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871. APEX spectrum of R Dor (159.0-368.5GHz)
ID:
ivo://CDS.VizieR/J/A+A/615/A8
Title:
APEX spectrum of R Dor (159.0-368.5GHz)
Short Name:
J/A+A/615/A8
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our current insights into the circumstellar chemistry of asymptotic giant branch (AGB) stars are largely based on studies of carbon-rich stars and stars with high mass-loss rates. In order to expand the current molecular inventory of evolved stars we present a spectral scan of the nearby, oxygen-rich star R Dor, a star with a low mass-loss rate (~2x10^-7^M_{sun}_/yr). We carried out a spectral scan in the frequency ranges 159.0-321.5GHz and 338.5-368.5GHz (wavelength range 0.8-1.9mm) using the SEPIA/Band-5 and SHeFI instruments on the APEX telescope and we compare it to previous surveys, including one of the oxygen-rich AGB star IK Tau, which has a high mass-loss rate (~5x10^-6^M_{sun}_/yr). The spectrum of R Dor is dominated by emission lines of SO_2_ and the different isotopologues of SiO. We also detect CO, H_2_O, HCN, CN, PO, PN, SO, and tentatively TiO_2_, AlO, and NaCl. Sixteen out of approximately 320 spectral features remain unidentified. Among these is a strong but previously unknown maser at 354.2GHz, which we suggest could pertain to H_2_SiO, silanone. With the exception of one, none of these unidentified lines are found in a similarly sensitive survey of IK Tau performed with the IRAM 30 m telescope. We present radiative transfer models for five isotopologues of SiO (^28^SiO, ^29^SiO, ^30^SiO, Si^17^O, Si^18^O), providing constraints on their fractional abundance and radial extent. We derive isotopic ratios for C, O, Si, and S and estimate that, based on our results for ^17^O/^18^O, R Dor likely had an initial mass in the range 1.3-1.6M_{sun}_, in agreement with earlier findings based on models of H_2_O line emission. From the presence of spectral features recurring in many of the measured thermal and maser emission lines we tentatively identify up to five kinematical components in the outflow of R Dor, indicating deviations from a smooth, spherical wind.
872. A planetary-mass companion to a solar-type star
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'.
873. APM cluster redshift survey
ID:
ivo://CDS.VizieR/J/MNRAS/269/151
Title:
APM cluster redshift survey
Short Name:
J/MNRAS/269/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present redshifts for a sample of 228 clusters selected from the APM Galaxy Survey, 188 of which are new redshift determinations. Redshifts are listed for 365 galaxies, and non-cluster galaxy redshifts have been rejected from this sample using a likelihood ratio test based on the projected and apparent magnitude distributions of each cluster region. We test this technique using clusters for which redshifts have been measured for more than 10 galaxies. Our redshift sample is nearly complete and has been used in previous papers to study the three-dimensional distribution of rich clusters of galaxies. 156 of the clusters in our sample are listed in the Abell catalogue or supplement, and the remainder are new cluster identifications.
874. APM elliptical galaxies radial velocities
ID:
ivo://CDS.VizieR/J/AJ/110/1032
Title:
APM elliptical galaxies radial velocities
Short Name:
J/AJ/110/1032
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 292 new redshifts of elliptical galaxies selected from the APM Bright Galaxy Survey. We use these data together with published redshifts and bj apparent magnitudes from the APM Bright Galaxy Survey in order to estimate the shape of the Luminosity Function of a total sample of 535 ellipticals. We use the Maximum Likelihood method for the determination of the best fitting parameters {alpha} and M^*^ of a Schechter Function. In order to provide tests for systematics and suitable error estimates we apply Monte Carlo techniques which are also used to deal with incompleteness effects in the data. In agreement with other authors our results indicate a relative lack of low luminosity ellipticals compared to other morphological types. The best fitting shape parameters derived are {alpha}=0.20+/-0.25 and M^*^_Bj_=-20.0+/-0.3. We do not find evidence for a dependence of these parameters on environment.
875. APOGEE and Gaia DR2 analysis of IC 166
ID:
ivo://CDS.VizieR/J/AJ/156/94
Title:
APOGEE and Gaia DR2 analysis of IC 166
Short Name:
J/AJ/156/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
IC 166 is an intermediate-age open cluster (OC) (~1 Gyr) that lies in the transition zone of the metallicity gradient in the outer disk. Its location, combined with our very limited knowledge of its salient features, make it an interesting object of study. We present the first high-resolution spectroscopic and precise kinematical analysis of IC 166, which lies in the outer disk with R_GC_~12.7 kpc. High-resolution H-band spectra were analyzed using observations from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment survey. We made use of the Brussels Automatic Stellar Parameter code to provide chemical abundances based on a line-by-line approach for up to eight chemical elements (Mg, Si, Ca, Ti, Al, K, Mn, and Fe). The {alpha}-element (Mg, Si, Ca, and whenever available Ti) abundances, and their trends with Fe abundances have been analyzed for a total of 13 high-likelihood cluster members. No significant abundance scatter was found in any of the chemical species studied. Combining the positional, heliocentric distance, and kinematic information, we derive, for the first time, the probable orbit of IC 166 within a Galactic model including a rotating boxy bar, and found that it is likely that IC 166 formed in the Galactic disk, supporting its nature as an unremarkable Galactic OC with an orbit bound to the Galactic plane.
876. APOGEE cool stars
ID:
ivo://CDS.VizieR/J/A+A/642/A81
Title:
APOGEE cool stars
Short Name:
J/A+A/642/A81
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Galactic center region, including the nuclear disk, has until recently been largely avoided in chemical census studies because of extreme extinction and stellar crowding. Large, near-IR spectroscopic surveys, such as the Apache Point Observatory Galactic Evolution Experiment (APOGEE), allow the measurement of metallicities in the inner region of our Galaxy. Making use of the latest APOGEE data release (DR16), we are able for the first time to study cool Asymptotic Giant branch (AGB) stars and supergiants in this region. The stellar parameters of five known AGB stars and one supergiant star (VR 5-7) show that their location is well above the tip of the red giant branch. We studied metallicities of 157 M giants situated within 150 pc of the Galactic center from observations obtained by the APOGEE survey with reliable stellar parameters from the APOGEE pipeline making use of the cool star grid down to 3200K. Distances, interstellar extinction values, and radial velocities were checked to confirm that these stars are indeed situated in the Galactic center region. We detect a clear bimodal structure in the metallicity distribution function, with a dominant metal-rich peak of [Fe/H]~+0.3dex and a metal-poor peak around {Fe/H]=-0.5dex, which is 0.2dex poorer than Baade's Window. The {alpha}-elements Mg, Si, Ca, and O show a similar trend to the Galactic bulge. The metal-poor component is enhanced in the {alpha}-elements, suggesting that this population could be associated with the classical bulge and a fast formation scenario. We find a clear signature of a rotating nuclear stellar disk and a significant fraction of high-velocity stars with v_gal_>300km/s; the metal-rich stars show a much higher rotation velocity (~200km/s) with respect to the metal-poor stars (~140km/s). The chemical abundances as well as the metallicity distribution function suggest that the nuclear stellar disk and the nuclear star cluster show distinct chemical signatures and might be formed differently.
877. APOGEE-2 data from DR16
ID:
ivo://CDS.VizieR/III/284
Title:
APOGEE-2 data from DR16
Short Name:
III/284
Date:
05 Jan 2022
Publisher:
CDS
Description:
The spectral analysis and data products in Data Release 16 (DR16; 2019 December) from the high-resolution near-infrared Apache Point Observatory Galactic Evolution Experiment (APOGEE)-2/Sloan Digital Sky Survey (SDSS)-IV survey are described. Compared to the previous APOGEE data release (DR14; 2017 July), APOGEE DR16 includes about 200000 new stellar spectra, of which 100000 are from a new southern APOGEE instrument mounted on the 2.5m du Pont telescope at Las Campanas Observatory in Chile. DR16 includes all data taken up to 2018 August, including data released in previous data releases. All of the data have been re-reduced and re-analyzed using the latest pipelines, resulting in a total of 473307 spectra of 437445 stars. Changes to the analysis methods for this release include, but are not limited to, the use of MARCS model atmospheres for calculation of the entire main grid of synthetic spectra used in the analysis, a new method for filling "holes" in the grids due to unconverged model atmospheres, and a new scheme for continuum normalization. Abundances of the neutron-capture element Ce are included for the first time. A new scheme for estimating uncertainties of the derived quantities using stars with multiple observations has been applied, and calibrated values of surface gravities for dwarf stars are now supplied. Compared to DR14, the radial velocities derived for this release more closely match those in the Gaia DR2 database, and a clear improvement in the spectral analysis of the coolest giants can be seen.
878. APOGEE-2 data from DR16 (Majewski+, 2017)
ID:
ivo://CDS.VizieR/J/AJ/154/94
Title:
APOGEE-2 data from DR16 (Majewski+, 2017)
Short Name:
J/AJ/154/94
Date:
13 Oct 2020 14:20:09
Publisher:
CDS
Description:
The second generation of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) observes the "archaeological" record embedded in hundreds of thousands of stars to explore the assembly history and evolution of the Milky Way Galaxy. APOGEE-2 maps the dynamical and chemical patterns of Milky Way stars with data from the 1-meter NMSU Telescope and the 2.5-meter Sloan Foundation Telescope at the Apache Point Observatory in New Mexico (APOGEE-2N), and the 2.5-meter du Pont Telescope at Las Campanas Observatory in Chile (APOGEE-2S).
879. APOGEE DR14:Binary companions of evolved stars
ID:
ivo://CDS.VizieR/J/AJ/156/18
Title:
APOGEE DR14:Binary companions of evolved stars
Short Name:
J/AJ/156/18
Date:
21 Oct 2021
Publisher:
CDS
Description:
Multi-epoch radial velocity measurements of stars can be used to identify stellar, substellar, and planetary-mass companions. Even a small number of observation epochs can be informative about companions, though there can be multiple qualitatively different orbital solutions that fit the data. We have custom-built a Monte Carlo sampler (The Joker) that delivers reliable (and often highly multimodal) posterior samplings for companion orbital parameters given sparse radial velocity data. Here we use The Joker to perform a search for companions to 96231 red giant stars observed in the APOGEE survey (DR14) with >=3 spectroscopic epochs. We select stars with probable companions by making a cut on our posterior belief about the amplitude of the variation in stellar radial velocity induced by the orbit. We provide (1) a catalog of 320 companions for which the stellar companion's properties can be confidently determined, (2) a catalog of 4898 stars that likely have companions, but would require more observations to uniquely determine the orbital properties, and (3) posterior samplings for the full orbital parameters for all stars in the parent sample. We show the characteristics of systems with confidently determined companion properties and highlight interesting systems with candidate compact object companions.
880. APOGEE-Kepler Cool Dwarf star ages determination
ID:
ivo://CDS.VizieR/J/ApJ/888/43
Title:
APOGEE-Kepler Cool Dwarf star ages determination
Short Name:
J/ApJ/888/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use models of stellar angular momentum evolution to determine ages for ~500 stars in the APOGEE-Kepler Cool Dwarfs sample. We focus on lower-main-sequence stars, where other age-dating tools become ineffective. Our age distributions are compared to those derived from asteroseismic and giant samples and solar analogs. We are able to recover gyrochronological ages for old, lower-main-sequence stars, a remarkable improvement over prior work in hotter stars. Under our model assumptions, our ages have a median relative uncertainty of 14%, comparable to the age precision inferred for more massive stars using traditional methods. We investigate trends of Galactic {alpha}-enhancement with age, finding evidence of a detection threshold between the age of the oldest {alpha}-poor stars and that of the bulk {alpha}-rich population. We argue that gyrochronology is an effective tool reaching ages of 10-12Gyr in K and early M dwarfs. Finally, we present the first effort to quantify the impact of detailed abundance patterns on rotational evolution. We estimate a ~15% bias in age for cool, {alpha}-enhanced (+0.4dex) stars when standard solar-abundance-pattern rotational models are used for age inference, rather than models that appropriately account for {alpha}-enrichment.

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