- ID:
- ivo://CDS.VizieR/J/MNRAS/472/3887
- Title:
- Kinematic data for stars in OB-associations
- Short Name:
- J/MNRAS/472/3887
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use stellar proper motions from the catalog TGAS (2016, Cat. I/337) to study the kinematics of OB-associations identified by Blaha and Humphreys (1989AJ.....98.1598B). The TGAS proper motions of OB-associations generally agree well with the Hipparcos proper motions. The parameters of the Galactic rotation curve obtained with TGAS and Hipparcos proper motions agree within the errors. The average internal velocity dispersion calculated for 18 OB-associations with more than 10 TGAS stars is sigma_v_=3.9km/s, which is considerably smaller, by a factor of 0.4, than the velocity dispersions derived from Hipparcos data. The effective contribution from binary OB-stars into the velocity dispersion sigma_v inside OB-associations is sigma_b_=1.2km/s. The median virial and stellar masses of OB-associations are equal to 7.1x10^5^ and 9.0x10^3^M_{sun}_, respectively. Thus OB-associations must be unbound objects provided they do not include a lot of dense gas. The median star-formation efficiency is epsilon=2.1%. Nearly one third of stars of OB-associations must lie outside their tidal radius. We found that the Per OB1 and Car OB1 associations are expanding with the expansion started in a small region of 11-27pc 7-10Myr ago. The average expansion velocity is 6.3km/s.
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- ID:
- ivo://CDS.VizieR/J/ApJ/783/131
- Title:
- Kinematic of stars in Galactic center
- Short Name:
- J/ApJ/783/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new kinematic measurements and modeling of a sample of 116 young stars in the central parsec of the Galaxy in order to investigate the properties of the young stellar disk. The measurements were derived from a combination of speckle and laser guide star adaptive optics imaging and integral field spectroscopy from the Keck telescopes. Compared to earlier disk studies, the most important kinematic measurement improvement is in the precision of the accelerations in the plane of the sky, which have a factor of six smaller uncertainties ({sigma}~10{mu}as/yr2). We have also added the first radial velocity measurements for eight young stars, increasing the sample at the largest radii (6''-12'') by 25%. We derive the ensemble properties of the observed stars using Monte Carlo simulations of mock data. There is one highly significant kinematic feature (~20{sigma}), corresponding to the well-known clockwise disk, and no significant feature is detected at the location of the previously claimed counterclockwise disk. The true disk fraction is estimated to be ~20%, a factor of ~2.5 lower than previous claims, suggesting that we may be observing the remnant of what used to be a more densely populated stellar disk. The similarity in the kinematic properties of the B stars and the O/WR stars suggests a common star formation event. The intrinsic eccentricity distribution of the disk stars is unimodal, with an average value of <e> =0.27+/-0.07, which we show can be achieved through dynamical relaxation in an initially circular disk with a moderately top-heavy mass function.
- ID:
- ivo://CDS.VizieR/J/ApJ/870/32
- Title:
- Kinematics in young star clusters & associations
- Short Name:
- J/ApJ/870/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Gaia mission has opened a new window into the internal kinematics of young star clusters at the sub-km/s level, with implications for our understanding of how star clusters form and evolve. We use a sample of 28 clusters and associations with ages from ~1-5Myr, where lists of members are available from previous X-ray, optical, and infrared studies. Proper motions from Gaia DR2 reveal that at least 75% of these systems are expanding; however, rotation is only detected in one system. Typical expansion velocities are on the order of ~0.5km/s, and in several systems, there is a positive radial gradient in expansion velocity. Systems that are still embedded in molecular clouds are less likely to be expanding than those that are partially or fully revealed. One-dimensional velocity dispersions, which range from {sigma}_1D_=1 to 3km/s, imply that most of the stellar systems in our sample are supervirial and that some are unbound. In star-forming regions that contain multiple clusters or subclusters, we find no evidence that these groups are coalescing, implying that hierarchical cluster assembly, if it occurs, must happen rapidly during the embedded stage.
- ID:
- ivo://CDS.VizieR/J/PAZh/32/906
- Title:
- Kinematics of Gould Belt Based on Open Clusters
- Short Name:
- J/PAZh/32/906
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have redetermined kinematic parameters of the Gould Belt using currently available data on the motion of nearby young (logt<7.91) open clusters, OB associations, and moving stellar groups. Our modeling shows that the residual velocities reach their maximum values of -4km/s for rotation (in the direction of Galactic rotation) and +4km/s for expansion at a distance from the kinematic center of 300pc. We have taken the following parameters of the Gould Belt center: R_0_=150pc and l_0_=128{deg}. The whole structure is shown to move relative to the local standard of rest at a velocity of 10.7+/-0.7km/s in the direction l=274+/-4{deg} and b=-1+/-3{deg}. Using the derived rotation velocity, we have estimated the virial mass of the Gould Belt to be 1.5 million solar masses.
- ID:
- ivo://CDS.VizieR/J/PAZh/33/643
- Title:
- Kinematics of Sco-Cen OB Association
- Short Name:
- J/PAZh/33/643
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A fine structure related to the kinematic peculiarities of three components of the Scorpius-Centaurus association (LCC = Lower Centaurus-Crux, UCL = Upper Centaurus-Lupus, and US = Upper Scorpius) has been revealed in the UV-velocity distribution of Gould Belt stars. We have been able to identify the most likely members of these groups by applying the method of analyzing the two-dimensional probability density function of stellar UV velocities that we developed. A kinematic analysis of the identified structural components has shown that, in general, the center-of-mass motion of the LCC, UCL, and US groups follows the motion characteristic of the Gould Belt, notably its expansion. The entire Scorpius-Centaurus complex is shown to possess a proper expansion with an angular velocity parameter of 46+/-8km/s/kpc for the kinematic center with l_0_=-40{deg} and R_0_=110pc found. Based on this velocity, we have estimated the characteristic expansion time of the complex to be 21+/-4Myr. The proper rotation velocity of the Scorpius-Centaurus complex is lower in magnitude, is determined less reliably, and depends markedly on the data quality.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2369
- Title:
- Kinematics of young associations/clusters
- Short Name:
- J/MNRAS/402/2369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young isolated radio-quiet neutron stars are still hot enough to be detectable at X-ray and optical wavelengths due to their thermal emission and can hence probe cooling curves. An identification of their birth sites can constrain their age. For that reason, we try to identify the parent associations for four of the so-called Magnificent Seven neutron stars for which proper motion and distance estimates are available. We are tracing back in time each neutron star and possible birth association centre to find close encounters. The associated time of the encounter expresses the kinematic age of the neutron star which can be compared to its characteristic spin-down age. Owing to observational uncertainties in the input data, we use Monte Carlo simulations and evaluate the outcome of our calculations statistically. RX J1856.5-3754 most probably originated from the Upper Scorpius association about 0.3Myr ago. RX J0720.4-3125 was either born in the young local association TW Hydrae about 0.4Myr ago or in Trumpler 10 0.5Myr in the past. Also RX J1605.3+3249 and RBS 1223 seem to come from a nearby young association such as the Scorpius-Centraurus complex or the extended Corona-Australis association. For RBS 1223 also a birth in Scutum OB2 is possible. We also give constraints on the observables as well as on the radial velocity of the neutron star. Given the birth association, its age and the flight time of the neutron star, we estimate the mass of the progenitor star. Some of the potential supernovae were located very nearby (<100pc) and thus should have contributed to the 10Be and 60Fe material found in the Earth's crust. In addition, we reinvestigate the previously suggested neutron star/runaway pair PSR B1929+10/zeta Ophiuchi and conclude that it is very likely that both objects were ejected during the same supernova event.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/100
- Title:
- Kinematic structure of the Galactic Center S cluster
- Short Name:
- J/ApJ/896/100
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the kinematics of 112 stars that mostly comprise the high-velocity S cluster and orbit the supermassive black hole Sgr A* at the center of the Milky Way. For 39 of them, orbital elements are known; for the remainder, we know proper motions. The distribution of the inclinations and the proper motion flight directions deviate significantly from a uniform distribution, which one expects if the orientation of the orbits are random. Across the central arcseconds, the S-cluster stars are arranged in two almost edge-on disks that are located at a position angle approximately +/-45{deg} with respect to the Galactic plane. The angular momentum vectors for stars in each disk point in both directions, i.e., the stars in a given disk rotate in opposite ways. The poles of this structure are located only about 25{deg} from the line of sight. This structure may be the result of a resonance process that started with the formation of the young B-dwarf stars in the cluster about 6Myr ago. Alternatively, it indicated the presence of a disturber at a distance from the center comparable to the distance of the compact stellar association IRS 13.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A34
- Title:
- KMOS O-type star detection in Tr 16-SE
- Short Name:
- J/A+A/648/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carina Nebula harbors a large population of high-mass stars, including at least 75 O-type and Wolf-Rayet (WR) stars, but the current census is not complete since further high-mass stars may be hidden in or behind the dense dark clouds that pervade the association. With the aim of identifying optically obscured O- and early B-type stars in the Carina Nebula, we performed the first infrared spectroscopic study of stars in the optically obscured stellar cluster Tr 16-SE, located behind a dark dust lane south of {eta} Car. We used the integral-field spectrograph KMOS at the ESO VLT to obtain H- and K-band spectra with a resolution of R~4000 ({Delta}{lambda}~5{AA}) for 45 out of the 47 possible OB candidate stars in Tr 16-SE, and we derived spectral types for these stars. We find 15 stars in Tr 16-SE with spectral types between O5 and B2 (i.e. high-mass stars with M>=8M_{sun}_), only two of which were known before. An additional nine stars are classified as (Ae)Be stars, i.e. intermediate-mass pre-main sequence stars, and most of the remaining targets show clear signatures of being late-type stars and are thus most likely foreground stars or background giants unrelated to the Carina Nebula. Our estimates of the stellar luminosities suggest that nine of the 15 O- and early B-type stars are members of Tr 16-SE, whereas the other six seem to be background objects. Our study increases the number of spectroscopically identified high-mass stars (M>=8M_{sun}_) in Tr 16-SE from two to nine and shows that Tr 16-SE is one of the larger clusters in the Carina Nebula. Our identification of three new stars with spectral types between O5 and O7 and four new stars with spectral types O9 to B1 significantly increases the number of spectroscopically identified O-type stars in the Carina Nebula.
- ID:
- ivo://CDS.VizieR/J/PAZh/25/276
- Title:
- KV Cyg, V435 Cyg, V699 Cyg UBVR photometry
- Short Name:
- J/PAZh/25/276
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a UBVR photometry observations are presented for eclipsing binaries KV Cyg, V435 Cyg and V699 Cyg. Each binary was observed 1989/91 with the 60 cm telescopes at Maidanak Observatory (Uzbekistan).
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/822
- Title:
- LAMOST candidate members of star clusters
- Short Name:
- J/MNRAS/448/822
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) stellar parameter pipeline at Peking University - LSP3, developed and implemented for the determinations of radial velocity Vr and stellar atmospheric parameters (effective temperature Teff, surface gravity logg, metallicity [Fe/H]) for the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC). We describe the algorithms of LSP3 and examine the accuracy of parameters yielded by it. The precision and accuracy of parameters yielded are investigated by comparing results of multi-epoch observations and of candidate members of open and globular clusters, with photometric calibration, as well as with independent determinations available from a number of external data bases, including the PASTEL archive, the APOGEE, SDSS and RAVE surveys, as well as those released in the LAMOST DR1. The uncertainties of LSP3 parameters are characterized and quantified as a function of the spectral signal-to-noise ratio (SNR) and stellar atmospheric parameters. We conclude that the current implementation of LSP3 has achieved an accuracy of 5.0km/s, 150K, 0.25dex, 0.15dex for the radial velocity, effective temperature, surface gravity and metallicity, respectively, for LSS-GAC spectra of FGK stars of SNRs per pixel higher than 10. The LSP3 has been applied to over a million LSS-GAC spectra collected hitherto. Stellar parameters yielded by the LSP3 will be released to the general public following the data policy of LAMOST, together with estimates of the interstellar extinction E(B-V) and stellar distances, deduced by combining spectroscopic and multiband photometric measurements using a variety of techniques.
