- ID:
- ivo://CDS.VizieR/J/MNRAS/301/1031
- Title:
- High resolution spectra of VLM stars
- Short Name:
- J/MNRAS/301/1031
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A high resolution optical spectral atlas for three very low-mass stars are provided, along with a high resolution observation of an atmospheric absorption calibrator. This is the data used to produce Figures 4-9 in the paper. These data were acquired with CASPEC on the ESO3.6m telescope. The FWHM resolution is 16km/s (eg. 0.043nm at 800nm), at a dispersion of 9km/s. Incomplete wavelength coverage produces inter-order gaps at wavelengths longer than 804.5nm.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/325/647
- Title:
- High-resolution spectra south of Taurus
- Short Name:
- J/A+A/325/647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Listed are results from our high-resolution data for all stars in our study area which were listed by either Magazzu et al. (1997A&AS..124..449M) or Alcala et al. (1996A&AS..119....7A), i.e. T Tauri candidates from the ROSAT All-Sky Survey. In table 1, we list all stars for which lithium was found either by Magazzu et al. (1997A&AS..124..449M) or in our CASPEC spectra, as well as two stars identified as wTTS by Alcala et al. (1996A&AS..119....7A). Listed are the designation, number of single-order echelle spectra taken, effective temperatures, projected rotational velocities, mean heliocentric radial velocities with errors, radial velocities in the local standard of rest, and remarks on variability in radial velocity as found in our high-resolution spectra. For comparison, we also list the results on spectral types of the stars (with `e' for H{alpha} emission) as found by Magazzu et al. (1997A&AS..124..449M) (or Alcala et al., 1996A&AS..119....7A) with low- and medium-resolution spectroscopy. In the last two columns, we list the (NLTE) lithium abundance (given on a scale where logN(H)=12) and the lithium excess above the relevant Pleiades upper envelope; upper limits indicate stars where the Magazzu et al. (1997A&AS..124..449M) spectra suffer from either low S/N or low resolution. In table 2, we list all stars where no lithium was detected -- neither by Magazzu et al. (1997A&AS..124..449M) nor in our CASPEC spectra.
183. Hipparcos red stars
- ID:
- ivo://CDS.VizieR/J/A+A/397/997
- Title:
- Hipparcos red stars
- Short Name:
- J/A+A/397/997
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For Hipparcos M, S, and C spectral type stars, we provide calibrated instantaneous (epoch) Cousins V-I color indices using newly derived HpV_T2_ photometry. Three new sets of ground-based Cousins VI data have been obtained for more than 170 carbon and red M giants, observed at SAAO in 1984 and 1987 (table1), at Siding Spring Observatory in 2002 (table2), and with the Automatic Photoelectric Telescopes located at Fairborn Observatory from 1996 (table3). These datasets in combination with the published sources of VI photometry served to obtain the calibration curves linking Hipparcos/Tycho Hp-V_T2_ with the Cousins V-I index. In total, 321 carbon stars and 4464 M- and S-type stars have new V-I indices. The standard error of the mean V-I is about 0.1mag or better down to Hp~9 although it deteriorates rapidly at fainter magnitudes. These V-I indices can be used to verify the published Hipparcos V-I color indices. Thus, we have identified a handful of new cases where, instead of the real target, a random field star has been observed. A considerable fraction of the DMSA/C and DMSA/V solutions for red stars appear not to be warranted. Most likely such spurious solutions may originate from usage of a heavily biased color in the astrometric processing.
- ID:
- ivo://CDS.VizieR/J/BaltA/20/89
- Title:
- Homegenized effective temperatures of 800 stars
- Short Name:
- J/BaltA/20/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some selected catalogs of the effective temperatures (Teff) for F, G and K stars are analyzed. By an improved technique we estimate the external errors of these catalogs from data intercomparisons. The Teff values are then averaged with the appropriate weights to produce a mean homogeneous catalog based on the selected data. This catalog, containing 800 stars, is compared with some other independent catalogs for estimating their external errors. The data may be used as a source of reliable homogeneous values of Teff, together with their errors.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A13
- Title:
- Homogeneous sample of F6-K4 Hyades stars
- Short Name:
- J/A+A/547/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar kinematic groups are kinematical coherent groups of stars that might have a common origin. These groups are dispersed throughout the Galaxy over time by the tidal effects of both Galactic rotation and disc heating, although their chemical content remains unchanged. The aim of chemical tagging is to establish that the abundances of every element in the analysis are homogeneous among the members. We study the case of the Hyades Supercluster to compile a reliable list of members (FGK stars) based on our chemical tagging analysis. For a total of 61 stars from the Hyades Supercluster, stellar atmospheric parameters (Teff, logg, {ksi}, and [Fe/H]) are determined using our code called StePar, which is based on the sensitivity to the stellar atmospherics parameters of the iron EWs measured in the spectra. We derive the chemical abundances of 20 elements and find that their [X/Fe] ratios are consistent with Galactic abundance trends reported in previous studies. The chemical tagging method is applied with a carefully developed differential abundance analysis of each candidate member of the Hyades Supercluster, using a well-known member of the Hyades cluster as a reference (vB 153). We find that only 28 stars (26 dwarfs and 2 giants) are members, i.e. that 46% of our candidates are members based on the differential abundance analysis. This result confirms that the Hyades Supercluster cannot originate solely from the Hyades cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/476/1347
- Title:
- HST/ACS flux time series for HD 189733
- Short Name:
- J/A+A/476/1347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We monitored three transits of the giant gas planet around the nearby K dwarf HD 189733 with the ACS camera on the Hubble Space Telescope. The resulting very-high accuracy light-curve (signal-to-noise ratio near 15000 on individual measurements, 35000 on 10-min averages) allows a direct geometric measurement of the orbital inclination, radius ratio and scale of the system: i=85.68+/-0.04, Rpl/R*=0.1572+/-0.0004, a/R*=8.92+/-0.09.
- ID:
- ivo://CDS.VizieR/J/ApJ/541/977
- Title:
- HST observations of low-mass stars in IC 348
- Short Name:
- J/ApJ/541/977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the low-mass population of the young cluster IC 348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative method for the spectral classification of late-type objects. Using photometric indices, constructed from HST/NICMOS narrowband imaging, that measure the strength of the 1.9{mu}m water band, we determine the spectral type and reddening for every M-type star in the field, thereby separating cluster members from the interloper population. Due to the efficiency of our spectral classification technique, our study is complete from ~0.7 to 0.015M_{sun}_. The mass function derived for the cluster in this interval, dN/dlogM{prop.to}M^0.5^, is similar to that obtained for the Pleiades, but appears significantly more abundant in brown dwarfs than the mass function for companions to nearby Sunlike stars. This provides compelling observational evidence for different formation and evolutionary histories for substellar objects formed in isolation versus as companions. Because our determination of the IMF is complete to very low masses, we can place interesting constraints on the role of physical processes such as fragmentation in the star and planet formation process and the fraction of dark matter in the Galactic halo that resides in substellar objects.
- ID:
- ivo://CDS.VizieR/J/A+A/442/165
- Title:
- IJKs photometry of late-type stars in Draco dSph
- Short Name:
- J/A+A/442/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the William Herschel Telescope in La Palma we made IJKs observations of an area of about 40'x30' of the Local Group galaxy Draco. This allows us to describe Draco's late-type stellar population across the whole galaxy at a photometric level 2mag deeper than the 2MASS survey. We detected the red giant branch (RGB) and measured the magnitude of the tip of the RGB in the three bands. From that in the I band we obtain a distance modulus of (m-M)_0=19.49+/-0.06(stat)+/-0.15(sys), in excellent agreement with a measurement from RR Lyrae stars. The peak of the (J-Ks)_0_ histogram at different M_Ks_ suggests that Draco has a mean [Fe/H]=-1.95+/-1.26 while fiducial RGB tracks of Galactic globular clusters indicate a mean [Fe/H]=-1.33+/-0.72 where the error corresponds to the spread around the mean value. There are significant differences between the colour-magnitude diagrams of stars in the inner, medium and outer areas of the galaxy. A metal poor (Z=0.0004) intermediate-age population (about 1.6Gyr old) is clearly present and emerges in particular between 6' and 12' from the centre of the galaxy. A few additional carbon star candidates have been identified from both their location in the colour-magnitude diagram and from an indication of variability. The large scale distribution of late-type stars is smooth but irregular in shape; this points at a variation of inclination with radius.
- ID:
- ivo://CDS.VizieR/J/A+A/429/837
- Title:
- IJKs photometry of late-type stars in NGC 6822
- Short Name:
- J/A+A/429/837
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations in the IJKs wave bands covering the central 20'x20' of the Local Group galaxy NGC 6822 have been made with the William Herschel Telescope in La Palma. They have allowed us to characterize, for the first time in the near-infrared across the whole galaxy, its late-type stellar population (i.e. red giant and asymptotic giant branch stars) and to derive from the ratio between carbon-rich and oxygen-rich asymptotic giant branch stars an indication about spatial variations in metallicity. These amount to about 1.56dex, twice of what has been previously found within each Magellanic Cloud using the same technique. We have calibrated our photometry on the DENIS (I-band) and 2MASS (J and Ks bands) data and obtained a distance modulus of (m-M)_0_=23.34(0.12) from the position of the tip of the RGB. The large scale distribution of late-type stars suggests that either the galaxy is viewed under a high inclination angle or it has a non-negligible thickness.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A132
- Title:
- IK Tau and HIP 20188 visible polarimetric imaging
- Short Name:
- J/A+A/628/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present visible polarimetric imaging observations of the oxygen-rich AGB star IK Tau obtained with SPHERE-ZIMPOL (phase 0.27) as well as interferometric observations with AMBER. The polarimetric imaging capabilities of SPHERE-ZIMPOL have allowed us to spatially resolve clumpy dust clouds at 20-50mas from the central star, which corresponds to 2-5R* when combined with a central star's angular diameter of 20.7+/-1.53 mas measured with AMBER. The diffuse, asymmetric dust emission extends out to ~73R*. We find that the TiO emission extends to 150 mas (15R*). The AMBER data in the CO lines also suggest a molecular outer atmosphere extending to ~1.5R*. The results of our 2-D Monte Carlo radiative transfer modelling of dust clumps suggest that the polarized intensity and degree of linear polarization can be reasonably explained by small-sized (0.1{mu}m) grains of Al_2_O_3, MgSiO_3, or Mg_2_SiO_4 in an optically thin shell ({tau}_550 nm=0.5+/-0.1) with an inner boundary radius of 3.5*. IK Tau's mass-loss rate is 20 to 50 times higher than the previously studied AGB stars W Hya, R Dor, and o Cet. Nevertheless, our observations of IK Tau revealed that clumpy dust formation occurs close to the star as seen in those low mass-rate AGB stars.
