- ID:
- ivo://CDS.VizieR/J/A+A/591/A96
- Title:
- Robust detection of CID double stars in SDSS
- Short Name:
- J/A+A/591/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey (SDSS) offers a unique possibility of not only detecting colour induced displacement (CID) double stars but also confirming these detections. Successive cuts are applied to the SDSS data release (DR) 12 database to reduce the size of the sample under consideration. The resulting dataset is then screened with a criterion based on the distance and orientation of the photocentres in different photometric bands. About 3200 distinct objects are classified as CID double stars, 40 of which are confirmed with at least a second detection. A consistency check further validates these detections.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/156/275
- Title:
- Rotational evolution of young, binary M dwarfs
- Short Name:
- J/AJ/156/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed K2 light curves for more than 3000 low-mass stars in the ~8 Myr old Upper Sco association, the ~125 Myr age Pleiades open cluster, and the ~700 Myr old Hyades and Praesepe open clusters to determine stellar rotation rates. Many of these K2 targets show two distinct periods, and for the lowest-mass stars in these clusters, virtually all of these systems with two periods are photometric binaries. The most likely explanation is that we are detecting the rotation periods for both components of these binaries. We explore the evolution of the rotation rate in both components of photometric binaries relative to one another and to nonphotometric binary stars. In Upper Sco and the Pleiades, these low-mass binary stars have periods that are much shorter on average and much closer to each other than would be true if drawn at random from the M dwarf single stars. In Upper Sco, this difference correlates strongly with the presence or absence of infrared excesses due to primordial circumstellar disks-the single-star population includes many stars with disks, and their rotation periods are distinctively longer on average than their binary star cousins of the same mass. By Praesepe age, the significance of the difference in rotation rate between the single and binary low-mass M dwarf stars is much less, suggesting that angular momentum loss from winds for fully convective zero-age main-sequence stars erases memory of the rotation rate dichotomy for binary and single very low mass stars at later ages.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A55
- Title:
- Rotational mixing in CEMP-s stars
- Short Name:
- J/A+A/606/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon-enhanced metal-poor (CEMP) stars with s-process enrichment (CEMP-s) are believed to be the products of mass transfer from an asymptotic giant branch (AGB) companion, which has long since become a white dwarf. The surface abundances of CEMP-s stars are thus commonly assumed to reflect the nucleosynthesis output of the first AGB stars. We have previously shown that, for this to be the case, some physical mechanism must counter atomic diffusion (gravitational settling and radiative levitation) in these nearly fully radiative stars, which otherwise leads to surface abundance anomalies clearly inconsistent with observations. Here we take into account angular momentum accretion by these stars. We compute in detail the evolution of typical CEMP-s stars from the zero-age main sequence, through the mass accretion, and up the red giant branch for a wide range of specific angular momentum ja of the accreted material, corresponding to surface rotation velocities, v_rot_, between about 0.3 and 300km/s. We find that only for j_a_>~10^17^cm^2^/s (v_rot_>20km/s, depending on mass accreted) angular momentum accretion directly causes chemical dilution of the accreted material. This could nevertheless be relevant to CEMP-s stars, which are observed to rotate more slowly, if they undergo continuous angular momentum loss akin to solar-like stars. In models with rotation velocities characteristic of CEMP-s stars, rotational mixing primarily serves to inhibit atomic diffusion, such that the maximal surface abundance variations (with respect to the composition of the accreted material) prior to first dredge-up remain within about 0.4dex without thermohaline mixing or about 0.5-1.5dex with thermohaline mixing. Even in models with the lowest rotation velocities (v_rot_<~1km/s), rotational mixing is able to severely inhibit atomic diffusion, compared to non-rotating models. We thus conclude that it offers a natural solution to the problem posed by atomic diffusion and cannot be neglected in models of CEMP-s stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/L31
- Title:
- Rotational periods and J_2_ of Kepler stars
- Short Name:
- J/ApJ/890/L31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-short-period planets (USPs) provide important clues to planetary formation and migration. It was recently found that the mutual inclinations of the planetary systems are larger if the inner orbits are closer (<~5R_*_) and if the planetary period ratios are larger (P_2_/P_1_>~5). This suggests that the USPs experienced both inclination excitation and orbital shrinkage. Here we investigate the increase in the mutual inclination due to stellar oblateness. We find that the stellar oblateness (within ~1Gyr) is sufficient to enhance the mutual inclination to explain the observed signatures. This suggests that the USPs can migrate closer to the host star in a near coplanar configuration with their planetary companions (e.g., disk migration+tides or in situ+tides), before mutual inclination gets excited due to stellar oblateness.
- ID:
- ivo://CDS.VizieR/J/ApJ/616/562
- Title:
- Rotational velocities in binaries
- Short Name:
- J/ApJ/616/562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We found in the published literature the rotational velocities for 162 B0-B9.5, 151 A0-A5, and 86 A6-F0 stars, all of luminosity classes V or IV, that are in spectroscopic or visual binaries with known orbital elements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/448
- Title:
- Rotational velocities of early-type binaires
- Short Name:
- J/MNRAS/392/448
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use information on the vsin(i) values of early-type binaries in order to search for correlations which may constrain the relative orientation of the stellar spin axes in binary systems. We find correlations in the case of close binaries which suggest that tidal synchronization is effective for binaries whose separation exceeds the stellar radius by more than an order of magnitude, in line with the theoretical predictions of Goldreich & Nicholson (1989ApJ...342.1079G) and the previous observational analysis of Giuricin et al. (1984A&A...135..393G). In the case of wide binaries, the vsin(i) values are not well correlated, which requires that the magnitude of the spin speeds is not tightly correlated. Under this assumption, we then find that the data provide no significant constraints on the degree of alignment of spin axes. The data are therefore compatible with scenarios (such as disc fragmentation or capture) which differ widely in the expected degree of spin alignment.
- ID:
- ivo://CDS.VizieR/J/AJ/144/130
- Title:
- Rotational velocities of nearby HIP B stars
- Short Name:
- J/AJ/144/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Projected rotational velocities (vsini) are presented for a sample of 350 early B-type main-sequence stars in the nearby Galactic disk. The stars are located within ~1.5kpc from the Sun, and the great majority within 700pc. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5m telescope at the Las Campanas Observatory in Chile. Spectral types were estimated based on relative intensities of some key line absorption ratios and comparisons to synthetic spectra. Effective temperatures were estimated from the reddening-free Q index, and projected rotational velocities were then determined via interpolation on a published grid that correlates the synthetic FWHM of the He_I_ lines at 4026, 4388 and 4471{AA} with vsini. As the sample has been selected solely on the basis of spectral types, it contains a selection of B stars in the field, in clusters, and in OB associations. The vsini distribution obtained for the entire sample is found to be essentially flat for vsini values between 0 and 150km/s, with only a modest peak at low projected rotational velocities. Considering subsamples of stars, there appears to be a gradation in the vsini distribution with the field stars presenting a larger fraction of the slow rotators and the cluster stars distribution showing an excess of stars with vsini between 70 and 130km/s. Furthermore, for a subsample of potential runaway stars we find that the vsini distribution resembles the distribution seen in denser environments, which could suggest that these runaway stars have been subject to dynamical ejection mechanisms.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/3
- Title:
- Rotation periods for Q3-Q14 KOIs
- Short Name:
- J/ApJ/801/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observed amplitude of the rotational photometric modulation of a star with spots should depend on the inclination of its rotational axis relative to our line of sight. Therefore, the distribution of observed rotational amplitudes of a large sample of stars depends on the distribution of their projected axes of rotation. Thus, comparison of the stellar rotational amplitudes of the Kepler objects of interest (KOIs) with those of Kepler single stars can provide a measure to indirectly infer the properties of the spin-orbit obliquity of Kepler planets. We apply this technique to the large samples of 993 KOIs and 33614 single Kepler stars in temperature range of 3500-6500K. We find with high significance that the amplitudes of cool KOIs are larger, on the order of 10%, than those of the single stars. In contrast, the amplitudes of hot KOIs are systematically lower. After correcting for an observational bias, we estimate that the amplitudes of the hot KOIs are smaller than the single stars by about the same factor of 10%. The border line between the relatively larger and smaller amplitudes, relative to the amplitudes of the single stars, occurs at about 6000K. Our results suggest that the cool stars have their planets aligned with their stellar rotation, while the planets around hot stars have large obliquities, consistent with the findings of Winn et al. (2010ApJ...718L.145W) and Albrecht et al. (2012, J/ApJ/757/18). We show that the low obliquity of the planets around cool stars extends up to at least 50 days, a feature that is not expected in the framework of a model that assumes the low obliquity is due to planet-star tidal realignment.
- ID:
- ivo://CDS.VizieR/J/ApJS/250/20
- Title:
- Rotation periods in TESS objects of interest (TOIs)
- Short Name:
- J/ApJS/250/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high-quality light curves from the Transiting Exoplanet Survey Satellite (TESS) represent a unique laboratory for the study of stellar rotation, which is a fundamental observable driving stellar and planetary evolution, including planetary atmospheres and impacting habitability conditions and the genesis of life around stars. As of 2020 April 14, this mission delivered public light curves for 1000 TESS objects of interest (TOIs), observed with a 2 minute cadence during the first 20 months of the mission. Here, we present a search for rotation signatures in these TOIs, using fast Fourier transform, Lomb-Scargle, and wavelet techniques, accompanied by a rigorous visual inspection. This effort revealed 163 targets with rotation signatures, 131 of which present unambiguous rotation periods ranging from 0.321 and 13.219 days, whereas 32 of them present dubious rotation periodicities. Of these stars, 109 show flux fluctuations whose root cause is not clearly identified. For 714 TOIs, the light curves show a noisy behavior, corresponding to typically low-amplitude signals. Our analysis has also revealed 10 TOI stars with pulsation periodicities ranging from 0.049 to 2.995 days and four eclipsing binaries. With upcoming TESS data releases, our periodicity analysis will be expanded to almost all TOI stars, thereby contributing in defining criteria for follow-up strategy itself, and the study of star-planet interactions, surface dynamic of host stars, and habitability conditions in planets, among other aspects. In this context, a living catalog is maintained on the Filtergraph visualization portal at http://filtergraph.com/tess_rotation_tois
- ID:
- ivo://CDS.VizieR/J/ApJ/900/118
- Title:
- RSGs in the LMC & sp. follow-up for LMC & SMC
- Short Name:
- J/ApJ/900/118
- Date:
- 20 Jan 2022 11:32:23
- Publisher:
- CDS
- Description:
- The binary fraction of unevolved massive stars is thought to be 70%-100% but there are few observational constraints on the binary fraction of the evolved version of a subset of these stars, the red supergiants (RSGs). Here we identify a complete sample of RSGs in the Large Magellanic Cloud (LMC) using new spectroscopic observations and archival UV, IR, and broadband optical photometry. We find 4090 RSGs with logL/L_{sun}_>3.5, with 1820 of them having logL/L_{sun}_>4, which we believe is our completeness limit. We additionally spectroscopically confirmed 38 new RSG + B-star binaries in the LMC, bringing the total known up to 55. We then estimated the binary fraction using a k-nearest neighbors algorithm that classifies stars as single or binary based on photometry with a spectroscopic sample as a training set. We take into account observational biases such as line-of-sight stars and binaries in eclipse while also calculating model- dependent corrections for RSGs with companions that our observations were not designed to detect. Based on our data, we find an initial result of 13.5_-6.67_^+7.56^% for RSGs with O- or B-type companions. Using the Binary Population and Spectral Synthesis models to correct for unobserved systems, this corresponds to a total RSG binary fraction of 19.5_-6.7_^+7.6^% . This number is in broad agreement with what we would expect given an initial OB binary distribution of 70%, a predicted merger fraction of 20%-30%, and a binary interaction fraction of 40%-50%.
