- ID:
- ivo://CDS.VizieR/J/A+A/457/265
- Title:
- The VLT-FLAMES Survey of Massive Stars
- Short Name:
- J/A+A/457/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis is presented of VLT-FLAMES spectroscopy for three Galactic clusters, NGC 3293, NGC 4755 and NGC 6611. Non-LTE model atmosphere calculations have been used to estimate effective temperatures (from either the helium spectrum or the silicon ionization equilibrium) and gravities (from the hydrogen spectrum). Projected rotational velocities have been deduced from the helium spectrum (for fast and moderate rotators) or the metal line spectrum (for slow rotators). The origin of the low gravity estimates for apparently near main sequence objects is discussed and is related to the stellar rotational velocity. The atmospheric parameters have been used to estimate cluster distances (which are generally in good agreement with previous determinations) and these have been used to estimate stellar luminosities and evolutionary masses. The observed Hertzsprung-Russell diagrams are compared with theoretical predictions and some discrepancies including differences in the main sequence luminosities are discussed. Cluster ages have been deduced and evidence for non-coeval star formation is found for all three of the clusters. Projected rotational velocities for targets in the older clusters, NGC 3293 and NGC 4755, have been found to be systematically larger than those for the field, confirming recent results in other similar age clusters. The distribution of projected rotational velocities are consistent with a Gaussian distribution of intrinsic rotational velocities. For the relatively unevolved targets in the older clusters, NGC 3293 and NGC 4755, the peak of the velocity distribution would be 250km/s with a full-width-half-maximum of approximately 180km/s. For NGC 6611, the sample size is relatively small but implies a lower mean rotational velocity. This may be evidence for the spin-down effect due to angular momentum loss through stellar winds, although our results are consistent with those found for very young high mass stars. For all three clusters we deduce present day mass functions with Gamma-values in the range of -1.5 to -1.8, which are similar to other young stellar clusters in the Milky Way.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/497/736
- Title:
- The young cluster IC 348.
- Short Name:
- J/ApJ/497/736
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry in BVRI was obtained for about 260 stars in and around IC 348, and multiobject spectroscopy for 80 of these. A somewhat larger region was surveyed for stars having H{alpha} in emission; over 110 emission-line stars brighter than about R=19 were discovered. Because H{alpha}emission could be detected to a limit near W=3{AA}, division into weak-line (WTTSs) and classical T Tauri stars (CTTSs) was possible on purely spectroscopic grounds. There is a steep rise in the number of emission-line stars below W(H{alpha})=10{AA}; the proportion of WTTSs to CTTSs in the area surveyed is 58:51. ROSAT detected only about 58% of the spectroscopic WTTSs and about 65% of the CTTSs, although these numbers are sensitive to the survey thresholds. The bulk of the ages of about 100 stars, read off the theoretical tracks of D'Antona & Mazzitelli (1994ApJS...90..467D), range between about 0.7 and 12Myr, but the emission-line stars, which are most likely to be members of IC 348, have a mean age of 1.3Myr. Allowance for unresolved binaries would increase this somewhat, but there is a firm upper limit at 2.95Myr. There is no indication that the ages of the emission-line stars depend upon W(H{alpha}): the IC 348 WTTSs as a population are not systematically older than the CTTSs, but there is a tendency for the WTTSs to be concentrated toward the center of IC 348, while the CTTSs are more widely distributed. There is a scattering of emission-H{alpha} stars over the entire area surveyed. There are too many to be explained as low-mass members of an earlier generation of star formation in Per OB2 or as foreground dMe stars. The mass frequency function, based on some 125 stars fitted to theoretical tracks, rises from 1.5M_{sun}_; to about 0.2M_{sun}_;, with a slope very much like that of the Scalo initial mass function. The optical cluster IC 348 radius is about 4.0', or 0.37pc. The total mass of optically detectable stars in this volume is 57M_{sun}_;, while the mean space density is about 520 stars/pc^3^. The amount of interstellar material remaining within the cluster is small in comparison. Star formation in the Per OB2/IC 348 region cannot be characterized by one unique age; it appears that stars have been forming in the region now occupied by the association for 10-20Myr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/3636
- Title:
- The young open cluster NGC 7067
- Short Name:
- J/MNRAS/466/3636
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 7067 is a young open cluster located in the direction between the first and the second Galactic quadrants and close to the Perseus spiral arm. This makes it useful for studies of the nature of the Milky Way spiral arms. Stromgren photometry taken with the Wide Field Camera at the Isaac Newton Telescope allowed us to compute individual physical parameters for the observed stars and hence to derive the cluster's physical parameters. Spectra from the 1.93-m telescope at the Observatoire de Haute-Provence helped to check and improve the results. We obtained photometry for 1233 stars, individual physical parameters for 515 and spectra for 9 of them. The 139 selected cluster members lead to a cluster distance of 4.4+/-0.4kpc, with an age below log10(t(yr))=7.3 and a present mass of 1260+/-160M_{sun}_. The morphology of the data reveals that the centre of the cluster is at (RA, DE) = (21:24:13.69, +48:00:39.2) J2000, with a radius of 6.1-arcmin. Stromgren and spectroscopic data allowed us to improve the previous parameters available for the cluster in the literature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/483/5508
- Title:
- Three new Galactic star clusters
- Short Name:
- J/MNRAS/483/5508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the serendipitous discovery of three new open clusters, named UFMG 1, UFMG 2 and UFMG 3 in the field of the intermediate-age cluster NGC 5999, by using Gaia DR2 data. A colour-magnitude filter tailored for a proper selection of main-sequence stars and red clump giants turned evident the presence of NGC 5999 and these three new stellar groups in proper motion space. Their structural parameters were derived from King-profile fittings over their projected stellar distributions and isochrone fits were performed on the clusters cleaned colour-magnitude diagrams built with Gaia bands to derive their astrophysical parameters. The clusters projected sky motion were calculated for each target using our members selection. Distances to the clusters were inferred from stellar parallaxes through a bayesian model, showing that they are marginally consistent with their isochronal distances , considering the random and systematic uncertainties involved. The new clusters are located in the nearby Sagittarius arm (d~1.5kpc) with NGC 5999 at the background (d~1.8kpc). They contain at least a few hundred stars of nearly solar metallicity and have ages between 100 and 1400Myr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2396
- Title:
- Time-series photometry of IC 348
- Short Name:
- J/MNRAS/462/2396
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present long-term photometric observations of the young open cluster IC 348 with a baseline time-scale of 2.4yr. Our study was conducted with several telescopes from the Young Exoplanet Transit Initiative (YETI) network in the Bessell R band to find periodic variability of young stars. We identified 87 stars in IC 348 to be periodically variable; 33 of them were unreported before. Additionally, we detected 61 periodic non-members of which 41 are new discoveries. Our wide field of view was the key to those numerous newly found variable stars. The distribution of rotation periods in IC 348 has always been of special interest. We investigate it further with our newly detected periods but we cannot find a statistically significant bimodality. We also report the detection of a close eclipsing binary in IC 348 composed of a low-mass stellar component (M>~0.09M_{sun}_) and a K0 pre-main sequence star (M~2.7M_{sun}_). Furthermore, we discovered three detached binaries among the background stars in our field of view and confirmed the period of a fourth one.
- ID:
- ivo://CDS.VizieR/J/BaltA/20/1
- Title:
- Tombaugh 5 Vilnius photometry
- Short Name:
- J/BaltA/20/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of eight-color CCD photometry of 674 stars in the direction of the open cluster Tombaugh 5 in Camelopardalis. The stars are observed in the Vilnius system supplemented by the broad-band I filter; the field is of 22' diameter, the limiting magnitude is V=17.7mag. The catalog contains the coordinates, V magnitudes, seven color indices, two-dimensional spectral types determined from photometric parameters, interstellar extinctions and distances. The color-magnitude diagram plotted for 480 individually dereddened stars is used to identify cluster members and to determine the distance (1.74kpc) and age (200-250Myr) of the cluster. The fain test cluster stars classified are of spectral class G0. The cluster contains two blue stragglers of spectral classes B2-B4, both of them seem to be visual binaries. The extinction AV for the cluster stars is non-uniform, being spread between 2 and 3mag, with a mean value of 2.42mag. The extinction vs. distance dependence can be modeled by the Parenago exponential curve with two dust concentrations in the Camelopardalis dark clouds at about 150pc and the Cam OB1 association clouds at 0.9-1.0kpc.
- ID:
- ivo://CDS.VizieR/II/131
- Title:
- Tonantzintla Pleiades Flare Stars
- Short Name:
- II/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The original catalog lists the flare stars discovered by different astronomical observatories over an area slightly larger than 20 square degrees in the Pleiades regions centered on Alcyone. Not all the flare stars are members of this cluster, membership indicators are provided in the catalog. The catalog, combining Tables 1 and 2 of the publication, gives the data for 1531 flares of 519 flare stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/170
- Title:
- Tracers of stellar mass-loss. II.
- Short Name:
- J/ApJ/856/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present integrated colors and surface brightness fluctuation magnitudes in the mid-infrared (IR), derived from stellar population synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14Gyr, and comprise metallicities between Z=0.0001 and Z=0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of "extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5{mu}m and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate-age populations, between 100Myr and 2-3Gyr.
- ID:
- ivo://CDS.VizieR/J/AJ/154/224
- Title:
- Transiting planets in young clusters from K2
- Short Name:
- J/AJ/154/224
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detection of transiting exoplanets around young stars is more difficult than for older systems owing to increased stellar variability. Nine young open cluster planets have been found in the K2 data, but no single analysis pipeline identified all planets. We have developed a transit search pipeline for young stars that uses a transit-shaped notch and quadratic continuum in a 12 or 24 hr window to fit both the stellar variability and the presence of a transit. In addition, for the most rapid rotators (P_rot_<2 days) we model the variability using a linear combination of observed rotations of each star. To maximally exploit our new pipeline, we update the membership for four stellar populations observed by K2 (Upper Scorpius, Pleiades, Hyades, Praesepe) and conduct a uniform search of the members. We identify all known transiting exoplanets in the clusters, 17 eclipsing binaries, one transiting planet candidate orbiting a potential Pleiades member, and three orbiting unlikely members of the young clusters. Limited injection recovery testing on the known planet hosts indicates that for the older Praesepe systems we are sensitive to additional exoplanets as small as 1-2 R_{Earth}_, and for the larger Upper Scorpius planet host (K2-33) our pipeline is sensitive to ~4 R_{Earth}_ transiting planets. The lack of detected multiple systems in the young clusters is consistent with the expected frequency from the original Kepler sample, within our detection limits. With a robust pipeline that detects all known planets in the young clusters, occurrence rate testing at young ages is now possible.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A81
- Title:
- Trumpler 14 and 16 in the Carina nebula
- Short Name:
- J/A+A/603/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first extensive spectroscopic study of the global population in star clusters Trumpler 16, Trumpler 14, and Collinder 232 in the Carina nebula, using data from the Gaia-ESO Survey, down to solar-mass stars. In addition to the standard homogeneous survey data reduction, a special processing was applied here because of the bright nebulosity surrounding Carina stars. We find about 400 good candidate members ranging from OB types down to slightly subsolar masses. About 100 heavily reddened early-type Carina members found here were previously unrecognized or poorly classified, including two candidate O stars and several candidate Herbig Ae/Be stars. Their large brightness makes them useful tracers of the obscured Carina population. The spectroscopically derived temperatures for nearly 300 low-mass members enables the inference of individual extinction values and the study of the relative placement of stars along the line of sight. We find a complex spatial structure with definite clustering of low-mass members around the most massive stars and spatially variable extinction. By combining the new data with existing X-ray data, we obtain a more complete picture of the three-dimensional spatial structure of the Carina clusters and of their connection to bright and dark nebulosity and UV sources. The identification of tens of background giants also enables us to determine the total optical depth of the Carina nebula along many sightlines. We are also able to put constraints on the star formation history of the region with Trumpler 14 stars found to be systematically younger than stars in other subclusters. We find a large percentage of fast-rotating stars among Carina solar-mass members, which provide new constraints on the rotational evolution of pre-main-sequence stars in this mass range.