- ID:
- ivo://CDS.VizieR/J/A+A/620/A180
- Title:
- Stellar properties of M dwarfs
- Short Name:
- J/A+A/620/A180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Being the most numerous and oldest stars in the galaxy, M dwarfs are objects of great interest for exoplanet searches. The presence of molecules in their atmosphere complicates our understanding of their atmospheric properties. But great advances have recently been made in the modeling of M dwarfs due to the revision of solar abundances. We aim to determine stellar parameters of M dwarfs using high resolution spectra (R~90000) simultaneously in the visible and the near-infrared. The high resolution spectra and broad wavelength coverage provide an unique opportunity to understand the onset of dust and cloud formation at cool temperatures. Furthermore, this study will help in understanding the physical processes which occur in a cool atmospheres, particularly, the redistribution of energy from the optical to the near-infrared. The stellar parameters of M dwarfs in our sample have been determined by comparing the high resolution spectra both in the optical and in the near-infrared simultaneously observed by CARMENES with the synthetic spectra obtained from the BT-Settl model atmosphere. The detailed spectral synthesis of these observed spectra both in the optical and in the near-infrared helps to understand the missing continuum opacity. For the first time, we derive fundamental stellar parameters of M dwarfs using the high resolution optical and near-infrared spectra simultaneously. We determine Teff, logg and [M/H] for 292 M dwarfs of spectral type M0 to M9, where the formation of dust and clouds are important. The derived Teff for the sample ranges from 2300 to 4000K, values of log g ranges from 4.5<=logg<=5.5 and the resulting metallicity ranges from -0.5<=[M/H]<=+0.5. We have also explored the possible differences in Teff, logg and [M/H] by comparing them with other studies of the same sample of M dwarfs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/1437
- Title:
- Stellar streams in Andromeda (M31)
- Short Name:
- J/MNRAS/390/1437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of five stellar streams ("A", "B", "Cr", "Cp" and "D") as well as the extended star cluster, EC4, which lies within Stream "C", all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for ~70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream "C" and Stream "D" to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H]~-0.7) stars at v_hel_=-349.5km/s, {sigma}_v,corr_~5.1+/-2.5km/s are proposed as a serendipitous detection of Stream "Cr", with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H]~-1.3) stars confined to a narrow, 15km/s velocity bin centred at v_hel_=-285.6, {sigma}_v,corr_=4.3^+1.7^_-1.4_km/s represent a kinematic detection of Stream "Cp", again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H]~-1.4, are found at v_hel_=-282 suggesting it could be related to Stream "Cp". No similarly obvious cold kinematic candidate is found for Stream "D", although candidates are proposed in both of two spectroscopic pointings along the stream (both at ~-400km/s). Spectroscopy near the edge of Stream "B" suggests a likely kinematic detection at v_hel_~-330, {sigma}_v,corr_~6.9km/s, while a candidate kinematic detection of Stream "A" is found (plausibly associated to M33 rather than M31) with v_hel_~-170, {sigma}_v,corr_=12.5km/s. The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar halo is largely made up of multiple kinematically cold streams.
- ID:
- ivo://CDS.VizieR/J/AJ/120/1808
- Title:
- Stroemgren photometry in LMC disk
- Short Name:
- J/AJ/120/1808
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new metallicity determinations for 39 red giants in a 220 arcmin2^2^ region, 1.8{deg} southwest of the bar of the Large Magellanic Cloud. These abundance measurements are based on spectroscopy of the Ca II infrared triplet.
- ID:
- ivo://CDS.VizieR/J/A+A/465/357
- Title:
- Stroemgren photometry in the Draco dSph galaxy
- Short Name:
- J/A+A/465/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we demonstrate how Stroemgren uvby photometry can be efficiently used to: 1. identify red giant branch stars that are members in a dwarf spheroidal galaxy; 2. derive age-independent metallicities for the same stars and quantify the associated errors. Stroemgren uvby photometry in a 11'x22' field centered on the Draco dwarf spheroidal galaxy was obtained using the Isaac Newton Telescope on La Palma. Members of the Draco dSph galaxy were identified using the surface gravity sensitive c1 index which discriminates between red giant and dwarf stars. Thus enabling us to distinguish the (red giant branch) members of the dwarf spheroidal galaxy from the foreground dwarf stars in our galaxy. The method is evaluated through a comparison of our membership list with membership classifications in the literature based on radial velocities and proper motions. The metallicity sensitive m1 index was used to derive individual and age-independent metallicities for the members of the Draco dSph galaxy. The derived metallicities are compared to studies based on high resolution spectroscopy and the agreement is found to be very good.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A40
- Title:
- Stroemgren photometry of Milky Way stars
- Short Name:
- J/A+A/521/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several large scale photometric and spectroscopic surveys are being undertaken to provide a more detailed picture of the Milky Way. Given the necessity of generalisation in the determination of, e.g., stellar parameters when tens and hundred of thousands of stars are considered it remains important to provide independent, detailed studies to verify the methods used in the surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/23
- Title:
- Subdwarf A stars vs ELM WDs radial velocities
- Short Name:
- J/ApJ/839/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution spectroscopy. However, colors and proper motions indicate that sdA stars are cooler and more luminous, and thus larger in radius, than published ELM WDs. We demonstrate that surface gravities derived from pure hydrogen models suffer a systematic ~1dex error for sdA stars, likely explained by metal line blanketing below 9000K. A detailed study of five eclipsing binaries with radial velocity orbital solutions and infrared excess establishes that these sdA stars are metal-poor ~1.2M_{sun}_ main sequence stars with ~0.8M_{sun}_ companions. While WDs must exist at sdA temperatures, only ~1% of a magnitude-limited sdA sample should be ELM WDs. We conclude that the majority of sdA stars are metal-poor A-F type stars in the halo, and that recently discovered pulsating ELM WD-like stars with no obvious radial velocity variations may be SX Phe variables, not pulsating WDs.
- ID:
- ivo://CDS.VizieR/J/PASP/113/1365
- Title:
- Super-metal-rich stars
- Short Name:
- J/PASP/113/1365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Lick spectral indices for a complete sample of 139 candidate super-metal-rich stars of different luminosity classes (MK type from I to V). For 91 of these stars we were able to identify, in an accompanying paper, the fundamental atmosphere parameters. This confirms that at least 2/3 of the sample consists of stars with [Fe/H] in excess of +0.1 dex. Optical indices for both observations and fiducial synthetic spectra have been calibrated to the Lick system according to Worthey et al. (1994, Cat. <J/ApJS/94/687>) and include the FeI indices of Fe5015, Fe5270, and Fe5335 and the MgI and MgH indices of Mg_2_ and Mg_b_ at 5180{AA}. The internal accuracy of the observations is found to be {sigma}(Fe5015)=10.32{AA}, {sigma}(Fe5270)=10.19{AA}, {sigma}(Fe5335)=10.22{AA}, {sigma}(Mg_2_)=10.004mag, and {sigma}(Mg_b_)=10.19{AA}. This is about a factor of 2 better than the corresponding theoretical indices from the synthetic spectra, the latter being a consequence of the intrinsic limitations in the input physics, as discussed by Chavez et al. (1997, Cat. <J/A+AS/126/267>).
- ID:
- ivo://CDS.VizieR/J/AJ/149/157
- Title:
- Surface intensity profiles for 10 M33 globular clusters
- Short Name:
- J/AJ/149/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the properties of 10 halo globular clusters (GCs) with luminosities L~=5-7x10^5^L_{sun}_ in the Local Group galaxy M33 using images from the Hubble Space Telescope WFPC2 in the F555W and F814W bands. We obtained the ellipticities, position angles, and surface brightness profiles for each GC. In general, the ellipticities of the M33 sample clusters are similar to those of the M31 clusters. The structural and dynamical parameters are derived by fitting the profiles to three different models combined with mass-to-light ratios (M/L values) from population-synthesis models. The structural parameters include core radii, concentration, half-light radii, and central surface brightness. The dynamical parameters include the integrated cluster mass, integrated binding energy, central surface mass density, and predicted line of sight velocity dispersion at the cluster center. The velocity dispersions of the four clusters predicted here agree well with the observed dispersions by Larsen et al. The results here showed that the majority of the sample halo GCs are better fitted by both the King model and the Wilson model than the Sersic model. In general, the properties of the clusters in M33, M31, and the Milky Way fall in the same regions of parameter spaces. The tight correlations of cluster properties indicate a "fundamental plane" for clusters, which reflects some universal physical conditions and processes operating at the epoch of cluster formation.
- ID:
- ivo://CDS.VizieR/J/AJ/161/134
- Title:
- Survey of stellar & planetary comp. within 25pc
- Short Name:
- J/AJ/161/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the impact of outer stellar companions on the occurrence rate of giant planets detected with radial velocities. We searched for stellar and planetary companions to a volume-limited sample of solar-type stars within 25pc. Using adaptive optics imaging observations from the Lick 3m and Palomar 200" Telescopes, we characterized the multiplicity of our sample stars, down to the bottom of the main sequence. With these data, we confirm field star multiplicity statistics from previous surveys. We additionally combined three decades of radial velocity (RV) data from the California Planet Search with newly collected RV data from Keck/HIRES and the Automated Planet Finder/Levy Spectrometer to search for planetary companions in these same systems. Using an updated catalog of both stellar and planetary companions, as well as detailed injection/recovery tests to determine our sensitivity and completeness, we measured the occurrence rate of planets among the single and multiple-star systems. We found that planets with masses in the range of 0.1-10M_J_ and with semimajor axes of 0.1-10au have an occurrence rate of 0.18_-0.03_^+0.04^ planets per star when they orbit single stars and an occurrence rate of 0.12{+/-}0.04 planets per star when they orbit a star in a binary system. Breaking the sample down by the binary separation, we found that only one planet-hosting binary system had a binary separation <100au, and none had a separation <50au. These numbers yielded planet occurrence rates of 0.20_-0.06_^+0.07^ planets per star for binaries with separation aB>100au and 0.04_-0.02_^+0.04^ planets per star for binaries with separation aB<100au. The similarity in the planet occurrence rate around single stars and wide primaries implies that wide binary systems should actually host more planets than single-star systems, since they have more potential host stars. We estimated a system-wide planet occurrence rate of 0.3 planets per wide binary system for binaries with separations aB>100au. Finally, we found evidence that giant planets in binary systems have a different semimajor-axis distribution than their counterparts in single-star systems. The planets in the single-star sample had a significantly higher occurrence rate outside of 1au than inside 1au by nearly 4{sigma}, in line with expectations that giant planets are most common near the snow line. However, the planets in the wide binary systems did not follow this distribution, but rather had equivalent occurrence rates interior and exterior to 1au. This may point to binary-mediated planet migration acting on our sample, even in binaries wider than 100au.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A150
- Title:
- SWEETCat I. Stellar parameters for host stars
- Short Name:
- J/A+A/556/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present new precise atmospheric parameters for stars with planets. We then take the opportunity to present a new catalogue of stellar parameters for FGK and M stars with planets detected by radial velocity, transit, and astrometry programs. Stellar atmospheric parameters and masses for the sample were derived assuming LTE and using high resolution and high signal-to-noise spectra. The methodology used is based on the measurement of equivalent widths for a list of iron lines and making use of iron ionization and excitation equilibrium principles. For the catalog, and whenever possible, we used parameters derived in previous works published by our team, using well defined methodologies for the derivation of stellar atmospheric parameters. This set of parameters amounts to over 65% of all planet host stars known, including more than 90% of all stars with planets discovered through radial velocity surveys. For the remaining targets, stellar parameters were collected from the literature.
