- ID:
- ivo://CDS.VizieR/J/AJ/160/268
- Title:
- Infrared photometry of binaries in Orion OB1
- Short Name:
- J/AJ/160/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Statistics of low-mass pre-main-sequence binaries in the Orion OB1 association with separations ranging from 0.6" to 20" (220 to 7400au at 370pc) are studied using images from the VISTA Orion mini survey and astrometry from Gaia. The input sample based on the CVSO catalog contains 1137 stars of K and M spectral types (masses between 0.3 and 0.9M{odot}), 1021 of which are considered to be association members. There are 135 physical binary companions to these stars with mass ratios above ~0.13. The average companion fraction is 0.09{+/-}0.01 over 1.2 decades in separation, slightly less than, but still consistent with, the field. We found a difference between the Ori OB1a and OB1b groups, the latter being richer in binaries by a factor of 1.6{+/-}0.3. No overall dependence of the wide- binary frequency on the observed underlying stellar density is found, although in the Ori OB1a off-cloud population, these binaries seem to avoid dense clusters. The multiplicity rates in Ori OB1 and in sparse regions like Taurus differ significantly, hinting that binaries in the field may originate from a mixture of diverse populations.
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- ID:
- ivo://CDS.VizieR/J/AJ/144/42
- Title:
- Infrared photometry of 90 KOIs
- Short Name:
- J/AJ/144/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All transiting planets are at risk of contamination by blends with nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or produce a false-positive detection when the target star is blended with eclipsing binary stars. This paper reports on high spatial-resolution adaptive optics images of 90 Kepler planetary candidates. Companion stars are detected as close as 0.1" from the target star. Images were taken in the near-infrared (J and Ks bands) with ARIES on the MMT and PHARO on the Palomar Hale 200inch telescope. Most objects (60%) have at least one star within 6" separation and a magnitude difference of 9. Eighteen objects (20%) have at least one companion within 2" of the target star; six companions (7%) are closer than 0.5". Most of these companions were previously unknown, and the associated planetary candidates should receive additional scrutiny. Limits are placed on the presence of additional companions for every system observed, which can be used to validate planets statistically using the BLENDER method. Validation is particularly critical for low-mass, potentially Earth-like worlds, which are not detectable with current-generation radial velocity techniques. High-resolution images are thus a crucial component of any transit follow-up program.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/171
- Title:
- IR data of debris disk vs metallicity of stars
- Short Name:
- J/ApJ/826/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We find that the initial dust masses in planetary debris disks are correlated with the metallicities of their central stars. We compiled a large sample of systems, including Spitzer, the Herschel DUNES and DEBRIS surveys, and WISE debris disk candidates. We also merged 33 metallicity catalogs to provide homogeneous [Fe/H] and {sigma}_[Fe/H]_ values. We analyzed this merged sample, including 222 detected disks (74 warm and 148 cold) around a total of 187 systems (some with multiple components) and 440 disks with only upper limits (125 warm and 315 cold) around a total of 360 systems. The disk dust masses at a common early evolutionary point in time were determined using our numerical disk evolutionary code, evolving a unique model for each of the 662 disks backward to an age of 1Myr. We find that disk-bearing stars seldom have metallicities less than [Fe/H]=-0.2 and that the distribution of warm component masses lacks examples with large mass around stars of low metallicity ([Fe/H]<-0.085). Previous efforts to find a correlation have been largely unsuccessful; the primary improvements supporting our result are (1) basing the study on dust masses, not just infrared excess detections; (2) including upper limits on dust mass in a quantitative way; (3) accounting for the evolution of debris disk excesses as systems age; (4) accounting fully for the range of uncertainties in metallicity measurements; and (5) having a statistically large enough sample.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A110
- Title:
- IR nebulae around bright massive stars
- Short Name:
- J/A+A/618/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies show that more than 70% of massive stars do not evolve as effectively single stars, but as members of interacting binary systems. The evolution of these stars is thus strongly altered compared to similar but isolated objects. We investigate the occurrence of parsec-scale mid-infrared nebulae around early-type stars. If they exist over a wide range of stellar properties, one possible overarching explanation is non-conservative mass transfer in binary interactions, or stellar mergers. For ~3850 stars (all OBA stars in the Bright Star Catalogue (BSC, Cat. V/50), Be stars, BeXRBs, and Be+sdO systems), we visually inspect WISE 22um images. Based on nebular shape and relative position, we distinguish five categories: offset bow shocks structurally aligned with the stellar space velocity, unaligned offset bow shocks, and centered, unresolved, and not classified nebulae. In the BSC, we find that 28%, 13%, and 0.4% of all O, B, and A stars, respectively, possess associated infrared (IR) nebulae. Additionally, 34/234 Be stars, 4/72 BeXRBs, and 3/17 Be+sdO systems are associated with IR nebulae. Aligned or unaligned bow shocks result from high relative velocities between star and interstellar medium (ISM) that are dominated by the star or the ISM, respectively. About 13% of the centered nebulae could be bow shocks seen head- or tail-on. For the rest, the data disfavor explanations as remains of parental disks, supernova remnants of a previous companion, and dust production in stellar winds. The existence of centered nebulae also at high Galactic latitudes strongly limits the global risk of coincidental alignments with condensations in the ISM. Mass loss during binary evolution seems a viable mechanism for the formation of at least some of these nebulae. In total, about 29% of the IR nebulae (2% of all OBA stars in the BSC) may find their explanation in the context of binary evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/657/1013
- Title:
- IR photometry of 2MASS/Spitzer white dwarfs
- Short Name:
- J/ApJ/657/1013
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We review the available near- and mid-infrared photometry for white dwarfs obtained from the Two Micron All Sky Survey (2MASS) and by the Spitzer Space Telescope. Both data sets have recently been used to seek white dwarfs with infrared excesses due to the presence of unresolved companions or circumstellar disks, and also to derive the atmospheric parameters of cool white dwarfs. We first attempt to evaluate the reliability of the 2MASS photometry by comparing it with an independent set of published JHK CIT magnitudes for 160 cool white dwarf stars, and also by comparing the data with the predictions of detailed model atmosphere calculations. The possibility of using 2MASS to identify unresolved M dwarf companions or circumstellar disks is then discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/126/1526
- Title:
- IR photometry of ultracool dwarfs
- Short Name:
- J/AJ/126/1526
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations of a sample of 134 ultracool objects (spectral types later than M7) coming from the Deep Near Infrared Survey (DENIS), Two Micron All Sky Survey (2MASS), and Sloan Digital Sky Survey (SDSS), with distances estimated to range from 7 to 105pc. Fifteen new ultracool binary candidates are reported here. Eleven known binaries are confirmed, and orbital motion is detected in some of them. We estimate that the closest binary systems in this sample have periods between 5 and 20yr, and thus dynamical masses will be derived in the near future. For the calculation of binary frequency, we restrict ourselves to systems with distances less than 20pc. After correction of the binaries bias, we find a ratio of visual binaries (at the HST limit of detection) of around 10%, and that 15% of the 26 objects within 20pc are binary systems with separations between 1 and 8AU. The observed frequency of ultracool binaries is similar to that of binaries with G-type primaries in the separation range from 2.1 to 140AU. There is also a clear deficit of ultracool binaries with separations greater than 15AU, and a possible tendency for the binaries to have mass ratios near unity. Most systems have indeed visual and near-infrared brightness ratios between 1 and 0.3. We discuss our results in the framework of current scenarios for the formation and evolution of free-floating brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJS/119/83
- Title:
- IUE sample of binaries with hot component
- Short Name:
- J/ApJS/119/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained or retrieved IUE spectra for over 100 middle- and late-type giant and supergiant stars whose spectra indicate the presence of a hot component earlier than type F2. The hot companions are classified accurately by temperature class from their far-UV spectra. The interstellar extinction of each system and the relative luminosities of the components are derived from analysis of the UV and optical fluxes, using a grid of UV intrinsic colors for hot dwarfs. We find that there is fair agreement in general between current UV spectral classification and ground-based hot component types, in spite of the difficulties of assigning the latter. There are a few cases in which the cool component optical classifications disagree considerably with the temperature classes inferred from our analysis of UV and optical photometry. The extinction parameter agrees moderately well with other determinations of B-V color excess. Many systems are worthy of further study especially to establish their spectroscopic orbits. Further work is planned to estimate luminosities of the cool components from the data herein; in many cases, these luminosities' accuracies should be comparable to or exceed those of the Hipparcos parallaxes.
- ID:
- ivo://CDS.VizieR/J/AJ/152/182
- Title:
- iz follow-up photometry of HAT-P-65 and HAT-P-66
- Short Name:
- J/AJ/152/182
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of the transiting exoplanets HAT-P-65b and HAT-P-66b, with orbital periods of 2.6055 and 2.9721 days, masses of 0.527+/-0.083M_J_ and 0.783+/-0.057M_J_, and inflated radii of 1.89+/-0.13R_J_ and 1.59_-0.10_^+0.16^R_J_, respectively. They orbit moderately bright (V=13.145+/-0.029 and V=12.993+/-0.052) stars of mass 1.212+/-0.050M_{Sun}_ and 1.255_-0.054_^+0.107^M_{Sun}_. The stars are at the main-sequence turnoff. While it is well known that the radii of close-in giant planets are correlated with their equilibrium temperatures, whether or not the radii of planets increase in time as their hosts evolve and become more luminous is an open question. Looking at the broader sample of well-characterized close-in transiting giant planets, we find that there is a statistically significant correlation between planetary radii and the fractional ages of their host stars, with a false-alarm probability of only 0.0041%. We find that the correlation between the radii of planets and the fractional ages of their hosts is fully explained by the known correlation between planetary radii and their present-day equilibrium temperatures; however, if the zero-age main-sequence equilibrium temperature is used in place of the present-day equilibrium temperature, then a correlation with age must also be included to explain the planetary radii. This suggests that, after contracting during the pre-main-sequence, close-in giant planets are reinflated over time due to the increasing level of irradiation received from their host stars. Prior theoretical work indicates that such a dynamic response to irradiation requires a significant fraction of the incident energy to be deposited deep within the planetary interiors.
- ID:
- ivo://CDS.VizieR/J/AJ/160/115
- Title:
- JHK observation of 75 OB stars in Cyg OB2
- Short Name:
- J/AJ/160/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the Near-Infrared Imager camera and ALTAIR adaptive optics system of the Gemini North telescope. We observed 74 O- and early-B-type stars in Cyg OB2 in the JHK infrared bands in order to detect binary and multiple companions. The observations are sensitive to equal-brightness pairs at separations as small as 0.08", and progressively fainter companions are detectable out to {Delta}K=9mag at a separation of 2". This faint contrast limit due to read noise continues out to 10" near the edge of the detector. We assigned a simple probability of chance alignment to each companion based upon its separation and magnitude difference from the central target star and upon areal star counts for the general star field of Cyg OB2. Companion stars with a field membership probability of less than 1% are assumed to be physical companions. This assessment indicates that 47% of the targets have at least one resolved companion that is probably gravitationally bound. Including known spectroscopic binaries, our sample includes 27 binary, 12 triple, and 9 systems with 4 or more components. These results confirm studies of high-mass stars in other environments that find that massive stars are born with a high-multiplicity fraction. The results are important for the placement of the stars in the Hertzsprung-Russell diagram, the interpretation of their spectroscopic analyses, and for future mass determinations through measurement of orbital motion.
- ID:
- ivo://CDS.VizieR/J/A+A/375/989
- Title:
- JHK photometry of Praesepe low-mass stars
- Short Name:
- J/A+A/375/989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table 1 contains the list of low-mass Praesepe stars observed with adaptive optics and which were not resolved as multiple systems.