- ID:
- ivo://CDS.VizieR/J/A+A/459/391
- Title:
- Dynamics of NGC 4636 globular cluster system
- Short Name:
- J/A+A/459/391
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first dynamical study of the globular cluster system of NGC 4636. It is the southernmost giant elliptical galaxy of the Virgo cluster and is claimed to be extremely dark matter dominated, according to X-ray observations. Globular clusters are used as dynamical tracers to investigate, by stellar dynamical means, the dark matter content of this galaxy. Several hundred medium resolution spectra were acquired at the VLT with FORS 2/MXU. We obtained velocities for 174 globular clusters in the radial range 0.90'<R<15.5', or 0.5-9R_e_ in units of effective radius. Assuming a distance of 15Mpc, the clusters are found at projected galactocentric distances in the range 4 to 70kpc, the overwhelming majority within 30kpc. The measured line-of-sight velocity dispersions are compared to Jeans-models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/899/121
- Title:
- 127 early type and pre-main-sequence stars in W4
- Short Name:
- J/ApJ/899/121
- Date:
- 15 Mar 2022 03:47:36
- Publisher:
- CDS
- Description:
- Stellar kinematics provides the key to understanding the formation process and dynamical evolution of stellar systems. Here, we present a kinematic study of the massive star-forming region (SFR) W4 in the Cassiopeia OB6 association using the Gaia Data Release 2 and high-resolution optical spectra. This SFR is composed of a core cluster (IC1805) and a stellar population distributed over 20pc, which is a typical structural feature found in many OB associations. According to a classical model, this structural feature can be understood in the context of the dynamical evolution of a star cluster. The core-extended structure exhibits internally different kinematic properties. Stars in the core have an almost isotropic motion, and they appear to reach virial equilibrium given their velocity dispersion (0.9{+/-}0.3km/s) comparable to that in a virial state (~0.8km/s). On the other hand, the distributed population shows a clear pattern of radial expansion. From the N-body simulation for the dynamical evolution of a model cluster in subvirial state, we reproduce the observed structure and kinematics of stars. This model cluster experiences collapse for the first 2Myr. Some members begin to radially escape from the cluster after the initial collapse, eventually forming a distributed population. The internal structure and kinematics of the model cluster appear similar to those of W4. Our results support the idea that the stellar population distributed over 20pc in W4 originate from the dynamical evolution of IC1805.
- ID:
- ivo://CDS.VizieR/J/A+AS/139/483
- Title:
- Early-type gal. kinematics in compact groups
- Short Name:
- J/A+AS/139/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of stellar kinematics for seven early-type galaxies in HCG 67, HCG 74, and HCG 79. These data are aimed at studying the relation between the environment and the dynamics, structure and stellar content of early-type galaxies. In the present three groups, the kinematic features we observed cannot be associated unambiguously to physical interactions. Visible morphological peculiarities do not appear correlated with kinematical perturbations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/2220
- Title:
- Early-type Sco-Cen members with literature RVs
- Short Name:
- J/MNRAS/453/2220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the serendipitous discovery of several young mid-M stars found during a search for new members of the 30-40Myr-old Octans Association. Only one of the stars may be considered a possible Octans(-Near) member. However, two stars have proper motions, kinematic distances, radial velocities, photometry and LII {lambda}6708 measurements consistent with membership in the 8-10Myr-old TW Hydrae Association. Another may be an outlying member of TW Hydrae but has a velocity similar to that predicted by membership in Octans. We also identify two new lithium-rich members of the neighbouring Scorpius-Centaurus OB Association (Sco-Cen). Both exhibit large 12 and 22{mu}m excesses and strong, variable H{alpha} emission which we attribute to accretion from circumstellar discs. Such stars are thought to be incredibly rare at the ~16Myr median age of Sco-Cen and they join only one other confirmed M-type and three higher mass accretors outside of Upper Scorpius. The serendipitous discovery of two accreting stars hosting large quantities of circumstellar material may be indicative of a sizeable age spread in Sco-Cen, or further evidence that disc dispersal and planet formation time-scales are longer around lower mass stars. To aid future studies of Sco-Cen, we also provide a newly compiled catalogue of 305 early-type Hipparcos members with spectroscopic radial velocities sourced from the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/342/671
- Title:
- Early-type spiral galaxies kinematics
- Short Name:
- J/A+A/342/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar and ionized-gas velocity curves and velocity-dispersion profiles along the major axis for six early-type spiral galaxies. Two of these galaxies, namely NGC 2179 and NGC 2775, are particularly suited for the study of dark matter halos. Using their luminosity profiles and modeling their stellar and gaseous kinematics, we derive the mass contributions of the luminous and the dark matter to the total potential. In NGC 2179 we find that the data (measured out to about the optical radius R_opt_) unambiguously require the presence of a massive dark halo. For the brighter and bigger object NGC 2775, we can rule out a significant halo contribution at radii R<~0.6R_opt_. Although preliminary, these results agree with the familiar mass distribution trend known for late-type spirals of comparable mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/110
- Title:
- Early-type stars in Taurus-Auriga
- Short Name:
- J/ApJ/771/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud (Rebull et al. 2010, J/ApJS/186/259), (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey (Skrutskie et al. 2006, VII/233), and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region (Finkbeiner et al. 2004AJ....128.2577F; Knapp et al. 2007AAS...211.2907K). We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), {tau} Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.
- ID:
- ivo://CDS.VizieR/J/ApJS/235/5
- Title:
- EA-type eclipsing binaries observed by LAMOST
- Short Name:
- J/ApJS/235/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs (0.4<P<1 days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.
- ID:
- ivo://CDS.VizieR/J/A+A/604/L6
- Title:
- EBLM J0555-57 photometry and RV
- Short Name:
- J/A+A/604/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of an eclipsing binary system with mass-ratio q After identifying a periodic photometric signal received by WASP, we obtained CORALIE spectroscopic radial velocities and follow-up light curves with the Euler and TRAPPIST telescopes. From a joint fit of these data we determine that EBLM J0555-57 consists of a sun-like primary star that is eclipsed by a low-mass companion, on a weakly eccentric 7.8-day orbit. Using a mass estimate for the primary star derived from stellar models, we determine a companion mass of 85+/-4M_Jup_ (0.081M_{sun}_) and a radius of 0.84^+0.14^_-0.04_R_Jup_ (0.084R_{sun}_) that is comparable to that of Saturn. EBLM J0555-57Ab has a surface gravity logg2=5.50^+0.03^_-0.13_ and is one of the densest non-stellar-remnant objects currently known. These measurements are consistent with models of low-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A119
- Title:
- EBLM J2349-32 photometry, RV and spectra
- Short Name:
- J/A+A/626/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some M-dwarfs around F-/G-type stars have been measured to be hotter and larger than predicted by stellar evolution models. Inconsistencies between observations and models need to be addressed with more mass, radius, and luminosity measurements of low-mass stars to test and refine evolutionary models. Our aim is to measure the masses, radii and ages of the stars in five low-mass eclipsing binary systems discovered by the WASP survey. We used WASP photometry to establish eclipse-time ephemerides and to obtain initial estimates for the transit depth and width. Radial velocity measurements were simultaneously fitted with follow-up photometry to find the best-fitting orbital solution. This solution was combined with measurements of atmospheric parameters to interpolate evolutionary models and estimate the mass of the primary star, and the mass and radius of the M-dwarf companion. We assess how the best fitting orbital solution changes if an alternative limb-darkening law is used and quantify the systematic effects of unresolved companions. We also gauge how the best-fitting evolutionary model changes if different values are used for the mixing length parameter and helium enhancement. We report the mass and radius of five M-dwarfs and find little evidence of inflation with respect to evolutionary models. The primary stars in two systems are near the "blue hook" stage of their post sequence evolution, resulting in two possible solutions for mass and age. We find that choices in helium enhancement and mixing-length parameter can introduce an additional 3-5% uncertainty in measured M-dwarf mass. Unresolved companions can introduce an additional 3-8% uncertainty in the radius of an M-dwarf, while the choice of limb-darkening law can introduce up to an additional 2% uncertainty. The choices in orbital fitting and evolutionary models can introduce significant uncertainties in measurements of physical properties of such systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/109
- Title:
- EBs in Ruprecht 147. II. EPIC 219568666 LC & RVs
- Short Name:
- J/ApJ/887/109
- Date:
- 30 Nov 2021
- Publisher:
- CDS
- Description:
- We report our spectroscopic monitoring of the detached, grazing, and slightly eccentric 12 day double-lined eclipsing binary EPIC 219568666 in the old nearby open cluster Ruprecht 147. This is the second eclipsing system to be analyzed in this cluster, following our earlier study of EPIC 219394517. Our analysis of the radial velocities combined with the light curve from the K2 mission yields absolute masses and radii for EPIC 219568666 of M_1_=1.121+/-0.013M_{sun}_ and R_1_=1.1779+/-0.0070R_{sun}_ for the F8 primary and M_2_=0.7334+/-0.0050M_{sun}_ and R_2_=0.640+/-0.017R_{sun}_ for the faint secondary. Comparison with current stellar evolution models calculated for the known metallicity of the cluster points to a primary star that is oversized, as is often seen in active M dwarfs, but this seems rather unlikely for a star of its mass and with a low level of activity. Instead, we suspect a subtle bias in the radius ratio inferred from the photometry, despite our best efforts to avoid it, which may be related to the presence of spots on one or both stars. The radius sum for the binary, which bypasses this possible problem, indicates an age of 2.76+/-0.61Gyr, which is in good agreement with a similar estimate from the binary in our earlier study.
