Subgiant Research Articles

There is no place like home – finding birth radii of stars in the Milky Way

ABSTRACT Stars move away from their birthplaces over time via a process known as radial migration, which blurs chemo–kinematic relations used for reconstructing the Milky Way (MW) formation history. To understand the true time evolution of the MW, one needs to take into account the effects of this process. We show that stellar birth radii can be derived directly from the data with minimum prior assumptions on the Galactic enrichment history. This is done by first recovering the time evolution of the stellar birth metallicity gradient, $\mathrm{ d}\mathrm{[Fe/H]}(R, \tau)/\mathrm{ d}R$, through its inverse relation to the metallicity range as a function of age today, allowing us to place any star with age and metallicity measurements back to its birthplace, R$_b$. Applying our method to a large high-precision data set of MW disc subgiant stars, we find a steepening of the birth metallicity gradient from 11 to 8 Gyr ago, which coincides with the time of the last massive merger, Gaia–Sausage–Enceladus (GSE). This transition appears to play a major role in shaping both the age–metallicity relation and the bimodality in the [$\alpha$/Fe]–[Fe/H] plane. By dissecting the disc into mono-R$_b$ populations, clumps in the low-[$\alpha$/Fe] sequence appear, which are not seen in the total sample and coincide in time with known star-formation bursts, possibly associated with the Sagittarius Dwarf Galaxy. We estimated that the Sun was born at $4.5\pm 0.4$ kpc from the Galactic centre. Our R$_b$ estimates provide the missing piece needed to recover the Milky Way formation history.

Most extremely low mass white dwarfs with non-degenerate companions are inner binaries of hierarchical triples

Abstract Extremely-low-mass white dwarfs (ELM WDs) with non-degenerate companions are believed to originate from solar-type main-sequence binaries undergoing stable Roche lobe overflow mass transfer when the ELM WD progenitor is at (or just past) the termination of the main-sequence. This implies that the orbital period of the binary at the onset of the first mass transfer phase must have been ≲ 3 − 5 d. This prediction in turn suggests that most of these binaries should have tertiary companions since ≈90 per cent of solar-type main-sequence binaries in that period range are inner binaries of hierarchical triples. Until recently, only precursors of this type of binaries have been observed in the form of EL CVn binaries, which are also known for having tertiary companions. Here, we present high-angular-resolution images of TYC 6992-827-1, an ELM WD with a sub-giant (SG) companion, confirming the presence of a tertiary companion. Furthermore, we show that TYC 6992-827-1, along with its sibling TYC 8394-1331-1 (whose triple companion was detected via radial velocity variations), are in fact descendants of EL CVn binaries. Both TYC 6992-827-1 and TYC 8394-1331-1 will evolve through a common envelope phase, which depending on the ejection efficiency of the envelope, might lead to a single WD or a tight double WD binary, which would likely merge into a WD within a few Gyr due to gravitational wave emission. The former triple configuration will be reduced to a wide binary composed of a WD (the merger product) and the current tertiary companion.

Measuring stellar surface rotation and activity with the PLATO mission

The Planetary Transits and Oscillations of stars mission (PLATO) will allow us to measure surface rotation and monitor photometric activity of tens of thousands of main sequence solar-type and subgiant stars. This paper is the first of a series dedicated to the preparation of the analysis of stellar surface rotation and photospheric activity with the near-future PLATO data. We describe in this work the strategy that will be implemented in the PLATO pipeline to measure stellar surface rotation, photometric activity, and long-term modulations. The algorithms are applied on both noise-free and noisy simulations of solar-type stars, which include activity cycles, latitudinal differential rotation, and spot evolution. PLATO simulated systematics are included in the noisy light curves. We show that surface rotation periods can be recovered with confidence for most of the stars with only six months of observations and that the recovery rate of the analysis significantly improves as additional observations are collected. This means that the first PLATO data release will already provide a substantial set of measurements for this quantity, with a significant refinement on their quality as the instrument obtains longer light curves. Measuring the Schwabe-like magnetic activity cycle during the mission will require that the same field be observed over a significant timescale (more than four years). Nevertheless, PLATO will provide a vast and robust sample of solar-type stars with constraints on the activity-cycle length. Such a sample is lacking from previous missions dedicated to space photometry.

Evolution of BD-14 3065b (TOI-4987b) from giant planet to brown dwarf as possible evidence of deuterium burning at old stellar ages

The present study confirms BD-14\,3065b as a transiting planet-brown dwarf in a triple-star system, with a mass near the deuterium-burning boundary. BD-14\,3065b has the largest radius observed within the sample of giant planets and brown dwarfs around post-main sequence stars. Its orbital period is 4.3 days and it transits a subgiant F-type star with a mass of $M_ odot $, a radius of $R_ odot $, an effective temperature of $T_ eff and a metallicity of $-0.34 By combining TESS photometry with high-resolution spectra acquired with the TRES and Pucheros+ spectrographs, we measured a mass of $M_p=12.37 and a radius of $R_p=1.926 Our discussion of potential processes that could be responsible for the inflated radius led us to conclude that deuterium burning is a plausible explanation for the heating taking place in BD-14\,3065b's interior. Detections of the secondary eclipse with TESS photometry enabled a precise determination of the eccentricity, $e_p=0.066 and reveal that BD-14\,3065b has a brightness temperature of $3520 130$\,K. With its unique characteristics, BD-14\,3065b presents an excellent opportunity to study its atmosphere via thermal emission spectroscopy.

New evidence of binarity in young α-rich turn-off and subgiant stars: fast rotation and strong magnetic activity

ABSTRACT Young α-rich (YAR) stars within the old Galactic thick disc exhibit a dual characteristic of relative youth determined with asteroseismology and abundance enhancement in α elements measured from high-resolution spectroscopy. The youth origin of YAR stars has been proposed to be binary evolution via mass transfer or stellar mergers. If that is the case, YAR stars should spin rapidly and thus be magnetically active, because they are mass and angular momentum gainers. In this study, to seek this binary footprint, we select YAR stars on the main-sequence turn-off or the subgiant branch (MSTO-SGB) from APOGEE DR17, whose ages and projected rotation velocities (vsin i) can be precisely measured. With APOGEE vsin i and LAMOST spectra, we find that YAR stars are indeed fast rotators and magnetically active. In addition, we observe low [C/N] ratios and high Gaia RUWE in some YAR stars, suggesting that these MSTO-SGB stars probably have experienced mass transfer from red-giant companions. Our findings underscore that magnetic activity can serve as a valuable tool for probing the binary evolution for other chemically peculiar stars, such as red giants with lithium anomalies and carbon-enhanced metal-poor stars.

Gaia21blx: Complete resolution of a binary microlensing event in the Galactic disk

Gravitational microlensing is a method that is used to discover planet-hosting systems at distances of several kiloparsec in the Galactic disk and bulge. We present the analysis of a microlensing event reported by the Gaia photometric alert team that might have a bright lens. In order to infer the mass and distance to the lensing system, the parallax measurement at the position of Gaia21blx was used. In this particular case, the source and the lens have comparable magnitudes and we cannot attribute the parallax measured by Gaia to the lens or source alone. Since the blending flux is important, we assumed that the Gaia parallax is the flux-weighted average of the parallaxes of the lens and source. Combining this assumption with the information from the microlensing models and the finite source effects we were able to resolve all degeneracies and thus obtained the mass, distance, luminosities and projected kinematics of the binary lens and the source. According to the best model, the lens is a binary system at $2.18 0.07$ kpc from Earth. It is composed of a G star with $0.95 odot $ and a K star with $0.53 odot $. The source is likely to be an F subgiant star at $2.38 1.71$ kpc with a mass of $1.10 odot $. Both lenses and the source follow the kinematics of the thin-disk population. We also discuss alternative models, that are disfavored by the data or by prior expectations, however.

Fossil Signatures of Main-sequence Convective Core Overshoot Estimated through Asteroseismic Analyses

Some physical processes that occur during a star's main-sequence evolution also affect its post-main-sequence evolution. It is well known that stars with masses above approximately 1.1 M ⊙ have well-mixed convective cores on the main sequence; however, the structure of the star in the neighborhood of the convective core regions is currently underconstrained. We use asteroseismology to study the properties of the stellar core, in particular convective boundary mixing through convective overshoot, in such intermediate-mass stars. These core regions are poorly constrained by the acoustic (p) mode oscillations observed for cool main-sequence stars. Consequently, we seek fossil signatures of main-sequence core properties during the subgiant and early first-ascent red giant phases of evolution. During these stages of stellar evolution, modes of mixed character that sample the deep interior can be observed. These modes sample the parts of the stars that are affected by the main-sequence structure of these regions. We model the global and near-core properties of 62 subgiant and early first-ascent red giant branch stars observed by the Kepler, K2, and TESS space missions. We find that the effective overshoot parameter, α ov,eff, increases from M = 1.0 M ⊙ to M = 1.2 M ⊙ before flattening out, although we note that the relationship between α ov,eff and mass will depend on the incorporated modeling choices of internal physics and nuclear reaction network. We also situate these results within existing studies of main-sequence convective core boundaries.

Detection of Solar-like Oscillations in Subgiant and Red Giant Stars Using 2 minute Cadence TESS Data

Based on all 2 minute cadence TESS light curves from Sector 1 to 60, we provide a catalog of 8651 solar-like oscillators, including frequency at maximum power ( νmax , with its median precision σ = 5.39%), large frequency separation (Δν, σ = 6.22%), and seismically derived masses, radii, and surface gravity values. In this sample, we have detected 2173 new oscillators and added 4373 new Δν measurements. Our seismic parameters are consistent with those from Kepler, K2, and previous TESS data. The median fractional residual in νmax is 1.63%, with a scatter of 14.75%, and in Δν it is 0.11%, with a scatter of 10.76%. We have detected 476 solar-like oscillators with νmax exceeding the Nyquist frequency of Kepler long-cadence data during the evolutionary phases of subgiants and the base of the red giant branch, which provide a valuable resource for understanding angular momentum transport.

TOI-1994b: A Low-mass Eccentric Brown Dwarf Transiting A Subgiant Star

We present the discovery of TOI-1994b, a low-mass brown dwarf transiting a hot subgiant star on a moderately eccentric orbit. TOI-1994 has an effective temperature of 7700−410+720 K, V magnitude of 10.51 mag and log(g) of 3.982−0.065+0.067 . The brown dwarf has a mass of 22.1−2.5+2.6 M J, a period of 4.034 days, an eccentricity of 0.341−0.059+0.054 , and a radius of 1.220−0.071+0.082 R J. TOI-1994b is more eccentric than other transiting brown dwarfs with similar masses and periods. The population of low-mass brown dwarfs may have properties similar to planetary systems if they were formed in the same way, but the short orbital period and high eccentricity of TOI-1994b may contrast this theory. An evolved host provides a valuable opportunity to understand the influence stellar evolution has on the substellar companion’s fundamental properties. With precise age, mass, and radius, the global analysis and characterization of TOI-1994b augments the small number of transiting brown dwarfs and allows the testing of substellar evolution models.

The GAPS Programme at TNG

Context. Stellar activity is the most relevant types of astrophysical noise that affect the discovery and characterization of extrasolar planets. On the other hand, the amplitude of stellar activity could hint at an interaction between the star and a close-in giant planet. Progress has been made in recent years in understanding how to deal with stellar activity and search for observational evidence of star-planet interactions. Aims. The aim of this work is to characterize the chromospheric activity of stars hosting short-period exoplanets by studying the correlations between the chromospheric emission (CE) in the Ca II H&K and the planetary parameters. Methods. We measured CE in the Ca II H&K lines using more than 1900 high-resolution spectra of a sample composed of 76 targets, observed with the HARPS-N spectrograph between 2012 and 2020. We transformed the fluxes into bolometric- and photospheric-corrected chromospheric emission ratios, R′HK. Furthermore, we completed the sample of hosts digging for data in previous works. Stellar parameters Teff, B–V, and V were retrieved homogeneously from the Gaia DR3. Then, M★, R★, and ages were determined from isochrone fitting. We retrieved planetary data from the literature and catalogs. The search for correlations between the log(R′HK) and planetary parameters have been performed through both Spearman’s rank and its statistics as well as the more sophisticated Gaussian mixture model method. Results. We found that the distribution of log(R′HK) for the transiting planet hosts is different from the distribution of field main-sequence and sub-giant stars. The log(R′HK) of planetary hosts is correlated with planetary parameters proportional to the planetary radius to the power of n (RPn, indicating a common origin for the correlations. The statistical analysis has also highlighted four clusters of host stars with different behavior in terms of their stellar activity with respect to the planetary surface gravity. Some of the host stars have a value of log(R′HK) that is lower than the basal level of activity for main sequence stars. The planets of these systems are very close to filling their Roche lobe, suggesting that they evaporate through hydrodynamic escape under the strong irradiation of the host star, creating shrouds that absorb the core of the chromospheric resonance lines.

The HST Nondetection of SN Ia 2011fe 11.5 yr after Explosion Further Restricts Single-degenerate Progenitor Systems

We present deep Hubble Space Telescope imaging of the nearby Type Ia supernova (SN Ia) 2011fe obtained 11.5 yr after explosion. No emission is detected at the SN location to a 1σ (3σ) limit of F555W > 30.2 (29.0) mag, or equivalently M V > 1.2 (−0.1) mag, neglecting the distance uncertainty to M101. We constrain the presence of donor stars impacted by the SN ejecta with the strictest limits thus far on compact (i.e., logg≳4 ) companions. H-rich zero-age main-sequence companions with masses ≥2 M ⊙ are excluded, a significant improvement upon the preexplosion imaging limit of ≈5 M ⊙. Main-sequence He stars with masses ≥1.0 M ⊙ and subgiant He stars with masses ≤0.8 M ⊙ are also disfavored by our late-time imaging. Synthesizing our limits on postimpact donors with previous constraints from preexplosion imaging, early-time radio and X-ray observations, and nebular-phase spectroscopy, essentially all formation channels for SN 2011fe invoking a nondegenerate donor star at the time of explosion are unlikely.

Chemical clocks and their time zones: understanding the [s/Mg]–age relation with birth radii

ABSTRACT The relative enrichment of s-process to α-elements ([s/α]) has been linked with age, providing a potentially useful avenue in exploring the Milky Way’s chemical evolution. However, the age–[s/α] relationship is non-universal, with dependencies on metallicity and current location in the Galaxy. In this work, we examine these chemical clock tracers across birth radii (${R}_\text{birth}$), recovering the inherent trends between the variables. We derive ${R}_\text{birth}$ and explore the [s/α]–age–${R}_\text{birth}$ relationship for 36 652 APOGEE DR17 red giant and 24 467 GALAH DR3 main-sequence turn-off and subgiant branch disc stars using [Ce/Mg], [Ba/Mg], and [Y/Mg]. We discover that the age–$\rm [{\it s}/Mg]$ relation is strongly dependent on birth location in the Milky Way, with stars born in the inner disc having the weakest correlation. This is congruent with the Galaxy’s initially weak, negative $\rm [{\it s}/Mg]$ radial gradient, which becomes positive and steep with time. We show that the non-universal relations of chemical clocks is caused by their fundamental trends with ${R}_\text{birth}$ over time, and suggest that the tight age–$\rm [{\it s}/Mg]$ relation obtained with solar-like stars is due to similar ${R}_\text{birth}$ for a given age. Our results are put into context with a Galactic chemical evolution model, where we demonstrate the need for data-driven nucleosynthetic yields.

33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble

We present new angular diameter measurements for 33 stars from the Navy Precision Optical Interferometer, reaching uncertainties on the limb-darkened diameter of 2% or less for 21 targets. We also determined the physical radius, bolometric flux, luminosity, and effective temperature for each star. Our sample is a mix of giant, subgiant, and dwarf stars, and span spectral classes from mid-A to to mid-K. We combined these 33 stars with samples from previous publications to analyze how the NPOI diameters compare to those obtained using other means, namely (V − K) color, the JMMC Stellar Diameters Catalog, and Gaia predictions.

On the orbital decay of the gas giant Kepler-1658b

ABSTRACT The gas giant Kepler-1658b has been inferred to be spiralling into its sub-giant F-type host star Kepler-1658a (KOI-4). The measured rate of change of its orbital period is $\stackrel{\bf \centerdot }{\textstyle {P}}_{\rm orb}\, =\, -\, 131^{+20}_{-22}\,\rm {ms\,yr^{ -1}}$, which can be explained by tidal dissipation in the star if its modified tidal quality factor is as low as $Q^{\, \prime }\approx 2.50\times {10}^{4}$. We explore whether this could plausibly be consistent with theoretical predictions based on applying up-to-date tidal theory in stellar models (varying stellar mass, age, and metallicity) consistent with our newly derived observational constraints. In most of our models matching the combined constraints on the stellar effective temperature and radius, the dissipation in the star is far too weak, capable of providing $Q^{\, \prime }\gtrsim 10^9$, hence contributing negligibly to orbital evolution. Using only constraints on the stellar radius, efficient tidal dissipation sufficient to explain observations is possible due to inertial waves in the convective envelope during the sub-giant phase, providing $Q^{\, \prime }\sim 10^4$, but this period in the evolution is very short-lived (shorter than 102 yr in our models). We show that dissipation in the planet is capable of explaining the observed $\dot{P}_\mathrm{orb}$ only if the planet rotates non-synchronously. Tidally induced pericentre precession is a viable explanation if the periastron argument is near 3π/2 and the planet's quadrupolar Love number is above 0.26. Further observations constraining the stellar and planetary properties in this system have the exciting potential to test tidal theories in stars and planets.

The orbital period of the recurrent nova V2487 Oph revealed

ABSTRACT We present the first reliable determination of the orbital period of the recurrent nova V2487 Oph (Nova Oph 1998). We derived a value of 0.753 ± 0.016 d (18.1 ± 0.4 h) from the radial velocity curve of the intense He ii λ4686 emission line as detected in time-series X-shooter spectra. The orbital period is significantly shorter than earlier claims, but it makes V2487 Oph one of the longest period cataclysmic variables known. The spectrum of V2487 Oph is prolific in broad Balmer absorptions that resemble a white dwarf spectrum. However, we show that they come from the accretion disc viewed at low inclination. Although highly speculative, the analysis of the radial velocity curves provides a binary mass ratio q ≈ 0.16 and a donor star mass M2 ≈ 0.21 M⊙, assuming the reported white dwarf mass M1 = 1.35 M⊙. A subgiant M-type star is tentatively suggested as the donor star. We were lucky to inadvertently take some of the spectra when V2487 Oph was in a flare state. During the flare, we detected high-velocity emission in the Balmer and He ii λ4686 lines exceeding −2000 km s−1 at close to orbital phase 0.4. Receding emission up to 1200 km s−1 at about phase 0.3 is also observed. The similarities with the magnetic cataclysmic variables may point to magnetic accretion on to the white dwarf during the repeating flares.

The Q Branch Cooling Anomaly Can Be Explained by Mergers of White Dwarfs and Subgiant Stars

Gaia's exquisite parallax measurements allowed for the discovery and characterization of the Q branch in the Hertzsprung–Russell diagram, where massive C/O white dwarfs (WDs) pause their dimming due to energy released during crystallization. Interestingly, the fraction of old stars on the Q branch is significantly higher than in the population of WDs that will become Q branch stars or that were Q branch stars in the past. From this, Cheng et al. inferred that ∼6% of WDs passing through the Q branch experience a much longer cooling delay than that of standard crystallizing WDs. Previous attempts to explain this cooling anomaly have invoked mechanisms involving supersolar initial metallicities. In this paper, we describe a novel scenario in which a standard composition WD merges with a subgiant star. The evolution of the resulting merger remnant leads to the creation of a large amount of 26Mg, which, along with the existing 22Ne, undergoes a distillation process that can release enough energy to explain the Q branch cooling problem without the need for atypical initial abundances. The anomalously high number of old stars on the Q branch may thus be evidence that mass transfer from subgiants to WDs leads to unstable mergers.

Analysing mixed modes of the four solar-like oscillating subgiant stars

ABSTRACT The observation of an unprecedented number of solar-like oscillating subgiant (SG) stars by the Kepler and TESS missions is crucial for the asteroseismic characterization of these stars, stellar population studies, and the study of stellar evolution theories. Owing to these missions, the fundamental parameters of the solar-like oscillating stars are precisely calculated from the evolution codes using the observed oscillation frequencies. Herein, we considered four solar-like oscillating SG stars. We obtained the fundamental parameters of the SG stars by constructing interior models using asteroseismic and non-asteroseismic observed parameters. The interior models of the four SG stars are constructed using the Modules for Experiments in Stellar Astrophysics code to effectively determine the fundamental properties. Using this method, the four solar-like oscillating SG stars are found to have masses and radii within the ranges of 1.16–1.75 M⊙ and 2.26–3.17 R⊙, respectively. The estimation accuracy of the typical asteroseismic radius, mass, and age is increased by fitting the observed and model reference frequencies. The typical uncertainties of the mass and radius are 3–4 ${{\ \rm per\ cent}}$ and 1–2 ${{\ \rm per\ cent}}$, respectively. Furthermore, the observed l = 1 frequencies, which showed a mixed mode for the first time, were also fitted to the models. Information regarding the gravity and density of the helium core was obtained by examining the mixed modes. Moreover, new asteroseismic methods for determining the age of SG stars are developed for the first time in this study.

Angular momentum and lithium transport from main sequence to sub-giant and red giant low-mass stars

Context. Asteroseismology provides a unique opportunity to probe the interiors of evolved stars and constrain their internal rotation. The correct reproduction of the core rotation evolution has not yet been achieved, although it is key to understanding the internal processes involved in low-mass stars. Aims. We explore the efficiency required to reproduce the general behaviour of the transport of angular momentum along the evolution in view of asteroseismic constraints from giant low-mass stars. We analyse the consequences and predictions for lithium and beryllium surface abundances from the main sequence to red giant phase. Methods. We computed a series of models, which included atomic diffusion, rotation-induced mixing, magnetic braking, and additional processes tailored for main sequence low-mass stars. We extended these models to more evolved phases and investigated an updated angular momentum transport by including a time-dependent extra viscosity related to the azimuthal magneto-rotational instability. We compared our predictions to the asteroseismic measurements of the core and surface rotation of a sample of sub-giant and red giant stars. We compared the model predictions for the lithium and beryllium surface evolution with the available observations. Results. We confirm that a time-dependent additional viscosity νadd(t) is required to reproduce the general behaviour of the core rotation rate along successive stellar evolutionary phases given the dependence on the differential rotation and the mass. We show that it results in stronger lithium and beryllium depletions for low-mass stars over evolution. We confirm that predicted lithium abundances at the red giant bump by classical models, commonly used as references, cannot reproduce the lithium depletion along the main sequence and evolved phases of stellar evolution. We show that the observed amount of lithium of stars less massive than 1 M⊙ leads to a discrepancy between model predictions and observations at the red giant bump. Conclusions. We show that a semi-parametric model can reproduce the rotational behaviour along the first phases of evolution well, with the exception of the sharp transition observed during the sub-giant phase. This suggests that two distinct transport processes may be involved. The processes required to transport chemicals during the main sequence phase and angular momentum until the red giant phase impact the lithium depletion all along the evolutionary duration. A good prediction of the lithium abundance at young phases places strong constraints on the predicted one at more evolved phases. It also highlights discrepancies between models and observations for the lowest mass stars and impacts the threshold that defines lithium-rich giant stars, showing that classical models tend to overestimate this threshold.

Angular momentum transport by magnetic fields in main-sequence stars with Gamma Doradus pulsators

Context. Asteroseismic studies show that cores of post-main-sequence stars rotate more slowly than theoretically predicted by stellar models with purely hydrodynamical transport processes. Recent studies of main-sequence stars, particularly Gamma Doradus (γ Dor) stars, have revealed the internal rotation rates for hundreds of stars, offering a counterpart on the main sequence for studies of angular momentum transport. Aims. We investigate whether such a disagreement between observed and predicted internal rotation rates is present in main-sequence stars by studying angular momentum transport in γ Dor stars. Furthermore, we test whether models of rotating stars with internal magnetic fields can reproduce their rotational properties. Methods. We computed rotating models with the Geneva stellar evolution code taking into account meridional circulation and shear instability. We also computed models with internal magnetic fields using a general formalism for transport by the Tayler-Spruit dynamo. We then compared these models to observational constraints for γ Dor stars that we compiled from the literature, thus combining the core rotation rates, projected rotational velocities from spectroscopy, and constraints on their fundamental parameters. Results. We show that combining the different observational constraints available for γ Dor stars enable us to clearly distinguish the different scenarios for internal angular momentum transport. Stellar models with purely hydrodynamical processes are in disagreement with the data, whereas models with internal magnetic fields can reproduce both core and surface constraints simultaneously. Conclusions. Similarly to results obtained for subgiant and red giant stars, angular momentum transport in radiative regions of γ Dor stars is highly efficient, in good agreement with predictions of models with internal magnetic fields.

Overview and Validation of the Asteroseismic Modeling Portal v2.0

The launch of NASA’s Kepler space telescope in 2009 revolutionized the quality and quantity of observational data available for asteroseismic analysis. While Kepler was able to detect solar-like oscillations in hundreds of main-sequence and subgiant stars, the Transiting Exoplanet Survey Satellite is now making similar observations for thousands of the brightest stars in the sky. The Asteroseismic Modeling Portal (AMP) is an automated and objective stellar model-fitting pipeline for asteroseismic data, which was originally developed to use models from the Aarhus Stellar Evolution Code. We briefly summarize an updated version of the AMP pipeline that uses Modules for Experiments in Stellar Astrophysics, and we present initial modeling results for the Sun and several solar analogs to validate the precision and accuracy of the inferred stellar properties.