- ID:
- ivo://CDS.VizieR/J/MNRAS/492/431
- Title:
- A planetary-mass companion to a solar-type star
- Short Name:
- J/MNRAS/492/431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Young Suns Exoplanet Survey (YSES) consists of a homogeneous sample of 70 young, solar-mass stars located in the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an average age of 15+/-3Myr. We report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211-6456207) that is located at a distance of 94.6+/-0.3pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with VLT/X-SHOOTER constrain the mass of the star to 1.00+/-0.02M_{sun}_ and an age of 16.7+/-1.4Myr. The companion TYC 8998-760-1 b is detected at a projected separation of 1.71arcsec, which implies a projected physical separation of 162au. Photometric measurements ranging from Y to M band provide a mass estimate of 14+/-3M_Jup_ by comparison to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q=0.013+/-0.003 with respect to the primary. We rule out additional companions to TYC 8998-760-1 that are more massive than 12M_Jup_ and farther than 12au away from the host. Future polarimetric and spectroscopic observations of this system with ground and space based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of the circumstellar environment around this 'young Sun'.
« Previous |
1 - 10 of 18
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/630/A150
- Title:
- Astrometric data for 211 GAPN sample
- Short Name:
- J/A+A/630/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a catalogue of central stars of planetary nebulae (CSPN) with reliable distances and positions obtained from Gaia Data Release 2 (DR2) astrometry. Distances derived from parallaxes allow us to analyse the galactic distribution and estimate other parameters such as sizes, kinematical ages, bolometric magnitudes, and luminosities. Our objective is to analyse the information regarding distances together with other available literature data about photometric properties, nebular kinematics, and stellar effective temperatures to throw new light on this rapid and rather unknown evolutionary phase. We seek to understand how Gaia distances compare with other indirect methods commonly used and, in particular, with those derived from non-local thermodynamic equilibrium (non-LTE) models; how many planetary nebulae (PNe) populate the Galaxy; and how are they spatially distributed. We also aim to comprehend their intrinsic luminosities, range of physical sizes of the nebulae; how to derive the values for their kinematical ages; and whether those ages are compatible with those derived from evolutionary models. We considered all PNe listed in catalogues from different authors and in Hong Kong/AAO/Strasbourg/H{alpha} (HASH) database. By X-matching their positions with Gaia DR2 astrometry we were able to identify 1571 objects in Gaia second archive, for which we assumed distances calculated upon a Bayesian statistical approach. From those objects, we selected a sample of PNe with good quality parallax measurements and distance derivations, we which refer to as our Golden Astrometry PNe sample (GAPN), and obtained literature values of their apparent sizes, radial and expansion velocities, visual magnitudes, interstellar reddening, and effective temperatures. We found that the distances derived from DR2 parallaxes compare well with previous astrometric derivations of the United States Naval Observatory and Hubble Space Telescope, but that distances inferred from non-LTE model fitting are overestimated and need to be carefully reviewed. From literature apparent sizes, we calculated the physical radii for a subsample of nebulae that we used to derive the so-called kinematical ages, taking into account literature expansion velocities. Luminosities calculated with DR2 distances were combined with literature central stars Teff values in a Hertzsprung-Russell (HR) diagram to infer information on the evolutionary status of the nebulae. We compared their positions with updated evolutionary tracks finding a rather consistent picture. Stars with the smallest associated nebular radii are located in the flat luminosity region of the HR diagram, while those with the largest radii correspond to objects in a later stage, getting dimmer on their way to become a white dwarf. Finally, we commented on the completeness of our catalogue and calculated an approximate value for the total number of PNe in the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A106
- Title:
- BV photometry of 6 SMC stellar clusters
- Short Name:
- J/A+A/561/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar clusters in the Small Magellanic Cloud (SMC) are useful probes to study the chemical and dynamical evolution of this neighbouring dwarf galaxy, enabling inspection of a large period covering over 10Gyr. The main goals of this work are the derivation of age, metallicity, distance modulus, reddening, core radius and central density profile for six sample clusters, in order to place them in the context of the Small Cloud evolution. The studied clusters are: AM 3, HW 1, HW 34, HW 40, Lindsay 2, and Lindsay 3, where HW 1, HW 34, and Lindsay 2 are studied for the first time. Optical Colour-Magnitude Diagrams (V, B-V CMDs) and radial density profiles were built from images obtained with the 4.1m SOAR telescope, reaching V~23. The determination of structural parameters were carried out applying King profile fitting. The other parameters were derived in a self-consistent way by means of isochrone fitting, which uses the likelihood statistics to identify the synthetic CMDs that best reproduce the observed ones. Membership probabilities were determined comparing the cluster and control field CMDs. Completeness and photometric uncertainties were obtained performing artificial star tests. The results confirm that these clusters (except HW 34, identified as a field fluctuation) are intermediate-age clusters, with ages between 1.2Gyr (Lindsay 3) and ~5.0Gyr (HW 1). In particular HW 1, Lindsay 2, and Lindsay 3 are located in a region that we called West Halo, where studies on ages and metallicity gradients are still lacking. Moreover Lindsay 2 was identified as a moderately metal-poor cluster with [Fe/H]=-1.4+/-0.2dex, lower than expected from the age-metallicity relation by Pagel & Tautvaisiene (1998MNRAS.299..535P). We also found distances varying from ~53 to 66kpc, compatible with the large depth of the SMC.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A176
- Title:
- Chemical composition of Ruprecht 147
- Short Name:
- J/A+A/619/A176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ruprecht 147 (NGC 6774) is the closest old open cluster, with a distance of less than 300pc and an age of about 2.5Gyr. It is therefore well suited for testing stellar evolution models and for obtaining precise and detailed chemical abundance information. We combined photometric and astrometric information coming from literature and the Gaia mission with very high-resolution optical spectra of stars in different evolutionary stages to derive the cluster distance, age, and detailed chemical composition. We obtained spectra of six red giants using HARPS-N at the Telescopio Nazionale Galileo (TNG). We also used European Southern Observatory (ESO) archive spectra of 22 main sequence (MS) stars, observed with HARPS at the 3.6m telescope. The very high resolution (115000) and the large wavelength coverage (about 380-680nm) of the twin instruments permitted us to derive atmospheric parameters, metallicity, and detailed chemical abundances of 23 species from all nucleosynthetic channels. We employed both equivalent widths and spectrum synthesis. We also re-derived the cluster distance and age using Gaia parallaxes, proper motions, and photometry in conjunction with the PARSEC stellar evolutionary models. We fully analysed those stars with radial velocity and proper motion/parallax in agreement with the cluster mean values. We also discarded one binary not previously recognised, and six stars near the MS turn-off because of their high rotation velocity. Our final sample consists of 21 stars (six giants and 15 MS stars). We measured metallicity (the cluster average [Fe/H] is +0.08, rms=0.07) and abundances of light, alpha, Fe-peak, and neutron-capture elements. The Li abundance follows the expectations, showing a tight relation between temperature and abundance on the MS, at variance with M67, and we did not detect any Li-rich giant.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A100
- Title:
- CMD and mass distribution of Ba stars
- Short Name:
- J/A+A/608/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H]=-0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5M_{sun}_, with a tail at higher masses up to 4.5M_{sun}_. This peak is seen as well in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1-2M_{sun}_) barium giants. This is probably because low-mass stars reach large radii at the tip of the red giant branch, which may have resulted in an early binary interaction. Among barium giants, the high-mass tail is however dominated by stars with a barium index (based on a visual inspection of the barium spectral line) less than unity, i.e., with a very moderate barium line strength. We believe that these stars are not genuine barium giants, but rather bright giants (or supergiants) where the barium lines are strengthened because of a positive luminosity effect. Moreover, contrary to previous claims, we do not see differences between the mass distributions of mild and strong barium giants.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A168
- Title:
- Cygnus OB2 O stars spectroscopic analysis
- Short Name:
- J/A+A/642/A168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, an extensive spectroscopic study of the whole known O-star population in the association is still lacking. In this work, we created the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing and new spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the distribution of rotational velocities, and determine the main stellar parameters for all the stars in the region that have not been detected as double-line spectroscopic binaries. We also derive radii, luminosities, and masses for those stars with reliable Gaia astrometry, in addition to creating the Hertzsprung- Russell Diagram to interpret the evolutionary status of the association. This work has shown the improvement reached when using accurate spectroscopic parameters and astrometry for the interpretation of the evolutionary status of a population, revealing, in the case of Cygnus OB2, at least two star-forming bursts at ~3 and ~5Myr. We find an apparent deficit of very fast rotators in the distribution of rotational velocities. The inspection of the dynamical distribution of the sample has allowed us to identify nine O stars with peculiar proper motions and discuss a possible dynamical ejection scenario or past supernova explosions in the region.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A87
- Title:
- Discovery of a resolved disk around Wray 15-788
- Short Name:
- J/A+A/624/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Protoplanetary disks are the birth environments of planetary systems. Therefore, the study of young, circumstellar environments is essential to understanding the processes taking place in planet formation and the evolution of planetary systems. We detect and characterize circumstellar disks and potential companions around solar-type, pre-main sequence stars in the Scorpius-Centaurus association (Sco-Cen). As part of our ongoing survey we carried out high-contrast imaging with VLT/SPHERE/IRDIS to obtain polarized and total intensity images of the young (11^+16^_-7_)Myr old) K3IV star Wray 15-788 within the Lower Centaurus Crux subgroup of Sco-Cen. For the total intensity images, we remove the stellar halo via an approach based on reference star differential imaging in combination with principal component analysis. Both total intensity and polarimetric data resolve a disk around the young, solar-like Sco-Cen member Wray 15-788. Modeling of the stellar spectral energy distribution suggests that this is protoplanetary disk at a transition stage. We detect a bright outer ring at a projected separation of ~370mas (~56au), hints of inner substructures at ~170mas (~28au), and a gap in between. Within a position angle range of only 60{deg}<{phi}<240{deg}, we are confident at the 5{sigma} level that we detect actual scattered light flux from the outer ring of the disk; the remaining part is indistinguishable from background noise. For the detected part of the outer ring we determine a disk inclination of i=21{deg}+/-6{deg} and a position angle of {varphi}=76{deg}+/-16{deg}. Furthermore, we find that Wray 15-788 is part of a binary system with the A2V star HD 98363 at a separation of ~50arcsec (~6900,au). The detection of only half of the outer ring might be due to shadowing by a misaligned inner disk. A potential substellar companion can cause the misalignment of the inner structures and can be responsible for clearing the detected gap from scattering material.However, we cannot rule out the possibility of a non-detection due to our limited signal-to-noise ratio, combined with brightness azimuthal asymmetry. From our data we can exclude companions more massive than 10M_{jup}_ within the gap at a separation of ~230mas (~35au). Additional data are required to characterize the disk's peculiar morphology and to set tighter constraints on the potential perturber's orbital parameters and mass.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A70
- Title:
- Gamma Vel cluster membership and IMF
- Short Name:
- J/A+A/589/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the properties of young open clusters, such as the Initial Mass Function (IMF), star formation history and dynamic evolution, is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process. We want to obtain a list, as complete as possible, of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and, for each method, we derived the most complete list of candidate cluster members. Then, we considered photometry, gravity and radial velocities as necessary conditions to select a subsample of candidates whose membership was confirmed by using the lithium and H{alpha} lines and X-rays as youth indicators. We found 242 confirmed and 4 possible cluster members for which we derived masses using very recent stellar evolutionary models. The cluster IMF in the mass range investigated in this study shows a slope of {alpha}=2.6+/-0.5 for 0.5<M/M_{sun}<1.3 and {alpha}=1.1+/-0.4 for 0.16<M/M_{sun}_<0.5 and is consistent with a standard IMF. The similarity of the IMF of the young population around gamma^2^ Vel to that in other star forming regions and the field suggests it may have formed through very similar processes.
- ID:
- ivo://CDS.VizieR/J/A+A/404/913
- Title:
- Kinematics and HR Diagrams of Southern Young Stars
- Short Name:
- J/A+A/404/913
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spatial distribution, the space velocities and age distribution of the pre-main sequence (PMS) stars belonging to Ophiuchus, Lupus and Chamaeleon star-forming regions (SFRs), and of the young early-type star members of the Scorpius-Centaurus (Sco-Cen) OB association. These young stellar associations extend over the galactic longitude range from 280 to 360 degrees, and are at a distance interval of around 100 and 200pc. We present a compilation of PMS and early-type stars members of the investigated SFRs and OB associations. For these lists of stars we give the data used for the study of kinematic properties: positions, adopted distances, proper motions and radial velocities (whenever available), and the basic stellar data, used for the construction of Hertzsprung-Russel diagrams. All data have been taken from the literature. We also present the derived XYZ positions on the Galactic system, UVW components of the space velocities, visual extinction, and bolometric luminosity.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A116
- Title:
- Low extinction TGAS HR Catalogue
- Short Name:
- J/A+A/609/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gaia Data Release 1 allows the recalibration of standard candles such as the red clump stars. To use those stars, they first need to be accurately characterised. In particular, colours are needed to derive interstellar extinction. As no filter is available for the first Gaia data release and to avoid the atmosphere model mismatch, an empirical calibration is unavoidable. The purpose of this work is to provide the first complete and robust photometric empirical calibration of the Gaia red clump stars of the solar neighbourhood through colour-colour, effective temperature-colour, and absolute magnitude-colour relations from the Gaia, Johnson, 2MASS, Hipparcos, Tycho-2, APASS-SLOAN, and WISE photometric systems, and the APOGEE DR13 spectroscopic temperatures. We used a 3D extinction map to select low reddening red giants. To calibrate the colour-colour and the effective temperature-colour relations, we developed a MCMC method that accounts for all variable uncertainties and selects the best model for each photometric relation. We estimated the red clump absolute magnitude through the mode of a kernel-based distribution function. We provide 20 colour versus G-Ks relations and the first Teff versus G-Ks calibration. We obtained the red clump absolute magnitudes for 15 photometric bands with, in particular, M_Ks_=(-1.606+/-0.009) and M_G_=(0.495+/-0.009)+(1.121+/-0.128)(G-Ks-2.1). We present a dereddened Gaia-TGAS HR diagram and use the calibrations to compare its red clump and its red giant branch bump with Padova isochrones.
