adsabs/SciX_UAT_keywords huggingface dataset:
Joint Analysis of Multicolor Photometry: A New Approach to Constrain the Nature of Multiple-star Systems Hosting Exoplanet Candidates

We present a new method to assess the properties of transiting planet candidates by multicolor photometry. By analyzing multicolor transit/eclipse light curves and apparent magnitudes of the target in parallel, this method attempts to identify the nature of the system and provide a quantitative constraint on the properties of unresolved companion(s). We demonstrate our method by observing the six systems hosting candidate transiting planets, identified by the K2 mission (EPIC 206036749, EPIC 206500801, EPIC 210513446, EPIC 211800191, EPIC 220621087, and EPIC 220696233). Applying our analysis code to the six targets, we find that EPIC 206036749, EPIC 210513446, and EPIC 211800191 are likely to be triple-star systems including eclipsing binaries, and EPIC 220696233 is likely a planetary system, albeit further observations are required to confirm the nature. Additionally, we confirm that the systematic errors in the derived system parameters arising from adopting specific isochrone models and observing instruments (passbands) are relatively small. While this approach alone is not powerful enough to validate or refute planet candidates, the technique allows us to constrain the properties of resolved/unresolved companions, and prioritize the planet candidates for further follow-up observations (e.g., radial-velocity measurements).

Keywords: exoplanet detection methods; exoplanet evolution; transit photometry; multi-color photometry; space telescopes; eclipsing binary stars
Standing Sausage Perturbations in Solar Coronal Loops with Diffuse Boundaries: An Initial Value Problem Perspective

Working in pressureless magnetohydrodynamics, we examine the consequences of some peculiar dispersive properties of linear fast sausage modes (FSMs) in one-dimensional cylindrical equilibria with a continuous radial density profile (ρ 0(r)). As recognized recently on solid mathematical grounds, cutoff axial wavenumbers may be absent for FSMs when ρ 0(r) varies sufficiently slowly outside the nominal cylinder. Trapped modes may therefore exist for arbitrary axial wavenumbers and density contrasts, their axial phase speeds in the long-wavelength regime differing little from the external Alfvén speed. If these trapped modes indeed show up in the solutions to the associated initial value problem (IVP), then FSMs have a much better chance to be observed than expected with classical theory and can be invoked to account for a considerably broader range of periodicities than practiced. However, with axial fundamentals in active region loops as an example, we show that this long-wavelength expectation is not seen in our finite-difference solutions to the IVP, the reason for which is then explored by superposing the necessary eigenmodes to construct solutions to the same IVP. At least for the parameters we examine, the eigenfunctions of trapped modes are characterized by a spatial extent well exceeding the observationally reasonable range of the spatial extent of initial perturbations, meaning a negligible fraction of energy that a trapped mode can receive. We conclude that the absence of cutoff wavenumbers for FSMs in the examined equilibrium does not guarantee a distinct temporal behavior.

Keywords: magnetohydrodynamics; solar corona; solar coronal seismology; solar coronal waves
A Comprehensive Study of the Spectral Variation and the Brightness Profile of Young Pulsar Wind Nebulae

We present a systematic study of particle transport by diffusion in young pulsar wind nebulae (PWNe). We selected nine bright sources that are well resolved with the Chandra X-ray Observatory. We analyzed archival data to obtain their radial profiles of photon index (Γ) and surface brightness (Σ) in a consistent way. These profiles were then fit with a pure diffusion model that was tested on Crab, 3C 58, and G21.5-0.9 before. In addition to the spectral softening due to the diffusion, we calculated the synchrotron power and built up the theoretical surface brightness profile. For each source, we performed separate fits to the Γ and Σ profiles. We found that these two profiles of most PWNe are similar, except for Crab and Vela. Both profiles can be well described by our model, suggesting that diffusion dominates the particle transport in most sampled PWNe. The discrepancy of parameters between the Γ and Σ profiles is relatively large for 3C 58 and G54.1+0.3. This difference could be attributed to the elongated shape, reflecting boundary, and the nonuniform magnetic field. Finally, we found no significant correlations between diffusion parameters and physical parameters of PWNe and pulsars.

Keywords: interstellar synchrotron emission; supernova remnants; neutron stars; rotation powered pulsars; x-ray sources
A New 2D Energy Balance Model for Simulating the Climates of Rapidly and Slowly Rotating Terrestrial Planets

Energy balance models (EBMs), alongside radiative-convective climate models and global climate models (GCMs), are useful tools for simulating planetary climates. Historically, planetary and exoplanetary EBMs have solely been 1D latitudinally dependent models with no longitudinal dependence, until the study of Okuya et al., which focused on simulating synchronously rotating planets. Following the work of Okuya et al., I have designed the first 2D EBM (PlaHab) that can simulate N2-CO2-H2O-H2 atmospheres of both rapidly and synchronously rotating planets, including Mars, Earth, and exoplanets located within their circumstellar habitable zones. PlaHab includes physics for both water and CO2 condensation. Regional topography can be incorporated. Here, I have specifically applied PlaHab to investigate the present Earth, early Mars, TRAPPIST-1 e, and Proxima Centauri b, representing examples of habitable (and potentially habitable) worlds in our solar system and beyond. I compare my EBM results against those of other 1D and 3D models, including those of the recent Trappist-1 Habitable Atmosphere comparison project. Overall, the EBM results are consistent with those of other 1D and 3D models, although inconsistencies among all models continue to be related to the treatment of clouds and other known differences between EBMs and GCMs, including heat transport parameterizations. Although 2D EBMs are a relatively new entry in the study of planetary/exoplanetary climates, their ease of use, speed, flexibility, wide applicability, and greater complexity (relative to 1D models) may indicate an ideal combination for the modeling of planetary and exoplanetary atmospheres alike.

Keywords: planetary atmospheres; solar system terrestrial planets; earth (planet); mars; extrasolar rocky planets; habitable planets; planetary climates; exoplanet atmospheres
SDSS-IV MaNGA: Exploring the Local Scaling Relations for N/O

We present, for the first time, the relationship between local stellar mass surface density, Σ*, and N/O derived from SDSS-IV MaNGA data, using a sample of 792,765 high signal-to-noise ratio star-forming spaxels. Using a combination of phenomenological modeling and partial correlation analysis, we find that Σ* alone is insufficient to predict the N/O in MaNGA spaxels and that there is an additional dependence on the local star formation rate surface density, ΣSFR. This effect is a factor of 3 stronger than the dependence of 12+log(O/H) on ΣSFR. Surprisingly, we find that the local N/O scaling relations also depend on the total galaxy stellar mass at fixed Σ* and the galaxy size at fixed stellar mass. We find that more compact galaxies are more nitrogen rich, even when Σ* and ΣSFR are controlled for. We show that ~50% of the variance of N/O is explained by the total stellar mass and size. Thus, the evolution of nitrogen in galaxies is set by more than just local effects and does not simply track the buildup of oxygen in galaxies. The precise form of the N/O-O/H relation is therefore sensitive to the sample of galaxies from which it is derived. This result casts doubt on the universal applicability of nitrogen-based strong-line metallicity indicators derived in the local universe.

Keywords: galaxy evolution; chemical enrichment; chemical abundances; interstellar abundances; scaling relations; galaxy properties; galaxy abundances
Dependences of Energetic Neutral Atoms Energy on the Solar Wind Energy and Solar Zenith Angle Observed by the Chang'E-4 Rover

Solar wind can directly interact with the lunar surface and bring a space weathering effect. Some solar wind protons can be scattered as energetic neutral atoms (ENAs), which include rich information of the solar wind-surface interaction. However, people still know little about the ENA truth on the lunar ground due to the lack of in situ measurements. Different from the previous in-orbit measurements, here we present the first ground-based ENA measurements by the Chang'E-4 rover and find a good correlation between the mean ENA energy and the solar wind energy. Moreover, the loss rate of ENA energy can strongly depend on both the solar wind energy and the solar zenith angle (SZA), in which the energy loss rate can be enhanced by 73% when the solar wind energy increases from 400 to 1400 eV and can be reduced by 32% when the SZA increases from 57° to 71°. Combined with numerical simulations by SDTrimSP code, we propose that the solar wind protons can penetrate deeper into the lunar surface with a longer path length when the solar wind energy is higher or the SZA is lower, which results in a larger energy loss rate for the scattered ENAs. Our results provide an important constraint for the solar wind-surface research and have general implications in studying the surficial space weathering of the Moon and other airless bodies.

Keywords: solar wind; lunar surface; the moon
Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b

Atmospheric characterization of temperate, rocky planets is the holy grail of exoplanet studies. These worlds are at the limits of our capabilities with current instrumentation in transmission spectroscopy and challenge our state-of-the-art statistical techniques. Here we present the transmission spectrum of the temperate super-Earth LHS 1140b using the Hubble Space Telescope (HST). The Wide Field Camera 3 (WFC3) G141 grism data of this habitable-zone (Teq = 235 K) super-Earth (R = 1.7 R⊕) shows tentative evidence of water. However, the signal-to-noise ratio, and thus the significance of the detection, is low and stellar contamination models can cause modulation over the spectral band probed. We attempt to correct for contamination using these models and find that, while many still lead to evidence for water, some could provide reasonable fits to the data without the need for molecular absorption although most of these cause features in the visible ground-based data which are nonphysical. Future observations with the James Webb Space Telescope would be capable of confirming, or refuting, this atmospheric detection.

Keywords: exoplanet atmospheres; hubble space telescope; space observatories; exoplanet atmospheric composition; habitable planets; habitable zone
Introducing piXedfit: A Spectral Energy Distribution Fitting Code Designed for Resolved Sources

We present piXedfit, pixelized spectral energy distribution (SED) fitting, a Python package that provides tools for analyzing spatially resolved properties of galaxies using multiband imaging data alone or in combination with integral field spectroscopy (IFS) data. It has six modules that can handle all tasks in the spatially resolved SED fitting. The SED-fitting module uses the Bayesian inference technique with two kinds of posterior sampling methods: Markov Chain Monte Carlo (MCMC) and random dense sampling of parameter space (RDSPS). We test the performance of the SED-fitting module using mock SEDs of simulated galaxies from IllustrisTNG. The SED fitting with both posterior sampling methods can recover physical properties and star formation histories of the IllustrisTNG galaxies well. We further test the performance of piXedfit modules by analyzing 20 galaxies observed by the CALIFA and MaNGA surveys. The data are comprised of 12-band imaging data from the Galaxy Evolution Explorer, SDSS, 2MASS, and WISE and the IFS data from CALIFA or MaNGA. The piXedfit package can spatially match (in resolution and sampling) the imaging and IFS data. By fitting only the photometric SEDs, piXedfit can predict the spectral continuum, Dn4000, Hα, and Hβ well. The star formation rate derived by piXedfit is consistent with that derived from Hα emission. The RDSPS method gives equally good fitting results as the MCMC and is much faster. As a versatile tool, piXedfit is equipped with a parallel computing module for efficient analysis of large data sets and will be made publicly available (https://github.com/aabdurrouf/piXedfit).

Keywords: astronomical methods; bayesian statistics; galaxy evolution; posterior distribution
Building the Largest Spectroscopic Sample of Ultracompact Massive Galaxies with the Kilo Degree Survey

Ultracompact massive galaxies (UCMGs), I.e., galaxies with stellar masses ${M}_{\star }\gt 8\times {10}^{10}{M}_{\odot }$ and effective radii ${R}_{{\rm{e}}}\lt 1.5\,\mathrm{kpc}$ , are very rare systems, in particular at low and intermediate redshifts. Their origin as well as their number density across cosmic time are still under scrutiny, especially because of the paucity of spectroscopically confirmed samples. We have started a systematic census of UCMG candidates within the ESO Kilo Degree Survey, together with a large spectroscopic follow-up campaign to build the largest possible sample of confirmed UCMGs. This is the third paper of the series and the second based on the spectroscopic follow-up program. Here, we present photometrical and structural parameters of 33 new candidates at redshifts $0.15\lesssim z\lesssim 0.5$ and confirm 19 of them as UCMGs, based on their nominal spectroscopically inferred ${M}_{\star }$ and ${R}_{{\rm{e}}}$ . This corresponds to a success rate of $\sim 58 \% $ , nicely consistent with our previous findings. The addition of these 19 newly confirmed objects allows us to fully assess the systematics on the system selection - and to finally reduce the number density uncertainties. Moreover, putting together the results from our current and past observational campaigns and some literature data, we build the largest sample of UCMGs ever collected, comprising 92 spectroscopically confirmed objects at $0.1\lesssim z\lesssim 0.5$ . This number raises to 116, allowing for a 3σ tolerance on the ${M}_{\star }$ and ${R}_{{\rm{e}}}$ thresholds for the UCMG definition. For all these galaxies, we have estimated the velocity dispersion values at the effective radii, which have been used to derive a preliminary mass-velocity dispersion correlation.

Keywords: early-type galaxies; galaxy formation; galaxy mergers; spectroscopy; galaxy counts; galaxy kinematics
Interstellar Extinction and Polarization of Stars in the Open Cluster NGC 6709

We present BVRI polarimetric measurements of 23 stars in the direction of the open cluster NGC 6709. Fifteen stars display wavelength-dependence of polarization which is typically due to selective extinction in the interstellar medium and could be fitted to the Serkwoski equation. Based on these stars, we obtained an average maximum degree of polarization of 0.722 ± 0.022% and an average wavelength at a maximum polarization of 0.615 ± 0.011 μm. The observed low polarization may be due to the alignment of grains along a more longitudinally-directed magnetic field in this region which would cause the aspect ratio of the grains to be reduced. This would have the observational consequence of decreased polarization as well as shifting ${\lambda }_{\max }$ toward longer wavelengths. Using the expression proposed by Whittet & van Breda we calculated the ratio of total-to-selective extinction as ${R}_{V}=(5.6\pm 0.3){\lambda }_{\max }=3.44\pm 0.06$ , higher than the nominal value of 3.1 for the general ISM. The remaining eight sample stars display an unusual wavelength-dependence that is similar to some Be stars. However, there are only two Be stars currently listed in this cluster, yet, based on our data, they both present reliable fits within the Serkowski equation. The overall alignment of the V-band polarization vectors implies polarization by selective extinction due to foreground dust. Using the Planck 353 GHz channel we find there is an agreement between polarization by emission and selective extinction. Since the optical polarization traces a magnetic field, this suggests that the magnetic field in this region is inclined to the Galactic plane, with an overall average Galactic position angle of 104 ± 12 (st. dev.) degrees.

Keywords: starlight polarization; fundamental parameters of stars; stellar associations; interstellar extinction
Investigating Anomalous Photochemistry in the Inner Wind of IRC+10216 through Interferometric Observations of HC3N

In recent years, many questions have arisen regarding the chemistry of photochemical products in the carbon-rich winds of evolved stars. To address them, it is imperative to constrain the distributions of such species through high-angular-resolution interferometric observations covering multiple rotational transitions. We used archival Atacama Large Millimeter/submillimeter Array observations to map rotational lines involving high energy levels of cyanoacetylene (HC3N) toward the inner envelope (radius < 8″/1000 au) of the carbon star IRC+10216. The observed lines include the J = 28 - 27, J = 30 - 29, and J = 38 - 37 transitions of HC3N in its ground vibrational state. In contrast to previous observations of linear carbon chains toward this asymptotic giant branch (AGB) star that show extended, hollow emission at 15″-20″ radii (e.g., C4H, C6H, and HC5N), the maps of the HC3N lines here show compact morphologies comprising various arcs and density enhancements, with significant emission from gas clumps at an angular distance of ~3″ (350 au) from the central AGB star. We compared visibility sampled non-LTE radiative transfer models with the observed brightness distributions, and derive a fractional abundance with respect to H2 of 10-8 for HC3N at the radii probed by these lines. These results are consistent with enhanced photochemistry occurring in warm (~200 K) regions of the circumstellar envelope. After application of a specialized chemical model for IRC+10216, we find evidence that the enhanced HC3N abundances in the inner wind are most likely due to a solar-type binary companion initiating photochemistry in this region.

Keywords: evolved stars; astrochemistry; carbon stars; circumstellar envelopes; chemical abundances
A Unified Model for Bipolar Outflows from Young Stars: The Interplay of Magnetized Wide-angle Winds and Isothermal Toroids

Large-scale morphology and time evolution are investigated for the unified model of bipolar outflows outlined in Shang et al. (2006), where an outflow forms by a radially directed, wide-angle magnetized wind interacting with magnetized isothermal toroids in various quasistatic states. The primary wide-angle wind is toroidally magnetized and maintains a cylindrically stratified density profile, mimicking the asymptotic solution of the cold X-wind model. We explore the interplay between the toroidally magnetized primary wind and the surrounding toroids threaded by poloidal magnetic fields and examine how the jet and shell morphology and fine structures within them vary with the physical parameters. The variation in flatness of the density distribution in the ambient isothermal toroids helps shape the varieties of lobe morphology and collimation. The presence of a stronger ambient poloidal field helps shape the outflow, forming a magnetic cocoon and nested multilayered cavities surrounding the wind-filled lobe, which is most evident in the more open configurations of the ambient toroids. The wind-toroid interface is prone to substantial shear and thus unstable to the Kelvin-Helmholtz instability. Magnetic forces in the compressed toroidally magnetized high-velocity wind can generate vorticity, leading to nonlinear patterns within the extended magnetized mixing layers. Magnetic disturbances generated by the interplay could modulate lobe shapes, density, and velocities, giving rise to visual impressions of thicker and rugged shells and apparent episodic distribution of matter. The system maintains a quasi-self-similar evolution in time, which serves as a proxy for understanding the underlying physical mechanisms driving it.

Keywords: magnetohydrodynamics; star formation; stellar-interstellar interactions; young stellar objects; low mass stars; magnetic fields; jets; magnetohydrodynamical simulations; stellar winds; protostars; stellar jets; stellar mass loss
The Chocolate Chip Cookie Model: Dust Geometry of Milky Way-like Disk Galaxies

We present a new two-component dust geometry model, the Chocolate Chip Cookie model, where the clumpy nebular regions are embedded in a diffuse stellar/interstellar medium disk, like chocolate chips in a cookie. By approximating the binomial distribution of the clumpy nebular regions with a continuous Gaussian distribution and omitting the dust scattering effect, our model solves the dust attenuation process for both the emission lines and stellar continua via analytical approaches. Our Chocolate Chip Cookie model successfully fits the inclination dependence of both the effective dust reddening of the stellar components derived from stellar population synthesis and that of the emission lines characterized by the Balmer decrement for a large sample of Milky Way-like (MW-like) disk galaxies selected from the main galaxy sample of the Sloan Digital Sky Survey. Our model shows that the clumpy nebular disk is about 0.55 times thinner and 1.6 times larger than the stellar disk for MW-like galaxies, whereas each clumpy region has a typical optical depth of τ cl,V ~ 0.5 in the V band. After considering the aperture effect, our model prediction on the inclination dependence of dust attenuation is also consistent with observations. Not only that, in our model, the dust attenuation curve of the stellar population naturally depends on the inclination, and its median case is consistent with the classical Calzetti law. As the modeling constraints are from the optical wavelengths, our model is unaffected by the optically thick dust component, which however could bias the model's prediction of the infrared emissions.

Keywords: galaxy structure; disk galaxies; extinction; interstellar dust; interstellar dust extinction