The formation and evolution of binary star systems still remain key questions in modern astronomy. Wide binary pairs (separations \(>10^3\) AU) are particularly intriguing because their low binding ...energies make it difficult for the stars to stay gravitationally bound over extended timescales,and thus probe the dynamics of binary formation and dissolution. Our previous SLoWPoKES I \& II catalogs provided the largest and most complete sample of wide binary pairs of low masses. Here we present an extension of these catalogs to a broad range of stellar masses: the Gaia Assorted Mass Binaries Long Excluded from SloWPoKES (GAMBLES), comprising 8,660 statistically significant wide pairs that we make available in a living online database. Within this catalog we identify a subset of 543 long-lived (dissipation timescale \(>\)1.5 Gyr) candidate binary pairs, of assorted mass, with typical separations between \(10^3-10^{5.5}\) AU (\(0.002-1.5\) pc), using the published distances and proper motions from the Tycho-Gaia Astrometric Solution and Sloan Digital Sky Survey photometry. Each pair has at most a false positive probability of 0.05; the total expectation is 2.44 false binaries in our sample. Among these, we find 22 systems with 3 components, 1 system with 4 components, and 15 pairs consisting of at least 1 possible red giant. We find the largest long-lived binary separation to be nearly 3.2 pc; even so, \(>76\%\) of GAMBLES long-lived binaries have large binding energies and dissipation lifetimes longer than 1.5 Gyr. Finally, we find the distribution of binary separations is clearly bimodal, corroborating the finding from SloWPoKES and suggesting multiple pathways for the formation and dissipation of the widest binaries in the Galaxy.
The Second APOKASC Catalog: The Empirical Approach Pinsonneault, Marc H.; Elsworth, Yvonne P.; Tayar, Jamie ...
The Astrophysical journal. Supplement series,
12/2018, Letnik:
239, Številka:
2
Journal Article
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We present a catalog of stellar properties for a large sample of 6676 evolved stars with Apache Point Observatory Galactic Evolution Experiment spectroscopic parameters and Kepler asteroseismic data ...analyzed using five independent techniques. Our data include evolutionary state, surface gravity, mean density, mass, radius, age, and the spectroscopic and asteroseismic measurements used to derive them. We employ a new empirical approach for combining asteroseismic measurements from different methods, calibrating the inferred stellar parameters, and estimating uncertainties. With high statistical significance, we find that asteroseismic parameters inferred from the different pipelines have systematic offsets that are not removed by accounting for differences in their solar reference values. We include theoretically motivated corrections to the large frequency spacing (Δ ) scaling relation, and we calibrate the zero-point of the frequency of the maximum power ( max) relation to be consistent with masses and radii for members of star clusters. For most targets, the parameters returned by different pipelines are in much better agreement than would be expected from the pipeline-predicted random errors, but 22% of them had at least one method not return a result and a much larger measurement dispersion. This supports the usage of multiple analysis techniques for asteroseismic stellar population studies. The measured dispersion in mass estimates for fundamental calibrators is consistent with our error model, which yields median random and systematic mass uncertainties for RGB stars of order 4%. Median random and systematic mass uncertainties are at the 9% and 8% level, respectively, for red clump stars.
We report the discovery in TESS data and validation of HD 56414 b (a.k.a. TOI-1228 b), a Neptune-size (\(R_{\rm p} = 3.71 \pm 0.20\, R_\oplus\)) planet with a 29-day orbital period transiting a young ...(Age = \(420 \pm 140\) Myr) A-type star in the TESS southern continuous viewing zone. HD 56414 is one of the hottest stars (\(T_{\rm eff} = 8500 \pm 150 \, {\rm K}\)) to host a known sub-Jovian planet. HD 56414 b lies on the boundary of the hot Neptune desert in planet radius -- bolometric insolation flux space, suggesting that the planet may be experiencing mass loss. To explore this, we apply a photoevaporation model that incorporates the high near ultraviolet continuum emission of A-type stars. We find that the planet can retain most of its atmosphere over the typical 1-Gyr main sequence lifetime of an A-type star if its mass is \(\ge 8 \, M_\oplus\). Our model also predicts that close-in Neptune-size planets with masses \(< 14 \, M_\oplus\) are susceptible to total atmospheric stripping over 1 Gyr, hinting that the hot Neptune desert, which has been previously observed around FGKM-type stars, likely extends to A-type stars.
The Sloan Digital Sky Survey IV (SDSS-IV) APOGEE-2 primary science goal was to observe red giant stars throughout the Galaxy to study its dynamics, morphology, and chemical evolution. The APOGEE ...instrument, a high-resolution 300 fiber H-band (1.55-1.71 micron) spectrograph, is also ideal to study other stellar populations in the Galaxy, among which are a number of star forming regions and young open clusters. We present the results of the determination of six stellar properties (\(T_{eff}\), \(\log{g}\), Fe/H, \(L/L_\odot\), \(M/M_\odot\), and ages) for a sample that is composed of 3360 young stars, of sub-solar to super-solar types, in sixteen Galactic star formation and young open cluster regions. Those sources were selected by using a clustering method that removes most of the field contamination. Samples were also refined by removing targets affected by various systematic effects of the parameter determination. The final samples are presented in a comprehensive catalog that includes all six estimated parameters. This overview study also includes parameter spatial distribution maps for all regions and Hertzprung-Russell (\(L/L_\odot\) vs. \(T_{eff}\)) diagrams. This study serves as a guide for detailed studies on individual regions, and paves the way for the future studies on the global properties of stars in the pre-main sequence phase of stellar evolution using more robust samples.
Very young (t \(\lesssim\) 10 Myrs) stars possess strong magnetic fields that channel ionized gas from the interiors of their circumstellar discs to the surface of the star. Upon impacting the ...stellar surface, the shocked gas recombines and emits hydrogen spectral lines. To characterize the density and temperature of the gas within these accretion streams, we measure equivalent widths of Brackett (Br) 11-20 emission lines detected in 1101 APOGEE spectra of 326 likely pre-main sequence accretors. For sources with multiple observations, we measure median epoch-to-epoch line strength variations of 10% in Br11 and 20% in Br20. We also fit the measured line ratios to predictions of radiative transfer models by Kwan & Fischer. We find characteristic best-fit electron densities of \(n_e\) = 10\(^{11} - 10^{12}\) cm\(^{-3}\), and excitation temperatures that are inversely correlated with electron density (from T\(\sim\)5000 K for \(n_e \sim 10^{12}\) cm\(^{-3}\), to T\(\sim\)12500 K at \(n_e \sim 10^{11}\) cm\(^{-3}\)). These physical parameters are in good agreement with predictions from modelling of accretion streams that account for the hydrodynamics and radiative transfer within the accretion stream. We also present a supplementary catalog of line measurements from 9733 spectra of 4255 Brackett emission line sources in the APOGEE DR17 dataset.
Binary stars in which oscillations can be studied in either or both
components can provide powerful constraints on our understanding of stellar
physics. The bright binary 12 Bo\"otis (12 Boo) is a ...particularly promising
system because the primary is roughly 60 per cent brighter than the secondary
despite being only a few per cent more massive. Both stars have substantial
surface convection zones and are therefore, presumably, solar-like oscillators.
We report here the first detection of solar-like oscillations and ellipsoidal
variations in the TESS light curve of 12 Boo. Though the solar-like
oscillations are not clear enough to unambiguously measure individual mode
frequencies, we combine global asteroseismic parameters and a precise fit to
the spectral energy distribution (SED) to provide new constraints on the
properties of the system that are several times more precise than values in the
literature. The SED fit alone provides new effective temperatures, luminosities
and radii of $6115\pm45\,\mathrm{K}$, $7.531\pm0.110\,\mathrm{L}_\odot$ and
$2.450\pm0.045\,\mathrm{R}_\odot$ for 12 Boo A and $6200\pm60\,\mathrm{K}$,
$4.692\pm0.095\,\mathrm{L}_\odot$ and $1.901\pm0.045\,\mathrm{R}_\odot$ for 12
Boo B. When combined with our asteroseismic constraints on 12 Boo A, we obtain
an age of $2.67^{+0.12}_{-0.16}\,\mathrm{Gyr}$, which is consistent with that
of 12 Boo B.
The Vera C. Rubin Observatory will undertake the Legacy Survey of Space and Time, providing an unprecedented, volume-limited catalog of star clusters in the Southern Sky, including Galactic and ...extragalactic star clusters. The Star Clusters subgroup of the Stars, Milky Way and Local Volume Working Group has identified key areas where Rubin Observatory will enable significant progress in star cluster research. This roadmap represents our science cases and preparation for studies of all kinds of star clusters from the Milky Way out to distances of tens of megaparsecs.
When main-sequence stars expand into red giants, they are expected to engulf close-in planets. Until now, the absence of planets with short orbital periods around post-expansion, core-helium-burning ...red giants has been interpreted as evidence that short-period planets around Sun-like stars do not survive the giant expansion phase of their host stars. Here we present the discovery that the giant planet 8 Ursae Minoris b orbits a core-helium-burning red giant. At a distance of only 0.5 au from its host star, the planet would have been engulfed by its host star, which is predicted by standard single-star evolution to have previously expanded to a radius of 0.7 au. Given the brief lifetime of helium-burning giants, the nearly circular orbit of the planet is challenging to reconcile with scenarios in which the planet survives by having a distant orbit initially. Instead, the planet may have avoided engulfment through a stellar merger that either altered the evolution of the host star or produced 8 Ursae Minoris b as a second-generation planet. This system shows that core-helium-burning red giants can harbour close planets and provides evidence for the role of non-canonical stellar evolution in the extended survival of late-stage exoplanetary systems.
To date, thousands of planets have been discovered, but there are regions of the orbital parameter space that are still bare. An example is the short period and intermediate mass/radius space known ...as the Neptunian desert, where planets should be easy to find but discoveries remain few. This suggests unusual formation and evolution processes are responsible for the planets residing here. We present the discovery of TOI-332 b, a planet with an ultra-short period of \(0.78\) d that sits firmly within the desert. It orbits a K0 dwarf with an effective temperature of \(5251 \pm 71\) K. TOI-332 b has a radius of \(3.20^{+0.16}_{-0.12}\) R\(_{\oplus}\), smaller than that of Neptune, but an unusually large mass of \(57.2 \pm 1.6\) M\(_{\oplus}\). It has one of the highest densities of any Neptune-sized planet discovered thus far at \(9.6^{+1.1}_{-1.3}\) gcm\(^{-3}\). A 4-layer internal structure model indicates it likely has a negligible hydrogen-helium envelope, something only found for a small handful of planets this massive, and so TOI-332 b presents an interesting challenge to planetary formation theories. We find that photoevaporation cannot account for the mass loss required to strip this planet of the Jupiter-like envelope it would have been expected to accrete. We need to look towards other scenarios, such as high-eccentricity migration, giant impacts, or gap opening in the protoplanetary disc, to try and explain this unusual discovery.
Hot Jupiters are generally observed to lack close planetary companions, a trend that has been interpreted as evidence for high-eccentricity migration. We present the discovery and validation of ...WASP-132 c (TOI-822.02), a 1.85 \(\pm\) 0.10 \(R_{\oplus}\) planet on a 1.01 day orbit interior to the hot Jupiter WASP-132 b. Transiting Exoplanet Survey Satellite (TESS) and ground-based follow-up observations, in conjunction with vetting and validation analysis, enable us to rule out common astrophysical false positives and validate the observed transit signal produced by WASP-132 c as a planet. Running the validation tools \texttt{vespa} and \texttt{triceratops} on this signal yield false positive probabilities of \(9.02 \times 10^{-5}\) and 0.0107, respectively. Analysis of archival CORALIE radial velocity data leads to a 3\(\sigma\) upper limit of 28.23 ms\(^{-1}\) on the amplitude of any 1.01-day signal, corresponding to a 3\(\sigma\) upper mass limit of 37.35 \(M_{\oplus}\). Dynamical simulations reveal that the system is stable within the 3\(\sigma\) uncertainties on planetary and orbital parameters for timescales of \(\sim\)100 Myr. The existence of a planetary companion near the hot Jupiter WASP-132 b makes the giant planet's formation and evolution via high-eccentricity migration highly unlikely. Being one of just a handful of nearby planetary companions to hot Jupiters, WASP-132 c carries with it significant implications for the formation of the system and hot Jupiters as a population.
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