Directed and elliptic flows of neutrons and light charged particles were measured for the reaction 197 Au+ 197 Au at 400 MeV/nucleon incident energy within the ASY-EOS experimental campaign at the GSI laboratory. The detection system consisted of the Large Area Neutron Detector LAND, combined with parts of the CHIMERA multidetector, of the ALADIN Time-of-flight Wall, and of the Washington-University Microball detector. The latter three arrays were used for the event characterization and reaction-plane reconstruction. In addition, an array of triple telescopes, KRATTA, 2 was used for complementary measurements of the isotopic composition and flows of light charged particles.From the comparison of the elliptic flow ratio of neutrons with respect to charged particles with UrQMD predictions, a value γ = 0.72 ± 0.19 is obtained for the power-law coefficient describing the density dependence of the potential part in the parametrization of the symmetry energy. It represents a new and more stringent constraint for the regime of supra-saturation density and confirms, with a considerably smaller uncertainty, the moderately soft to linear density dependence deduced from the earlier FOPI-LAND data. The densities probed are shown to reach beyond twice saturation.
We present three giant stars from the ongoing Penn State-Toruń Planet Search with the Hobby-Eberly Telescope, which exhibit radial velocity variations that point to a presence of planetary -mass companions around them. BD+49 828 is a M = 1.52 ± 0.22 M K0 giant with a m sin i = 1.6 +0.4 −0.2 M J minimum mass companion in a = 4.2 +0.32 −0.2 AU (2590 +300 −180 d), e = 0.35 +0.24 −0.10 orbit. HD 95127, a log L/L = 2.28 ± 0.38, R = 20 ± 9 R , M = 1.20 ± 0.22 M K0 giant has a msini=5.01 +0.61 −0.44 M J minimum mass companion in a = 1.28 +0.01 −0.01 AU (482 +5 −5 d), e = 0.11 +0.15 −0.06 orbit. Finally, HD 216536, is a M = 1.36 ± 0.38 M K0 giant with a m sin i = 1.47 +0.20 −0.12 M J minimum mass companion in a = 0.609 +0.002 −0.002 AU (148.6 +0.7−0.7 d), e = 0.38 +0.12 −0.10 orbit. Both, HD 95127 b and HD 216536 b in their compact orbits, are very close to the engulfment zone and hence prone to ingestion in the near future. BD+49 828 b is among the longest period planets detected with the radial velocity technique until now and it will remain unaffected by
Context. Lithium-rich giant stars are rare objects. For some of them, Li enrichment exceeds the abundance of this element found in solar system meteorites, suggesting that these stars have gone through a Li enhancement process. Aims. We identified a Li-rich giant HD 107028 with A(Li) > 3.3 in a sample of evolved stars observed within the PennState Toruń Planet Search. In this work we study different enhancement scenarios and we try to identify the one responsible for Li enrichment in HD 107028. Methods. We collected high-resolution spectra with three different instruments, covering different spectral ranges. We determined stellar parameters and abundances of selected elements with both equivalent width measurements and analysis, and spectral synthesis. We also collected multi-epoch high-precision radial velocities in an attempt to detect a companion. Results. Collected data show that HD 107028 is a star at the base of the red giant branch (RGB). Except for high Li abundance, we have not identified any other anomalies in its chemical composition, and there is no indication of a low-mass or stellar companion. We exclude Li production at the luminosity function bump on the RGB as the effective temperature and luminosity suggest that the evolutionary state is much earlier than the RGB bump. We also cannot confirm the Li enhancement by contamination as we do not observe any anomalies that are associated with this scenario. Conclusions. After evaluating various scenarios of Li enhancement we conclude that the Li-overabundance of HD 107028 originates from main-sequence evolution, and may be caused by diffusion processes.
Context. Stars that have evolved off the main sequence are crucial for expanding the frontiers of knowledge on exoplanets toward higher stellar masses and for constraining star-planet interaction mechanisms. These stars have an intrinsic activity, however, which complicates the interpretation of precise radial velocity (RV) measurements, and therefore they are often avoided in planet searches. Over the past ten years, we have monitored about 1000 evolved stars for RV variations in search for low-mass companions under the Penn State -Toruń Centre for Astronomy Planet Search program with the Hobby-Eberly Telescope. Selected prospective candidates that required higher RV precision measurements have been followed with HARPS-N at the 3.6 m Telescopio Nazionale Galileo. Aims. We aim to detect planetary systems around evolved stars, to be able to build sound statistics on the frequency and intrinsic nature of these systems, and to deliver in-depth studies of selected planetary systems with evidence of star-planet interaction processes. Methods. We obtained 69 epochs of precise RV measurements for TYC 1422-614-1 collected over 3651 days with the Hobby-Eberly Telescope, and 17 epochs of ultra-precise HARPS-N data collected over 408 days. We complemented these RV data with photometric time-series from the All Sky Automatic Survey archive. Results. We report the discovery of a multiple planetary system around the evolved K2 giant star TYC 1422-614-1. The system orbiting the 1.15 M star is composed of a planet with mass m sin i = 2.5 M J in a 0.69 AU orbit, and a planet or brown dwarf with m sin i = 10 M J in an orbit of 1.37 AU. The multiple planetary system orbiting TYC 1422-614-1 is the first finding of the TAPAS project, a HARPS-N monitoring of evolved planetary systems identified with the Hobby-Eberly Telescope.
Aims. We present the complete spectroscopic analysis of 455 stars observed within the Penn State -Toruń Centre for Astronomy Planet Search (PTPS) with the High Resolution Spectrograph of the 9.2 m Hobby-Eberly Telescope. We also present the total sample of 744 evolved stars of the PTPS and discuss masses of stellar hosts in our and other surveys devoted to evolved planetary systems. Methods. Stellar atmospheric parameters were determined through a strictly spectroscopic LTE analysis of equivalent widths of Fe I and Fe II lines. Rotational velocities were obtained from fitting synthetic spectra. Radial velocities were obtained from fitting a Gaussian function to the cross-correlation function. We determined stellar masses, ages, and luminosities with a Bayesian analysis of theoretical isochrones. The radii were calculated either from derived masses and log g or from T eff and luminosities. Results. We present basic atmospheric parameters ( T eff , log g, v t and [Fe/H]), rotation velocities, and absolute radial velocities as well as luminosities, masses, ages and radii for 402 stars (including 11 single-line spectroscopic binaries) that are mostly subgiants and giants. For 272 of them we present parameters for the first time. For another 53 stars we present estimates of T eff and log g based on photometric calibrations. More than half of the objects were found to be subgiants, but there is also a large group of giants, and a few stars appear to be dwarfs. The results show that the sample is composed of stars with masses ranging from 0.52 to 3.21 M , 17 of which have masses ≥2.0 M . The stellar radii range from 0.66 to 36.04 R , with the vast majority having radii between 2.0 and 4.0 R . They are generally less metal abundant than the Sun with a median [Fe/H] = −0.07. For 62 stars that we have in common with other planet searches, the stellar atmospheric parameters we found agree very well. We also present basic properties of the complete list of 744 stars that form the PTPS sample of evolved stars. We examined stellar masses for 1255 stars in five other planet searches and found that some of them are probably significantly overestimated. From applying our uniformly determined stellar masses, we confirm the apparent increase of companion masses for evolved stars, and we explain this as well as the lack of close-in planets with the limited effective radial velocity precision for these stars that is due to their activity.
Context. Our knowledge of the intrinsic parameters of exoplanets is as precise as our determinations of their stellar hosts parameters. In the case of radial velocity searches for planets, stellar masses appear to be crucial. But before estimating stellar masses properly, detailed spectroscopic analysis is essential. With this paper we conclude a general spectroscopic description of the Pennsylvania-Toruń Planet Search (PTPS) sample of stars. Aims. We aim at a detailed description of basic parameters of stars representing the complete PTPS sample. We present atmospheric and physical parameters for dwarf stars observed within the PTPS along with updated physical parameters for the remaining stars from this sample after the first Gaia data release. Methods. We used high resolution (R=60 000) and high signal-to-noise-ratio (S/N=150-250) spectra from the Hobby-Eberly Telescope and its High Resolution Spectrograph. Stellar atmospheric parameters were determined through a strictly spectroscopic local thermodynamic equilibrium analysis (LTE) of the equivalent widths of Fe I and Fe II lines. Stellar masses, ages, and luminosities were estimated through a Bayesian analysis of theoretical isochrones. Results. We present T eff , log g, [Fe/H], micrturbulence velocities, absolute radial velocities, and rotational velocities for 156 stars from the dwarf sample of PTPS. For most of these stars these are the first determinations. We refine the definition of PTPS subsamples of stars (giants, subgiants, and dwarfs) and update the luminosity classes for all PTPS stars. Using available Gaia and Hipparcos parallaxes, we redetermine the stellar parameters (masses, radii, luminosities, and ages) for 451 PTPS stars. Conclusions. The complete PTPS sample of 885 stars is composed of 132 dwarfs, 238 subgiants, and 515 giants, of which the vast majority are of roughly solar mass; however, 114 have masses higher than 1.5 M and 30 of over 2 M . The PTPS extends toward much less metal abundant and much more distant stars than other planet search projects aimed at detecting planets around evolved stars; 29% of our targets belong to the Galactic thick disc and 2% belong to the halo.
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