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3821. The solar neighborhood. XLII. New nearby subdwarfs
ID:
ivo://CDS.VizieR/J/AJ/154/191
Title:
The solar neighborhood. XLII. New nearby subdwarfs
Short Name:
J/AJ/154/191
Date:
21 Oct 2021
Publisher:
CDS
Description:
Parallaxes, proper motions, and optical photometry are presented for 51 systems consisting of 37 cool subdwarf and 14 additional high proper motion systems. Thirty-seven systems have parallaxes reported for the first time, 15 of which have proper motions of at least 1"/yr. The sample includes 22 newly identified cool subdwarfs within 100 pc, of which three are within 25 pc, and an additional five subdwarfs from 100 to 160 pc. Two systems-LSR 1610-0040 AB and LHS 440 AB-are close binaries exhibiting clear astrometric perturbations that will ultimately provide important masses for cool subdwarfs. We use the accurate parallaxes and proper motions provided here, combined with additional data from our program and others, to determine that effectively all nearby stars with tangential velocities greater than 200 km/s are subdwarfs. We compare a sample of 167 confirmed cool subdwarfs to nearby main sequence dwarfs and Pleiades members on an observational Hertzsprung-Russell diagram using M_V_ versus (V-K_s_) to map trends of age and metallicity. We find that subdwarfs are clearly separated for spectral types K5-M5, indicating that the low metallicities of subdwarfs set them apart in the H-R diagram for (V-K_s_)=3-6. We then apply the tangential velocity cutoff and the subdwarf region of the H-R diagram to stars with parallaxes from Gaia Data Release 1 and the MEarth Project to identify a total of 29 new nearby subdwarf candidates that fall clearly below the main sequence.
3822. The solar neighborhood. XLIV. RECONS discoveries
ID:
ivo://CDS.VizieR/J/AJ/155/265
Title:
The solar neighborhood. XLIV. RECONS discoveries
Short Name:
J/AJ/155/265
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe the 44 systems discovered to be within 10 pc of the Sun by the RECONS team, primarily via the long-term astrometry program at the CTIO/SMARTS 0.9 m that began in 1999. The systems-including 41 with red dwarf primaries, 2 white dwarfs, and 1 brown dwarf-have trigonometric parallaxes greater than 100 mas, with errors of 0.4-2.4 mas in all but one case. We provide updated astrometric, photometric (VRIJHK magnitudes), spectral type, and multiplicity information here. Among these are 14 systems that are new entries to the 10 pc sample, including the first parallaxes for 9 systems and new values for 5 systems that had previous parallaxes with errors greater than 10 mas or values placing them beyond 10 pc. We also provide new data for 22 systems known to lie within 10 pc and 9 systems reported to be closer than that horizon but for which new parallaxes place them further away, bringing the total to 75 systems. The 44 systems added by RECONS comprise one of every 7 systems known within 10 pc. We illustrate the evolution of the 10 pc sample from the 191 systems known when the final Yale Parallax Catalog was published in 1995 to the 317 systems known today. Even so close to the Sun, additional discoveries of white, red, and brown dwarfs are possible, both as primaries and secondaries, although we estimate that at least 90% of the stellar systems closer than 10 pc have now been identified.
3823. The Solar Neighborhood. XLVII. Mdwarfs with STIS
ID:
ivo://CDS.VizieR/J/AJ/161/172
Title:
The Solar Neighborhood. XLVII. Mdwarfs with STIS
Short Name:
J/AJ/161/172
Date:
18 Jan 2022
Publisher:
CDS
Description:
We use HST/STIS optical spectroscopy of 10 M-dwarfs in five closely separated binary systems to test models of M-dwarf structure and evolution. Individual dynamical masses ranging from 0.083 to 0.405M{sun} for all stars are known from previous work. We first derive temperature, radius, luminosity, surface gravity, and metallicity by fitting the BT-Settl atmospheric models. We verify that our methodology agrees with empirical results from long-baseline optical interferometry for stars of similar spectral types. We then test whether or not evolutionary models can predict those quantities given the stars' known dynamical masses and the conditions of coevality and equal metallicity within each binary system. We apply this test to five different evolutionary model sets: the Dartmouth models, the MESA/MIST models, the models of Baraffe et al., the PARSEC models, and the YaPSI models. We find marginal agreement between evolutionary model predictions and observations, with few cases where the models respect the condition of coevality in a self-consistent manner. We discuss the pros and cons of each family of models and compare their predictive power.
3824. The solar neighborhood.XLVI. New M dwarf binaries
ID:
ivo://CDS.VizieR/J/AJ/160/215
Title:
The solar neighborhood.XLVI. New M dwarf binaries
Short Name:
J/AJ/160/215
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use 20yr of astrometric data from the REsearch Consortium On Nearby Stars (RECONS) program on the Cerro Tololo Inter-American Observatory/SMARTS 0.9m telescope to provide new insight into multiple star systems in the solar neighborhood. We provide new and updated parallaxes for 210 systems and derive nine high-quality astrometric orbits with periods of 2.49-16.63yr. Using a total of 542 systems parallaxes from RECONS, we compare systems within 25pc to Gaia DR2 to define criteria for selecting unresolved astrometric multiples from the DR2 results. We find that three out of four unresolved multistar red dwarf systems within 25pc in DR2 have parallax_error >=0.32mas, astrometric_gof_al>=56, astrometric_excess-noise_sig>=108.0, ruwe>=2.0, and parallaxes more than ~10% different from the long-term RECONS results. These criteria have broad applications to any work targeting nearby stars, from studies seeking binary systems to efforts targeting single stars for planet searches.
3825. The solar neighborhood .XXXX. New young stars
ID:
ivo://CDS.VizieR/J/AJ/154/151
Title:
The solar neighborhood .XXXX. New young stars
Short Name:
J/AJ/154/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
As a step toward completing and characterizing the census of the solar neighborhood, we present astrometric, photometric, and spectroscopic observations of 32 systems observed with the Cerro Tololo Inter-American Observatory 0.9 m and 1.5 m telescopes. Astrometry from the 0.9 m indicates that among the 17 systems that had no previous published trigonometric parallaxes, 14 are within 25 pc. In the full sample, nine systems have proper motions larger than 0.5"/yr, including 2MASS J02511490-0352459, which exceeds 2.0"/yr. VRI photometry from the 0.9 m and optical spectra from the 1.5 m indicate that the targets have V=11-22 mag and spectral types M3.0V-L3.0V. For 2MASS J23062928-0502285 (TRAPPIST-1), we present updated astrometry and photometric variability based on over 12 years of observations. Of the nine binaries in the sample, two promise mass determinations in the next decade: LHS 6167AB, an M4.5V system for which we present an accurate parallax placing the binary at 9.7 pc, and 2MASS J23515048-2537367AB, an M8.5V system at 21.1 pc for which we present the first evidence of an unseen, low-mass companion. Most importantly, Na I and K I gravity indicators, H{alpha} measurements, long-term photometric variability, locations on the H-R diagram, and kinematic assessments indicate that as many as 13 of the systems are young, including candidate members of young moving groups, with ages less than ~120 Myr.
3826. The SOS project. IV. NGC 1624 and NGC 1931
ID:
ivo://CDS.VizieR/J/AJ/149/127
Title:
The SOS project. IV. NGC 1624 and NGC 1931
Short Name:
J/AJ/149/127
Date:
21 Oct 2021
Publisher:
CDS
Description:
Young open clusters located in the outer Galaxy provide us with an opportunity to study star formation activity in a different environment from the solar neighborhood. We present a UBVI and H{alpha} photometric study of the young open clusters NGC 1624 and NGC 1931 that are situated toward the Galactic anticenter. Various photometric diagrams are used to select the members of the clusters and to determine the fundamental parameters. NGC 1624 and NGC 1931 are, on average, reddened by <E(B-V)>=0.92+/-0.05 and 0.74+/-0.17mag, respectively. The properties of the reddening toward NGC 1931 indicate an abnormal reddening law (R_V,cl_=5.2+/-0.3). Using the zero-age main sequence fitting method we confirm that NGC 1624 is 6.0+/-0.6kpc away from the Sun, whereas NGC 1931 is at a distance of 2.3+/-0.2kpc. The results from isochrone fitting in the Hertzsprung-Russell diagram indicate the ages of NGC 1624 and NGC 1931 to be less than 4 and 1.5-2.0Myr, respectively. We derived the initial mass function (IMF) of the clusters. The slope of the IMF ({Gamma}_NGC1624_=-2.0+/-0.2 and {Gamma}_NGC1931_=-2.0+/-0.1) appears to be steeper than that of the Salpeter/Kroupa IMF. We discuss the implication of the derived IMF based on simple Monte-Carlo simulations and conclude that the property of star formation in the clusters does not seem to be significantly different from that in the solar neighborhood.
3827. The SOS. VII. UBVI photometry of open cluster IC 1590
ID:
ivo://CDS.VizieR/J/AJ/162/140
Title:
The SOS. VII. UBVI photometry of open cluster IC 1590
Short Name:
J/AJ/162/140
Date:
21 Mar 2022 00:39:36
Publisher:
CDS
Description:
Young open clusters are ideal laboratories to understand the star formation process. We present deep UBVI and H{alpha} photometry for the young open cluster IC1590 in the center of the HII region NGC281. Early-type members are selected from UBV photometric diagrams, and low-mass pre-main-sequence (PMS) members are identified by using H{alpha} photometry. In addition, the published X-ray source list and Gaia astrometric data are also used to isolate probable members. A total of 408 stars are selected as members. The mean reddening obtained from early-type members is <E(B-V)>=0.40{+/-}0.06(s.d.). We confirm the abnormal extinction law for the intracluster medium. The distance modulus to the cluster determined from the zero-age main-sequence fitting method is 12.3{+/-}0.2mag (d=2.88{+/-}0.28kpc), which is consistent with the distance d=2.70_-0.20_^+0.24^kpc from the recent Gaia parallaxes. We also estimate the ages and masses of individual members by means of stellar evolutionary models. The mode of the age of PMS stars is about 0.8Myr. The initial mass function of IC1590 is derived. It appears to be a steeper shape ({Gamma}=-1.49{+/-}0.14) than that of the Salpeter/Kroupa initial mass function for the high-mass regime (m>1M{sun}). The signature of mass segregation is detected from the difference in the slopes of the initial mass functions for the inner (r<2.5') and outer regions of this cluster. We finally discuss the star formation history in NGC281.
3828. The Spitzer Kepler Survey (SpiKeS) catalog
ID:
ivo://CDS.VizieR/J/ApJS/254/11
Title:
The Spitzer Kepler Survey (SpiKeS) catalog
Short Name:
J/ApJS/254/11
Date:
17 Jan 2022 00:38:57
Publisher:
CDS
Description:
The ~200000 targets monitored for photometric variability during the Kepler prime mission include the best-studied group of stars in the sky, due both to the extensive time history provided by Kepler and to the substantial amount of ancillary data provided by other investigators or compiled by the Kepler team. To complement this wealth of data, we surveyed the entire Kepler field using the 3.6 and 4.5{mu}m bands of the Warm Spitzer Space Telescope, obtaining photometry in both bands for almost 170000 objects. We demonstrate relative photometric precision ranging from better than ~1.5% for the brighter stars down to slightly greater than ~2% for the faintest stars monitored by Kepler. We describe the data collection and analysis phases of this work and identify several stars with large infrared excess, although none that is also known to be the host of an exoplanetary system.
3829. The Spitzer-SDSS-GALEX Spectroscopic Survey
ID:
ivo://CDS.VizieR/J/ApJ/741/79
Title:
The Spitzer-SDSS-GALEX Spectroscopic Survey
Short Name:
J/ApJ/741/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) provides a new sample of 101 star-forming galaxies at z<0.2 with unprecedented multi-wavelength coverage. New mid- to far-infrared spectroscopy from the Spitzer Space Telescope is added to a rich suite of previous imaging and spectroscopy, including ROSAT, Galaxy Evolution Explorer, Sloan Digital Sky Survey, Two Micron All Sky Survey, and Spitzer/SWIRE. Sample selection ensures an even coverage of the full range of normal galaxy properties, spanning two orders of magnitude in stellar mass, color, and dust attenuation. In this paper we present the SSGSS data set, describe the science drivers, and detail the sample selection, observations, data reduction, and quality assessment.
3830. The SSRS2 Sample
ID:
ivo://CDS.VizieR/J/AJ/108/1987
Title:
The SSRS2 Sample
Short Name:
J/AJ/108/1987
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we continue our investigation on the isophotal nature, accuracy, and uniformity of the magnitude system adopted in the Southern Sky Redshift Survey extension (SSRS2). Extending our earlier work, we examine galaxies in the equatorial region, primarily in the declination range -17.5 deg <= Dec. <= 0 deg, over a large range of right ascension, covering the southern and northern Galactic caps. For this purpose, we have obtained CCD isophotal magnitudes in the B and R bands for 265 galaxies of different morphological types. Using this larger sample we confirm our earlier claim that the m(SSRS2) magnitudes are very nearly the magnitude measured within the isophote mu_B = 26 mag/arcsec^2, with a dispersion of about 0.30 mag. The relative zero-point offset between our m(SSRS2) magnitudes and CCD photometry is -0.02 mag from all data we have obtained. However, we detect a variation of the zero-point across different regions of the sky of +/- 0.10 mag for regions at large angular separations. We also estimate that the zero-point offset between the m(SSRS2) and Zwicky systems is relatively small (~0.10 mag), which should allow us to combine the data from the SSRS2 and the CfA2 Redshift Survey.