Condensation Temperature Tc Research Articles

The largest metallicity difference in twin systems: High-precision abundance analysis of the benchmark pair Krios and Kronos

Aims. We conducted a high-precision differential abundance analysis of the remarkable binary system HD 240429/30 (Krios and Kronos, respectively), whose difference in metallicity is one of the highest detected to date in systems with similar components (~0.20 dex). A condensation temperature TC trend study was performed to search for possible chemical signatures of planet formation. In addition, other potential scenarios are proposed to explain this disparity. Methods. Fundamental atmospheric parameters (Teff, log g, [Fe/H], υturb) were calculated using the latest version of the FUNDPAR code in conjunction with ATLAS12 model atmospheres and the MOOG code, considering the Sun and then Kronos as references, employing high-resolution MAROON-X spectra. We applied a full line-by-line differential technique to measure the abundances of 26 elements in both stars with equivalent widths and spectral synthesis taking advantage of the non-solar-scaled opacities to achieve the highest precision. Results. We find a difference in metallicity of ~0.230 dex: Kronos is more metal rich than Krios. This result denotes a challenge for the chemical tagging method. The analysis encompassed the examination of the diffusion effect and primordial chemical differences, concluding that the observed chemical discrepancies in the binary system cannot be solely attributed to any of these processes. The results also show a noticeable excess of Li of approximately 0.56 dex in Kronos, and an enhancement of refractories with respect to Krios. A photometric study with TESS data was carried out, without finding any signal of possible transiting planets around the stars. Several potential planet formation scenarios were also explored to account for the observed excess in both metallicity and lithium in Kronos; none was definitively excluded. While planetary engulfment is a plausible explanation, considering the ingestion of an exceptionally high mass, approximately ~27.8 M⊕, no scenario is definitively ruled out. We emphasize the need for further investigations and refinements in modelling; indispensable for a comprehensive understanding of the intricate dynamics within the Krios and Kronos binary system.

Possibility of Exciton Bose-Einstein Condensation in CdSe Nanoplatelets.

The quasi-two-dimensional exciton subsystem in CdSe nanoplatelets is considered. It is theoretically shown that Bose-Einstein condensation (BEC) of excitons is possible at a nonzero temperature in the approximation of an ideal Bose gas and in the presence of an "energy gap" between the ground and the first excited states of the two-dimensional exciton center of inertia of the translational motion. The condensation temperature (Tc) increases with the width of the "gap" between the ground and the first excited levels of size quantization. It is shown that when the screening effect of free electrons and holes on bound excitons is considered, the BEC temperature of the exciton subsystem increases as compared to the case where this effect is absent. The energy spectrum of the exciton condensate in a CdSe nanoplate is calculated within the framework of the weakly nonideal Bose gas approximation, considering the specifics of two-dimensional Born scattering.

Condensation temperature of strongly interacting 39K condensates in the mean-field and semi-classical approximations

We consider the effect of inter-atom interactions on the condensation temperature Tc of an atomic Bose-Einstein condensate. We find an analytic expression of the shift in Tc induced by interactions with respect the ideal non-interacting case, in the mean-field and semi-classical approximations. Such a shift is expressed in terms of the ratio a/λTc between the s-wave scattering length a and the thermal wavelength λTc. This result is used to discuss the tension between mean-field predictions and observations in strongly interacting K39 condensates. It is shown that such a tension is solved taking into account the details of the Feshbach resonance used to tune a in the experiments.

Theoretical study on the application of isothermal compression technology in vapor‐compression refrigeration systems with an isothermal piston

AbstractVapor‐compression refrigeration systems are widely used in refrigeration equipment. Theoretically, the process is typically divided into two isobaric processes: an adiabatic isentropic compression process and adiabatic isentropic throttling process. The refrigeration compressor is the main energy‐consuming component in vapor‐compression refrigeration systems. However, this device has a large energy loss and low overall efficiency in the adiabatic isentropic compression process. In this study, a modified vapor‐compression refrigeration cycle with an isothermal piston is proposed to realize near‐isothermal compression of a refrigerator to significantly reduce the energy loss in the compression process and improve the system performance. A real‐gas compression process model is established, and the heat transfer index Hex is set. By changing the heat transfer index Hex, the performances of the vapor‐compression refrigeration system under ideal and real compression conditions are compared and analyzed. Compared with a traditional vapor‐compression refrigeration system, the coefficient of performance of the compressor with an isothermal compression process is increased by approximately 17%. The results also demonstrate that the lower the evaporation temperature Te and higher the condensation temperature Tc, the greater the optimization effect of the isothermal compression.

Revisiting the 16 Cygni planet host at unprecedented precision and exploring automated tools for precise abundances

The binary system 16 Cygni is key in studies of the planet-star chemical composition connection, as only one of the stars is known to host a planet. This allows us to better assess the possible influence of planet interactions on the chemical composition of stars that are born from the same cloud and thus should have a similar abundance pattern. In our previous work, we found clear abundance differences for elements with Z ≤ 30 between both components of this system and a trend of these abundances as a function of the condensation temperature (Tc), which suggests a spectral chemical signature related to planet formation. In this work we show that our previous findings are still consistent even if we include more species, such as the volatile N and neutron capture elements (Z > 30). We report a slope with Tc of 1.56 ± 0.24 × 10−5 dex K−1, that is good agreement with our previous work. We also performed some tests using ARES and iSpec to measure automatically the equivalent width and found Tc slopes in reasonable agreement with our results as well. In addition, we determined abundances for Li and Be by spectral synthesis, finding that 16 Cyg A is richer not only in Li but also in Be, when compared to its companion. This may be evidence of planet engulfment, indicating that the Tc trend found in this binary system may be a chemical signature of planet accretion in the A component, rather than an imprint of the giant planet rocky core formation on 16 Cyg B.

High-precision analysis of binary stars with planets

Aims. We explore for the first time the probable chemical signature of planet formation in the remarkable binary system HD 106515. Star A hosts a massive long-period planet with ~9 MJup detected by radial velocity, while there is no planet detected at the B star. We also refine stellar and planetary parameters by using non-solar-scaled opacities when modelling the stars. Methods. We carried out a simultaneous determination of stellar parameters and abundances by applying for the first time non-solar-scaled opacities in this binary system, in order to reach the highest possible precision. We used a line-by-line strictly differential approach, using the Sun and then the A star as reference. Stellar parameters were determined by imposing an ionization and excitation balance of Fe lines, with an updated version of the FUNDPAR program, ATLAS12 model atmospheres, and the MOOG code. Opacities for an arbitrary composition were calculated through the opacity sampling method. The chemical patterns were compared with solar-twins condensation temperature Tc trends from the literature and also mutually between both stars. We take the opportunity to compare and discuss the results of the classical solar-scaled method and the high-precision procedure applied here. Results. Stars A and B in the binary system HD 106515 do not seem to be depleted in refractory elements, which is different when comparing the Sun with solar twins. The terrestrial planet formation would have been less efficient in the stars of this binary system. Together with HD 80606/7, this is the second binary system that does not seem to present a (terrestrial) signature of planet formation, when both systems host an eccentric giant planet. This is in agreement with numerical simulations, where the early dynamical evolution of eccentric giant planets clears out most of the possible terrestrial planets in the inner zone. We refined the stellar mass, radius, and age for both stars and found a notable difference of ~78% in R⋆ compared to previous works. We also refined the planet mass to mp sini = 9.08 ± 0.20 MJup, which differs by ~6% compared with the literature. In addition, we showed that the non-solar-scaled solution is not compatible with the classical solar-scaled method, and some abundance differences are comparable to non-local thermodynamic equilibrium (NLTE) or galactic chemical evolution (GCE) effects especially when using the Sun as reference. Therefore, we encourage the use of non-solar-scaled opacities in high-precision studies such as the detection of Tc trends.

Measurement and modeling the gas/particle partitioning of organochlorine pesticides (OCPs) in atmosphere at low temperatures

The gas/particle (G/P) partition of organochlorine pesticides (OCPs) has been widely investigated and well documented, but rare at low temperature. In this study, seventy-four pairs of air samples in two sampling sites in northeastern China at a wide ambient temperature range of ~63 °C (−40 to +23 °C) were simultaneously collected in both gaseous and particulate phases and eighteen OCPs in these samples were measured and analyzed, among which, partition quotient (KP) values for fifteen OCPs were determined. Seven models including those have never been used for OCPs were applied to predict the values of KP, and the results were compared with the monitoring data for the fifteen OCPs. It was found out that, L-M-Y model provided advantages over the other models, with the best agreement to the monitoring data for analyzed OCPs (90.1 ± 11.1% data points within ±1 log unit, RMSE: 0.53 ± 0.18). The predicted maximum partition (MP) domain for eleven OCPs was observed with high values of their logarithm of octanol-air partition coefficient (log KOA > 12.5), where the log KP values become a constant (−1.53), indicating that the G/P partition of OCPs is in steady state but not the equilibrium. The Li-Ma-Yang (L-M-Y model) model, considering the wet and dry depositions of particles, elucidates the necessity of non-equilibrium term for the OCPs at low temperature. These results indicate that the L-M-Y model is valid for OCPs, which renders it highly promising for describing the partition behaviors in atmosphere for SVOCs, particularly at low temperature. An equation to calculate the condensation temperature TC was also derived, which gave a new understanding on the situation of chemicals with equal distribution between gaseous and particulate phases of OCPs and other similar SVOCs, especially in Polar Regions.

Performance comparison of two absorption-compression hybrid refrigeration systems using R1234yf/ionic liquid as working pair

R1234yf (2,3,3,3-tetrafluoroprop-1-ene)/ionic liquid is a kind of environment-friendly working pair, which can overcome the disadvantages of H2O/LiBr and NH3/H2O. In this work, three new working pairs R1234yf/[HMIM][TfO], R1234yf/[HMIM][PF6], R1234yf/[HMIM][BF4] were proposed and new solubility data for them were determined. Two new absorption-compression hybrid refrigeration systems were proposed to improve the cooling performances of the single-effect absorption refrigeration system using R1234yf/[HMIM][TfO], R1234yf/[HMIM][PF6] and R1234yf/[HMIM][BF4] as working pair. The effects of compressor position, compression ratio (r), generation temperature (Tg), evaporation temperature (Te), condensation temperature (Tc) and absorption temperature (Ta) on the coefficient of performance (COP) and circulation ratio (f) were analyzed. Comparison result shows that the two systems can effectively improve the cooling performance of the single-effect absorption refrigeration system including increasing COP, reducing the heat load of condenser and f, and enlarge the operation range of Tg, Ta, and Te. Putting compressor between evaporator and absorber is a better choice than putting it between generator and condenser. R1234yf/[HMIM][TfO] shows better cooling performance than R1234yf/[HMIM][PF6] and R1234yf/[HMIM][BF4] due to its favorable thermophysical properties.

Using non-solar-scaled opacities to derive stellar parameters

Aims. In an effort to improve spectroscopic methods of stellar parameters determination, we implemented non-solar-scaled opacities in a simultaneous derivation of fundamental parameters and abundances. We wanted to compare the results with the usual solar-scaled method using a sample of solar-type and evolved stars. Methods. We carried out a high-precision determination of stellar parameters and abundances by applying non-solar-scaled opacities and model atmospheres. Our sample is composed of 20 stars, including main sequence and evolved objects. The stellar parameters were determined by imposing ionization and excitation equilibrium of Fe lines, with an updated version of the FUNDPAR program, together with plane-parallel ATLAS12 model atmospheres and the MOOG code. Opacities for an arbitrary composition and vmicro were calculated through the opacity sampling (OS) method. We used solar-scaled models in the first step, and then continued the process, but scaled to the abundance values found in the previous step (i.e. non-solar-scaled). The process finishes when the stellar parameters of one step are the same as in the previous step, i.e. we use a doubly iterated method. Results. We obtained a small difference in stellar parameters derived with non-solar-scaled opacities compared to classical solar-scaled models. The differences in Teff, log g, and [Fe/H] amount to 26 K, 0.05 dex, and 0.020 dex for the stars in our sample. These differences can be considered the first estimation of the error due to the use of classical solar-scaled opacities to derive stellar parameters with solar-type and evolved stars. We note that some chemical species could also show an individual variation greater than those of the [Fe/H] (up to ~0.03 dex) and varying from one species to another, obtaining a chemical pattern difference between the two methods. This means that condensation temperature Tc trends could also present a variation. We include an example showing that using non-solar-scaled opacities, the solution found with the classical solar-scaled method indeed cannot always verify the excitation and ionization balance conditions required for a model atmosphere. We discuss in the text the significance of the differences obtained when using solar-scaled versus non-solar-scaled methods. Conclusions. We consider that the use of the non-solar-scaled opacities is not mandatory in every statistical study with large samples of stars. However, for those high-precision works whose results depend on the mutual comparison of different chemical species (such as the analysis of condensation temperature Tc trends), we consider its application to be worthwhile. To date, this is probably one of the most precise spectroscopic methods for stellar parameter derivation.

High-precision abundances of elements inKeplerLEGACY stars

HARPS-N spectra with S/N > 250 and MARCS model atmospheres were used to derive abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, and Y in ten stars from the Kepler LEGACY sample (including the binary pair 16 Cyg A and B) selected to have metallicities in the range -0.15 < [Fe/H] < +0.15 and ages between 1 and 7 Gyr. Stellar gravities were obtained from seismic data and effective temperatures were determined by comparing non-LTE iron abundances derived from FeI and FeII lines. Available non-LTE corrections were also applied when deriving abundances of the other elements. The results support the [X/Fe]-age relations previously found for solar twins. [Mg/Fe], [Al/Fe], and [Zn/Fe] decrease by ~0.1 dex over the lifetime of the Galactic thin disk due to delayed contribution of iron from Type Ia supernovae relative to prompt production of Mg, Al, and Zn in Type II supernovae. [Y/Mg] and [Y/Al], on the other hand, increase by ~0.3 dex, which can be explained by an increasing contribution of s-process elements from low-mass AGB stars as time goes on. The trends of [C/Fe] and [O/Fe] are more complicated due to variations of the ratio between refractory and volatile elements among stars of similar age. Two stars with about the same age as the Sun show very different trends of [X/H] as a function of elemental condensation temperature Tc and for 16 Cyg, the two components have an abundance difference, which increases with Tc. These anomalies may be connected to planet-star interactions.

Experimental study of organic Rankine cycle in the presence of non-condensable gases

Non-condensable gases (NCGs) are inevitable in organic Rankine cycle (ORC) system, and they have adverse impacts. A small-scale ORC test platform using scroll expander and R123 was constructed to investigate the NCGs effect. The expander backpressure (i.e. condenser outlet pressure) and electricity output were examined on different conditions of NCGs mass fraction (xNCG), hot side temperature (Th) and condensation temperature (Tc). Two new parameters, namely reduced coefficient of pressure ratio (RCOPR) and filling ratio of reservoir (FROR), were proposed to reveal the mechanism of ORC performance degradation in the presence of NCGs. The results show that the partial pressure of NCGs (PNCG) in reservoir at work differed from that at static state. Unlike R123, NCGs were blocked by the reservoir and had no access to the pump. The accumulation of NCGs led to unexpected expander backpressure, which could be 0.68 bar higher than the saturation pressure when Th = 140 °C, Tc = 50 °C and xNCG = 1.3%. PNCG generally increased as FROR rose. The FROR changed with Th, Tc and R123 mass flow rate. The relative increment in electricity output of the ORC with xNCG = 1.3% over that with xNCG = 12% was significant, and could reach 114% when Th = 100 °C and Tc = 50 °C.

Signatures of rocky planet engulfment in HAT-P-4

Aims. To explore the possible chemical signature of planet formation in the binary system HAT-P-4, by studying abundance vs condensation temperature Tc trends. The star HAT-P-4 hosts a planet detected by transits while its stellar companion does not have any detected planet. We also study the Lithium content, which could shed light on the problem of Li depletion in exoplanet host stars. Conclusions. The exoplanet host star HAT-P-4 is found to be ~0.1 dex more metal rich than its companion, which is one of the highest differences in metallicity observed in similar systems. This could have important implications for chemical tagging studies, disentangling groups of stars with a common origin. We rule out a possible peculiar composition for each star as lambda Boo, delta Scuti or a Blue Straggler. The star HAT-P-4 is enhanced in refractory elements relative to volatile when compared to its stellar companion. Notably, the Lithium abundance in HAT-P-4 is greater than in its companion by ~0.3 dex, which is contrary to the model that explains the Lithium depletion by the presence of planets. We propose a scenario where, at the time of planet formation, the star HAT-P-4 locked the inner refractory material in planetesimals and rocky planets, and formed the outer gas giant planet at a greater distance. The refractories were then accreted onto the star, possibly due to the migration of the giant planet. This explains the higher metallicity, the higher Lithium content, and the negative Tc trend detected. A similar scenario was recently proposed for the solar twin star HIP 68468, which is in some aspects similar to HAT-P-4. We estimate a mass of at least Mrock ~ 10 Mearth locked in refractory material in order to reproduce the observed Tc trends and metallicity.

Evolved stars and the origin of abundance trends in planet hosts

Tentative evidence that the properties of evolved stars with planets may be different from what we know for MS hosts has been recently reported. We aim to test whether evolved stars with planets show any chemical peculiarity that could be related to the planet formation process. We determine in a consistent way the metallicity and individual abundances of a large sample of evolved (subgiants and red giants) and MS stars with and without known planetary companions. No differences in the <[X/Fe]> vs. condensation temperature (Tc) slopes are found between the samples of planet and non-planet hosts when all elements are considered. However, if the analysis is restricted to only refractory elements, differences in the Tc-slopes between stars with and without known planets are found. This result is found to be dependent on the stellar evolutionary stage, as it holds for MS and subgiant stars, while there seem to be no difference between planet and non-planet hosts among the sample of giants. A search for correlations between the Tc-slope and the stellar properties reveals significant correlations with the stellar mass and the stellar age. The data also suggest that differences in terms of mass and age between MS planet and non-planet hosts may be present. Our results are well explained by radial mixing in the Galaxy. The sample of giant contains stars more massive and younger than their MS counterparts. This leads to a sample of stars possibly less contaminated by stars not born in the solar neighbourhood, leading to no chemical differences between planet and non planet hosts. The sample of MS stars may contain more stars from the outer disc (specially the non-planet host sample) which might led to the differences observed in the chemical trends.

Temperature condensation trend in the debris-disk binary systemζ2Reticuli

We explore condensation temperature Tc trends in the unique binary system Zet1 Ret - Zet2 Ret, to determine whether there is a depletion of refractories, which could be related to the planet formation process. The star Zet2 Ret hosts a debris disk which was detected by an IR excess and confirmed by direct imaging and numerical simulations, while Zet1 Ret does not present IR excess nor planets. We carried out a high-precision abundance determination in both components of the binary system via a line-by-line, strictly differential approach. The stellar parameters Teff , log g, [Fe/H] and vturb were determined by imposing differential ionization and excitation equilibrium of Fe I and Fe II lines, with an updated version of the program FUNDPAR. The star Zet1 Ret resulted slightly more metal rich than Zet2 Ret by 0.02 dex. In the differential calculation of Zet1 Ret using Zet2 Ret as reference, the abundances of the refractory elements resulted higher than the volatile elements, and the trend of the refractory elements with Tc showed a positive slope. These facts together show a lack of refractory elements in Zet2 Ret (a debris-disk host) relative to Zet1 Ret. The Tc trend would be in agreement with the proposed signature of planet formation (Melendez et al. 2009) rather than possible Galactic Chemical Evolution or age effects, which are largely diminished here. Then, following the interpretation of Melendez et al. (2009), we propose an scenario in which the refractory elements depleted in Zet2 Ret are possibly locked-up in the rocky material that orbits this star and produce the debris disk observed around this object. We estimated a lower limit of Mrock = 3 Me for the rocky mass of depleted material, which is compatible with a rough estimation of 3-50 Me of a debris disk mass around a solar-type star (Krivov et al. 2008). (abridged)

Methane Adsorption in Model Mesoporous Material, SBA-15, Studied by Small-Angle Neutron Scattering

The understanding of methane adsorption is important for many industrial applications, especially for the shale gas production, where it is critical to understand the adsorption/desorption of methane in pores even as small as a few nanometers. Using small-angle neutron scattering (SANS), we have studied the adsorption of deuterated methane (CD4) into one model mesoporous material, SBA-15, with pore diameter approximately 6.8 nm at the temperature range from 20 to 295 K at low pressure (≈100 kPa). A new scattering model is developed to analyze the SANS patterns of gas adsorption in SBA-15. The surface roughness of the SBA-15 matrix is estimated. The gas adsorption behaviors on the surface regions are extracted from the fitting. The rough surface of the pores is found to retain a large amount of CD4 at the temperature above the capillary condensation temperature (Tc). At temperatures below Tc, the confined liquid and solid methane are estimated to be less dense than the corresponding bulk liquid and solid m...

HD 80606: searching for the chemical signature of planet formation

(Abridged) Binary systems with similar components are ideal laboratories which allow several physical processes to be tested, such as the possible chemical pattern imprinted by the planet formation process. Aims. We explore the probable chemical signature of planet formation in the remarkable binary system HD 80606 - HD 80607. The star HD 80606 hosts a giant planet with 4 MJup detected by both transit and radial velocity techniques, being one of the most eccentric planets detected to date. We study condensation temperature Tc trends of volatile and refractory element abundances to determine whether there is a depletion of refractories that could be related to the terrestrial planet formation. Methods. We carried out a high-precision abundance determination in both components of the binary system, using a line-by-line strictly differential approach, using the Sun as a reference and then using HD 80606 as reference. We used an updated version of the program FUNDPAR, together with ATLAS9 model atmospheres and the MOOG code. Conclusions. From the study of Tc trends, we concluded that the stars HD 80606 and HD 80607 do not seem to be depleted in refractory elements, which is different for the case of the Sun. Then, the terrestrial planet formation would have been less efficient in the components of this binary system than in the Sun. The lack of a trend for refractory elements with Tc between both stars implies that the presence of a giant planet do not neccesarily imprint a chemical signature in their host stars, similar to the recent result of Liu et al. (2014). This is also in agreement with Melendez et al. (2009), who suggest that the presence of close-in giant planets might prevent the formation of terrestrial planets. Finally, we speculate about a possible planet around the star HD 80607.

Multi-objective optimization of evaporation and condensation temperatures for subcritical organic Rankine cycle

A multi-objective function F(X) by the incorporation of single-objective functions, i.e., net power output Wnet, exergy drop of the exhaust gas from inlet to outlet ΔEg, total exergy destruction rate I and system total cost C2013, has been put forward as the subcritical organic Rankine cycle (ORC) performance indicator and solved with the method of linear weighted evaluation function. The optimization of the evaporation temperature Te and condensation temperature Tc of subcritical ORC has been carried out by the use of pure working fluids R600a, R245fa, R601a, R601, R123, and non-azeotropic mixed working fluids R600a/R601a, R245fa/R601a, R245fa/R601, R600a/R245fa. The results reveal that there exist optimal evaporation temperature Te,opt and condensation temperature Tc,opt minimizing the multi-objective function F(X); while Te,opt and Tc,opt can not exactly exist when choosing single-objective functions, i.e., Wnet, I, C2013 and ΔEg as the performance indicators. Although Te,opt and Tc,opt vary with different working fluids, the ORC performance of mixed working fluids is not always better than that of pure working fluids. The multi-objective optimization of ORC shows superiority to the single-objective optimization, owning to its pursuit of the best comprehensive performance.

A toy climate model for Mars

A “toy climate model” TCM was constructed for Mars. It returns the midday surface and near-surface air temperatures, given the orbital parameters, season (Ls), latitude, thermal inertia, albedo, surface pressure and dust visible optical depth (τ). The TCM is based on the surface energy balance with radiation terms calibrated against line-by-line calculations and surface heat flux terms against 1D model simulations. The TCM air temperatures match various lander observations reasonably well, e.g. the 3.4 martian years of recovered T1.6m from Viking Lander 1.The results demonstrate strong sensitivity of Ts and T1.6m to the dust load. All the VL1 years suggest major dust storms around Ls 270–300°, while τ appears only moderate in the simultaneous VL2 observations. The TCM was further extended to increased surface pressures, using moist 1D simulations. The greenhouse warming remained modest and the diurnal range was small in a thick CO2 atmosphere. As the CO2 condensation temperature Tc increases rapidly with pressure, the range of afternoon temperatures at various latitudes remains quite narrow in a thick atmosphere. The TCM can also deal with orbital parameter variations. A high-eccentricity, high-obliquity case was demonstrated for the present 7mb (Tc 150K) and a 1bar CO2 atmosphere (Tc 195K). High obliquity of 45° led to quite wide winter polar ice caps, which extended down to the subtropics. In the 1bar case even the equatorial Ts was close to Tc at aphelion; a major dust storm at that time led to a tropical CO2 ice cover.

Trapped Bose–Einstein condensates with Planck-scale induced deformation of the energy–momentum dispersion relation

We show that harmonically trapped Bose–Einstein condensates can be used to constrain Planck-scale physics. In particular we prove that a Planck-scale induced deformation of the Minkowski energy–momentum dispersion relation δE≃ξ1mcp/2Mp produces a shift in the condensation temperature Tc of about ΔTc/Tc0≃10−6ξ1 for typical laboratory conditions. Such a shift allows to bound the deformation parameter up to |ξ1|≲104. Moreover we show that it is possible to enlarge ΔTc/Tc0 and improve the bound on ξ1 lowering the frequency of the harmonic trap. Finally we compare the Planck-scale induced shift in Tc with similar effects due to interboson interactions and finite size effects.

ELEMENTAL ABUNDANCE DIFFERENCES IN THE 16 CYGNI BINARY SYSTEM: A SIGNATURE OF GAS GIANT PLANET FORMATION?

The atmospheric parameters of the components of the 16Cygni binary system, in which the secondary has a gas giant planet detected, are measured accurately using high quality observational data. Abundances relative to solar are obtained for 25 elements with a mean error of 0.023 dex. The fact that 16CygA has about four times more lithium than 16CygB is normal considering the slightly different masses of the stars. The abundance patterns of 16CygA and B, relative to iron, are typical of that observed in most of the so-called solar twin stars, with the exception of the heavy elements (Z>30), which can, however, be explained by Galactic chemical evolution. Differential (A-B) abundances are measured with even higher precision (0.018 dex, on average). We find that 16CygA is more metal-rich than 16CygB by 0.041+/-0.007 dex. On an element-to-element basis, no correlation between the A-B abundance differences and dust condensation temperature (Tc) is detected. Based on these results, we conclude that if the process of planet formation around 16CygB is responsible for the observed abundance pattern, the formation of gas giants produces a constant downwards shift in the photospheric abundance of metals, without a Tc correlation. The latter would be produced by the formation of terrestrial planets instead, as suggested by other recent works on precise elemental abundances. Nevertheless, a scenario consistent with these observations requires the convective envelopes of 1 Msun stars to reach their present-day sizes about three times quicker than predicted by standard stellar evolution models.