- ID:
- ivo://CDS.VizieR/J/A+A/648/A65
- Title:
- The sHRD of OB stars in NGC 2070
- Short Name:
- J/A+A/648/A65
- Date:
- 06 Dec 2021 13:26:57
- Publisher:
- CDS
- Description:
- We present the spectroscopic analysis of 333 OB-type stars extracted from VLT-MUSE observations of the central 30x30pc of NGC 2070 in the Tarantula Nebula on the Large Magellanic Cloud, the majority of which are analysed for the first time. The distribution of stars in the spectroscopic Hertzsprung-Russell diagram (sHRD) shows 281 stars in the main sequence. We find two groups in the main sequence, with estimated ages of 2.1+/-0.8 and 6.2+/-2Myr. A subgroup of 52 stars is apparently beyond the main sequence phase, which we consider to be due to emission-type objects and/or significant nebular contamination affecting the analysis. As in previous studies, stellar masses derived from the sHRD are systematically larger than those obtained from the conventional HRD, with the differences being largest for the most massive stars. Additionally, we do not find any trend between the estimated projected rotational velocity and evolution in the sHRD. The projected rotational velocity distribution presents a tail of fast rotators that resembles findings in the wider population of 30 Doradus. We use published spectral types to calibrate the HeI{lambda}4921/HeII{lambda}5411 equivalent-width ratio as a classification diagnostic for early-type main sequence stars when the classical blue-visible region is not observed. Our model-atmosphere analyses demonstrate that the resulting calibration is well correlated with effective temperature.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/149/127
- Title:
- The SOS project. IV. NGC 1624 and NGC 1931
- Short Name:
- J/AJ/149/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young open clusters located in the outer Galaxy provide us with an opportunity to study star formation activity in a different environment from the solar neighborhood. We present a UBVI and H{alpha} photometric study of the young open clusters NGC 1624 and NGC 1931 that are situated toward the Galactic anticenter. Various photometric diagrams are used to select the members of the clusters and to determine the fundamental parameters. NGC 1624 and NGC 1931 are, on average, reddened by <E(B-V)>=0.92+/-0.05 and 0.74+/-0.17mag, respectively. The properties of the reddening toward NGC 1931 indicate an abnormal reddening law (R_V,cl_=5.2+/-0.3). Using the zero-age main sequence fitting method we confirm that NGC 1624 is 6.0+/-0.6kpc away from the Sun, whereas NGC 1931 is at a distance of 2.3+/-0.2kpc. The results from isochrone fitting in the Hertzsprung-Russell diagram indicate the ages of NGC 1624 and NGC 1931 to be less than 4 and 1.5-2.0Myr, respectively. We derived the initial mass function (IMF) of the clusters. The slope of the IMF ({Gamma}_NGC1624_=-2.0+/-0.2 and {Gamma}_NGC1931_=-2.0+/-0.1) appears to be steeper than that of the Salpeter/Kroupa IMF. We discuss the implication of the derived IMF based on simple Monte-Carlo simulations and conclude that the property of star formation in the clusters does not seem to be significantly different from that in the solar neighborhood.
- ID:
- ivo://CDS.VizieR/J/AJ/162/140
- Title:
- The SOS. VII. UBVI photometry of open cluster IC 1590
- Short Name:
- J/AJ/162/140
- Date:
- 21 Mar 2022 00:39:36
- Publisher:
- CDS
- Description:
- Young open clusters are ideal laboratories to understand the star formation process. We present deep UBVI and H{alpha} photometry for the young open cluster IC1590 in the center of the HII region NGC281. Early-type members are selected from UBV photometric diagrams, and low-mass pre-main-sequence (PMS) members are identified by using H{alpha} photometry. In addition, the published X-ray source list and Gaia astrometric data are also used to isolate probable members. A total of 408 stars are selected as members. The mean reddening obtained from early-type members is <E(B-V)>=0.40{+/-}0.06(s.d.). We confirm the abnormal extinction law for the intracluster medium. The distance modulus to the cluster determined from the zero-age main-sequence fitting method is 12.3{+/-}0.2mag (d=2.88{+/-}0.28kpc), which is consistent with the distance d=2.70_-0.20_^+0.24^kpc from the recent Gaia parallaxes. We also estimate the ages and masses of individual members by means of stellar evolutionary models. The mode of the age of PMS stars is about 0.8Myr. The initial mass function of IC1590 is derived. It appears to be a steeper shape ({Gamma}=-1.49{+/-}0.14) than that of the Salpeter/Kroupa initial mass function for the high-mass regime (m>1M{sun}). The signature of mass segregation is detected from the difference in the slopes of the initial mass functions for the inner (r<2.5') and outer regions of this cluster. We finally discuss the star formation history in NGC281.
- ID:
- ivo://CDS.VizieR/J/AN/334/673
- Title:
- The stellar content of Trumpler 37
- Short Name:
- J/AN/334/673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With an apparent cluster diameter of 1.5deg and an age of ~4Myr, Trumpler 37 is an ideal target for photometric monitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources of variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensive view of variable phenomena in this region. In this first paper we present the cluster properties and membership determination as derived from an extensive investigation of the literature. We also compared the coordinate list to some YETI images. For 1872 stars we found literature data. Among them 774 have high probability of being member and 125 a medium probability. Based on infrared data we re-calculate a cluster extinction of 0.9-1.2mag. We can confirm the age and distance to be 3-5Myr and ~870pc. Stellar masses are determined from theoretical models and the mass function is fitted with a power-law index of {alpha}=1.90 (0.1-0.4M_{sun}_) and {alpha}=1.12 (1-10M_{sun}_).
- 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.
- 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.
