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4821. Orion Nebula Cluster population
ID:
ivo://CDS.VizieR/J/AJ/113/1733
Title:
Orion Nebula Cluster population
Short Name:
J/AJ/113/1733
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the first phase of a study of the stellar population comprising the Orion Nebula Cluster (ONC). Approximately 50% of the ~3500 stars identified to date within ~2.5pc of the namesake Trapezium stars are optically visible, and in this paper we focus on that sample with I<2.5mag. The large number and number density of stars (n_peak_>10^4^pc^-3^), the wide range in the stellar mass (~0.1-50M_{sun}_), and the extreme youth (<1-2Myr) of the stellar population, make the ONC the best site for investigating: (1) the detailed shape of a truly "initial" mass spectrum; (2) the apparent age spread in a region thought to have undergone triggered star formation; (3) the time sequence of star formation as a function of stellar mass; and (4) trends of all of the above with cluster radius.
4822. Orion pre-main sequence RIJH light curves
ID:
ivo://CDS.VizieR/J/A+A/508/1313
Title:
Orion pre-main sequence RIJH light curves
Short Name:
J/A+A/508/1313
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed an intensive photometric monitoring of the PMS stars falling in a field of about 10x10 arcminutes in the vicinity of the Orion Nebula Cluster (ONC). Photometric data were collected between November 2006 and January 2007 with the REM telescope in the VRIJHK' bands. The largest number of observations is in the I band (about 2700 images) and in J and H bands (about 500 images in each filter). From the observed rotational modulation, induced by the presence of surface inhomogeneities, we derived the rotation periods for 16 stars and improved previous determinations for the other 13. The analysis of the spectral energy distributions and, for some stars, of high-resolution spectra provided us with the main stellar parameters (luminosity, effective temperature, mass, age, and vsini). We also report the serendipitous detection of two strong flares in two of these objects. In most cases, the light-curve amplitudes decrease progressively from the R to H band as expected for cool starspots, while in a few cases, they can only be modelled by the presence of hot spots, presumably ascribable to magnetospheric accretion. The application of our own spot model to the simultaneous light curves in different bands allowed us to deduce the spot parameters and particularly to disentangle the spot temperature and size effects on the observed light curves.
4823. Orion Trapezium cluster
ID:
ivo://CDS.VizieR/J/AJ/117/1375
Title:
Orion Trapezium cluster
Short Name:
J/AJ/117/1375
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have imaged an area ~5arcmin^2^ at the center of the Trapezium cluster in Orion in the K band using the University of Hawaii (UH) adaptive optics system at the UH 2.2 m telescope. Our survey detects 292 stars brighter than K=18.2mag and resolves pairs to the 0.23" diffraction limit of the telescope. The binary fraction in the angular separation range 0.3"-0.6", corresponding to 132-264AU at 440pc, is indistinguishable from that of the solar-like stars in the solar neighborhood. Proplyds are associated with both single stars and visual binaries. About half the stars in our sample have also been measured at V and I by Prosser et al. (1994ApJ...421..517P); most of these seem to be about 10^6^yr old, observed through moderate extinction, and having some excess emission at K. The luminosity function turns over before the stellar limit of ~13.5mag, indicating that the cluster does not contain a large population of massive brown dwarfs.
4824. Oscillations in KOI-976's Kepler photometry
ID:
ivo://CDS.VizieR/J/AJ/158/88
Title:
Oscillations in KOI-976's Kepler photometry
Short Name:
J/AJ/158/88
Date:
21 Oct 2021
Publisher:
CDS
Description:
We measure the bulk system parameters of the seismically active, rapidly rotating {delta}-Scuti KOI-976 and constrain the orbit geometry of its transiting binary companion using a combined approach of asteroseismology and gravity-darkening light curve analysis. KOI-976 is a 1.62+/-0.2 M_{sun}_ star with a measured v sin(i) of 120+/-2 km/s and seismically induced variable signal that varies by ~0.6% of the star's total photometric brightness. We take advantage of the star's oblate shape and seismic activity to perform three measurements of its obliquity angle relative to the plane of the sky. We first apply a rotational splitting theory to the star's variable signal observed in short-cadence Kepler photometry to constrain KOI-976's obliquity angle, and then subtract off variability from that data set using the linear algorithm for significance reduction software LASR. We perform gravity-darkened fits to Kepler variability-subtracted short-cadence photometry and to Kepler's phase-folded long-cadence photometry to obtain two more measurements of the star's obliquity. We find that the binary system transits in a grazing configuration with measured obliquity values of 36{deg}+/-17{deg}, 46{deg}+/-16{deg}, and 43{deg}+/-20{deg}, respectively, for the three measurements. We perform these analyses as a way to demonstrate overcoming the challenges high-mass stars can present to transit light curve fitting and to prepare for the large number of exoplanets that the Transiting Exoplanet Survey Satellite will discover orbiting A/F stars.
4825. Oscillations in the PMS star V346 Ori
ID:
ivo://CDS.VizieR/J/A+A/399/271
Title:
Oscillations in the PMS star V346 Ori
Short Name:
J/A+A/399/271
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of periodicities in the light curve of the Pre-Main Sequence (PMS) Herbig Ae star V346 Ori. We interpret variations in the light curve of the star as the superposition of at least two periodic signals that result from delta Scuti-type stellar oscillations. The computation of linear non-adiabatic radial pulsation models for PMS stars reproduces these periods for a 1.55M_{sun}_ star with Teff=7410K and log(L/L_{sun}_)=0.74 pulsating in the fundamental and in the second overtone. If our assumption of radial oscillations is indeed correct, the star's location on the HR diagram places it at a distance significantly smaller than that of the Orion star forming region, hence raising questions regarding the evolutionary status of V346 Ori. Observations with better time sampling and spanning a longer period of time are needed if the latter question is to be addressed fully.
4826. OSSOS. VII. TNOs complete data release
ID:
ivo://CDS.VizieR/J/ApJS/236/18
Title:
OSSOS. VII. TNOs complete data release
Short Name:
J/ApJS/236/18
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Outer Solar System Origins Survey (OSSOS), a wide-field imaging program in 2013-2017 with the Canada-France-Hawaii Telescope, surveyed 155deg^2^ of sky to depths of m_r_=24.1-25.2. We present 838 outer solar system discoveries that are entirely free of ephemeris bias. This increases the inventory of trans-Neptunian objects (TNOs) with accurately known orbits by nearly 50%. Each minor planet has 20-60 Gaia/Pan-STARRS-calibrated astrometric measurements made over 2-5 oppositions, which allows accurate classification of their orbits within the trans-Neptunian dynamical populations. The populations orbiting in mean-motion resonance with Neptune are key to understanding Neptune's early migration. Our 313 resonant TNOs, including 132 plutinos, triple the available characterized sample and include new occupancy of distant resonances out to semimajor axis a ~130au. OSSOS doubles the known population of the nonresonant Kuiper Belt, providing 436 TNOs in this region, all with exceptionally high-quality orbits of a uncertainty {sigma}_a_<=0.1%; they show that the belt exists from a>~37au, with a lower perihelion bound of 35au. We confirm the presence of a concentrated low-inclination a~44 au "kernel" population and a dynamically cold population extending beyond the 2:1 resonance. We finely quantify the survey's observational biases. Our survey simulator provides a straightforward way to impose these biases on models of the trans-Neptunian orbit distributions, allowing statistical comparison to the discoveries. The OSSOS TNOs, unprecedented in their orbital precision for the size of the sample, are ideal for testing concepts of the history of giant planet migration in the solar system.
4827. OSSOS. XII. Subaru/HSC obs. of 65 TNOs
ID:
ivo://CDS.VizieR/J/ApJS/244/19
Title:
OSSOS. XII. Subaru/HSC obs. of 65 TNOs
Short Name:
J/ApJS/244/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present variability measurements and partial light curves of trans-Neptunian objects (TNOs) from a two-night pilot study using Hyper Suprime-Cam (HSC) on the Subaru Telescope (Maunakea, Hawaii, USA). Subaru's large aperture (8m) and HSC's large field of view (1.77deg^2^) allow us to obtain measurements of multiple objects with a range of magnitudes in each telescope pointing. We observed 65 objects with m_r_=22.6-25.5mag in just six pointings, allowing 20-24 visits of each pointing over the two nights. Our sample, all discovered in the recent Outer Solar System Origins Survey (OSSOS), spans absolute magnitudes of H_r_=6.2-10.8mag and thus investigates smaller objects than previous light curve projects have typically studied. Our data supports the existence of a correlation between the light curve amplitude and absolute magnitude seen in other works but does not support a correlation between the amplitude and orbital inclination. Our sample includes a number of objects from different dynamical populations within the trans-Neptunian region, but we do not find any relationship between variability and the dynamical class. We were only able to estimate periods for 12 objects in the sample and found that a longer baseline of observations is required for a reliable period analysis. We find that 31 objects (just under half of our sample) have variability of {Delta}_mag_ greater than 0.4mag during all of the observations; in smaller 1.25hr, 1.85hr, and 2.45hr windows, the median {Delta}_mag_ is 0.13, 0.16, and 0.19mag, respectively. The fact that variability on this scale is common for small TNOs has important implications for discovery surveys (such as OSSOS or the Large Synoptic Survey Telescope) and color measurements.
4828. Outbursts and disk variability in Be stars
ID:
ivo://CDS.VizieR/J/AJ/155/53
Title:
Outbursts and disk variability in Be stars
Short Name:
J/AJ/155/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
In order to study the growth and evolution of circumstellar disks around classical Be stars, we analyze optical time-series photometry from the KELT survey with simultaneous infrared and visible spectroscopy from the Apache Point Observatory Galactic Evolution Experiment survey and Be Star Spectra database for a sample of 160 Galactic classical Be stars. The systems studied here show variability including transitions from a diskless to a disk-possessing state (and vice versa), and persistent disks that vary in strength, being replenished at either regularly or irregularly occurring intervals. We detect disk-building events (outbursts) in the light curves of 28% of our sample. Outbursts are more commonly observed in early- (57%), compared to mid- (27%) and late-type (8%) systems. A given system may show anywhere between 0 and 40 individual outbursts in its light curve, with amplitudes ranging up to ~0.5 mag and event durations between ~2 and 1000 days. We study how both the photometry and spectroscopy change together during active episodes of disk growth or dissipation, revealing details about the evolution of the circumstellar environment. We demonstrate that photometric activity is linked to changes in the inner disk, and show that, at least in some cases, the disk growth process is asymmetrical. Observational evidence of Be star disks both growing and clearing from the inside out is presented. The duration of disk buildup and dissipation phases are measured for 70 outbursts, and we find that the average outburst takes about twice as long to dissipate as it does to build up in optical photometry. Our analysis hints that dissipation of the inner disk occurs relatively slowly for late-type Be stars.
4829. Outbursts in the Be star HR 2501
ID:
ivo://CDS.VizieR/J/A+A/401/271
Title:
Outbursts in the Be star HR 2501
Short Name:
J/A+A/401/271
Date:
21 Oct 2021
Publisher:
CDS
Description:
Several mostly unrelated periods or time scales characterize the variability of HR 2501. This star is a new lambda Eri star with a period of 0.79187d. This star also exhibits a mid- to long-term variability of characteristic time ~500d, most probably a consequence of the recurrent outbursts of matter from the rapidly rotating Be star towards its disk.
4830. Outer bulge O-rich Mira's JHKL photometry
ID:
ivo://CDS.VizieR/J/MNRAS/455/2216
Title:
Outer bulge O-rich Mira's JHKL photometry
Short Name:
J/MNRAS/455/2216
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report periods and JHKL observations for 643 oxygen-rich Mira variables found in two outer bulge fields at b=-7{deg} and l=+/-8{deg} and combine these with data on 8057 inner bulge Miras from the OGLE, Macho and 2MASS surveys, which are concentrated closer to the Galactic centre. Distance moduli are estimated for all these stars. Evidence is given showing that the bulge structure is a function of age. The longer period Miras (LogP>2.6, age~5Gyr and younger) show clear evidence of a bar structure inclined to the line of sight in both the inner and outer regions. The distribution of the shorter period (metal-rich globular cluster age) Miras, appears spheroidal in the outer bulge. In the inner region these old stars are also distributed differently from the younger ones and possibly suggest a more complex structure. These data suggest a distance to the galactic centre R_0_, of 8.9kpc, with an estimated uncertainty of ~0.4kpc. The possible effect of helium enrichment on our conclusions is discussed.