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1821. K-Line photometry of stars in Population I clusters
ID:
ivo://CDS.VizieR/II/44
Title:
K-Line photometry of stars in Population I clusters
Short Name:
II/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photoelectric photometry of the K-line of calcium has been performed for the A stars of five open clusters (Hyades, Pleiades, IC 2391, IC 2602, and NGC 6475) and one association (Orion). All observations were carried out simultaneously with the field stars measurements in Paper II (II/43), with the 16-inch (40cm) and 36-inch (91cm) telescopes of the Cerro Tololo Inter-American Observatory, between May 1969 and January 1970.
1822. K-M stars of class I candidate RSGs in Gaia DR2
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.
1823. KMT-2018-BLG-1025Lb I light curve
ID:
ivo://CDS.VizieR/J/A+A/649/A90
Title:
KMT-2018-BLG-1025Lb I light curve
Short Name:
J/A+A/649/A90
Date:
22 Feb 2022
Publisher:
CDS
Description:
We aim to find missing microlensing planets hidden in the unanalyzed lensing events of previous survey data. For this purpose, we conduct a systematic inspection of high-magnification microlensing events, with peak magnifications Apeak>~30, in the data collected from high-cadence surveys in and before the 2018 season. From this investigation, we identify an anomaly in the lensing light curve of the event KMT-2018-BLG-1025. The analysis of the light curve indicates that the anomaly is caused by a very low mass-ratio companion to the lens. We identify three degenerate solutions, in which the ambiguity between a pair of solutions (solutions B) is caused by the previously known close-wide degeneracy, and the degeneracy between these and the other solution (solution A) is a new type that has not been reported before. The estimated mass ratio between the planet and host is q~0.8x10^-4^ for the solution A and q~1.6x10^-4^ for the solutions B. From the Bayesian analysis conducted with measured observables, we estimate that the masses of the planet and host and the distance to the lens are (Mp, Mh, DL)~(6.1M_{sun}_, 0.22M_Earth_, 6.7kpc) for the solution A and ~(4.4M_{sun}_, 0.08M_Earth_, 7.5kpc) for the solutions B. The planet mass is in the category of a super-Earth regardless of the solutions, making the planet the eleventh super-Earth planet, with masses lying between those of Earth and the Solar system's ice giants, discovered by microlensing.
1824. KMTNet LCs of ~1000 main-belt asteroids
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.
1825. KMTNet, MOA and OGLE light curve of KMT-2019-BLG-0371
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.
1826. KMTNet & OGLE I-band photometry of KMT-2019-BLG-0842
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.
1827. KMTNet-SAAO observation of near-Earth asteroids
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.
1828. Knots in the deep [FeII]+[SiI] image of the SNR Cas A
ID:
ivo://CDS.VizieR/J/ApJ/866/139
Title:
Knots in the deep [FeII]+[SiI] image of the SNR Cas A
Short Name:
J/ApJ/866/139
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a long-exposure (~10hr), narrowband image of the supernova (SN) remnant Cassiopeia A (Cas A) centered at 1.644{mu}m emission. The passband contains [FeII] 1.644{mu}m and [SiI] 1.645{mu}m lines, and our "deep [FeII]+[SiI] image" provides an unprecedented panoramic view of Cas A, showing both shocked and unshocked SN ejecta, together with shocked circumstellar medium at subarcsecond (~0.7" or 0.012pc) resolution. The diffuse emission from the unshocked SN ejecta has a form of clumps, filaments, and arcs, and their spatial distribution correlates well with that of the Spitzer [SiII] infrared emission, suggesting that the emission is likely due to [SiI] not [FeII] as in shocked material. The structure of the optically invisible western area of Cas A is clearly seen for the first time. The area is filled with many quasi-stationary flocculi (QSFs) and fragments of the disrupted ejecta shell. We identified 309 knots in the deep [FeII]+[SiI] image and classified them into QSFs and fast-moving knots (FMKs). The comparison with previous optical plates indicates that the lifetime of most QSFs is >~60yr. The total H+He mass of QSFs is ~0.23M_{sun}_, implying that the mass fraction of dense clumps in the progenitor's mass ejection immediately prior to the SN explosion is about 4%-6%. FMKs in the deep [FeII]+[SiI] image mostly correspond to S-rich ejecta knots in optical studies, while those outside the southeastern disrupted ejecta shell appear Fe-rich. The mass of the [FeII] line emitting, shocked dense Fe ejecta is ~3x10^-5^M_{sun}_.
1829. Known members of Orion A with Gaia DR2 data
ID:
ivo://CDS.VizieR/J/ApJ/884/6
Title:
Known members of Orion A with Gaia DR2 data
Short Name:
J/ApJ/884/6
Date:
04 Dec 2021
Publisher:
CDS
Description:
The star-forming region of the Orion Nebula (ONC) is ideal to study the stellar dynamics of young stars in a clustered environment. Using Gaia DR2 we search for pre-main sequence stars with unusually high proper motions that may be representative of a dynamical ejection from unstable young triple systems or other close three-body encounters. We identify 26 candidate stars that are likely to have had such an encounter in the last 1Myr. Nine of these stars could be traced back to the densest central-most region of the ONC, the Trapezium, while five others have likely interactions with other OB-type stars in the cluster. Seven stars originate from other nearby populations within the Orion Complex that coincidentally scattered toward the ONC. A definitive point of origin cannot be identified for the remaining sources. These observations shed light on the frequency of the ejection events in young clusters.
1830. K2 observations of type Ia supernova SN 2018oh
ID:
ivo://CDS.VizieR/J/ApJ/870/L1
Title:
K2 observations of type Ia supernova SN 2018oh
Short Name:
J/ApJ/870/L1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an exquisite 30minute cadence Kepler (K2) light curve of the Type Ia supernova (SNIa) 2018oh All-Sky Automated Survey for Supernovae (ASASSN-18bt), starting weeks before explosion, covering the moment of explosion and the subsequent rise, and continuing past peak brightness. These data are supplemented by multi-color Panoramic Survey Telescope (Pan-STARRS1) and Rapid Response System 1 and Cerro Tololo Inter-American Observatory 4m Dark Energy Camera (CTIO 4-m DECam) observations obtained within hours of explosion. The K2 light curve has an unusual two-component shape, where the flux rises with a steep linear gradient for the first few days, followed by a quadratic rise as seen for typical supernovae (SNe) Ia. This "flux excess" relative to canonical SNIa behavior is confirmed in our i-band light curve, and furthermore, SN2018oh is especially blue during the early epochs. The flux excess peaks 2.14{+/-}0.04 days after explosion, has a full width at half maximum (FWHM) of 3.12{+/-}0.04 days, a blackbody temperature of T=17500_-9000_^+11500^K, a peak luminosity of 4.3{+/-}0.2x10^37^erg/s, and a total integrated energy of 1.27{+/-}0.01x10^43^erg. We compare SN2018oh to several models that may provide additional heating at early times, including collision with a companion and a shallow concentration of radioactive nickel. While all of these models generally reproduce the early K2 light curve shape, we slightly favor a companion interaction, at a distance of ~2x10^12^cm based on our early color measurements, although the exact distance depends on the uncertain viewing angle. Additional confirmation of a companion interaction in future modeling and observations of SN2018oh would provide strong support for a single-degenerate progenitor system.