- ID:
- ivo://CDS.VizieR/J/MNRAS/469/401
- Title:
- Known LT dwarfs in the Gaia DR1
- Short Name:
- J/MNRAS/469/401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify and investigate known ultracool stars and brown dwarfs that are being observed or indirectly constrained by the Gaia mission. These objects will be the core of the Gaia ultracool dwarf sample composed of all dwarfs later than M7 that Gaia will provide direct or indirect information on. We match known L and T dwarfs to the Gaia first data release, the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer AllWISE survey and examine the Gaia and infrared colours, along with proper motions, to improve spectral typing, identify outliers and find mismatches. There are 321 L and T dwarfs observed directly in the Gaia first data release, of which 10 are later than L7. This represents 45 per cent of all the known LT dwarfs with estimated GaiaG magnitudes brighter than 20.3mag. We determine proper motions for the 321 objects from Gaia and the Two Micron All Sky Survey positions. Combining the Gaia and infrared magnitudes provides useful diagnostic diagrams for the determination of L and T dwarf physical parameters. We then search the Tycho-Gaia astrometric solution, Gaia first data release subset, to find any objects with common proper motions to known L and T dwarfs and a high probability of being related. We find 15 new candidate common proper motion systems.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/3651
- Title:
- L and T dwarfs from UKIDSS LAS
- Short Name:
- J/MNRAS/449/3651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectroscopic analysis of a large sample of late-M, L, and T dwarfs from the United Kingdom Deep Infrared Sky Survey. Using the YJHK photometry from the Large Area Survey and the red-optical photometry from the Sloan Digital Sky Survey we selected a sample of 262 brown dwarf candidates and we have followed-up 196 of them using the echelle spectrograph X-shooter on the Very Large Telescope. The large wavelength coverage (0.30-2.48um) and moderate resolution (R~5000-9000) of X-shooter allowed us to identify peculiar objects including 22 blue L dwarfs, 2 blue T dwarfs, and 2 low-gravity M dwarfs. Using a spectral indices-based technique, we identified 27 unresolved binary candidates, for which we have determined the spectral type of the potential components via spectral deconvolution. The spectra allowed us to measure the equivalent width of the prominent absorption features and to compare them to atmospheric models. Cross-correlating the spectra with a radial velocity standard, we measured the radial velocity of our targets, and we determined the distribution of the sample, which is centred at -1.7+/-1.2km/s with a dispersion of 31.5km/s. Using our results, we estimated the space density of field brown dwarfs and compared it with the results of numerical simulations. Depending on the binary fraction, we found that there are (0.85+/-0.55)x10^-3^ to (1.00+/-0.64)x10^-3^ objects per cubic parsec in the L4-L6.5 range, (0.73+/-0.47)x10^-3^ to (0.85+/-0.55)x10^-3^ objects per cubic parsec in the L7-T0.5 range, and (0.74+/-0.48)x10^-3^ to (0.88+/-0.56)x10^-3^ objects per cubic parsec in the T1-T4.5 range. We notice that there seems to be an excess of objects in the L-T transition with respect to the late-T dwarfs, a discrepancy that could be explained assuming a higher binary fraction than expected for the L-T transition, or that objects in the high-mass end and low-mass end of this regime form in different environments, i.e. following different initial mass functions.
- ID:
- ivo://CDS.VizieR/J/PASJ/57/109
- Title:
- Late-G giants abundances
- Short Name:
- J/PASJ/57/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Towards clarifying the properties of late-G giants, for which we are currently conducting a planet-search project at Okayama Astrophysical Observatory, an extensive spectroscopic study has been performed for our first target sample of fifty-seven G6-G9 III stars, in order to establish the atmospheric parameters (Teff, logg, vt, and [Fe/H]), the stellar mass along with the evolutionary status, and the photospheric abundances of various elements. It was confirmed that the conventional spectroscopic method of parameter determination using Fe I / II lines with the assumption of LTE works successfully for these evolved stars. We determined the abundances (relative to the Sun) of 19 elements, and examined how their [X/Fe] ratios behave themselves with the run of [Fe/H].
- ID:
- ivo://CDS.VizieR/J/A+A/442/281
- Title:
- Late-type giants BVRIJHKL and Teff calibration
- Short Name:
- J/A+A/442/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new synthetic broad-band photometric colors for late-type giants based on synthetic spectra calculated with the PHOENIX model atmosphere code. The grid covers effective temperatures Teff=3000...5000K, gravities logg=-0.5...+3.5, and metallicities [M/H]=+0.5...-4.0.
- ID:
- ivo://CDS.VizieR/J/MNRAS/246/54
- Title:
- Late-type giants in Baade's window
- Short Name:
- J/MNRAS/246/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities have been measured for an unbiased sample of 239 late-type M giants in the b=-4{deg} galactic bulge window (Baade's window). The radial velocities were acquired at the AAT Observatory.
- ID:
- ivo://CDS.VizieR/J/AJ/83/1090
- Title:
- Late-type M dwarfs towards the SGP
- Short Name:
- J/AJ/83/1090
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog, including finding charts, is presented which contains 282 faint stars of spectral type M3 and later, located in an area of 173 square degrees near the South Galactic Pole. The catalog is based on a spectroscopic survey undertaken with the Curtis Schmidt at CTIO and provides a finding list of M stars free of any possible kinematic bias. The majority of these stars are expected to be dwarfs. To the same limiting magnitude, the observed surface density is comparable to that of the faint M stars in the direction of the North Galactic Pole, named 273 over 190 square degrees.
- ID:
- ivo://CDS.VizieR/J/A+A/425/489
- Title:
- Late-type stars in the inner Milky Way
- Short Name:
- J/A+A/425/489
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a narrow-band infrared imaging survey of a narrow strip (12' wide) around the Galactic equator between 6{deg} and 21{deg} of galactic longitude aimed at detecting field stars with strong CO absorption, mainly late-type giants and supergiants. Our observations include follow-up low resolution spectroscopy (R=980) of 191 selected candidates in the H and K bands.
- ID:
- ivo://CDS.VizieR/J/MNRAS/328/45
- Title:
- Late-type stars members of young groups
- Short Name:
- J/MNRAS/328/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper of a series aimed at studying the properties of late-type members of young stellar kinematic groups. We concentrate our study on classical young moving groups such as the Local Association (Pleiades moving group, 2-150Myr), IC 2391 supercluster (35Myr), Ursa Major group (Sirius supercluster, 300Myr), and Hyades supercluster (600Myr), as well as on recently identified groups such as the Castor moving group (200Myr). In this paper we compile a preliminary list of single late-type possible members of some of these young stellar kinematic groups. Stars are selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria such as their level of chromospheric activity, rotation rate and lithium abundance. Precise measurements of proper motions and parallaxes taken from the Hipparcos Catalogue, as well as from the Tycho-2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V, W) and to apply Eggen's kinematic criteria in order to determine the membership of the selected stars to the different groups.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/473
- Title:
- Late-type star spectra
- Short Name:
- J/A+AS/123/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work we present spectroscopic observations centered in the spectral lines most widely used as optical indicators of chromospheric activity (H{alpha}, H{beta}, Ca II H & K, and He I D{3}) in a sample of F, G, K and M chromospherically inactive stars. The spectra have been obtained with the aim of providing a library of high and mid-resolution spectra to be used in the application of the spectral subtraction technique to obtain the active-chromosphere contribution to these lines in chromospherically active single and binary stars. This library can also be used for spectral classification purposes. A digital version with all the spectra is available via ftp and the World Wide Web (WWW) in both ASCII and FITS formats
- ID:
- ivo://CDS.VizieR/J/PASP/111/1169
- Title:
- Late-type stars toward galactic antirotation
- Short Name:
- J/PASP/111/1169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-resolution objective-prism spectra (1360{AA}/mm at H{gamma}) of 184 late-type stars in the Galactic antirotation direction have been obtained with the Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory. The stars have been classified into three groups: F6-G2, G3-K0, and K1-M8. Subsequent observations on the BV and DDO systems have been obtained. The correlation between the thin-prism classes and the DDO classes is as expected, with no significant systematic differences of note. A comparison of Guide Star Catalog magnitudes, corrected to V, is also made, with favorable results. The stars in this list are expected to be useful for studying the structure and star formation history of the Milky Way.
