- ID:
- ivo://CDS.VizieR/J/A+A/646/A77
- Title:
- Chromospheric activity from AMBRE-HARPS
- Short Name:
- J/A+A/646/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main objective of this project is to characterise chromospheric activity of FGK stars from the HARPS archive. We start, in this first paper, by presenting a catalogue of homogeneous determined chromospheric emission (CE), stellar atmospheric parameters and ages for 1,674 FGK main sequence (MS), subgiant, and giant stars. The analysis of CE level and variability is also performed. We measured CE in the CaII lines using more than 180000 high-resolution spectra from the HARPS spectrograph, as compiled in the AMBRE project, obtained between 2003 and 2019. We converted the fluxes to bolometric and photospheric corrected chromospheric emission ratio, R'_HK_. Stellar atmospheric parameters T_eff_, logg, and [Fe/H] were retrieved from the literature or determined using an homogeneous method. M_{star}_, R_{star}_, and ages were determined from isochrone fitting. We show that our sample has a distribution of CE for MS stars that is consistent with an unbiased sample of solar-neighbour MS stars. We analysed the CE distribution for the different luminosity classes and spectral types and confirmed the existence of the very inactive stars (VIS) and very active stars (VAS) populations at R'_HK_<-5.1 and >-4.2dex, respectively. We found indications that the VIS population is composed mainly of subgiant and giant stars and that R'_HK_=-5.1dex marks a transition in stellar evolution. Overall, CE variability decreases with decreasing CE level but its distribution is complex. There appears to be at least three regimes of variability, for inactive, active and very active stars, with the inactive and active regimes separated by a diagonal, extended Vaughan-Preston (VP) gap. We show that stars with low activity levels do not necessarily have low variability. In the case of K dwarfs which show high CE variability, inactive and active stars have similar levels of activity variability. This means that activity levels alone are not enough to infer about the activity variability of a star. We also explained the shape of the VP gap observed in the distribution of CE by using the CE variability-level diagram. In the CE variability-level diagram, the Sun is located in the high variability region of the inactive MS stars zone. A method to extract the probability density function of the CE variability for a given R'_HK_ level is discussed, and a python code to retrieve it is provided.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/574
- Title:
- Circumstellar discs at white dwarfs
- Short Name:
- J/MNRAS/449/574
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs whose atmospheres are polluted by terrestrial-like planetary debris have become a powerful and unique tool to study evolved planetary systems. This paper presents results for an unbiased Spitzer Infrared Array Camera search for circumstellar dust orbiting a homogeneous and well-defined sample of 134 single white dwarfs. The stars were selected without regard to atmospheric metal content but were chosen to have (1) hydrogen-rich atmospheres, (2) 17000<Teff<25000K and correspondingly young post-main-sequence ages of 15-270Myr, and (3) sufficient far-ultraviolet brightness for a corresponding Hubble Space Telescope COS snapshot. Five white dwarfs were found to host an infrared bright dust disc, three previously known, and two reported here for the first time, yielding a nominal 3.7^+2.4^_-1.0_ percent of white dwarfs in this post-main-sequence age range with detectable circumstellar dust. Remarkably, the complementary Hubble observations indicate that a fraction of 27 percent show metals in their photosphere that can only be explained with ongoing accretion from circumstellar material, indicating that nearly 90 percent of discs escape detection in the infrared, likely due to small emitting surface area. This paper also presents the distribution of disc fractional luminosity as a function of cooling age for all known dusty white dwarfs, suggesting possible disc evolution scenarios and indicating an undetected population of circumstellar discs.
- ID:
- ivo://CDS.VizieR/J/AJ/160/24
- Title:
- Circumstellar dust of 104 stars with GPIES
- Short Name:
- J/AJ/160/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a ~4yr direct imaging survey of 104 stars to resolve and characterize circumstellar debris disks in scattered light as part of the Gemini Planet Imager (GPI) Exoplanet Survey. We targeted nearby (<~150pc), young (<~500Myr) stars with high infrared (IR) excesses (LIR/L_{star}_>10^-5^), including 38 with previously resolved disks. Observations were made using the GPI high-contrast integral field spectrograph in H-band (1.6{mu}m) coronagraphic polarimetry mode to measure both polarized and total intensities. We resolved 26 debris disks and 3 protoplanetary/transitional disks. Seven debris disks were resolved in scattered light for the first time, including newly presented HD117214 and HD156623, and we quantified basic morphologies of five of them using radiative transfer models. All of our detected debris disks except HD156623 have dust-poor inner holes, and their scattered-light radii are generally larger than corresponding radii measured from resolved thermal emission and those inferred from spectral energy distributions. To assess sensitivity, we report contrasts and consider causes of nondetections. Detections were strongly correlated with high IR excess and high inclination, although polarimetry outperformed total intensity angular differential imaging for detecting low-inclination disks (<~70{deg}). Based on postsurvey statistics, we improved upon our presurvey target prioritization metric predicting polarimetric disk detectability. We also examined scattered-light disks in the contexts of gas, far-IR, and millimeter detections. Comparing H-band and ALMA fluxes for two disks revealed tentative evidence for differing grain properties. Finally, we found no preference for debris disks to be detected in scattered light if wide-separation substellar companions were present.
- 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/MNRAS/469/521
- Title:
- CO, C & O gas content of debris discs predictions
- Short Name:
- J/MNRAS/469/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper uses observations of dusty debris discs, including a growing number of gas detections in these systems, to test our understanding of the origin and evolution of this gaseous component. It is assumed that all debris discs with icy planetesimals create second generation CO, C and O gas at some level, and the aim of this paper is to predict that level and assess its observability. We present a new semi-analytical equivalent of the numerical model of Kral et al. (2016MNRAS.461.1614K) allowing application to large numbers of systems. That model assumes CO is produced from volatile-rich solid bodies at a rate that can be predicted from the debris discs fractional luminosity. CO photodissociates rapidly into C and O that then evolve by viscous spreading. This model provides a good qualitative explanation of all current observations, with a few exceptional systems that likely have primordial gas. The radial location of the debris and stellar luminosity explain some non-detections, e.g. close-in debris (like HD 172555) is too warm to retain CO, while high stellar luminosities (like {eta} Tel) result in short CO lifetimes. We list the most promising targets for gas detections, predicting >15 CO detections and >30 CI detections with ALMA, and tens of CII and O I detections with future far-IR missions. We find that CO, CI, CII and OI gas should be modelled in non-LTE for most stars, and that CO, CI and OI lines will be optically thick for the most gas-rich systems. Finally, we find that radiation pressure, which can blow out CI around early-type stars, can be suppressed by self-shielding.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3665
- Title:
- CoMaLit. III. LC2 catalog
- Short Name:
- J/MNRAS/450/3665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The measurement of the mass of clusters of galaxies is crucial for their use in cosmology and astrophysics. Masses can be efficiently determined with weak lensing (WL) analyses. I compiled literature catalogues of WL clusters (LC2). Cluster identifiers, coordinates, and redshifts have been standardized. WL masses were reported to over-densities of 2500, 500, 200, and to the virial one in the reference {Lambda}CDM model. Duplicate entries were carefully handled. I produced three catalogues: LC2-single, with 485 unique groups and clusters analysed with the single-halo model; LC2-substructure, listing substructures in complex systems; LC2-all, listing all the 822 WL masses found in the literature. The catalogues and future updates are publicly available at http://pico.bo.astro.it/~sereno/CoMaLit/LC2/ .
- ID:
- ivo://CDS.VizieR/J/ApJ/757/141
- Title:
- Companion IR detection limits in young associations
- Short Name:
- J/ApJ/757/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The frequency and properties of multiple star systems offer powerful tests of star formation models. Multiplicity surveys over the past decade have shown that binary properties vary strongly with mass, but the functional forms and the interplay between frequency and semimajor axis remain largely unconstrained. We present the results of a large-scale survey of multiplicity at the bottom of the initial mass function in several nearby young associations, encompassing 78 very low mass members observed with Keck laser guide star adaptive optics. Our survey confirms the overall trend observed in the field for lower-mass binary systems to be less frequent and more compact, including a null detection for any substellar binary systems with separations wider than ~7AU. Combined with a Bayesian re-analysis of existing surveys, our results demonstrate that the binary frequency and binary separations decline smoothly between masses of 0.5M_{sun}_ and 0.02M_{sun}_, though we cannot distinguish the functional form of this decline due to a degeneracy between the total binary frequency and the mean binary separation. We also show that the mass ratio distribution becomes progressively more concentrated at q~1 for declining masses, though a small number of systems appear to have unusually wide separations and low-mass ratios for their mass. Finally, we compare our results to synthetic binary populations generated by smoothed particle hydrodynamic simulations, noting the similarities and discussing possible explanations for the differences.
- ID:
- ivo://CDS.VizieR/J/AJ/151/85
- Title:
- Companions to APOGEE stars. I.
- Short Name:
- J/AJ/151/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In its three years of operation, the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE-1) observed >14000 stars with enough epochs over a sufficient temporal baseline for the fitting of Keplerian orbits. We present the custom orbit-fitting pipeline used to create this catalog, which includes novel quality metrics that account for the phase and velocity coverage of a fitted Keplerian orbit. With a typical radial velocity precision of ~100-200 m/s, APOGEE can probe systems with small separation companions down to a few Jupiter masses. Here we present initial results from a catalog of 382 of the most compelling stellar and substellar companion candidates detected by APOGEE, which orbit a variety of host stars in diverse Galactic environments. Of these, 376 have no previously known small separation companion. The distribution of companion candidates in this catalog shows evidence for an extremely truncated brown dwarf (BD) desert with a paucity of BD companions only for systems with a<0.1-0.2 AU, with no indication of a desert at larger orbital separation. We propose a few potential explanations of this result, some which invoke this catalog's many small separation companion candidates found orbiting evolved stars. Furthermore, 16 BD and planet candidates have been identified around metal-poor ([Fe/H]<-0.5) stars in this catalog, which may challenge the core accretion model for companions >10 M_Jup_. Finally, we find all types of companions are ubiquitous throughout the Galactic disk with candidate planetary-mass and BD companions to distances of ~6 and ~16 kpc, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/450/681
- Title:
- Companions to close spectroscopic binaries
- Short Name:
- J/A+A/450/681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed a sample of 165 solar-type spectroscopic binaries (SB) with periods from 1 to 30 days for higher-order multiplicity. 62 targets have been observed with the NACO adaptive optics system and 13 new physical tertiary companions were detected. Another 12 new wide companions (5 still tentative) were retrieved from the 2MASS (<II/246>) sky survey. Our binaries belong to 161 stellar systems; of these 64 are triple, 11 quadruple and 7 quintuple. After correction for incomplete detection, the fraction of SBs with additional companions is 63+/-5%. We find that this fraction is a strong function of the SB period P, reaching 96% for P<3d and dropping to 36% for P>12d. Period distributions of SBs with and without tertiaries are significantly different, but their mass ratio distributions are identical. New statistical data on the multiplicity of close SBs indicate that their periods and mass ratios were established very early, but periods of SBs within triples were further shortened by angular momentum exchange with companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/897/111
- Title:
- Compilation of black hole, bulge and stellar masses
- Short Name:
- J/ApJ/897/111
- Date:
- 16 Mar 2022 00:27:27
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of the active galactic nucleus in the nearby (D=14.1Mpc) low-mass galaxy IC750, which has circumnuclear 22GHz water maser emission. The masers trace a nearly edge-on, warped disk ~0.2pc in diameter, coincident with the compact nuclear X-ray source that lies at the base of the ~kiloparsec-scale extended X-ray emission. The position-velocity structure of the maser emission indicates that the central black hole (BH) has a mass less than 1.4x105M{sun}. Keplerian rotation curves fitted to these data yield enclosed masses between 4.1x104M{sun} and 1.4x105M{sun}, with a mode of 7.2x104M{sun}. Fitting the optical spectrum, we measure a nuclear stellar velocity dispersion {sigma }*=110.7_-13.4_^+12.1^km/s. From near-infrared photometry, we fit a bulge mass of (7.3{+/-}2.7)x108M{sun} and a stellar mass of 1.4x1010M{sun}. The mass upper limit of the intermediate-mass BH in IC750 falls roughly two orders of magnitude below the MBH-{sigma}* relation and roughly one order of magnitude below the MBH-MBulge and MBH-M* relations-larger than the relations' intrinsic scatters of 0.58{+/-}0.09dex, 0.69dex, and 0.65{+/-}0.09dex, respectively. These offsets could be due to larger scatter at the low-mass end of these relations. Alternatively, BH growth is intrinsically inefficient in galaxies with low bulge and/or stellar masses, which causes the BHs to be undermassive relative to their hosts, as predicted by some galaxy evolution simulations.
