- ID:
- ivo://CDS.VizieR/J/MNRAS/336/879
- Title:
- G and K dwarfs UBV(RI)c and ubvy photometry
- Short Name:
- J/MNRAS/336/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K dwarfs have lifetimes older than the present age of the Galactic disc, and are thus ideal stars for investigating the chemical evolution of the disc. We have developed several photometric metallicity indicators for K dwarfs, based on a sample of accurate spectroscopic metallicities for 34 disc and halo G and K dwarfs. The photometric metallicities lead us to develop a metallicity index for K dwarfs based only on their position in the colour-absolute-magnitude diagram. Metallicities have been determined for 431 single K dwarfs drawn from the Hipparcos catalogue, selecting the stars by absolute magnitude and removing multiple systems. The sample is essentially a complete reckoning of the metal content in nearby K dwarfs. We use stellar isochrones to mark the stars by mass, and select a subset of 220 of the stars, which is complete within a narrow mass interval. We fit the data with a model of the chemical evolution of the solar cylinder. We find that only a modest cosmic scatter is required to fit our age-metallicity relation. The model assumes two main infall episodes for the formation of the halo-thick disc and thin disc, respectively. The new data confirm that the solar neighbourhood formed on a long time-scale of the order of 7Gyr.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/2251
- Title:
- G0-G3 main-sequence stars with V<15
- Short Name:
- J/MNRAS/444/2251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The basic stellar atmospheric parameters (effective temperature, surface gravity and global metallicity) were determined simultaneously for a sample of 233 stars, limited in magnitude (V<15), with spectral types between G0 and G3 and luminosity class V (main sequence). The analysis was based on spectroscopic observations collected at the Observatorio Astrofisico Guillermo Haro and using a set of Lick-like indices defined in the spectral range 3800-4800{AA}. An extensive set of indices computed in a grid of theoretical spectra was used as a comparison tool in order to determine the photospheric parameters. The method was validated by matching the results from spectra of the asteroids Vesta and Ceres with the Sun parameters. The main results were as follows: (i) the photospheric parameters were determined for the first time for 213 objects in our sample and (ii) a sample of 20 new super-metal-rich star candidates was found.
- ID:
- ivo://CDS.VizieR/J/A+A/597/A108
- Title:
- GJ 536 HARPS and HARPS-N data
- Short Name:
- J/A+A/597/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a super-Earth orbiting the star GJ 536 based on the analysis of the radial-velocity time series from the HARPS and HARPS-N spectrographs. GJ 536 b is a planet with a minimum mass Msini of 5.36+/-0.69M_{Earth}_ with an orbital period of 8.7076+/-0.0025 days at a distance of 0.066610(13) AU, and an orbit that is consistent with circular. The host star is the moderately quiet M1 V star GJ 536, located at 10 pc from the Sun. We find the presence of a second signal at 43 days that we relate to stellar rotation after analysing the time series of Ca II H&K and Halpha spectroscopic indicators and photometric data from the ASAS archive. We find no evidence linking the short period signal to any activity proxy. We also tentatively derived a stellar magnetic cycle of less than 3 years.
134. GJ 625 HARPS-N data
- ID:
- ivo://CDS.VizieR/J/A+A/605/A92
- Title:
- GJ 625 HARPS-N data
- Short Name:
- J/A+A/605/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-velocity (RV) time series from the HARPS-N spectrograph, consisting in 151 HARPS-N measurements taken over 3.5yr. GJ 625 b is a planet with a minimum mass Msini of 2.82+/-0.51 M_Earth_ with an orbital period of 14.628+/-0.013 days at a distance of 0.078AU of its parent star. The host star is the quiet M2 V star GJ 625, located at 6.5pc from the Sun. We find the presence of a second radial velocity signal in the range 74-85 days that we relate to stellar rotation after analysing the time series of CaII H&K and H{alpha} spectroscopic indicators, the variations of the FWHM of the CCF and and the APT2 photometric light curves. We find no evidence linking the short period radial velocity signal to any activity proxy.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A20
- Title:
- GJ 740 radial velocities
- Short Name:
- J/A+A/648/A20
- Date:
- 29 Nov 2021 07:26:47
- Publisher:
- CDS
- Description:
- M-dwarfs have proven to be ideal targets for planetary radial velocity (RV) searches due to their higher planet-star mass contrast, which favors the detection of low-mass planets. The abundance of super-Earth and Earth-like planets detected around this type of stars encourages us to continue this search on hosts without reported planetary companions. The HADES and CARMENES programs aim to carry out extensive searches of exoplanetary systems around M-type stars in the northern hemisphere, allowing us to address statistically the properties of the planets orbiting these objects. In this work, we performed a spectroscopic and photometric study on one of the program stars (GJ 740), which exhibits a short-period RV signal compatible with a planetary companion. We carried out a spectroscopic analysis based on 129 HARPS-N spectra taken over a time-span of 6 yr combined with 57 HARPS spectra taken over 4yr, and 32 CARMENES spectra taken during more than 1 yr, resulting in a dataset with a time coverage of 10yr. We also relied on 459 measurements from the public ASAS survey with a time-coverage of 8yr along with 5yr of photometric magnitudes from the EXORAP project taken in the V, B, R and I filters to carry out a photometric study. Both analyses were made using Markov Chain Monte Carlo (MCMC) simulations and Gaussian Process regression to model the activity of the star. We present the discovery of a short-period super-Earth with an orbital period of 2.37756^+0.00013^_-0.00011_d and a minimum mass of 2.96^+0.50^_-0.48_Me. We update the previously reported characterization of the magnetic cycle and rotation period of the star, obtaining values of Prot=35.563+/-0.071d and Pcycle=2800+/-150d. The RV time-series exhibits a possibly periodic long-term signal which might be related to a Saturn-mass planet of ~100Me.
- ID:
- ivo://CDS.VizieR/J/ApJ/691/342
- Title:
- griBVI photometry in M37
- Short Name:
- J/ApJ/691/342
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of conducting a deep (14.5<~r<~23), 20 night survey for transiting planets in the rich ~550Myr old open cluster M37, we have measured the rotation periods of 575 stars, which lie near the cluster main sequence, with masses 0.2M_{sun}_<~M<~1.3M_{sun}_. This is the largest sample of rotation periods for a cluster older than 500Myr. Using this rich sample we investigate a number of relations between rotation period, color, and the amplitude of photometric variability.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1757
- Title:
- GX Gem radial velocities and light curves
- Short Name:
- J/AJ/135/1757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 12,155 new differential photometric observations in the V filter made with the Undergraduate Research Studies in Astronomy and NF\Observatory WebScopes, as well as 33 radial velocities from spectroscopic observations of the detached, 4.04 day double-lined eclipsing binary star GX Gem. Absolute dimensions of the components are determined from these new, and also from previously published, data with high precision (less than 0.7% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 1.488+/-0.011 solar masses and 2.327+/-0.012 solar radii for the primary, and 1.467+/-0.010 solar masses and 2.238+/-0.012 solar radii for the secondary. The effective temperatures and interstellar reddening of the stars are accurately determined from the spectra, uvby{beta}, and UBV photometry: 6195+/-100K for the primary, 6165+/-100K for the secondary, corresponding to spectral types of F7 and F7 V, and 0.068mag for the color excess E(b-y). Spectral line widths give rotational velocities that are synchronous with the mean orbital motion in a circular orbit.
- ID:
- ivo://CDS.VizieR/II/24
- Title:
- H-{alpha} Photometry of Northern Late-Type Stars I.
- Short Name:
- II/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations are presented of the strength of the H-{alpha} absorption line in the spectra of approximately 600 northern F, G and K stars of differing luminosities and chemical compositions. Most of the stars in this catalogue were previously observed by Griffin and Redman (1960MNRAS.120..287G), Deeming (1960MNRAS.121...52D), and Griffin (1961MNRAS.122..181G). Data given in this catalog include HD number, MK spectral classification, high velocity, (B-V) color index, magnesium b ratio, sodium D line ratio and H-{alpha} ratio.
- ID:
- ivo://CDS.VizieR/II/22
- Title:
- H{alpha} photometry of Southern F-G dwarfs
- Short Name:
- II/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- H{alpha} photometry is presented for 172 southern F, G, and K type stars, mostly of luminosity classes V and IV. The bands measured, using a spectroscopic resolution of 3.4{AA}/mm, were: H{alpha}: 6546.5-6582.5{AA} comparison regions: 6469.0-6505.0{AA} and 6624.0-6660.0{AA}.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A13
- Title:
- HARPS M dwarf sample magnetic activity
- Short Name:
- J/A+A/600/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Atmospheric magnetic fields in stars with convective envelopes heat stellar chromospheres, and thus increase the observed flux in the CaII H and K doublet. Starting with the historical Mount Wilson monitoring program, these two spectral lines have been widely used to trace stellar magnetic activity, and as a proxy for rotation period (Prot) and consequently for stellar age. Monitoring stellar activity has also become essential in filtering out false-positives due to magnetic activity in extra-solar planet surveys. The CaII emission is traditionally quantified through the R'_HK_-index, which compares the chromospheric flux in the doublet to the overall bolometric flux of the star. Much work has been done to characterize this index for FGK-dwarfs, but M dwarfs - the most numerous stars of the Galaxy - were left out of these analyses and no calibration of their CaII H and K emission to an R'_HK_ exists to date. We set out to characterize the magnetic activity of the low- and very-low-mass stars by providing a calibration of the R'_HK_-index that extends to the realm of M dwarfs, and by evaluating the relationship between R'_HK_ and the rotation period.. We calibrated the bolometric and photospheric factors for M dwarfs to properly transform the S-index (which compares the flux in the CaII H and K lines to a close spectral continuum) into the R'_HK_. We monitored magnetic activity through the CaII H and K emission lines in the HARPS M dwarf sample.
