Advanced Evolutionary Phases Research Articles

Using Asteroseismology to Calibrate the Physical Parameters of Confirmed Exoplanets and Their Evolved Host Stars

Asteroseismology offers a profound window into stellar interiors and has emerged as a pivotal technique in exoplanetary research. This study harnesses the Transiting Exoplanet Survey Satellite observations to reveal, for the first time, the asteroseismic oscillations of four exoplanet-hosting stars. Through meticulous analysis, we extracted their asteroseismic signatures, enabling the precise determination of stellar masses, radii, luminosities, and surface gravities. These parameters exhibit markedly reduced uncertainties compared to those derived from spectroscopic methods. Crucially, the exoplanets orbiting these stars were initially identified via radial velocity measurements. The refinement of host stellar masses necessitates a corresponding adjustment in planetary characteristics. Employing asteroseismology, we recalibrated the exoplanets’ minimum masses and semimajor axes—a novel approach in the field. For instance, the exoplanet HD 5608 b's minimum mass, denoted as Msini , was ascertained to be 1.421 ± 0.091M J through the integration of asteroseismic and radial velocity data. Similarly, two planets within the 7 CMa system yielded Msini values of 1.940 ± 0.064M J and 0.912 ± 0.067M J , respectively. Two planets in the HD 33844 system presented Msini figures of 1.726 ± 0.145M J and 1.541 ± 0.182M J , while the HIP 67851 system's planets registered Msini at 1.243 ± 0.139M J and a notably higher 5.387 ± 0.699M J . This investigation extends beyond mere parameter refinement, it underscores the synergy between asteroseismology and exoplanetology, yielding unprecedented precision in system metrics. Focusing on a quartet of K-type giants in advanced evolutionary phases, our work positions these systems as invaluable astrophysical laboratories, offering insights into the potential trajectory of our own solar system's fate.

Exploring the Governance of Entrepreneurial Ecosystems for Productive High Growth

This paper aims to empirically identify the characteristics and governance types of regional entrepreneurial ecosystems (EEs) associated with productive high-growth entrepreneurship (PHGE). We developed a unique database comprised of public statistics on high-growth enterprises and regional EEs in Poland over the course of 2011–2018. The Hierarchical Clustering on Principal Components and a taxonomic analysis were used to identify how different types of EE governance relate to varying levels of high-growth enterprises’ performance. We have identified and described the relationships between PHGE and diverse clusters of EE governance and evolution stages toward developed structures. Two clusters proved similarly effective in generating PHGE and they represent alternative EE governance solutions as well as the most advanced evolutionary phases. The proposed conceptualizations of productive high-growth entrepreneurship and EE governance types advance the understanding and measurement of these phenomena. The profiling and configurational approach adopted in this research reflects the heterogeneity of EE governance types and outcomes and can be further replicated in other research settings.

The Presupernova Core Mass–Radius Relation of Massive Stars: Understanding Its Formation and Evolution

Abstract We present a fine grid of solar metallicity models of massive stars (320 in the range 12 ≤ M( ) ≤ 27.95), extending from the main sequence up to the onset of the collapse, in order to quantitatively determine how their compactness ξ 2.5, defined by O’Connor & Ott, scales with the carbon–oxygen core mass at the beginning of core collapse. We find a well defined, nonmonotonic (but not scattered) trend of the compactness with the carbon–oxygen core mass that is strictly (and mainly) correlated to the behavior, i.e., birth, growth, and disappearance, of the various carbon convective episodes that follow one another during the advanced evolutionary phases. Though both the mass size of the carbon–oxygen core and the amount of 12C left by the central He burning play a major role in sculpting the final mass–radius relation, it is the abundance of 12C that is ultimately responsible for the final degree of compactness of a star, because it controls the ability of the carbon-burning shell to advance in mass before the final collapse.

Taking snapshots of the jet-ISM interplay with ALMA

AbstractWe present an update of our ongoing project to characterise the impact of radio jets on the interstellar medium (ISM). This is done by tracing the distribution, kinematics and excitation of the molecular gas at high spatial resolution using ALMA. The radio active galactic nuclei (AGN) studied are in the interesting phase of having a recently born radio jet. In this stage, the plasma jets can have the largest impact on the ISM, as also predicted by state-of-the-art simulations. The two targets we present have quite different ages, allowing us to get snapshots of the effects of radio jets as they grow and evolve. Interestingly, both also host powerful quasar emission, making them ideal for studying the full impact of AGN. The largest mass outflow rate of molecular gas is found in a radio galaxy () hosting a newly born radio jet still in the early phase of emerging from an obscuring cocoon of gas and dust. Although the molecular mass outflow rate is high (few hundred), the outflow is limited to the inner few hundred pc region. In a second object (), the jet is larger (a few kpc) and is in a more advanced evolutionary phase. In this object, the distribution of the molecular gas is reminiscent of what is seen, on larger scales, in cool-core clusters hosting radio galaxies. Interestingly, gas deviating from quiescent kinematics (possibly indicating an outflow) is not very prominent, limited only to the very inner region, and has a low mass outflow rate. Instead, on kpc scales, the radio lobes appear associated with depressions in the distribution of the molecular gas. This suggests that the lobes have broken out from the dense nuclear region. However, the AGN does not appear to be able, at present, to stop the star formation observed in this galaxy. These results support the idea that the effects of the radio source start in the very first phases by producing outflows which, however, tend to be limited to the kpc region. After that, the effects turn into producing large-scale bubbles which could, in the long term, prevent the surrounding gas from cooling. Thus, our results provide a way to characterise the effect of radio jets in different phases of their evolution and in different environments, bridging the studies done for radio galaxies in clusters.

Rotating models of young solar-type stars

We study the predicted rotational evolution of solar-type stars from the pre-main sequence to the solar age with 1D rotating evolutionary models including physical ingredients. We computed rotating evolution models of solar-type stars including an external stellar wind torque and internal transport of angular momentum following the method of Maeder and Zahn with the code STAREVOL. We explored different formalisms and prescriptions available from the literature. We tested the predictions of the models against recent rotational period data from extensive photometric surveys, lithium abundances of solar-mass stars in young clusters, and the helioseismic rotation profile of the Sun. We find a best-matching combination of prescriptions for both internal transport and surface extraction of angular momentum. This combination provides a very good fit to the observed evolution of rotational periods for solar-type stars from early evolution to the age of the Sun. Additionally, we show that fast rotators experience a stronger coupling between their radiative region and the convective envelope. Regardless of the set of prescriptions, however, we cannot simultaneously reproduce surface angular velocity and the internal profile of the Sun or the evolution of lithium abundance. We confirm the idea that additional transport mechanisms must occur in solar-type stars until they reach the age of the Sun. Whether these processes are the same as those needed to explain recent asteroseismic data in more advanced evolutionary phases is still an open question.

THE CARINA PROJECT. VII. TOWARD THE BREAKING OF THE AGE-METALLICITY DEGENERACY OF RED GIANT BRANCH STARS USING THECU, B, IINDEX

We present an analysis of photometric and spectroscopic data of the Carina dSph galaxy, testing a new approach similar to that used to disentangle multiple populations in Galactic globular clusters (GCs). We show that a proper colour combination is able to separate a significant fraction of the red giant branch (RGB) of the two main Carina populations (the old one, \sim 12 Gyr, and the intermediate-age one, 4-8 Gyr). In particular, the c_UBI=(U-B)-(B-I) pseudo-colour allows us to follow the RGB of both populations along a relevant portion of the RGB. We find that the oldest stars have more negative c_UBI pseudo-colour than intermediate-age ones. We correlate the pseudo-colour of RGB stars with their chemical properties, finding a significant trend between the iron content and the c_UBI. Stars belonging to the old population are systematically more metal poor ([Fe/H]=-2.32\pm0.08 dex) than the intermediate-age ones ([Fe/H]=-1.82\pm0.03 dex). This gives solid evidence on the chemical evolution history of this galaxy, and we have a new diagnostic that can allow us to break the age-metallicity degeneracy of H-burning advanced evolutionary phases. We compared the distribution of stars in the c_UBI plane with theoretical isochrones, finding that no satisfactory agreement can be reached with models developed in a theoretical framework based on standard heavy element distributions. Finally, we discuss possible systematic differences when compared with multiple populations in GCs.

Dynamical evolution and spatial mixing of multiple population globular clusters

Numerous spectroscopic and photometric observational studies have provided strong evidence for the widespread presence of multiple stellar populations in globular clusters. In this paper, we study the long-term dynamical evolution of multiple population clusters, focusing on the evolution of the spatial distributions of the first- (FG) and second-generation (SG) stars. In previous studies, we have suggested that SG stars formed from the ejecta of FG AGB stars are expected initially to be concentrated in the cluster inner regions. Here, by means of N-body simulations, we explore the time-scales and the dynamics of the spatial mixing of the FG and the SG populations and their dependence on the SG initial concentration. Our simulations show that, as the evolution proceeds, the radial profile of the SG/FG number ratio, NSG/NFG, is characterized by three regions: (1) a flat inner part; (2) a declining part in which FG stars are increasingly dominant and (3) an outer region where the NSG/NFG profile flattens again (the NSG/NFG profile may rise slightly again in the outermost cluster regions). Until mixing is complete and the NSG/NFG profile is flat over the entire cluster, the radial variation of NSG/NFG implies that the fraction of SG stars determined by observations covering a limited range of radial distances is not, in general, equal to the SG global fraction, (NSG/NFG)glob. The distance at which NSG/NFG equals (NSG/NFG)glob is approximately between 1 and 2 cluster half-mass radii. The time-scale for complete mixing depends on the SG initial concentration, but in all cases complete mixing is expected only for clusters in advanced evolutionary phases, having lost at least 60–70 per cent of their mass due to two-body relaxation (in addition to the early FG loss due to the cluster expansion triggered by SNII ejecta and gas expulsion).The results of our simulations suggest that in many Galactic globular clusters the SG should still be more spatially concentrated than the FG.

Evolutionary properties of stellar standard candles: Red clump, AGB clump and white dwarfs

AbstractThe location of the white dwarf cooling sequence in the colour–magnitude diagram of simple stellar populations, the magnitude of the red clump and the magnitude of the asymptotic giant branch clump are three stellar distance indicators based on advanced evolutionary phases of low-mass stars. With the present observational capabilities, they can be applied to reach distances ranging from the Galactic disk and halo populations, to galaxies within the Local Group. Techniques devised to exploit these distance indicators are presented, together with a discussion of their calibration and the main sources of systematic errors. A first semi-empirical calibration of the asymptotic giant branch absolute magnitude in both the I and K bands is also derived.

Seyfert’s Sextet: where is the gas?

Seyfert's Sextet (a.k.a HCG 79) is one of the most compact and isolated galaxy groups in the local Universe. It shows a prominent diffuse light component that accounts for ~50% of the total observed light. This likely indicates that the group is in an advanced evolutionary phase, which would predict a significant hot gaseous component. Previous X-ray observations had suggested a low luminosity for this system, but with large uncertainties and poor resolution. We present the results from a deep (70 ks), high resolution Chandra observation of Seyfert's Sextet, requested with the aim of separating the X-ray emission associated with the individual galaxies from that of a more extended inter-galactic component. We discuss the spatial and spectral characteristics of this group we derive with those of a few similar systems also studied in the X-ray band. The high resolution X-ray image indicates that the majority of the detected emission does not arise in the compact group but is concentrated towards the NW and corresponds to what appears to be a background galaxy cluster. The emission from the group alone has a total luminosity of ~1x10^40 erg/s in the (0.5-5) keV band. Most of the luminosity can be attributed to the individual sources in the galaxies, and only ~2x10^39 erg/s is due to a gaseous component. However, we find that this component is also mostly associated with the individual galaxies of the Sextet, leaving little or no residual in a truly IGM component. The extremely low luminosity of the diffuse emission in Seyfert's Sextet might be related to its small total mass.

MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA)

Stellar physics and evolution calculations enable a broad range of research in astrophysics. Modules for Experiments in Stellar Astrophysics (MESA) is a suite of open source libraries for a wide range of applications in computational stellar astrophysics. A newly designed 1-D stellar evolution module, MESA star, combines many of the numerical and physics modules for simulations of a wide range of stellar evolution scenarios ranging from very-low mass to massive stars, including advanced evolutionary phases. MESA star solves the fully coupled structure and composition equations simultaneously. It uses adaptive mesh refinement and sophisticated timestep controls, and supports shared memory parallelism based on OpenMP. Independently usable modules provide equation of state, opacity, nuclear reaction rates, and atmosphere boundary conditions. Each module is constructed as a separate Fortran 95 library with its own public interface. Examples include comparisons to other codes and show evolutionary tracks of very low mass stars, brown dwarfs, and gas giant planets; the complete evolution of a 1 Msun star from the pre-main sequence to a cooling white dwarf; the Solar sound speed profile; the evolution of intermediate mass stars through the thermal pulses on the He-shell burning AGB phase; the interior structure of slowly pulsating B Stars and Beta Cepheids; evolutionary tracks of massive stars from the pre-main sequence to the onset of core collapse; stars undergoing Roche lobe overflow; and accretion onto a neutron star. Instructions for downloading and installing MESA can be found on the project web site (http://mesa.sourceforge.net/).

A three-phase model proposal for the evolution of scientific communication: from first print periodicals to current electronic communication system

Scientific communication has undergone deep transformations, since the emergence of Internet. Aiming to provide further thought on the evolution of scientific communication, this paper features a historical overview of the scientific communication advances over the last twenty years through a three-phase model for the evolution of the electronic journal and the preprints services, and presents Brazilian contemporary panorama for scientific communication. The three-phase model presented in this work is an adaptation of that one proposed by Tenopir et al. (2003) to describe the patterns of journal use by scientists since 1990. The early evolutionary phase followed the emergence of the first digital journals and the creation of repositories in the Web for publishing preliminary versions of scientific literature on the author’s initiative; by that time, most academics reproved electronic publishing initiatives. From 1996 and forward, in the consolidation phase, electronic journals were commonly identical to their print counterparts; the acceptance of the electronic format began to increase, and preprint services got underway in several disciplines. The advanced evolutionary phase started with the world discussion on open access to scientific information. The comparison of the current electronic journal with that viewed by enthusiasts in the first years of the 1990s shows that some aspects still remain to be improved in electronic formal and informal communication, towards effective dissemination of scientific information.

High‐Resolution H2O Maser Observations towardIRASSources in Bright‐Rimmed Clouds

Bright-rimmed clouds (BRCs) are clouds that have been compressed by an external ionization shock front. We present the first high-resolution VLA observations of 20 of these BRCs in the northern hemisphere. We detected water maser emission from three objects: IRAS 21346+5714 (BRC 36), IRAS 21388+5622 (BRC 37), and IRAS 21445+5712 (BRC 39). The low detection rate supports the evidence that BRCs produce mostly low-luminosity objects, for which maser emission is weak and episodic, and suggests that the embedded sources are in a more advanced evolutionary phase than Class 0 objects.

Final stages of massive stars. SN explosion and explosive nucleosynthesis

We review the presupernova evolution, the explosion and the explosive nucleosynthesis of massive stars in the range 11–120 M ๏ . We mainly focus on the advanced evolutionary phases prior to the explosion, i.e. from the core He exhaustion up to the onset of the iron core collapse.

Low-mass star formation in bright rimmed clouds

AbstractBright Rimmed Clouds (BRCs) are clouds that have been compressed by an external ionization-shock front which focuses the neutral gas into compact globules. The boundary layer between the neutral gas and the gas ionized by the incident photons is often called “bright rim” but the clumps are sometimes classified also as speck globules or cometary globules depending on their appearance. Small globules with bright rims have been considered to be potential sites of star formation and have been studied in several individual regions. We present the first high resolution VLA observations of 20 of these BRCs, but only three detections were obtained. The low detection rate seems to support the idea that BRCs produce mostly low-luminosity objects, for which maser emission is weak and episodic, and that the embedded sources are in a more advanced evolutionary phase than class 0 objects.

Accurate and Deep Wide Field Photometry: The Stellar Perspective

We discuss how a wide field imager with very high spatial resolution on a relatively small telescope–but located in an observing site with very good seeing–might constrain the fraction of binary stars in Galactic globular clusters. We also mention the role that the new data might play in investigating advanced evolutionary phases of low-mass stars. Moreover, we discuss the role that an Extremely Large Telescope might have on the longstanding problem of cosmic distances and stellar populations. In particular, we discuss the impact that the detection of Cepheids in galaxies at the distance of the Coma cluster and of RR Lyrae stars in galaxies at the distance of the Virgo cluster might have on the calibration of secondary distance indicators.

Comments on the Evolution of Massive Stars

We describe in a brief form present results we have obtained from a careful and up to date study of the evolution of massive stars including their advanced evolutionary phases beyond the oxygen burning phase. We describe the effects of mass loss, treatment of convection in inhomogeneous stellar layers and the rate of the 12 C( α, γ ) 16 O reaction on the properties of stellar models in the interesting case of a 25 M ๏ star of solar-like initial metallicity.

The12C(α, γ)16O Reaction Rate and the Evolution of Stars in the Mass Range 0.8 ≤ M/M⊙ ≤ 25

We discuss the influence of the 12C(α, γ)16O reaction rate on the central He burning of stars in the mass range 0.8-25 M☉, as well as its effects on the explosive yields of a 25 M☉ star of solar chemical composition. We find that the central He burning is only marginally affected by a change in this cross section within the currently accepted uncertainty range. The only (important) quantity that varies significantly is the amount of C left by the He burning. Since the 12C(α, γ)16O is efficient in a convective core, we have also analyzed the influence of the convective mixing in determining the final C abundance left by the central He burning. Our main finding is that the adopted mixing scheme does not influence the final C abundance provided the outer border of the convective core remains essentially fixed (in mass) when the central He abundance drops below 0.1 dex by mass fraction; vice versa, even a slight shift (in mass) of the border of the convective core during the last part of the central He burning could appreciably alter the final C abundance. Hence, we stress that it is wiser to discuss the advanced evolutionary phases as a function of the C abundance left by the He burning rather than as a function of the efficiency of the 12C(α, γ)16O reaction rate. Only a better knowledge of this cross section and/or the physics of the convective motions could help in removing the degeneracy between these two components. We also prolonged the evolution of the two 25 M☉ stellar models up to the core collapse and computed the final explosive yields. Our main results are that the intermediate-light elements, Ne, Na, Mg, and Al (which are produced in the C convective shell), scale directly with the C abundance left by the He burning because they depend directly on the amount of available fuel (i.e., C and/or Ne). All the elements whose final yields are produced by any of the four explosive burnings (complete explosive Si burning, incomplete explosive Si burning, explosive O burning, and explosive Ne burning) scale inversely with the C abundance left by the He burning because the mass-radius relation in the deep interior of a star steepens as the C abundance reduces. We confirm previous findings according to which a low C abundance (0.2 dex by mass fraction) is required to obtain yields with a scaled solar distribution.

A New Study ofs‐Process Nucleosynthesis in Massive Stars

We present a comprehensive study of s-process nucleosynthesis in 15, 20, 25, and 30 M☉ stellar models having solar-like initial composition. The stars are evolved up to ignition of central neon with a 659 species network coupled to the stellar models. In this way, the initial composition from one burning phase to another is consistently determined, especially with respect to neutron capture reactions. The aim of our calculations is to gain a full account of the s-process yield from massive stars. In the present work, we describe our code in detail and then focus primarily on results from the s-process during central helium burning. We also illuminate some major uncertainties affecting the calculations. In order to motivate future work on burning in advanced stellar phases, we briefly present some results on the s-process in carbon shell burning; however, we leave a complete analysis of the s-process during the advanced evolutionary phases to a subsequent paper. Our results can help to constrain the yield of the s-process material from massive stars during their presupernova evolution.

Review of abundances for mid-Teff range stars

Among the mid-Teff (5000–7000 K) range stars, those on or near the main sequence are particularly important, because they provide much information on Galactic evolution and nucleosynthesis of the elements. This is due to the fact that these stars represent an age range from 0 to 15 Gyr, and a metallicity range from [Fe/H] ⋍ −4.0 to +0.3. Furthermore, it is likely that the present composition of elements in their atmospheres is similar to the composition of the interstellar gas from which they were formed, and that the present kinematics of the stars give information about their birthplaces. Hence, by observing selected samples of nearby F and G main sequence and subgiant stars one has the possibility to study the chemical and dynamical history of our Galaxy. Due to space limitation the present review is limited to these F and G stars. Supergiants are not discussed, but it should be emphasized, that their abundances are important for studies of advanced stellar evolutionary phases and determinations of the chemical composition of nearby galaxies. e.g. the Magellanic Clouds (Hill et al. 1995).

Evolutionary sequences of stellar models with new radiative opacities. VI. $Z=0.0001$

We present a large grid of stellar evolutionary models with the initial chemical composition (Z = 0:0001;Y =0 :23). These tracks are conceived to extend the grid of stellar models described in the previous papers of this series, and are computed with the new radiative opacities by Iglesias et al. (1992) and convective overshoot. The tracks span the range of initial masses from 0:6 M to 100 M, and extend from the zero age main sequence (ZAMS) till very advanced evolutionary phases. Specically, low- and intermediate-mass stars are followed till the beginning of the thermally pulsing regime of the asymptotic red giant branch phase (TP-AGB), while massive stars are followed till the core C-ignition. With respect to previous papers of this series, these models incorporate a number of small modications in the input physics, particularly on the equation of state, which now incorporates the eect of Coulomb interactions between charged particles. The eect of these modications is discussed. The corresponding theoretical isochrones are presented.