Research Centre for Astronomy and Earth SciencesHUN-REN
Phosphorus enhanced (P-rich; [P/Fe] > 0.8) giants have been found among mildly metal-poor fiels stars, but in only one star in a globular cluster (GC), M4 (NGC 6121). Also, in a sample of bulge spheroid stars, some of them showed a moderate P-enhancement in the range +0.5 < [P/Fe] < +1.0. In this paper we derive the P abundance of moderately metal-poor ([Fe/H] ~-1) GC stars, aiming to check if the phenomenon could be related to the unusual multiple stellar populations found in most GCs. Here we present the detection of P-moderately enhanced stars among two out of seven bulge GCs (Tonantzintla 1, and NGC 6316_, with metallicities similar to those of the bulge field P-rich stars. Using H-band high-resolution (R~22,500) spectra from the APOGEE-2 survey, we present the first high-resolution abundance analysis of [P/Fe] from the PI 16482.932 A line in a sample of selected bulge GCs. We find that all P-rich stars tend to also be N-rich, that hints at the origin of P-rich stars as second-generation stars in GCs. However no other correlations of P and other elements are found, that are usually indicators of second-generation stars. Further studies with larger samples and comparisons with field stars will be needed before any firm conclusions are drawn.
We propose a numerical method to efficiently compute quantum generating functions (QGF) for a wide class of observables in one-dimensional quantum systems at high temperature. We obtain high-accuracy estimates for the cumulants and reconstruct full counting statistics from the QGF. We demonstrate its potential on spin S=1/2S=1/2 anisotropic Heisenberg chain, where we can reach time scales hitherto inaccessible to state-of-the-art classical and quantum simulations. Our results challenge the conjecture of the Kardar--Parisi--Zhang universality for isotropic integrable quantum spin chains.
We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star V410 Tau based on data collected mostly with SPIRou, the near-infrared (NIR) spectropolarimeter recently installed at the Canada-France-Hawaii Telescope, as part of the SPIRou Legacy Survey large programme, and with TESS between October and December 2019. Using Zeeman-Doppler Imaging (ZDI), we obtained the first maps of photospheric brightness and large-scale magnetic field at the surface of this young star derived from NIR spectropolarimetric data. For the first time, ZDI is also simultaneously applied to high-resolution spectropolarimetric data and very-high-precision photometry. V410 Tau hosts both dark and bright surface features and magnetic regions similar to those previously imaged with ZDI from optical data, except for the absence of a prominent dark polar spot. The brightness distribution is significantly less contrasted than its optical equivalent, as expected from the difference in wavelength. The large-scale magnetic field (~410 G), found to be mainly poloidal, features a dipole of ~390 G, again compatible with previous studies at optical wavelengths. NIR data yield a surface differential rotation slightly weaker than that estimated in the optical at previous epochs. Finally, we measured the radial velocity of the star and filtered out the stellar activity jitter using both ZDI and Gaussian Process Regression down to a precision of ~0.15 and 0.08 kms1\mathrm{km\,s^{-1}} RMS, respectively, confirming the previously published upper limit on the mass of a potential close-in massive planet around V410 Tau.
In this paper we present the "Small Bodies: Near and Far" Infrared Database, an easy-to-use tool intended to facilitate the modeling of thermal emission of small Solar System bodies. Our database collects thermal emission measurements of small Solar Systems targets that are otherwise available in scattered sources and gives a complete description of the data, with all information necessary to perform direct scientific analyses and without the need to access additional, external resources. This public database contains representative data of asteroid observations of large surveys (e.g. AKARI, IRAS and WISE) as well as a collection of small body observations of infrared space telescopes (e.g. the Herschel Space Observatory) and provides a web interface to access this data (this https URL). We also provide an example for the direct application of the database and show how it can be used to estimate the thermal inertia of specific populations, e.g. asteroids within a given size range. We show how different scalings of thermal inertia with heliocentric distance (i.e. temperature) may affect our interpretation of the data and discuss why the widely-used radiative conductivity exponent (α\alpha=-3/4) might not be adequate in general, as hinted by previous studies.
Intermediate Mass Black Hole (IMBH) mergers with masses 10410610^4 - 10^6 MM_{\odot} are expected to produce gravitational waves (GWs) detectable by the Laser Interferometer Space Antenna (LISA) with high signal to noise ratios out to redshift 20. IMBH mergers are expected to take place within dwarf galaxies, however, the dynamics, timescales, and effect on their hosts are largely unexplored. In a previous study, we examined how IMBHs would pair and merge within nucleated dwarf galaxies. IMBHs in nucleated hosts evolve very efficiently, forming a binary system and coalescing within a few hundred million years. Although the fraction of dwarf galaxies (10710^7 M_{\odot} \leq M1010M_{\star} \leq 10^{10} M_{\odot}) hosting nuclear star clusters is between 60-100\%, this fraction drops to 20-70\% for lower-mass dwarfs (M107M_{\star}\approx 10^7 M_{\odot}), with the largest drop in low-density environments. Here, we extend our previous study by performing direct NN-body simulations to explore the dynamics and evolution of IMBHs within non-nucleated dwarf galaxies, under the assumption that IMBHs exist within these dwarfs. To our surprise, none of IMBHs in our simulation suite merge within a Hubble time, despite many attaining high eccentricities e0.70.95e \sim 0.7-0.95. We conclude that extremely low stellar density environments in the centers of non-nucleated dwarfs do not provide an ample supply of stars to interact with IMBHs binary resulting in its stalling, in spite of triaxiality and high eccentricity, common means to drive a binary to coalescence. Our findings underline the importance of considering all detailed host properties to predict IMBH merger rates for LISA.
Researchers applied the Functional Renormalization Group (FRG) to Active Model B+ (AMB+) to investigate scaling behaviors and phase transitions in active matter. The study indicates that microphase separation is a first-order transition and challenges prior understandings of bulk phase separation by showing the F4 fixed point is disconnected from the Wilson-Fisher fixed point in this nonperturbative framework.
This paper presents a safety-critical control framework to maintain bounded lateral motions for vehicles braking on asymmetric surfaces. We synthesize a brake controller that assists drivers and guarantees safety against excessive lateral motions (i.e., prevents the vehicle from spinning out) while minimizing the stopping distance. We address this safety-critical control problem in the presence of input constraints, since braking forces are limited by the available friction on the road. We use backup control barrier functions for safe control design. As this approach requires the construction of a backup set and a backup controller, we propose a novel, systematic method to creating valid backup set-backup controller pairs based on feedback linearization and continuous-time Lyapunov equations. We use simple examples to demonstrate our proposed safety-critical control method. Finally, we implement our approach on a four-wheel vehicle model for braking on asymmetric surfaces and present simulation results.
The Rosette complex is a well studied region of the galactic plane which presents the apparent characteristics of a triggered star forming region. This is however still debated as no strong evidence corroborates this statement. We focus on characterizing the young stellar population in the Rosette complex to improve our understanding of the processes that regulate the star formation in this region. We propose an original method that relies on the joint analysis of the star color and density in the near-infrared. It leads to mapping the molecular cloud spatial distribution and detecting the embedded clusters with their characterization in terms of member number and age estimation. We have identified 13 clusters, 2 of which are new discoveries, and we estimate that the total number of young stellar objects in the Rosette ranges between 4000 and 8000 members. We find that the age distribution of the young clusters is not consistent with a general triggered scenario for the star formation in this molecular cloud. This study proves that the Rosette complex evolution is not governed by the influence of its OB star population. It suggests that the simple morphological appearance of an active region is not sufficient to conclude much about the triggering role in the star formation process. Our method of constraining the cluster properties using UKIDSS and WISE data has proven efficient, and studies of other regions of the galactic plane would definitely benefit from this approach.
Context. The dust and gas temperature in proto-planetary disks play critical roles in determining their chemical evolution and influencing planet formation processes. Aims. We attempted an accurate measurement of the dust and CO temperature profile in the edge-on disk of the Flying Saucer. Methods. We used the unique properties of the Flying Saucer, its edge-on geometry and its fortunate position in front of CO clouds with different brightness temperatures to provide independent constraints on the dust temperature. We compared it with the dust temperature derived using the radiative transfer code DiskFit and the CO gas temperature. Results. We find clear evidence for a substantial gas temperature vertical gradient, with a cold (10 K) disk mid-plane and a warmer CO layer where T(r) is 27 K at 100 au, dropping with exponent 0.3. Direct evidence for CO depletion in the mid-plane, below about 1 scale height, is also found. At this height, the gas temperature is 15-20 K, consistent with the expected CO freeze out temperature. The dust disk appears optically thin at 345 GHz, and exhibits moderate settling.
The composition of the solar corona differs from that of the photosphere, with the plasma thought to fractionate in the solar chromosphere according to the First Ionisation Potential (FIP) of the different elements. This produces a FIP bias, wherein elements with a low FIP are preferentially enhanced in the corona compared to their photospheric abundance, but direct observations of this process remain elusive. Here we use a series of spectroscopic observations of Active Region AR 12759 as it transited the solar disc over a period of 6 days from 2-7 April 2020 taken using the Hinode Extreme ultraviolet Imaging Spectrometer (EIS) and Interface Region Imaging Spectrograph (IRIS) instruments to look for signatures of plasma fractionation in the solar chromosphere. Using the Si X/S X and Ca XIV/Ar XIV diagnostics, we find distinct differences between the FIP bias of the leading and following polarities of the active region. The widths of the IRIS Si IV lines exhibited clear differences between the leading and following polarity regions, indicating increased unresolved wave activity in the following polarity region compared to the leading polarity region, with the chromospheric velocities derived using the Mg II lines exhibiting comparable, albeit much weaker, behaviour. These results are consistent with plasma fractionation via resonant/non-resonant waves at different locations in the solar chromosphere following the ponderomotive force model, and indicate that IRIS could be used to further study this fundamental physical process.
We study finite temperature dynamical correlation functions of the magnetization operator in the one-dimensional Ising quantum field theory. Our approach is based on a finite temperature form factor series and on a Fredholm determinant representation of the correlators. While for space-like separations the Fredholm determinant can be efficiently evaluated numerically, for the time-like region it has convergence issues inherited from the form factor series. We develop a method to compute the correlation functions at time-like separations based on the analytic continuation of the space-time coordinates to complex values. Using this numerical technique, we explore all space-time and temperature regimes in both the ordered and disordered phases including short, large, and near-light-cone separations at low and high temperatures. We confirm the existing analytic predictions for the asymptotic behavior of the correlations except in the case of space-like correlations in the paramagnetic phase. For this case we derive a new closed form expression for the correlation length that has some unusual properties: it is a non-analytic function of both the space-time direction and the temperature, and its temperature dependence is non-monotonic.
We propose a numerical method to efficiently compute quantum generating functions (QGF) for a wide class of observables in one-dimensional quantum systems at high temperature. We obtain high-accuracy estimates for the cumulants and reconstruct full counting statistics from the QGF. We demonstrate its potential on spin S=1/2S=1/2 anisotropic Heisenberg chain, where we can reach time scales hitherto inaccessible to state-of-the-art classical and quantum simulations. Our results challenge the conjecture of the Kardar--Parisi--Zhang universality for isotropic integrable quantum spin chains.
Few spectra of directly-imaged exoplanets have been obtained in the mid-infrared (> 3 μ\mum). This region is particularly rich in molecular spectral signatures, whose measurements can help recover atmospheric parameters and provide a better understanding of giant planet formation and atmospheric dynamics. In the past years, exoplanet interferometry with the VLTI/GRAVITY instrument has provided medium-resolution spectra of a dozen substellar companions in the near infrared. The 100-meter interferometric baselines allow for the stellar and planetary signals to be efficiently disentangled at close angular separations (< 0.3''). We aim to extend this technique to the mid-infrared using MATISSE, the VLTI's mid-infrared spectro-interferometer. We take advantage of the fringe tracking and off-axis pointing capabilities recently brought by the GRA4MAT upgrade. Using this new mode, we observed the giant planet β\beta Pictoris b in L and M bands (2.75-5 μ\mum) at a spectral resolution of 500. We developed a method to correct chromatic dispersion and non-common paths effects in the fringe phase and modelled the planet astrometry and stellar contamination. We obtained a high-signal-to-noise spectrum of β\beta Pictoris b, showing the planet continuum in L (for the first time) and M bands, which contains broad absorption features of H2_2O and CO. In conjunction with a new GRAVITY spectrum, we modelled it with the ForMoSA nested sampling tool and the Exo-REM grid of atmospheric models, and found a solar carbon-to-oxygen ratio in the planet atmosphere. This study opens the way to the characterization of fainter and closer-in planets with MATISSE, which could complement the JWST at angular separations too close for it to obtain exoplanet spectra. Starting in 2025, the new adaptive optics system brought by the GRAVITY+ upgrade will further extend the detection limits of MATISSE.
We present a new technique to generate the light curves of RRab stars in different photometric bands (II and VV bands) using Artificial Neural Networks (ANN). A pre-computed grid of models was used to train the ANN, and the architecture was tuned using the II band light curves. The best-performing network was adopted to make the final interpolators in the II and VV bands. The trained interpolators were used to predict the light curve of RRab stars in the Magellanic Clouds, and the distances to the LMC and SMC were determined based on the reddening independent Wesenheit index. The estimated distances are in good agreement with the literature. The comparison of the predicted and observed amplitudes, and Fourier amplitude ratios showed good agreement, but the Fourier phase parameters displayed a few discrepancies. To showcase the utility of the interpolators, the light curve of the RRab star EZ Cnc was generated and compared with the observed light curve from the Kepler mission. The reported distance to EZ Cnc was found to be in excellent agreement with the updated parallax measurement from Gaia EDR3. Our ANN interpolator provides a fast and efficient technique to generate a smooth grid of model light curves for a wide range of physical parameters, which is computationally expensive and time-consuming using stellar pulsation codes.
Long-lived radioactive nuclides, such as 40^{40}K, 232^{232}Th, 235^{235}U and 238^{238}U, contribute to persistent heat production in the mantle of terrestrial-type planets. As refractory elements, the concentrations of Th and U in a terrestrial exoplanet are implicitly reflected in the photospheric abundances in the stellar host. However, a robust determination of these stellar abundances is difficult in practice owing to the general paucity and weakness of the relevant spectral features. We draw attention to the refractory, rr-process element europium, which may be used as a convenient and practical proxy for the population analysis of radiogenic heating in exoplanetary systems. As a case study, we present a determination of Eu abundances in the photospheres of α\alpha Cen A and B. We find that europium is depleted with respect to iron by \sim 0.1 dex and to silicon by \sim 0.15 dex compared to solar in both binary components. To first order, the measured Eu abundances can be converted to the abundances of 232^{232}Th, 235^{235}U and 238^{238}U with observational constraints while the abundance of 40^{40}K is approximated independently with a Galactic chemical evolution model. We find that the radiogenic heat budget in an α\alpha-Cen-Earth is 73.46.9+8.373.4^{+8.3}_{-6.9} TW upon its formation and 8.81.3+1.78.8^{+1.7}_{-1.3} TW at the present day, respectively 23±523\pm5 % and 54±554\pm5 % lower than that in the Hadean and modern Earth. As a consequence, mantle convection in an α\alpha-Cen-Earth is expected to be overall weaker than that of the Earth (assuming other conditions are the same) and thus such a planet would be less geologically active, suppressing its long-term potential to recycle its crust and volatiles. With Eu abundances being available for a large sample of Sun-like stars, the proposed approach can extend our ability to make predictions about the nature of other rocky worlds.
Lattice vibrations are highly sensitive to crystal symmetries and their changes across phase transitions. The latter can modify irreducible (co)representations and corresponding infrared and Raman selection rules of phonons. This concept is established for relativistic magnetic point groups, simultaneously transforming spatial and spin coordinates. However, in altermagnets described by non-relativistic spin groups with disjunct symmetry operations for both vector spaces, the phonon selection rules have remained unexplored. Here, we present a detailed study of the infrared- and Raman-active modes in the collinear antiferromagnet and altermagnet candidate Co2_2Mo3_3O8_8. Comparing to ab initio calculations accurately capturing the eigenfrequencies, we identify all expected phonon modes at room temperature and deduce their selection rules using both symmetry approaches. Importantly, we observe the change of selection rules upon antiferromagnetic ordering, agreeing with the relativistic symmetry approach, while the spin group formalism predicts no changes. Therefore, optical phonons can reveal the appropriate symmetry treatment.
Aims. We introduce a novel way to identify new compact hierarchical triple stars by exploiting the huge potential of Gaia DR3 and also its future data releases. We aim to increase the current number of compact hierarchical triples significantly. Methods. We utilize several eclipsing binary catalogs from different sky surveys totaling more than 1 million targets for which we search for Gaia DR3 Non-single Star orbital solutions with periods substantially longer than the eclipsing periods of the binaries. Those solutions in most cases should belong to outer orbits of tertiary stars in those systems. We also try to validate some of our best-suited candidates using TESS eclipse timing variations. Results. We find 403 objects with suitable Gaia orbital solutions of which 27 are already known triple systems. This makes 376 newly identified hierarchical triple system candidates in our sample. We analyze the cumulative probability distribution of the outer orbit eccentricities and find that it is very similar to the ones found by earlier studies based on the observations of the Kepler and OGLE missions. We found measurable non-linear eclipse timing variations or third-body eclipses in the TESS data for 192 objects which we also consider to be confirmed candidates. Out of these, we construct analytical light-travel time effect models for the eclipse timing variations of 22 objects with well-sampled TESS observations. We compare the outer orbital parameters from our solutions with the ones from the Gaia solutions and find that the most reliable orbital parameter is the orbital period, while the values of the other parameters should be used with caution.
Blue large-amplitude pulsators (BLAPs) are a recently discovered group of hot pulsating stars whose evolutionary status remains uncertain. Their supposed progenitors are either 0.3M\simeq 0.3M_{\odot} shell H-burning stars or 1.0M\simeq 1.0M_{\odot} core He-burning stars, both relying on mass loss or a merger event in a (rarely observed) close interacting binary system. With the goal to understand the stellar masses of BLAPs, we therefore carried out a linear non-adiabatic analysis of a grid of models computed using mesa-rsp, with appropriate input stellar parameters ZXMLTeffZXMLT_{\rm eff} and convection parameter sets. We discuss the impact of stellar mass, metallicity, helium abundance and convection parameters on the theoretical instability regions of BLAPs. We also derive new theoretical period relations; our theoretical period relations using low stellar masses seem to be in better agreement with the observed period relations. Although only two BLAPS have been observed to be multi-periodic oscillator so far, we analyse theoretical P1O/PFP_{1O}/P_F ratios and compare these values with other classical pulsators. Furthermore, we provide the first asteroseismic mass estimate for the triple-mode pulsator, OGLE-BLAP-030 which seems to be well-constrained in the range of 0.620.64M0.62-0.64 M_{\odot} with a high metallicity of Z=0.07Z=0.07, albeit with a few sources of uncertainty involved. This would place the BLAP star intermediate to the two proposed mass scenarios so far.
We have discovered a triply eclipsing triple-star system, TIC 290061484, with the shortest known outer period, Pout, of only 24.5 days. This "eclipses" the previous record set by lambda Tauri at 33.02 days, which held for 68 yr. The inner binary, with an orbital period of Pin = 1.8 days, produces primary and secondary eclipses and exhibits prominent eclipse timing variations with the same periodicity as the outer orbit. The tertiary star eclipses, and is eclipsed by, the inner binary with pronounced asymmetric profiles. The inclinations of both orbits evolve on observable timescales such that the third-body eclipses exhibit dramatic depth variations in TESS data. A photodynamical model provides a complete solution for all orbital and physical parameters of the triple system, showing that the three stars have masses of 6.85, 6.11, and 7.90 MSun, radii near those corresponding to the main sequence, and Teff in the range of 21,000-23,700 K. Remarkably, the model shows that the triple is in fact a subsystem of a hierarchical 2+1+1 quadruple with a distant fourth star. The outermost star has a period of ~3200 days and a mass comparable to the stars in the inner triple. In ~20 Myr, all three components of the triple subsystem will merge, undergo a Type II supernova explosion, and leave a single remnant neutron star. At the time of writing, TIC 290061484 is the most compact triple system and one of the tighter known compact triples (i.e., Pout/Pin = 13.7).
Ultra-hot Jupiters present a unique opportunity to understand the physics and chemistry of planets at extreme conditions. WASP-12b stands out as an archetype of this class of exoplanets. We performed comprehensive analyses of the transits, occultations, and phase curves of WASP-12b by combining new CHEOPS observations with previous TESS and Spitzer data to measure the planet's tidal deformation, atmospheric properties, and orbital decay rate. The planet was modeled as a triaxial ellipsoid parameterized by the second-order fluid Love number, h2h_2, which quantifies its radial deformation and provides insight into the interior structure. We measured the tidal deformation of WASP-12b and estimated a Love number of h2=1.550.49+0.45h_2=1.55_{-0.49}^{+0.45} (at 3.2σ\sigma) from its phase curve. We measured occultation depths of 333±24333\pm24ppm and 493±29493\pm29ppm in the CHEOPS and TESS bands, respectively, while the dayside emission spectrum indicates that CHEOPS and TESS probe similar pressure levels in the atmosphere at a temperature of 2900K. We also estimated low geometric albedos of 0.086±0.0170.086\pm0.017 and 0.01±0.0230.01\pm0.023 in the CHEOPS and TESS passbands, respectively, suggesting the absence of reflective clouds in the dayside of the WASP-12b. The CHEOPS occultations do not show strong evidence for variability in the dayside atmosphere of the planet. Finally, we refine the orbital decay rate by 12% to a value of -30.23±\pm0.82 ms/yr. WASP-12b becomes the second exoplanet, after WASP-103b, for which the Love number has been measured (at 3sigmasigma) from the effect of tidal deformation in the light curve. However, constraining the core mass fraction of the planet requires measuring h2h_2 with a higher precision. This can be achieved with high signal-to-noise observations with JWST since the phase curve amplitude, and consequently the induced tidal deformation effect, is higher in the infrared.
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