear envelope models show that the range of effective temperatures in which SMR RR Lyrae variables present a stable limit cycle is smaller than that of pulsators characterized by lower metal abundances. In fact, the width of the instability strip at the zero-age horizontal branch luminosity level decreases from 1400 to 1100 K. Also taking into account the peculiar narrow mass range characterizing SMR pulsators, we estimate that these two factors alone cause a decrease in the occurrence of RR Lyrae pulsators by a factor of 7 compared with metal-poor, globular cluster-like stellar populations. We find that canonical analytical relations connecting the nonlinear periods of metal-poor variables to their luminosity, mass, and effective temperature cannot be safely extrapolated to the range of SMR pulsators. We show that gravonuclear instabilities largely increase the lifetimes of stars crossing the instability strip at luminosity levels higher than the HB luminosity, thus increasing the expected occurrence of luminous low-mass variables. We show that both periods and light curves of different groups of type II Cepheids with periods shorter than 6 days, presented by Diethelm, can be all reproduced by suitable variations in the effective temperature or in the luminosity level of our SMR post-HB models, supporting evidence of a substantial homogeneity of these variables. On the basis of both evolutionary and pulsation findings, we finally predict the rate of period change for a typical type II, metal-rich, field Cepheid across the instability strip and discuss an observational test for validating the present theoretical scenarios. In an appendix, we discuss in detail the physics of gravonuclear instabilities, which appear as a surprisingly exact confirmation of the theoretical predictions given by Schwarzschild & Harm as early as 1965.

Spectra of late type stars from 4800 to 9000 Å

We present optical spectra of 21 stars from 4800 to 8920 A, covering essentially the late spectral types, G, K, M and the luminosity classes I and III. Half of the stars are super metal rich (SMR) ones. The spectra were obtained at a resolution of 1.25 A using the Aurelie spectrograph, equipped with a linear array CCD-like detector, attached to the OHP 1.52 m telescope. Also presented are the spectra of 7 stars, covering the region 5000 9783 Aa t ar esolution of 8.5A , observed at the CFHT with the Herzberg spectrograph. The spectral types are F, G, K, M and the luminosity classes III and V. Five stars are SMR. These spectra have been obtained with the aim of extending existing libraries used for population synthesis purposes. The inclusion of SMR stars in a stellar library dedicated to the study of stellar populations in the central part of galaxies is crucial as abundance gradients have been observed in the optical range.

JHK imaging of a field in Baade's Window

A 256 × 256 Hg:Cd:Te array has been used to obtaine J, H, and K images of a field in Baade's Window. The data extend down to K∼16, which is near the base of the red giant branch at the distance of the Galactic bulge. The distribution of data points on the (K, J-K) and (J-H, H-K) diagrams is similar to that defined by previous aperture measurements. Furthermore, the redward edge of the data envelope on the (K, J-K) diagram roughly follows the giant branch of the cluster M67 to K∼15, indicating that the blanketing agent thought to dominate the broad-band photometric properties of super metal-rich stars must be present over a broad range of photospheric temperatures and surface gravities.

Old stellar populations. II - an analysis of K-giant spectra

view Abstract Citations (384) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Old stellar populations. II. an analysis of K-giant spectra. Faber, S. M. ; Friel, E. D. ; Burstein, D. ; Gaskell, C. M. Abstract Eleven strong absorption features are studied in a sample of 110 K-giant stars, based on spectra taken at 9-A resolution, including such features as CN 4170 A, G-band, H-beta, Mg b, MgH, two Fe lines, NaD, and two TiO bands. The surface features sensitive to surface gravity are determined; it is noted that the most accurate gravity indicator appears to be the index Mg2. Previously identified super metal-rich stars generally show the strongest lines of iron, CN, Mg, and NaD; essentially all intermediate and strong blends are also markedly enhanced in these stars. Finally, iron-line residual Delta-Fe is shown to be a good measure of metallicity and at the same time independent of surface gravity. Publication: The Astrophysical Journal Supplement Series Pub Date: April 1985 DOI: 10.1086/191024 Bibcode: 1985ApJS...57..711F Keywords: Absorption Spectra; Abundance; Giant Stars; K Stars; Metallic Stars; Spectrum Analysis; Stellar Spectra; Atmospheric Composition; Globular Clusters; Late Stars; Metallicity; Populations; Spectral Resolution; Astrophysics full text sources ADS | data products SIMBAD (102) Related Materials (5) Part 1: 1984ApJ...287..586B Part 3: 1986AJ.....91.1130B Part 4: 1993ApJS...86..153G Part 5: 1994ApJS...94..687W Part 6: 1998ApJS..116....1T

Luminosity of M giants in the nuclear bulge of the Galaxy

view Abstract Citations (52) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Luminosity of M giants in the nuclear bulge of the Galaxy Frogel, J. A. ; Whitford, A. E. Abstract A color-luminosity diagram for 20 galactic bulge giants around NGC 6522 shows that Blanco types M7-M9 are on the upper asymptotic giant branch at a bolometric magnitude of -4.5, significantly fainter than the giant luminosities adopted in the Tinsley-Gunn galaxy population model but certainly more luminous than the He core flash luminosity assumed to be the upper limit in the models of Aaronson, Cohen, Mould, and Malkan. Distorted energy distributions and nonstandard colors relative to solar neighborhood M giants are attributed to a super-metal-rich (SMR) composition as is observed in bulge K giants by Whitford and Rich. Long main-sequence lifetimes for such SMR stars imply that those of initial mass ranging from 0.95 to 1.15 do not become giants until after 12-billion years. The additional mass over the usual initial mass of 0.8 for a metal-poor globular cluster star of the same age could be sufficient to fuel ascent onto the upper asymptotic branch, although it is still possible that some of the bulge giants are luminous because they are massive and young. Publication: The Astrophysical Journal Pub Date: August 1982 DOI: 10.1086/183838 Bibcode: 1982ApJ...259L...7F Keywords: Galactic Bulge; Giant Stars; M Stars; Milky Way Galaxy; Stellar Evolution; Stellar Luminosity; Asymptotic Giant Branch Stars; Galactic Nuclei; Spectral Energy Distribution; Stellar Color; Astrophysics full text sources ADS |

A comparison of turbulence in normal and super-metal-rich K giant stars

view Abstract Citations (28) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A comparison of turbulence in normal and super-metal-rich K giant stars. Gray, D. F. ; Martin, B. E. Abstract The microturbulence, macroturbulence, and rotation in five normal and three super-metal-rich (SMR) K giant stars have been measured by Fourier analysis of line profiles. There appears to be no systematic difference between the two groups of stars. This implies that differences in mechanical energy dissipation are not likely to be the cause of the differences in temperature distributions that exists between normal and SMR stars. Further, it shows that the difference in temperature contributions in these stars cannot be used to establish a link between temperature enhancements and turbulence. Values of macroturbulence dispersion are near 4 km/s, while rotational velocities of 2.5-3 km/s are found. Publication: The Astrophysical Journal Pub Date: July 1979 DOI: 10.1086/157171 Bibcode: 1979ApJ...231..139G Keywords: Atmospheric Models; Atmospheric Turbulence; Giant Stars; K Stars; Late Stars; Metallic Stars; Stellar Atmospheres; Stellar Models; Abundance; Atmospheric Temperature; Fourier Analysis; Photosphere; Stellar Rotation; Stellar Temperature; Tables (Data); Temperature Distribution; Astrophysics; Atmospheres:K Giants; K Giants:Microturbulence; Late-Type Stars:Turbulence; Metal-Rich Stars:Rotation full text sources ADS | data products SIMBAD (8)

Upper photospheric temperature models of K giants - A comparison of super-metal-rich giants with normal giants

view Abstract Citations (21) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Upper photospheric temperature models of K giants: a comparison of super-metal-rich giants with normal giants. Desikachary, K. ; Gray, D. F. Abstract The LTE version of K-line synthesis that takes partial coherency effects into account is applied to the Ca II K-line wings in the spectra of four normal K giants (Beta Gem, Nu Cyg, Rho Oph, Alpha Ari) and two super-metal-rich (SMR) K giants (Alpha Ser, Beta Oph) in order to derive upper-photospheric temperature models. A model-atmosphere flux-calibration procedure that precludes the necessity of a measured angular diameter is used in the analysis of the K-line wing profiles, on the basis of which the SMR and normal K giants are compared quantitatively. The results show that temperature enhancements of 200 to 300 K in excess of radiative-equilibrium models are required in the upper photospheres of all six stars and that the upper photospheres of the SMR star models are up to 180 K cooler than those of the normal models. The temperature enhancements are interpreted as departures from radiative equilibrium, and the differential cooling in the SMR stars is tentatively attributed to enhanced CN and CO line absorption. Publication: The Astrophysical Journal Pub Date: December 1978 DOI: 10.1086/156672 Bibcode: 1978ApJ...226..907D Keywords: Giant Stars; K Lines; K Stars; Metallic Stars; Photosphere; Stellar Models; Stellar Temperature; Calcium; Stellar Spectrophotometry; Thermodynamic Equilibrium; Astrophysics; Atmospheres:K Giants; K Giants:Line Profiles; K Giants:Metal-Rich Stars; Stellar Atmospheres: Models full text sources ADS | data products SIMBAD (7) Related Materials (1) Erratum: 1980ApJ...236.1056D

The evolution of super-metal-rich stars and the interpretation of old galactic clusters

The influence of initial helium content on the evolutionary characteristics of super-metalrich stars (Z=0.10) has been investigated. The evolution of models in the range −0.05<logL/L⊙<1.0 has been followed up to the relative luminosity maximum in the subgiant branch, and under the assumptionY=0.20 orY=0.40.

Giant elliptical galaxies: The Salpeter initial luminosity function and interstellar matter

It is argued that a Salpeter initial luminosity function is consistent with the observed integral properties of giant elliptical galaxies if the gaseous material lost by evolving stars can be retained in the system for times of the order of 108 yr. One model which emerges is of a highly condensed system consisting mainly of metal-poor population II stars with an admixture (1.5%–15%) of super-metalrich stars born from the gaseous debris, which at the present time constitutes 0.05%–0.5% of the total mass. HighM/L ratios result from obscuration of the starlight, and the missing radiation reappears in the form of a strong I-R flux at wavelengths of the order of 100 μ. The difference in colour betweengE anddE galaxies is explained in terms of interstellar reddening, and strong interstellar metallic absorption lines are also expected. The model leads to a negligible evolutionary correction to the cosmological deceleration parameterq0. An alternative model, in which the stars arenot metal poor, has a more condensed, heavily obscured nucleus, surrounded by the unobscured central bulge of the Galaxy which provides most of the light. In this version a large evolutionary correction would be required.