ABSTRACT
Following Lin and Shu, the spiral structure in the Milky Way disc is considered as an oscillating density-wave pattern. As such, regular enhancements in density are relatedly linked to ...systematic variations in velocity of young stars and stellar clusters, and interstellar gas. We explain measured line-of-sight velocities of 252 open clusters with ages <100 Myr of Tarricq et al. in the 3-kpc-scale solar neighbourhood in terms of a density wave. New estimates of the parameters of solar peculiar motion and Galactic differential rotation corrected for the effects of small-amplitude density waves, the radial and tangential components of systematic motion of clusters due to the spiral arms as well as the geometrical and dynamical parameters of the waves are suggested.
ABSTRACT
Distances and line-of-sight velocities of 964 Gaia Data Release 2 (DR2) OB stars of Xu et al. within 3 kpc from the Sun and 500 pc from the Galactic mid-plane with accuracies of <50 per cent ...are selected. The data are used to find small systematic departures of velocities from the mean circular motion for the stars in the solar neighborhood due to the spiral compression-type (Lin–Shu-type) waves, or spiral density waves, e.g. those produced by real instabilities of spontaneous gravity disturbances, a central bar or a companion system. A key point of the study is that our results are consistent with the ones extracted from the asymptotic density-wave theory. Revised parameters of density waves in the solar vicinity of the Galaxy are also provided.
A machine-learning technique with two-dimension convolutional neural network is proposed for detecting exoplanet transits. To test this new method, five different types of deep-learning models with ...or without folding are constructed and studied. The light curves of the Kepler Data Release 25 are employed as the input of these models. The accuracy, reliability, and completeness are determined and their performances are compared. These results indicate that a combination of two-dimension convolutional neural network with folding would be an excellent choice for the future transit analysis.
ABSTRACT
To investigate the dynamical properties of globular clusters, surface brightness and kinematic data were collected and fitted to a family of lowered isothermal models called limepy models. ...For the 18 globular clusters studied, the amounts of concentration, truncation, and anisotropy were determined. In addition, the cluster mass, half-mass radius, distance, and mass-to-light ratio were also obtained. In general, limepy models can describe these clusters well. Among these 18 clusters, NGC 5139, 6388, and 7078 have been claimed to be candidates for hosting intermediate-mass black holes in the literature. The models could not appropriately fit the central proper-motion velocity dispersion of NGC 5139, nor the slope of the proper-motion velocity dispersion profile of NGC 6388. Thus, more dedicated models with intermediate-mass black holes or a group of stellar-mass black holes at cluster centres may need to be considered. Regarding NGC 7078, our model with some degree of anisotropy can fit the data. Finally, a strong concentration–truncation anticorrelation and a truncation–semimajor-axis correlation were revealed, which could be the observational imprint of the dynamical evolution of globular clusters.
A statistical method is used to derive both the Sun’s distance r0 from the Galactic Center (GC) and the 3D geometry of the inner (< 25 kpc) halo. The spatial distribution of the 138 Gaia EDR3 ...globular clusters (GCs) with distances established on a combination of HST and literature data of Baumgardt and Vasiliev (2021) is explored. An estimate by using these ancient objects of the pressure-supported subsystem of the Galaxy with newly derived distances leads to the mean r0=7.81±0.14 kpc. The distribution of GCs within 25 kpc is almost spherically symmetric, and has the shape of an ellipsoid with a major axis of its symmetry slightly elongated toward the Sun and two minor axes of almost the same length. The obtained scale-length ratio of the major axis to the minor axis in the plane and to the vertical axis of the ellipsoid is ≈ 1:0.8:0.7. Based on the papers of a series, for practical use we argue to employ the following Sun’s distances from the GC and the plane: r0=8.15±0.15 kpc and z0=15±5 pc.
•The space distribution of the Gaia EDR3 globular clusters with newly derived distances within the halo radius of ≈ 25 kpc in the Galaxy is studied.•A maximum likelihood statistical method is used to derive indirectly the Sun’s distance from the Galactic Center r0≈8 kpc.•The distribution of clusters of the inner halo is almost spherically symmetric with the obtained scale-length axis ratio of ≈ 1 : 0.8 : 0.7.•The old bulge and halo may form a continuous subsystem and the bulk of the bulge objects may represent the inner extension of a halo in the system.•The Sun’s distances from the Galactic Center and the plane r0=8.15±0.15 kpc and z0=15±5 pc are suggested for practical usage.
ABSTRACT
A statistical method is employed in tandem with new VISTA Variables in the Via Lactea (VVV) near-infrared observations to determine the Sun’s distance from the Galactic Centre (r0, GC), the ...Sun’s height from the local mid-plane (z0), and to likewise infer the shape of the Galactic ∼10 Gyr old bulge. Specifically, the conclusions stem from an investigation of 715 high-latitude (|b| > 1°) and centrally symmetric concentrated Type II Cepheids (T2Cs) recently identified in the VVV survey by Braga et al. The analysis yields r0 = 8.35 ± 0.10 kpc and z0 = 10 ± 2 pc. The T2Cs distribution within the effective bulge radius rbulge = 2–3 kpc is an ellipsoid exhibiting axial ratios of ≈1:0.7:0.6, with the major axis inclined at an angle θ ≈ −3° to the Sun–GC sightline. T2Cs do not trace a prominent barred structure at distances >1 kpc from the GC. A key conclusion is that analyses of independent optical and infrared Optical Gravitational Lensing Experiment (OGLE) and VVV observations yield consistent results (e.g. r0 > 8.0 kpc and both observations display a comparable shape of an ellipsoid), thus providing a constrained and reduced systematic uncertainty.
ABSTRACT
We report the conditional occurrences between three planetary types: super-Earths (m sin i < 10 M⊕, P < 100 d), warm Jupiters (m sin i > 95 M⊕, 10 < P < 100 d), and cold Jupiters (m sin i > ...95 M⊕, P > 400 d) for sun-like stars. We find that while the occurrence of cold Jupiters in systems with super-Earths is $22.2\substack{+8.3 \\ -5.4}$ per cent, compared to 10 per cent for the absolute occurrence rate of cold Jupiters, the occurrence of super-Earths in systems with cold Jupiters is $66.0\substack{+18.0 \\ -16.0}$ per cent, compared to 30 per cent for the absolute occurrence rate of super-Earths for Sun-like stars. We find that the enhancement of super-Earths in systems with cold Jupiters is evident for Sun-like stars, in agreement with several previous studies. We also conduct occurrence studies between warm Jupiters and super-Earths, and between warm Jupiters and cold Jupiters, to consolidate our methods. We conduct an independent observational test to study the effects of cold Jupiters against the inner multiplicity using the well-established giant planet host star metallicity correlation for all transiting planets found to date. The conditional occurrences we find here can be used to constrain the validity of various planetary formation models. The extremely interesting correlations between the super-Earths, cold Jupiters, and warm Jupiters can also be used to understand the formation histories of these planetary types.
ABSTRACT
A statistical method is used to determine both the Sun’s distance r0 from the Galactic Centre and the 3D structure of the old stellar population of the Galactic bulge. The space distribution ...of 16 221 high latitude type-RRab RR Lyrae stars from the optical OGLE survey located towards the bulge is explored. An estimate by using RR Lyraes leads to a mean r0 = 8.28 ± 0.14 kpc within the effective bulge radius of rbulge = 2–3 kpc. The distribution of RR Lyraes within rbulge has the shape of an ellipsoid slightly elongated almost towards the Sun with a major axis of its symmetry a and two minor axes b and c of about the same length. The axial ratio is a: b: c ≈ 1: 0.7: 0.7. These age-old, metal-poor, and kinematically hot stars do not trace a strong bar-like structure in the direction of the bulge at distances >1 kpc from the Galactic Centre, as b/a ∼ 1.
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