- ID:
- ivo://CDS.VizieR/J/A+A/372/71
- Title:
- King 5 and Berkeley 20 UBVRI photometry
- Short Name:
- J/A+A/372/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multicolour CCD photometry for two poorly studied open clusters (King 5 and Be 20). Photometry for a field near King 5 was also carried out to estimate the contamination by field stars. The colour magnitude diagrams (CMD) of the clusters show a well defined main sequence extending to the limit of the photometry, V~=20mag. The reddening for King 5, estimated from the colour-colour diagram, is ~0.82, whereas that for Be 20 as estimated by comparing theoretical main-sequence (MS) with the observed MS is 0.10. The morphology of the CMDs indicates that these clusters are old. The CMD of Be 20 shows a globular cluster-like horizontal branch. In case of King 5 the comparison of observational CMDs with the standard isochrones of VandenBerg (1985ApJS...58..711V) indicates an apparent discrepancy between the shape of the turnoff and isochrones. The CMDs of King 5 seem to be better understood in terms of stellar models with convective overshoot. The comparison of the CMDs with the stellar models by Bertelli et al. (1985A&A...150...33B) with convective overshoot produces a good fit for a metallicity Z=0.008 and an age of 1Gyr for King 5 and 5Gyr for Be 20. An apparent distance modulus (m-M)=14.0 and 15.1 has been estimated for King 5 and Be 20 respectively. They correspond to a distance of 1900+/-100pc and 9026+/-480pc, respectively. The radial density distribution in King 5 indicates that there is an excess of low mass stars in the outer region of the cluster, whereas the density distribution in Be 20 shows a good fit with the empirical King (1962AJ.....67..471K) model. For both clusters, observations have also been carried out to search for variable stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/829/L9
- Title:
- K2 LC of HD 3167 and Robo-AO image
- Short Name:
- J/ApJ/829/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of two super-Earth-sized planets transiting the bright (V=8.94, K=7.07) nearby late G-dwarf HD 3167, using data collected by the K2 mission. The inner planet, HD 3167 b, has a radius of 1.6R_{Earth}_ and an ultra-short orbital period of only 0.96d. The outer planet, HD 3167 c, has a radius of 2.9R_{Earth}_ and orbits its host star every 29.85 days. At a distance of just 45.8+/-2.2pc, HD3167 is one of the closest and brightest stars hosting multiple transiting planets, making HD 3167 b and c well suited for follow-up observations. The star is chromospherically inactive with low rotational line-broadening, ideal for radial velocity observations to measure the planets' masses. The outer planet is large enough that it likely has a thick gaseous envelope that could be studied via transmission spectroscopy. Planets transiting bright, nearby stars like HD 3167 are valuable objects to study leading up to the launch of the James Webb Space Telescope.
- ID:
- ivo://CDS.VizieR/J/MNRAS/355/20
- Title:
- K magnitudes of 74MHz radio sources
- Short Name:
- J/MNRAS/355/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present near-infrared K-band imaging of a sample of ultra-steep-spectrum (USS) radio sources selected at 74-MHz. The dual selection criteria of low frequency and USS mean that we should be sensitive to the highest-redshift (z>5) radio galaxies. We have obtained K-band magnitudes for all of the objects in our sample of 26 and discuss the properties of each.
- ID:
- ivo://CDS.VizieR/J/A+A/469/459
- Title:
- K magnitudes of N159-5 (LMC)
- Short Name:
- J/A+A/469/459
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution near-infrared imaging of the compact HII region N159-5 and its immediate environment in the giant-star forming region N159 in the LMC. N159-5 was observed at high spatial resolution ~0.11"-0.25" in the K-band using the ESO Very Large Telescope UT4 (VLT), equipped with the NAOS adaptive optics system. Our data reveal that N159-5 has a complex morphology formed mainly by two wings and probably a single central bright star, embedded in diffuse emission of ~4.5" diameter. A remarkable embedded tight cluster of approximatively the same size, containing at least 38 faint stars coinciding with N159-5, is also detected. Such clusters can be found in galactic HII regions like the star-forming regions SH2 269 or M42. At the location of the radio peak, especially in the bright western wing, this cluster is rich in stars. Spectroscopic observations reveal that the diffuse region is constituted mainly of dust continuum and that the bright star #2-55 could be of type O8 V. A comparison with the radio observation flux of N159-5 published in the literature seems to show that the bright star #2-55 is not the only ionization source of N159-5. Towards N159-5 molecular H_2_ emission is detected. A model of the region is proposed.
- ID:
- ivo://CDS.VizieR/J/A+A/440/121
- Title:
- K magnitudes of OB stars in UCHIIs
- Short Name:
- J/A+A/440/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained high resolution (R=10000) K-band spectra of candidate young massive stars deeply embedded in (ultra-) compact HII regions (UCHIIs). These objects were selected from a near-infrared survey of 44 fields centered on IRAS sources with UCHII colours. Often, the near-infrared counterpart of the IRAS source is a young embedded cluster hosting massive stars. In these clusters, three types of objects are identified. The first type (38 objects) consists of "naked" OB stars whose K-band spectra are dominated by photospheric emission. We classify the K-band spectra of the OB-type cluster members using near-infrared classification criteria. A few of them have a very early (O3-O4 V) spectral type, consistent with a young age of the embedded clusters. The spectral classification provides an important constraint on the distance to the embedded cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/158/20
- Title:
- K-M stars of class I candidate RSGs in Gaia DR2
- Short Name:
- J/AJ/158/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate individual distances and luminosities of a sample of 889 nearby candidate red supergiants (RSGs) with reliable parallaxes ({omega}/{sigma}_{omega}_>4 and RUWE<2.7) from Gaia Data Release 2 (DR2, Cat. I/345). The sample was extracted from the historical compilation of spectroscopically derived spectral types by Skiff (Cat. B/mk), and consists of K-M stars that are listed with class I at least once. The sample includes well-known RSGs from Humphreys (1978ApJS...38..309H), Elias et al. (1985ApJS...57...91E), Jura & Kleinmann (1990ApJS...73..769J), and Levesque et al. (2005ApJ...628..973L). Infrared and optical measurements from the Two Micron All Sky Survey, Catalog of Infrared Observations (CIO), Midcourse Space Experiment, Wide-field Infrared Survey Explorer, MIPSGAL, Galactic Legacy Infrared Midplane Extraordinaire (GLIMPSE), and The Naval Observatory Merged Astrometric Dataset catalogs allow us to estimate the stellar bolometric magnitudes. We analyze the stars in the luminosity versus effective temperature plane and confirm that 43 sources are highly probably RSGs with M_bol_< -7.1 mag. Of the stars in the sample, 43% have masses >7 M_{sun}_. Another ~30% of the sample consists of giant stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/237/19
- Title:
- KMTNet LCs of ~1000 main-belt asteroids
- Short Name:
- J/ApJS/237/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VRI spectrophotometry of 1003 main-belt asteroids (MBAs) observed with the Sutherland, South Africa node of the Korea Microlensing Telescope Network (KMTNet). All of the observed MBAs were serendipitously captured in KMTNet's large 2{deg}x2{deg} field of view during a separate targeted near-Earth Asteroid study. Our broadband spectrophotometry is reliable enough to distinguish among four asteroid taxonomies and we confidently categorize 836 of the 1003 observed targets as either a S-, C-, X-, or D-type asteroid by means of a machine learning algorithm approach. Our data show that the ratio between S-type MBAs and (C+X+D)-type MBAs, with H magnitudes between 12 and 18 (12km>~diameter>~0.75km), is almost exactly 1:1. Additionally, we report 0.5-3hr (median: 1.3hr) light-curve data for each MBA and we resolve the complete rotation periods and amplitudes for 59 targets. Of the 59 targets, 2 have rotation periods potentially below the theoretical zero-cohesion boundary limit of 2.2hr. We report lower limits for the rotation periods and amplitudes for the remaining targets. Using the resolved and unresolved light curves we determine the shape distribution for this population using a Monte Carlo simulation. Our model suggests a population with an average elongation b/a=0.74+/-0.07 and also shows that this is independent of asteroid size and taxonomy.
- ID:
- ivo://CDS.VizieR/J/AJ/162/17
- Title:
- KMTNet, MOA and OGLE light curve of KMT-2019-BLG-0371
- Short Name:
- J/AJ/162/17
- Date:
- 16 Mar 2022 00:13:06
- Publisher:
- CDS
- Description:
- We show that the perturbation at the peak of the light curve of microlensing event KMT-2019-BLG-0371 is explained by a model with a mass ratio between the host star and planet of q~0.08. Due to the short event duration (t_E_~6.5days), the secondary object in this system could potentially be a massive giant planet. A Bayesian analysis shows that the system most likely consists of a host star with a mass M_h_=0.09_-0.05_^+0.14^Msun and a massive giant planet with a mass M_p_=7.70_-3.90_^+11.34^M_Jup_. However, the interpretation of the secondary as a planet (i.e., as having M_p_<13M_Jup_) rests entirely on the Bayesian analysis. Motivated by this event, we conduct an investigation to determine which constraints meaningfully affect Bayesian analyses for microlensing events. We find that the masses inferred from such a Bayesian analysis are determined almost entirely by the measured value of {theta}_E_ and are relatively insensitive to other factors such as the direction of the event (l, b), the lens-source relative proper motion {mu}_rel_, or the specific Galactic model prior.
- ID:
- ivo://CDS.VizieR/J/AJ/160/255
- Title:
- KMTNet & OGLE I-band photometry of KMT-2019-BLG-0842
- Short Name:
- J/AJ/160/255
- Date:
- 09 Mar 2022
- Publisher:
- CDS
- Description:
- We report the discovery of a cold planet with a very low planet/host mass ratio of q=(4.09{+/-}0.27)x10^-5^, which is similar to the ratio of Uranus/Sun (q=4.37x10^-5^) in the solar system. The Bayesian estimates for the host mass, planet mass, system distance, and planet-host projected separation are M_host_=0.76{+/-}0.40M{sun}, M_planet_=10.3{+/-}5.5M{Earth}, D_L_=3.3{+/-}1.3kpc, and a{perp}=3.3{+/-}1.4 au, respectively. The consistency of the color and brightness expected from the estimated lens mass and distance with those of the blend suggests the possibility that the most blended light comes from the planet host, and this hypothesis can be established if high-resolution images are taken during the next (2020) bulge season. We discuss the importance of conducting optimized photometry and aggressive follow-up observations for moderately or very high magnification events to maximize the detection rate of planets with very low mass ratios.
- ID:
- ivo://CDS.VizieR/J/AJ/154/162
- Title:
- KMTNet-SAAO observation of near-Earth asteroids
- Short Name:
- J/AJ/154/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here VRI spectrophotometry of 39 near-Earth asteroids (NEAs) observed with the Sutherland, South Africa, node of the Korea Microlensing Telescope Network (KMTNet). Of the 39 NEAs, 19 were targeted, but because of KMTNet's large 2{deg}x2{deg} field of view, 20 serendipitous NEAs were also captured in the observing fields. Targeted observations were performed within 44 days (median: 16 days, min: 4 days) of each NEA's discovery date. Our broadband spectrophotometry is reliable enough to distinguish among four asteroid taxonomies and we were able to confidently categorize 31 of the 39 observed targets as either an S-, C-, X-, or D-type asteroid by means of a Machine Learning algorithm approach. Our data suggest that the ratio between "stony" S-type NEAs and "not-stony" (C+X+D)-type NEAs, with H magnitudes between 15 and 25, is roughly 1:1. Additionally, we report ~1 hr light curve data for each NEA, and of the 39 targets, we were able to resolve the complete rotation period and amplitude for six targets and report lower limits for the remaining targets.
