Within the context of a large project aimed at studying early F-, A- and late B-type stars we present the abundance analysis of the photospheres of 21 members of the open cluster NGC 5460, an intermediate age cluster (logt ~ 8.2) previously unstudied with spectroscopy. Our study is based on medium and high resolution spectra obtained with the FLAMES instrument of the ESO/VLT. We show that cluster members have a nearly solar metallicity, and that there is evidence that the abundances of magnesium and iron are correlated with the effective temperature, exhibiting a maximum around Teff=10500 K. No correlations are found between abundances and projected equatorial velocity, except for marginal evidence of barium being more abundant in slower than in faster rotating stars. We discovered two He-weak stars, and a binary system where the hotter component is a HgMn star. We provide new estimates for the cluster distance (720 +/- 50 pc), age (logt = 8.2 +/- 0.1), and mean radial velocity (-17.9 +/- 5.2 km/s).
We report results of spectroscopic and photometric observations of ten delta Scuti stars and one eclipsing binary in the open cluster NGC1817, and of ten delta Scuti stars and two other variables in the open cluster NGC7062. For all targets in NGC1817 and for three targets in NGC7062, the radial velocity and projected rotational velocity are determined. For all stars, the effective temperature and surface gravity is measured. Two delta Scuti stars, NGC1817-V1 and NGC7062-V1, and the eclipsing binary, NGC1817-V18, are discovered to be single-lined spectroscopic binaries. The eclipsing binary de…
The young open cluster NGC 6611 includes among its candidate members a class of peculiar objects with interesting properties: blue stars with infrared IR excesses. These stars show excesses in IR bands, signature of the presence of a circumstellar disk, but optical colors typical of older field stars. In order to confirm their membership to the cluster, it is therefore important to use new spectroscopic observations, together with previous photometric data. We aim at confirming the membership of these objects and at investigating their physical properties to verify whether the observed colors …
We present results from long-term optical photometric and spectroscopic observations of 5 pre-main sequence stars, located in the vicinity of the bight nebula NGC 7129. We obtained UBVRI photometric observations in the field centered on the star V391 Cep, north-west of the bright nebula NGC 7129. Our multicolor CCD observations spanned the period from February 1998 to November 2016. At the time of our photometric monitoring, a total of thirteen medium-resolution optical spectra of the stars were obtained. The results from our photometric study show that all stars exhibit strong variability in …
We present the current state of the WOCS radial-velocity (RV) survey for the rich open cluster NGC 6819 (2.5 Gyr) including 93 spectroscopic binary orbits with periods ranging from 1.5 to 8,000 days. These results are the product of our ongoing RV survey of NGC 6819 using the Hydra Multi-Object Spectrograph on the WIYN 3.5 m telescope. We also include a detailed analysis of multiple prior sets of optical photometry for NGC 6819. Within a 1-degree field of view, our stellar sample includes the giant branch, the red clump, and blue straggler candidates, and extends to almost 2 mag below the main…
We present 98 spectroscopic binary orbits resulting from our ongoing radial-velocity survey of the old (7 Gyr) open cluster NGC 188. All but 13 are high-probability cluster members based on both radial-velocity and proper-motion membership analyses. Fifteen of these member binaries are double lined. Our stellar sample spans a magnitude range of 10.8 <=V<= 16.5 (1.14-0.92 Msun) and extends spatially to 17 pc (~13 core radii). All of our binary orbits have periods ranging from a few days to on the order of 10^3 days, and thus are hard binaries that dynamically power the cluster. For each binary,…
Aims. We present the results obtained from a long-term spectroscopic campaign devoted to the multiplicity of O-type stars in the young open cluster NGC2244 and in the Mon OB2 association. Methods. Our spectroscopic monitoring was performed over several years, allowing us to probe different time-scales. For each star, several spectral diagnostic tools are applied, in order to search for line shifts and profile variations. We also measure the projected rotational velocity and revisit the spectral classification. Results. In our sample, several stars were previously considered as spectroscopic bi…
The NASA space telescope Kepler has provided unprecedented time-series observations which have revolutionised the field of asteroseismology, i.e. the use of stellar oscillations to probe the interior of stars. The Kepler-data include observations of stars in open clusters, which are particularly interesting for asteroseismology. One of the clusters observed with Kepler is NGC 6811, which is the target of the present paper. However, apart from high-precision time-series observations, sounding the interiors of stars in open clusters by means of asteroseismology also requires accurate and precise…
In an optical color-magnitude diagram sub-subgiants (SSGs) lie red of the main sequence and fainter than the base of the red giant branch in a region not easily populated by standard stellar-evolution pathways. In this paper, we present multi-epoch radial velocities for five SSG candidates in the old and metal-rich open cluster NGC 6791 (8 Gyr, [Fe/H] = +0.30). From these data we are able to make three-dimensional kinematic membership determinations and confirm four SSG candidates to be likely cluster members. We also identify three member SSGs as short-period binary systems and present their …
The very young open cluster NGC 6383 centered on the O-star binary HD 159176 is an interesting place for studying the impact of early-type stars with strong radiation fields and powerful winds on the formation processes of low-mass stars. To investigate this process, it is necessary to determine the characteristics (age, presence, or absence of circumstellar material) of the population of low-mass pre-main-sequence (PMS) stars in the cluster. We obtained deep U B V (R I)_c H-alpha photometric data of the entire cluster as well as medium-resolution optical spectroscopy of a subsample of X-ray s…
We present K-band Multi-Object Spectrograph (KMOS) observations of 18 Red Supergiant (RSG) stars in the Sculptor Group galaxy NGC 55. Radial velocities are calculated and are shown to be in good agreement with previous estimates, confirming the supergiant nature of the targets and providing the first spectroscopically confirmed RSGs in NGC 55. Stellar parameters are estimated for 14 targets using the $J$-band analysis technique, making use of state-of-the-art stellar model atmospheres. The metallicities estimated confirm the low-metallicity nature of NGC 55, in good agreement with previous stu…
We examine the spectroscopic binary population for two massive nearby regions of clustered star formation, the Orion Nebula Cluster and NGC 2264, supplementing the data presented by Tobin et al. (2009, 2015) with more recent observations and more extensive analysis. The inferred multiplicity fraction up to 10 AU based on these observations is $5.3\pm 1.2$% for NGC 2264 and $5.8\pm 1.1$% for the ONC; they are consistent with the distribution of binaries in the field in the relevant parameter range. Eight of the multiple systems in the sample have enough epochs to make an initial fit for the orb…
W 601 (NGC 6611 601) is one of the handful of known magnetic Herbig Ae/Be stars. We report the analysis of a large dataset of high-resolution spectropolarimetry. The star is a previously unreported spectroscopic binary, consisting of 2 B2 stars with a mass ratio of 1.8, masses of 12 M$_\odot$ and 6.2 $M_\odot$, in an eccentric 110-day orbit. The magnetic field belongs to the secondary, W 601 B. The H$α$ emission is consistent with an origin in W 601 B's centrifugal magnetosphere; the star is therefore not a classical Herbig Be star in the sense that its emission is not formed in an accretion d…
A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These "anomalous" clusters, which we refer to as "iron-complex" clusters, are differentiated from normal clusters by exhibiting large (>0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abunda…
We present preliminary results of seismic modeling of Beta Cephei-type stars in NGC 6910 based on simultaneous photometric and spectroscopic observations carried out in 2013 in Bialkow (photometry) and Apache Point (spectroscopy) observatories.
In this paper we analyse the evolutionary status and properties of the old open cluster NGC 2355, located in the Galactic anticentre direction, as a part of the long term programme BOCCE. NGC 2355 was observed with LBC@LBT using the Bessel $B$, $V$, and $I_c$ filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, as done in other papers of this series. Additional spectroscopic observations with FIES@NOT of three giant stars were used to determine the chemical properties of the cluster. Our analysis shows that NGC 2355 has metallicity sligh…
Aims. We demonstrate the high multiplex advantage of crowded field 3D spectroscopy using the new integral field spectrograph MUSE by means of a spectroscopic analysis of more than 12,000 individual stars in the globular cluster NGC 6397. Methods. The stars are deblended with a PSF fitting technique, using a photometric reference catalogue from HST as prior, including relative positions and brightnesses. This catalogue is also used for a first analysis of the extracted spectra, followed by an automatic in-depth analysis using a full-spectrum fitting method based on a large grid of PHOENIX spect…
We present spectroscopic follow-up observations of 68 red, faint candidates from our multi-epoch, multi-wavelength, previously published survey of NGC 2264. Using near-infrared spectra from VLT/KMOS, we measure spectral types and extinction for 32 young low-mass sources. We confirm 13 as brown dwarfs in NGC 2264, with spectral types between M6 and M8, corresponding to masses between 0.02 and 0.08$M_{\odot}$. These are the first spectroscopically confirmed brown dwarfs in this benchmark cluster. 19 more objects are found to be young M-type stars of NGC 2264 with masses of 0.08 to 0.3$\,M_{\odot…
We present the chemical abundance analysis of 19 upper main-sequence stars of the young open cluster NGC 6250 (log t ~ 7.42 yr). This work is part of a project aimed at setting observational constraints on the theory of atomic diffusion in stellar photospheres, by means of a systematic study of the abundances of the chemical elements of early F-, A- and late B-type stars of well-determined age. Our data set consists of low-, medium- and high-resolution spectra obtained with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument of the ESO Very Large Telescope (VLT). To perform ou…
We present observations proving the close binary nature of the central stars belonging to the planetary nebulae (PNe) NGC 6326 and NGC 6778. Photometric monitoring reveals irradiated lightcurves with orbital periods of 0.372 and 0.1534 days, respectively, constituting firm evidence that they passed through a common-envelope (CE) phase. Unlike most surveys for close binary central stars (CSPN) however, the binary nature of NGC 6326 was first revealed spectroscopically and only later did photometry obtain an orbital period. Gemini South observations revealed a large 160 km/s shift between the ne…
Integral field spectroscopy (IFS) provides a unique capability to spectroscopically study extended sources over a 2D field of view, but it also requires new techniques and tools. In this paper, we present an automatic code, Spectroscopic Analysis Tool for intEgraL fieLd unIt daTacubEs, SATELLITE, designed to fully explore such capability in the characterization of extended objects, such as planetary nebulae, H II regions, galaxies, etc. SATELLITE carries out 1D and 2D spectroscopic analysis through a number of pseudo-slits that simulate slit spectrometry, as well as emission line imaging. The …
We present a spectral analysis of the UV-bright star vZ 1128 in M3 based on observations with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Space Telescope Imaging Spectrograph (STIS), and the Keck HIRES echelle spectrograph. By fitting the H I, He I, and He II lines in the Keck spectrum with non-LTE H-He models, we obtain Teff = 36,600 K, log g = 3.95, and log N(He)/N(H) = -0.84. The star's FUSE and STIS spectra show photospheric absorption from C, N, O, Al, Si, P, S, Fe, and Ni. No stellar features from elements beyond the iron peak are observed. Both components of the N V 1240 doub…
Using photometry and high resolution spectroscopy we investigate for the first time the physical connection between the open clusters NGC 5617 and Trumpler 22. Based on new CCD photometry we report their spatial proximity and common age of ~70 Myr. Based on high resolution spectra collected using the HERMES and UCLES spectrographs on the Anglo-Australian telescope, we present radial velocities and abundances for Fe, Na, Mg, Al, Si, Ca and Ni. The measured radial velocities are -38.63 +/-2.25 km/s for NGC 5617 and -38.46 +/-2.08 km/s for Trumpler 22. The mean metallicity of NGC 5617 was found t…
We present a VLT/FORS1 imaging and spectroscopic survey of the Wolf-Rayet (WR) population in the Sculptor group spiral galaxy NGC 7793. We identify 74 emission line candidates from archival narrow-band imaging, from which 39 were observed with the Multi Object Spectroscopy (MOS) mode of FORS1. 85% of these sources displayed WR features. Additional slits were used to observe HII regions, enabling an estimate of the metallicity gradient of NGC 7793 using strong line calibrations, from which a central oxygen content of log (O/H) + 12 = 8.6 was obtained, falling to 8.25 at R_25. We have estimated …
Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey
Universidad Andres Bello（安德斯贝洛大学）；Vatican Observatory（梵蒂冈天文台）；Universidad Nacional de Córdoba（科尔多瓦国立大学）；Universidade Federal de Santa Catarina（圣卡塔琳娜联邦大学）；Universidad Bernardo O’Higgins（贝尔纳多·奥希金斯大学）；Universidad de Antofagasta（安托法加斯塔大学）；European Southern Observatory（欧洲南方天文台）
利用 KMOS VVVX-GalCen 光谱巡天的视向速度，确认了开放星团 NGC 2437 中存在未分辨三合星系统序列，并发现其比例高于较老星团，表明这些系统会合并或瓦解。
We obtain high resolution spectra of nine red giant branch stars in NGC 6681 and perform the first detailed abundance analysis of stars in this cluster. We confirm cluster membership for these stars based on consistent radial velocities of 214.5$\pm$3.7 km/s and find a mean [Fe/H] = -1.63$\pm$0.07 dex and [α/Fe] = 0.42$\pm$0.11 dex. Additionally, we confirm the existence of a Na-O anti-correlation in NGC 6681 and identify two populations of stars with unique abundance trends. With the use of HST photometry from Sarajedini et al. (2007) and Piotto et al. (2015) we are able to identify these two…
High-dispersion spectra of 333 stars in the open cluster NGC 6819, obtained using the HYDRA spectrograph on the WIYN 3.5m telescope, have been analyzed to determine the abundances of iron and other metals from lines in the 400 A region surrounding the Li 6708 A line. Our spectra, with signal-to-noise per pixel (SNR) ranging from 60 to 300, span the luminosity range from the tip of the red giant branch to a point two magnitudes below the top of the cluster turnoff. We derive radial and rotational velocities for all stars, as well as [Fe/H] based on 17 iron lines, [Ca/H], [Si/H], and [Ni/H] in t…
The benefit of a multi-band high resolution spectroscopic monitoring for studying stellar transients: the NGC 300 OT2008-1 UVES spectrum as a test case
INAF-OATS（意大利国家天体物理研究所奥斯塔天文台）；Dipartimento di Fisica “Enrico Fermi”, Università di Pisa（比萨大学费米物理系）；INAF-OAPD（意大利国家天体物理研究所帕多瓦天文台）
We present an abundance analysis of 96 horizontal branch (HB) stars in NGC2808, a globular cluster exhibiting a complex multiple stellar population pattern. These stars are distributed in different portions of the HB and cover a wide range of temperature. By studying the chemical abundances of this sample, we explore the connection between HB morphology and the chemical enrichment history of multiple stellar populations. For stars lying on the red HB, we use GIRAFFE and UVES spectra to determine Na, Mg, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Y, Ba, and Nd abundances. For colder, blue HB stars, we…
Stellar population studies of globular clusters have suggested that the brightest clusters in the Galaxy might actually be the remnant nuclei of dwarf spheroidal galaxies. If the present Galactic globular clusters formed within larger stellar systems, they are likely surrounded by extra-tidal halos and/or tails made up of stars that were tidally stripped from their parent systems. The stellar surroundings around globular clusters are therefore one of the best places to look for the remnants of an ancient dwarf galaxy. Here an attempt is made to search for tidal debris around the supernovae enr…
We present the abundance analysis for a sample of 18 red giant branch stars in the metal-poor globular cluster NGC 4147 based on medium and high resolution spectra. This is the first extensive spectroscopic study of this cluster. We derive abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Y, Ba, and Eu. We find a metallicity of [Fe/H]=-1.84+-0.02 and an alpha-enhancement of +0.38+-0.05 (errors on the mean), typical of halo globular clusters in this metallicity regime. A significant spread is observed in the abundances of light elements C, N, O, Na, and Al. In particular we found a Na-…
NGC1851 possibly shows a spread in [Fe/H], but the relation between this spread and the division in the SGB is unknown. We obtained blue (3950-4600 A) intermediate resolution (R~8,000) spectra for 47 stars on the bright and 30 on the faint SGB of NGC 1851 (b-SGB and f-SGB, respectively). The determination of the atmospheric parameters to extremely high internal accuracy leads to small errors when comparing different stars in the cluster. We found that the b-SGB is slightly more metal-poor than the f-SGB, with [Fe/H]=-1.227+/-0.009 and [Fe/H]=-1.162+/- 0.012, respectively. This implies that the…
The open cluster NGC 6633 was observed with CoRoT in 2011 and simultaneous high-resolution spectroscopy was obtained with the SOPHIE and HARPS spectrographs. One of the four targets was not found to be a cluster member. For all stars we provide estimates of the seismic and spectroscopic parameters.
We present a spectroscopic analysis of main sequence (MS) stars in the young globular cluster NGC1818 (age~40 Myrs) in the Large Magellanic Cloud. Our photometric survey on Magellanic Clouds clusters has revealed that NGC1818, similarly to the other young objects with age 600 Myrs, displays not only an extended MS Turn-Off (eMSTO), as observed in intermediate-age clusters (age~1-2 Gyrs), but also a split MS. The most straightforward interpretation of the double MS is the presence of two stellar populations: a sequence of slowly-rotating stars lying on the blue-MS and a sequence of fast rotator…
We report the results of a CCD imaging survey, complimented by astrometric and spectroscopic follow-up studies, that aims to probe the fate of heavy-weight intermediate mass stars by unearthing new, faint, white dwarf members of the rich, nearby, intermediate age open clusters NGC3532 and NGC2287. We identify a total of four white dwarfs with distances, proper motions and cooling times which can be reconciled with membership of these populations. We find that WDJ0643-203 in NGC2287, with an estimated mass of M=1.02-1.16Msun, is potentially the most massive white dwarf so far identified within …
We present spectral observations of 130 young stellar objects (YSOs) in the Serpens Cloud Core and NGC 1333 embedded clusters. The observations consist of near-IR spectra in the H and K-bands, from SpeX on the IRTF and far-red spectra (6000 - 9000 A) from Hectospec on the MMT. These YSOs were identified in previous Spitzer and Chandra observations, and the evolutionary classes of the YSOs were determined from the Spitzer mid-IR photometry. With these spectra, we search for corroborating evidence for the pre-main sequence nature of the objects, study the properties of the detected emission line…
We present a narrow-band VLT/FORS1 imaging survey of the SAB(rs)cd spiral galaxy NGC 5068, located at a distance of 5.45Mpc, from which 160 candidate Wolf-Rayet sources have been identified, of which 59 cases possess statistically significant 4686 excesses. Follow-up Gemini/GMOS spectroscopy of 64 candidates, representing 40% of the complete photometric catalogue, confirms Wolf-Rayet signatures in 30 instances, corresponding to a 47% success rate. 21 out of 22 statistically significant photometric sources are spectroscopically confirmed. Nebular emission detected in 30% of the Wolf-Rayet candi…
A spectroscopic analysis of stellar spectra can be carried out using different approaches; different methods, line lists, atomic parameters, solar abundances etc. The resulting atmospheric parameters from these choices can vary beyond quoted uncertainties in the literature. Here we characterize these differences by systematically comparing some of the commonly adopted ingredients; line lists, equivalent width measurements and atomic parameters. High resolution and high signal-to-noise spectroscopic data of one helium-core-burning red giant star in each of the three open clusters, NGC6819, M67 …
We present deep high angular resolution observations of the high-mass protostar NGC 7538S, which is in the center of a cold dense cloud core with a radius of 0.5 pc and a mass of ~2,000 Msun. These observations show that NGC 7538S is embedded in a compact elliptical core with a mass of 85 - 115 Msun. The star is surrounded by a rotating accretion disk, which powers a very young, hot molecular outflow approximately perpendicular to the rotating accretion disk. The accretion rate is very high, ~ 1.4 - 2.8 10^-3 Msun yr^-1. Evidence for rotation of the disk surrounding the star is seen in all lar…
We present a moderate-resolution spectroscopic analysis of the 10-25 Myr clusters NGC 7160 and NGC 2232, using observations obtained with the WIYN 3.5-m telescope. Both NGC 7160 and NGC 2232 are found to have super-solar metallicities, with a mean [Fe/H] = 0.16 \pm 0.03 (s.e.m.) for NGC 7160, and 0.22 \pm 0.09 (s.e.m.) or 0.32 \pm 0.08 for NGC 2232, depending on the adopted temperature scale. NGC 7160 exhibits solar distributions of Na, Fe-peak, and α-elements. NGC 2232 is underabundant in light elements Al and Si, by ~0.25 and ~ 0.15 dex, respectively; [Ni/Fe] is roughly solar. The abundance …
Spectroscopy of 333 NGC 6819 stars and Gaia astrometry are used to map Li evolution from the giant branch tip to 0.5 mag below the Li dip. Isochrone comparison with [Fe/H] = -0.04, based upon neural network spectroscopic analysis, produces an age of 2.25 (2.4) Gyr for E(B-V) = 0.16 (0.14) and (m-M) = 12.40 (12.29). Despite originating outside the Li dip, only 10% of single subgiants/giants have measurable Li. Above the Li dip, the limiting A(Li) for single stars is 3.2 +/- 0.1 but the lower range is comparable to that found within the dip. The F-dwarf Li dip profile agrees with the Hyades/Prae…
NGC 3532 is an extremely rich open cluster embedded in the Galactic disc, hitherto lacking a comprehensive, documented membership list. We provide membership probabilities from new radial velocity observations of solar-type and low-mass stars in NGC 3532, in part as a prelude to a subsequent study of stellar rotation in the cluster. Using extant optical and infra-red photometry we constructed a preliminary photometric membership catalogue, consisting of 2230 dwarf and turn-off stars. We selected 1060 of these for observation with the AAOmega spectrograph at the Anglo-Australian Telescope and 3…
We present a direct N-body simulation modeling the evolution of the old (7 Gyr) open cluster NGC 188. This is the first N-body open cluster simulation whose initial binary population is directly defined by observations of a specific open cluster: M35 (150 Myr). We compare the simulated color-magnitude diagram at 7 Gyr to that of NGC 188, and discuss the blue stragglers produced in the simulation. We compare the solar-type main sequence binary period and eccentricity distributions of the simulation to detailed observations of similar binaries in NGC 188. These results demonstrate the importance…
The 3-D and kinematic structure of the Eskimo nebula, NGC 2392, has been notoriously difficult to interpret in detail given its complex morphology, multiple kinematic components and its nearly pole-on orientation along the line of sight. We present a comprehensive, spatially resolved, high resolution, long-slit spectroscopic mapping of the Eskimo planetary nebula. The data consist of 21 spatially resolved, long-slit echelle spectra tightly spaced over the Eskimo and along its bipolar jets. This data set allows us to construct a velocity-resolved [NII] channel map of the nebula with a resolutio…
In this work, we present a spectroscopic study of very massive stars found outside the center of the massive stellar cluster NGC3603. From the analysis of SOAR spectroscopic data and related optical-NIR photometry, we confirm the existence of several very massive stars in the periphery of NGC 3603. The first group of objects (MTT58, WR42e and RFS7) is compound by three new Galactic exemplars of the OIf*/WN type, all of them with probable initial masses well above 100 Msun and estimated ages of about 1 Myr. Based on Goodman blue-optical spectrum of MTT68, we can confirm the previous finding in …
We present a photometric and spectroscopic study of multiple populations along the asymptotic-giant branch (AGB) of the intermediate-metallicity globular clusters (GCs) NGC2808 and NGC6121 (M4). Chemical abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Zn, Y, and Ce in AGB stars from high-resolution FLAMES+UVES@VLT spectra are reported for both clusters. Our spectroscopic results have been combined with multi-wavelength photometry from the HST UV survey of Galactic GCs and ground-based photometry, plus proper motions derived by combining stellar positions from ground-based image…
We present the spectroscopic analysis of 333 OB-type stars extracted from VLT-MUSE observations of the central 30 x 30 pc of NGC 2070 in the Tarantula Nebula on the Large Magellanic Cloud, the majority of which are analysed for the 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$\pm$0.8 and 6.2$\pm$2 Myr. A subgroup of 52 stars is apparently beyond the main sequence phase, which we consider to be due to emission-type objects and/or signific…
We present the analysis of 34 light curves in $V$ and $I$ of 17 giant stars in the globular cluster NGC 3201, to check if such stars are variable and if their variability has some kind of impact on the iron abundance as obtained from spectroscopic measurements. First, we computed the Generalized Lomb-Scargle and Phase Dispersion Minimization periodograms on the sample to check if the stars were variables. In this way, 7 stars of the sample were found to be non-variable, 2 stars are considered as possible variables, and 8 stars were found to be variable, with periods ranging from $0.0881\pm0.00…
NGC1850 is the nearest Young Massive Cluster of the Local Group with a mass similar to those of Galactic globular clusters. Recent studies have revealed an extended morphology of its MSTO, which can be interpreted as a spread in either age or internal rotation. An accurate spectroscopic determination of its chemical properties is still missing. We analyse spectra obtained with MUSE in adaptive optics mode of 1167 stars in both components of this cluster (NGC1850A and NGC1850B). Thanks to this dataset, we measure an average metallicity of <[M/H]>=-0.31 +/- 0.01, a mean Ba abundance of <[Ba/Fe]>…
A new detailed examination of white dwarfs in NGC3532 and NGC2287
本文介绍了中等年龄疏散星团NGC 3532和NGC 2287的白矮星候选成员的光度和光谱研究结果。在调查的9个天体中，确定有6个可能是星团的成员，4个在NGC 3532，2个在NGC 2287。对于这六颗白矮星，我们使用我们对它们冷却时间的估计以及星系团的年龄来限制它们祖先恒星的寿命和质量。我们研究了这些物体在初始质量-最终质量空间中的位置，发现它们现在没有提供先前调查所建议的初始质量-最终质量关系中的大量分散的证据。相反，我们证明，当结合目前的数据从其他太阳金属性疏散星团和天狼星双星系统，他们暗示在IFMR是陡峭的初始质量范围3 M $_{\odot}$ $\simless$ M $_{\rm init}$ $\simless$ 4 M $_{\odot}$比在祖质量立即低于和高于此。这种形式通常与恒星演化模型的预测一致，并且可以帮助人口合成模型再现在白矮星质量分布主峰的高质量端观察到的相对急剧下降。
We present and analyse 120 spectroscopic binary and triple cluster members of the old (4 Gyr) open cluster M67 (NGC 2682). As a cornerstone of stellar astrophysics, M67 is a key cluster in the WIYN Open Cluster Study (WOCS); radial-velocity (RV) observations of M67 are ongoing and extend back over 45 years, incorporating data from seven different telescopes, and allowing us to detect binaries with orbital periods <~10^4 days. Our sample contains 1296 stars (604 cluster members) with magnitudes of 10 <= V <= 16.5 (about 1.3 to 0.7 Msolar), from the giants down to ~4 mag below the main-sequence …
The quantitative study of the physical properties and chemical abundances of large samples of massive blue stars at different metallicities is a powerful tool to understand the nature and evolution of these objects. Their analysis beyond the Milky Way is challenging, nonetheless it is doable and the best way to investigate their behavior in different environments. Fulfilling this task in an objective way requires the implementation of automatic analysis techniques that can perform the analyses systematically, minimizing at the same time any possible bias. As part of the ARAUCARIA project we ca…
We introduce the stellar sample of the WIYN Open Cluster Study radial-velocity survey for the rich open cluster NGC 7789 (1.6 Gyr, [Fe/H] = +0.02). This sample lies within an 18$'$ circular radius from the cluster center (10 pc in projection, or about 2 core radii), and includes giants, red-clump stars, blue stragglers, red stragglers, sub-subgiants, and main-sequence stars down to one mag below the turnoff. Our survey began in 2005 and comprises more than 9,000 radial-velocity measurements from the Hydra Multi-Object Spectrograph on the WIYN 3.5m telescope. We identify 564 likely cluster memb…
Spectroscopic analysis of RGB stars in nine open clusters
Universidade Federal do Rio Grande do Sul（南里奥格兰德联邦大学）；Andrews University（安德鲁斯大学）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文中心）；Universidade de São Paulo（圣保罗大学）；University Bourgogne Franche-Comté（勃艮第弗朗什-孔泰大学）；University of Geneva（日内瓦大学）；Université de Toulouse（图卢兹大学）
We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, one globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass less than 0.018-0.030 M$_{\odot}$, which harbors a flaring disk. Using the H$α$ emission line, we charact…
