- ID:
- ivo://CDS.VizieR/J/A+A/649/A178
- Title:
- NGC6791 V604 Lyr disentangled component spectra
- Short Name:
- J/A+A/649/A178
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Models of stellar structure and evolution can be constrained using accurate measurements of the parameters of eclipsing binary members of open clusters. Multiple binary stars provide the means to tighten the constraints, and in turn, to improve the precision and accuracy of the age estimate of the host cluster. In the previous two papers of this series, we demonstrated the use of measurements of multiple eclipsing binaries in the old open cluster NGC6791 to set tighter constraints on the properties of stellar models than was previously possible, thereby improving both the accuracy and precision of the cluster age. We identify and measure the properties of a non-eclipsing cluster member, V56 (Cl* NGC 6791 KR V56), in NGC 6791 and demonstrate how this provides additional model constraints that support and strengthen our previous findings. We analyse multi-epoch spectra of V56 from FLAMES in conjunction with the existing photometry and measurements of eclipsing binaries in NGC6971. The parameters of the V56 components are found to be Mp=1.103+/-0.008M_{sun}_ and Ms=0.974+/-0.007M_{sun}_, Rp=1.764+/-0.099R_{sun}_ and Rs=1.045+/-0.057R_{sun}_, Teff,p=5447+/-125K and Teff,s=5552+/-125K, and surface [Fe/H]=+0.29+/-0.06 assuming that they have the same abundance. The derived properties strengthen our previous best estimate of the cluster age of 8.3+/-0.3Gyr and the mass of stars on the lower RGB, M_RGB_=1.15+/-0.02M_{sun}_ for NGC 6791. These numbers therefore continue to serve as verification points for other methods of age and mass measures, such as asteroseismology.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/128/1684
- Title:
- NGC 2264: VRIH{alpha} photometry
- Short Name:
- J/AJ/128/1684
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young open cluster NGC 2264 was observed on 2002 January 67 with the CFH12K mosaic CCD on the 3.6m Canada-France-Hawaii Telescope to investigate the shape of the initial mass function (IMF). In order to select the pre-main-sequence (PMS) members more completely, Chandra X-Ray Observatory archival data were retrieved and used for the identification of X-ray-emitting weak-line T Tauri stars. In addition, the (R-I, V-I) diagram was used to exclude background late-type giants, and a statistical approach was applied to estimate the number of contaminating foreground main-sequence stars.
- ID:
- ivo://CDS.VizieR/J/AJ/137/5086
- Title:
- NGC 188 V12 VI light curves
- Short Name:
- J/AJ/137/5086
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time series radial velocity, and photometric observations of a solar-type double-lined eclipsing binary star (V12) in the old open cluster NGC 188. We use these data to determine the spectroscopic orbit and the photometric elements for V12.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A78
- Title:
- NGC2264 weak-line T Tauri lithium abundances
- Short Name:
- J/A+A/590/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of lithium abundance in cool dwarfs provides a unique probe of non-standard processes in stellar evolution. Aims. We investigate here the lithium content of young low-mass stars in the 5 Myr-old star forming region NGC 2264 and its relationship with rotation. We combine lithium equivalent width measurements (EW(Li)) from the Gaia-ESO Survey with the determination of rotational periods from the CSI 2264 survey. We consider only bona fide non accreting cluster members in order to minimize uncertainties on EW(Li). We report the existence of a relationship between lithium content and rotation in NGC 2264 at an age of 5Myr. The Li-rotation connection is seen over a restricted temperature range (Teff=800-4400K) where fast rotators are Li-rich compared to slow ones. This correlation is similar to, albeit of lower amplitude than, the Li-rotation connection previously reported for K dwarfs in the 125Myr-old Pleiades cluster. We investigate whether the non-standard pre-main sequence models developed so far to explain the Pleiades results, which are based on episodic accretion, pre-main sequence core-envelope decoupling, and/or radius inflation due to enhanced magnetic activity, can account for an early development of the Li-rotation connection. While radius inflation appears to be the most promising possibility, each of these models has issues. We therefore also discuss external causes that might operate during the first few Myr of pre-main sequence evolution, such as planet engulfment and/or steady disk accretion, as possible candidates for the common origin for Li-excess and fast rotation in young low-mass pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/J/A+A/312/818
- Title:
- NGC 2516 X-ray sources
- Short Name:
- J/A+A/312/818
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT PSPC detector was used to obtain a deep pointing with its center on the young open cluster NGC 2516 and total integration time of 9284 sec. Altogether 64 X-ray sources were detected showing strong concentration towards the optical cluster centre. This suggests that most of the sources are actually associated with NGC 2516. 42 of these sources could be identified with optical stars in the field of the cluster; after correction for a mean offset between optical and nominal ROSAT positions of about 13", optical star and X-ray source positions are found to agree, on the average, within about 9", while maximum observed positional differences amount to 27". X-ray sources identified with optical cluster stars include HR 3147 (=HD 66194; B2.5IVe), the visually brightest B star in the cluster, three close visual late B-type binaries (h 4027 A,B, h 4031 A,B, and I 1104 A,B) with projected separations ranging between about 4x10^16^cm and 6x10^16^cm, as well as several (six) chemically peculiar Bp/Ap(Si) and Ap(SrCrEu) stars.
- ID:
- ivo://CDS.VizieR/J/AJ/132/2296
- Title:
- NICMOS observations of Mon R2 cluster
- Short Name:
- J/AJ/132/2296
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed Hubble Space Telescope NICMOS2 F110W-, F160W-, F165M-, and F207M-band images covering the central 1'x1' region of the cluster associated with Mon R2 in order to constrain the initial mass function (IMF) down to 20M_J_. The flux ratio between the F165M and F160W bands was used to measure the strength of the water-band absorption feature and select a sample of 12 out of the total sample of 181 objects that have effective temperatures between 2700 and 3300K.
- ID:
- ivo://CDS.VizieR/J/AJ/126/1665
- Title:
- NICMOS observations of NGC 2024
- Short Name:
- J/AJ/126/1665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of NICMOS observations of the embedded cluster associated with NGC 2024. An analysis of the cluster color-magnitude diagram (CMD) using the models of D'Antona & Mazzitelli and Baraffe et al. (published in 1997MmSAI..68..807D and 1998, Cat. <J/A+A/337/403>, respectively) indicates that the ratio of intermediate-mass (1.0-10.0M_{sun}_) to low-mass (0.1-1.0M_{sun}_) stars is consistent with the stellar initial mass function (IMF) for the field. In addition to the CMD analysis, we present results on the multiplicity of stars in the region. Three companions (in a sample of 95 potential primaries) were found, with angular separations between 0.4" and 1.0", translating to a projected linear separation of 184-460AU for an estimated distance of 460pc. The completeness of binary detections is assessed using recovery fractions calculated by a series of tests using artificially generated companions to potential primaries in the data frames. We find that the binary fraction in NGC 2024 is consistent with that of Duquennoy & Mayor (published in 1991A&A...248..485D) for solar neighborhood stars over the range of separations and companion masses appropriate for our survey.
- ID:
- ivo://CDS.VizieR/J/A+A/595/A22
- Title:
- Nine new open clusters within 500pc from the Sun
- Short Name:
- J/A+A/595/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the results of the Milky Way Star Clusters (MWSC) survey was the detection of a slight under-density of old (ca. 1Gyr) clusters within the nearest kilo-parsec from the Sun. This under-density may be due to an ineffectiveness in the detection of larger structures with lower surface brightness. We report on our attempts to reveal such clusters. We derived proper motions from a combination of Tycho-2 with URAT1, and obtained a mean precision of about 1.4mas/yr per co-ordinate for 1.3 million stars north of -20{deg} declination. We cut the sky into narrow proper motion slices and searched for spatial over-densities of stars in each slice. We then examined stars from over-densities in optical and near-infrared colour-magnitude diagrams to determine if they are compatible with isochrones of a cluster. We estimated the field star contamination using our data and the Besancon Galactic model. We detected nine hitherto unknown open clusters in the vicinity of the Sun with ages between 70Myr and 1Gyr, and distances between 200 and 500pc.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A39
- Title:
- NIR photometry in 10 nearby spiral galaxies
- Short Name:
- J/A+A/542/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spiral structure is a prominent feature in many disk galaxies and is often outlined by bright, young objects. We study the distribution of young stellar clusters in grand-design spiral galaxies and thereby determine whether strong spiral perturbations can influence star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/486/453
- Title:
- NIR photometry of early-type stars in Cyg OB2
- Short Name:
- J/A+A/486/453
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cygnus OB2 is one of the richest OB associations in the local Galaxy, and is located in a vast complex containing several other associations, clusters, molecular clouds, and HII regions. However, the stellar content of Cygnus OB2 and its surroundings remains rather poorly known largely due to the considerable reddening in its direction at visible wavelength. We investigate the possible existence of an extended halo of early-type stars around Cygnus OB2, which is hinted at by near-infrared color-color diagrams, and its relationship to Cygnus OB2 itself, as well as to the nearby association Cygnus OB9 and to the star forming regions in the Cygnus X North complex. Candidate selection is made with photometry in the 2MASS all-sky point source catalog. The early-type nature of the selected candidates is confirmed or discarded through our infrared spectroscopy at low resolution. In addition, spectral classifications in the visible are presented for many lightly-reddened stars.
