Andrzej Niedzielski

Context. The Pennsylvania-Toruń Planet Search, which operates on a sample of ∼1000 northern-hemisphere stars, has been underway since 2004. Stars with radial velocity (RV) amplitudes exceeding 2 km s ⁻¹ represent a backup subprogram sample dedicated to monitoring binary stars with multiple instruments. Aims. We used almost 21 years of combined RV measurements to search for Doppler signals consistent with stellar or brown dwarf companions and to produce a catalog of both known and previously unpublished binary stars in our planet-search sample. Methods. We analyzed the combined RV measurements, searching for stellar companions and obtaining orbital solutions for both known and new binary systems. We also searched for periods in available long-term photometric monitoring data from All Sky Automated Survey (ASAS), and applied Gaia astrometric data whenever available. Results. We report the results of long-term RV monitoring of 16 systems: new detections of low-mass companions to 11 stars and updated orbital elements based on combined sets of our new and literature data for five systems. For two objects (TYC 3318-00789-1 and TYC 3318-01538-1), we find evidence of activity or the influence of another unseen companion, possibly due to line-profile variations or unresolved spectral contamination. We present true masses for three systems in our sample: TYC 1931-1040-1, TYC 3451-1449-1, and TYC 3667-1636-1. We obtained these masses using Gaia DR3 non-single star data.

Context. Gaia Data Release 3 (DR3) provides astrophysical parameters for hundreds of millions of stars but the [M/H] from its GSP-Phot module suffer from systematic bias. Aims. In this paper, we estimate stellar metallicities from Gaia DR3 data, using the homogeneous spectroscopic iron abundances [Fe/H] of LAMOST DR10 as training labels. Methods. We have cross-matched LAMOST DR10 [Fe/H] with Gaia DR3 and trained a gradient-boosted decision-tree regressor (XGBoost) on 1.20 million AFGK stars, using only Gaia -derived inputs and proxies. We validated the estimates on held-out LAMOST stars, on GALAH DR4 and APOGEE DR17, and on 46 open clusters, and applied the model to measure the radial metallicity gradient of the disk of the Milky Way. Results. On the held-out test set, the model reaches a mean absolute error of 0.052 dex and R ² = 0.94 with negligible bias, against 0.242 dex for GSP-Phot on the same stars. The estimates transfer well to external surveys with a mean absolute error of 0.066 dex (GALAH) and 0.068 dex (APOGEE). For open clusters, the median difference between our estimated [Fe/H] and [Fe/H] from spectroscopy surveys is 0.041 dex, which is smaller than both GSP-Phot (0.248 dex) and previous work on an APOGEE-trained XGBoost model (0.067 dex). When we applied our model to the disk, it recovers a broken thin disk radial gradient (inner +0.119, outer −0.058 dexkpc ⁻¹ with a break near 5.9 kpc) and an open-cluster gradient of −0.066 dex kpc ⁻¹ , both in agreement with previous high-resolution spectroscopy works. Conclusions. Our estimated [Fe/H] values are accurate to 0.05 dex to 0.07 dex for AFGK stars within the range [Fe/H] ≳ −2.5; below this limit the predictions should be treated as lower bounds. The catalogue and the trained model are publicly available on Zenodo. These estimates are suitable for chemical studies of the Milky Way.

Context. We present the current status of and new results from our search for exoplanets in a sample of solar-mass evolved stars observed with the HARPS-N and the 3.6 m Telescopio Nazionale Galileo (TNG), and the High-Resolution Spectrograph (HRS) and the 9.2 m Hobby-Eberly Telescope (HET). Aims. The aim of this project is to detect and characterize planetary-mass companions to solar-mass stars in a sample of 122 targets at various stages of evolution from the main sequence to the red giant branch, mostly subgiants and giants, selected from the Pennsylvania-Toruń Planet Search sample, and to use this sample to study relations between stellar properties, such as metallicity, luminosity, and the planet occurrence rate. Methods. This work is based on precise radial velocity (RV) measurements. We have observed the program stars for up to 14 yr with the HET/HRS and the TNG/HARPS-N. Results. We present the analysis of RV measurements with the HET/HRS and the TNG/HARPS-N of four solar-mass stars, HD 4760, HD 96992, BD+02 3313, and TYC 0434-04538-1. We found that HD 4760 hosts a companion with a minimum mass of 13.9 M_J (a = 1.14 au, e = 0.23); HD 96992 is a host to a m sin i = 1.14 M_J companion on an a = 1.24 au and e = 0.41 orbit, and TYC 0434-04538-1 hosts an m sin i = 6.1 M_J companion on an a = 0.66 au and e = 0.08 orbit. In the case of BD+02 3313 we found a correlation between the measured RVs and one of the stellar activity indicators, suggesting that the observed RV variations may either originate in stellar activity or be caused by the presence of an unresolved companion. We also discuss the current status of the project and a statistical analysis of the RV variations in our sample of target stars. Conclusions. In our sample of 122 solar-mass stars, 49 ± 5% of them appear to be single and 16 ± 3% spectroscopic binaries. The three giants hosting low-mass companions presented in this paper join the six previously identified giants in the sample.

Massive exoplanets on extremely tight orbits, such as WASP-12 b, induce equilibrium tides in their host stars. Following the orbital motion of the planet, the tidal fluid flow in the star can be detected with the radial velocity method. Its signature manifests as the second harmonics of the orbital frequency that mimics a nonzero orbital eccentricity. Using the new radial velocity measurements acquired with the HARPS-N spectrograph at the Telescopio Nazionale Galileo and combining them with the literature data, we show that the apparent eccentricity of WASP-12 b’s orbit is nonzero at a 5.8σ level, and the longitude of periastron of this apparently eccentric orbit is close to 270°. This orbital configuration is compatible with a model composed of a circular orbit and a signature of tides raised in the host star. The radial velocity amplitude of those tides was found to be consistent with the equilibrium tide approximation. The tidal deformation is predicted to produce a flux modulation with an amplitude of 80 ppm that could be detected using space-borne facilities.

We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature’s fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiber- fed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 μm at a spectral resolution of ~100,000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU.

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], microturbulence 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.

Context.We present the latest results of our search for planets with HARPS-N at the 3.6 m Telescopio NazionaleGalileounder the Tracking Advanced Planetary Systems project: an in-depth study of the 15 most Li abundant giants from the PennState – Toruń Planet Search sample.Aims.Our goals are first, to obtain radial velocities of the most Li-rich giants we identified in our sample to search for possible low-mass substellar companions, and second, to perform an extended spectral analysis to define the evolutionary status of these stars.Methods.This work is based on high-resolution spectra obtained with theHobby-EberlyTelescope and its High Resolution Spectrograph, and with the HARPS-N spectrograph at the Telescopio NazionaleGalileo. Two stars, HD 181368 and HD 188214, were also observed with UVES at the VLT to determine beryllium abundances.Results.We report i) the discovery of two new planetary systems around the Li-rich giant stars: HD 238914 and TYC 3318-01333-1 (a binary system); ii) reveal a binary Li-rich giant, HD 181368; iii) although our current phase coverage is not complete, we suggest the presence of planetary mass companions around TYC 3663-01966-1 and TYC 3105-00152-1; iv) we confirm the previous result for BD+48 740 and present updated orbital parameters, and v) we find a lack of a relation between the Li enhancement and the Be abundance for the stars HD 181368 and HD 188214, for which we acquired blue spectra.Conclusions.We found seven stars with stellar or potential planetary companions among the 15 Li-rich giant stars. The binary star frequency of the Li-rich giants in our sample appears to be normal, but the planet frequency is twice that of the general sample, which suggests a possible connection between hosting a companion and enhanced Li abundance in giant stars. We also found most of the companions orbits to be highly eccentric.