- ID:
- ivo://CDS.VizieR/J/AJ/80/972
- Title:
- Dwarf K and M stars at low latitudes
- Short Name:
- J/AJ/80/972
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 100 dwarf K and M stars found on objective-prism plates taken at low galactic latitudes, mostly in the southern sky. Most stars were recognized from the strength of the sodium D lines, and the majority have known proper motions of 0.1" or more per annum. Ninety-nine of these stars lack previous spectral classification; one lacks previous observation of line emission. Most have below the limits of the DM charts, and for there we provide identification charts.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/879/105
- Title:
- Effective temperatures of low-mass stars
- Short Name:
- J/ApJ/879/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution, near-infrared spectra will be the primary tool for finding and characterizing Earth-like planets around low-mass stars. Yet, the properties of exoplanets cannot be precisely determined without accurate and precise measurements of the host star. Spectra obtained with the Immersion Grating Infrared Spectrometer simultaneously provide diagnostics for most stellar parameters, but the first step in any analysis is the determination of the effective temperature. Here we report the calibration of high-resolution H-band spectra to accurately determine the effective temperature for stars between 4000 and 3000K (~K8-M5) using absorption line-depths of FeI, OH, and Al I. The field star sample used here contains 254 K and M stars with temperatures derived using BT-Settl synthetic spectra. We use 106 stars with precise temperatures in the literature to calibrate our method, with typical errors of about 140K, and systematic uncertainties less than ~120K. For the broadest applicability, we present Teff-line-depth-ratio relationships, which we test on 12 members of the TW Hydrae Association and at spectral resolving powers between ~10000 and 120000. These ratios offer a simple but accurate measure of effective temperatures in cool stars that are distance and reddening independent.
- ID:
- ivo://CDS.VizieR/J/AJ/141/166
- Title:
- HATNet variability survey of K and M dwarfs
- Short Name:
- J/AJ/141/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using light curves from the HATNet survey for transiting extrasolar planets we investigate the optical broad-band photometric variability of a sample of 27, 560 field K and M dwarfs selected by color and proper-motion (V-K>~3.0, mu>30mas/yr, plus additional cuts in J-H vs. H-Ks and on the reduced proper motion). We apply a variety of variability selection algorithms on the light curves to search for periodic and quasi-periodic variations, and for large-amplitude, long-duration flare events. To set the selection thresholds we conduct Monte Carlo simulations of light curves with realistic noise properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/17
- Title:
- HAZMAT. V. UV and X-ray evolution of K stars
- Short Name:
- J/ApJ/872/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowing the high-energy radiation environment of a star over a planet's formation and evolutionary period is critical in determining if that planet is potentially habitable and if any biosignatures could be detected, as UV radiation can severely change or destroy a planet's atmosphere. Current efforts for finding a potentially habitable planet are focused on M stars, yet K stars may offer more habitable conditions due to decreased stellar activity and more distant and wider habitable zones (HZs). While M star activity evolution has been observed photometrically and spectroscopically, there has been no dedicated investigation of K star UV evolution. We present the first comprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. We used members of young moving groups and clusters ranging in age from 10 to 625Myr combined with field stars and their archived GALEX UV and ROSAT X-ray data to determine how the UV and X-ray radiation evolve. We find that the UV and X-ray flux incident on an HZ planet is 5-50 times lower than that of HZ planets around early-M stars and 50-1000 times lower than those around late-M stars, due to both an intrinsic decrease in K dwarf stellar activity occurring earlier than for M dwarfs and the more distant location of the K dwarf HZ.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/41
- Title:
- HD 128311 radial velocity and astrometric data
- Short Name:
- J/ApJ/795/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used high-cadence radial velocity measurements from the Hobby-Eberly Telescope with published velocities from the Lick 3 m Shane Telescope, combined with astrometric data from the Hubble Space Telescope (HST) Fine Guidance Sensors to refine the orbital parameters of the HD 128311 system, and determine an inclination of 55.95{deg}+/-14.55{deg} and true mass of 3.789_-0.432_^+0.924^ M_JUP_ for HD 128311 c. The combined radial velocity data also reveal a short period signal which could indicate a third planet in the system with an Msin i of 0.133+/-0.005 M_JUP_or stellar phenomena. Photometry from the T12 0.8 m automatic photometric telescope at the Fairborn Observatory and HST are used to determine a photometric period close to, but not within the errors of the radial velocity signal. We performed a cross-correlation bisector analysis of the radial velocity data to look for correlations with the photometric period and found none. Dynamical integrations of the proposed system show long-term stability with the new orbital parameters of over 10 million years. Our new orbital elements do not support the claims of HD 128311 b and c being in mean motion resonance.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/1356
- Title:
- Hercules stream K giants analysis
- Short Name:
- J/MNRAS/460/1356
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An abundance analysis is reported of 58-K giants identified by Famaey et al. (2005, J/A+A/430/165) as highly probable members of the Hercules stream selected from stars north of the celestial equator in the Hipparcos catalogue. The giants have compositions spanning the interval [Fe/H] from -0.17 to +0.42 with a mean value of +0.15 and relative elemental abundances [El/Fe] representative of the Galactic thin disc. Selection effects may have biased the selection from the Hipparcos catalogue against the selection of metal-poor stars. Our reconsideration of the recent extensive survey by Bensby et al. of FG dwarfs, including metal-poor stars, provides a [Fe/H] distribution for the Hercules stream, which is similar to that from the 58 giants. It appears that the stream is dominated by metal-rich stars from the thin disc. We discuss suggestions in the literature that the stream includes metal-poor stars from the thick disc.
- ID:
- ivo://CDS.VizieR/J/AJ/105/1962
- Title:
- K and M stars photometry
- Short Name:
- J/AJ/105/1962
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broadband UBVRI photometry is presented for 687 stars from among the dwarf K and M stars found spectroscopically by Vyssotsky [1958AJ.....63..211V]. Of these, 211 are without previous photometry.
- ID:
- ivo://CDS.VizieR/J/A+AS/97/835
- Title:
- K giants at the South Galactic Pole
- Short Name:
- J/A+AS/97/835
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/other/RAA/17.76
- Title:
- K giant stars along Sagittarius streams
- Short Name:
- J/other/RAA/17.7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Large Sky-Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 3 provided 341 691 K giant stars with stellar parameters. Based on the models of Law & Majewski (2010ApJ...714..229L), we identified 252 K giant stars in the leading stream associated with the Sagittarius (Sgr) dwarf galaxy. We obtained 132 K giant stars belonging to the trailing arm of Sgr using the model of Belokurov et al. We studied the metallicity distribution of member stars along the streams and found a flat gradient in the first wrap of the leading stream, -(0.88+/-0.3)x10^-3^dex/deg in the second wrap of the leading stream and -(1.2+/-0.3)x10^-3^dex/deg in the first wrap of the trailing stream. Moreover, we obtained a combined metallicity gradient with our sample and data from the literature. We also analyzed the properties of an overdensity, which is located in the leading stream of the Sgr.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/65
- Title:
- LAMOST K giants in Galactic halo substructures
- Short Name:
- J/ApJ/880/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a large halo K-giant sample by combining the positions, distances, radial velocities, and metallicities of over 13000 LAMOST DR5 halo K giants with the Gaia DR2 proper motions, which covers a Galactocentric distance range of 5-120kpc. Using a position-velocity clustering estimator (the 6Distance), we statistically quantify the presence of position-velocity substructure at high significance: K giants have more close pairs in position-velocity space than a smooth stellar halo. We find that the amount of substructure in the halo increases with increasing distance and metallicity. With a percolation algorithm named friends-of-friends to identify groups, we identify members belonging to Sagittarius (Sgr) Streams, Monoceros Ring, Virgo Overdensity, Hercules-Aquila Cloud, Orphan Streams, and other unknown substructures and find that the Sgr streams account for a large part of grouped stars beyond 20kpc and enhance the increase of substructure with distance and metallicity. For the first time, we identify spectroscopic members of Monoceros Ring in the southern and northern Galactic hemispheres, which presents a rotation of about 185km/s and a mean metallicity of -0.66dex.
