- ID:
- ivo://CDS.VizieR/J/A+A/643/A148
- Title:
- Lupus DANCe. Census and 6D structure with Gaia-DR2
- Short Name:
- J/A+A/643/A148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its stellar population. We use the second data release of the Gaia space mission combined with published ancillary radial velocity data to revise the census of stars and investigate the 6D structure of the Lupus complex. Methods: We performed a new membership analysis of the Lupus association based on astrometric and photometric data over a field of 160deg^2^ around the main molecular clouds of the complex and compared the properties of the various subgroups in this region. We identified 137 high-probability members of the Lupus association of young stars, including 47 stars that had never been reported as members before. Many of the historically known stars associated with the Lupus region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus association. Our new sample of members covers the magnitude and mass range from G~=8 to G~=18mag and from 0.03 to 2.4M_{sun}_, respectively. We compared the kinematic properties of the stars projected towards the molecular clouds Lupus 1 to 6 and showed that these subgroups are located at roughly the same distance (about 160~pc) and move with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups are coeval (with median ages ranging from about 1 to 3Myr). The Lupus association appears to be younger than the population of young stars in the Corona-Australis star-forming region recently investigated by our team using a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral types shows little variation compared to other star-forming regions. In this paper, we provide an updated sample of cluster members based on Gaia data and construct the most complete picture of the 3D structure and 3D space motion of the Lupus complex.
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- ID:
- ivo://CDS.VizieR/J/A+A/600/A20
- Title:
- Lupus YSOs X-shooter spectroscopy
- Short Name:
- J/A+A/600/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass accretion rate, M_acc_, is a key quantity for the understanding of the physical processes governing the evolution of accretion discs around young low-mass (M_{star}_<=2.0M_{sun}_) stars and substellar objects (YSOs). We present here the results of a study of the stellar and accretion properties of the (almost) complete sample of class II and transitional YSOs in the Lupus I, II, III and IV clouds, based on spectroscopic data acquired with the VLT/X-shooter spectrograph. Our study combines the dataset from our previous work with new observations of 55 additional objects. We have investigated 92 YSO candidates in total, 11 of which have been definitely identified with giant stars unrelated to Lupus. The stellar and accretion properties of the 81 bona fide YSOs, which represent more than 90% of the whole class II and transition disc YSO population in the aforementioned Lupus clouds, have been homogeneously and self-consistently derived, allowing for an unbiased study of accretion and its relationship with stellar parameters. The accretion luminosity, L_acc_, increases with the stellar luminosity, L*, with an overall slope of ~1.6, similar but with a smaller scatter than in previous studies. There is a significant lack of strong accretors below L*~=0.1L_{sun}_, where L_acc_ is always lower than 0.01L*. We argue that the L_acc_-L* slope is not due to observational biases, but is a true property of the Lupus YSOs. The log M_acc_-logM* correlation shows a statistically significant evidence of a break, with a steeper relation for M*<=0.2M_{sun}_ and a flatter slope for higher masses. The bimodality of the M_acc_-M* relation is confirmed with four different evolutionary models used to derive the stellar mass. The bimodal behaviour of the observed relationship supports the importance of modelling self-gravity in the early evolution of the more massive discs, but other processes, such as photo-evaporation and planet formation during the YSO's lifetime, may also lead to disc dispersal on different timescales depending on the stellar mass. The sample studied here more than doubles the number of YSOs with homogeneously and simultaneously determined L_acc_ and luminosity, L_line_, of many permitted emission lines. Hence, we also refined the empirical relationships between L_acc_ and L_line_ on a more solid statistical basis.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/9
- Title:
- Machine-learning investigation of the open cluster M67
- Short Name:
- J/ApJ/869/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we use a machine-learning method, random forest (RF), to identify reliable members of the old (4Gyr) open cluster M67 based on the high-precision astrometry and photometry taken from the second Gaia data release (Gaia-DR2). The RF method is used to calculate membership probabilities of 71117 stars within 2.5{deg} of the cluster center in an 11-dimensional parameter space, the photometric data are also taken into account. Based on the RF membership probabilities, we obtain 1502 likely cluster members (>=0.6), 1361 of which are high-probability cluster members (>=0.8). Based on high-probability memberships with high-precision astrometric data, the mean parallax (distance) and proper-motion of the cluster are determined to be 1.1327+/-0.0018mas (883+/-1pc) and (<{mu}_{alpha}_cos{delta}>,<{mu}_{delta}_>)=(-10.9378+/-0.0078,-2.9465 +/-0.0074)mas/yr, respectively. We find the cluster to have a mean radial velocity of +34.06+/-0.09km/s, using 74 high-probability cluster members with precise radial-velocity measures. We investigate the spatial structure of the cluster, the core and limiting radius are determined to be 4.80'+/-0.11' (~1.23+/-0.03pc) and 61.98'+/-1.50' (~15.92+/-0.39pc), respectively. Our results reveal that an escaped member with high membership probability (~0.91) is located at a distance of 77' (~20pc) from the cluster center. Furthermore, our results reveal that at least 26.4% of the main-sequence stars in M67 are binary stars. We confirm that significant mass segregation has taken place within M67.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A82
- Title:
- Mapping accretion variability in NGC 2264
- Short Name:
- J/A+A/570/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our study aims at characterizing the accretion properties of several hundred members of the star-forming region NGC 2264 (3Myr). We performed a deep u,g,r,i mapping of the cluster with CFHT/MegaCam, and monitored the simultaneous u+r variability of its members over a baseline of two weeks. Stellar parameters are determined homogeneously for about 750 monitored young objects, 40% of which are accreting T Tauri stars. Accretion properties and accretion variability are investigated and characterized from UV excess measurements. Non-accreting members of the cluster define the reference UV emission level over which flux excess is detected and measured.
- ID:
- ivo://CDS.VizieR/J/ApJ/755/154
- Title:
- Mass accretion rates from HST in the ONC
- Short Name:
- J/ApJ/755/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present observational understanding of the evolution of the mass accretion rates (dM/dt_acc_) in pre-main-sequence stars is limited by the lack of accurate measurements of dM/dt_acc_ over homogeneous and large statistical samples of young stars. Such observational effort is needed to properly constrain the theory of star formation and disk evolution. Based on Hubble Space Telescope/WFPC2 observations, we present a study of dM/dt_acc_ for a sample of ~700 sources in the Orion Nebula Cluster, ranging from the hydrogen-burning limit to M*~2M_{sun}_. We derive dM/dt_acc_ from both the U-band excess and the H{alpha} luminosity (L_H{alpha}_), after determining empirically both the shape of the typical accretion spectrum across the Balmer jump and the relation between the accretion luminosity (L_acc_) and L_H{alpha}_, which is L_acc_/L_{sun}_=(1.31+/-0.03).L_H{alpha}/L_{sun}_+(2.63+/-0.13). Given our large statistical sample, we are able to accurately investigate relations between dM/dt_acc_ and the parameters of the central star such as mass and age.
- ID:
- ivo://CDS.VizieR/V/19
- Title:
- Masses and Ages of Stars in 68 Open Clusters
- Short Name:
- V/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the evolutionary masses and ages of about 7000 stars in 68 open clusters, as derived from their positions in the theoretical HR diagram. Cluster ages range from 10^6^ to some 10^9^ years, and their population varies from 30 to 700 members. For each cluster we have a table with ages and masses of stars. The file, clusters.dat may include for each cluster, the name (or NGC/IC number), cluster class, assumed color index E(B-V), true distance modulus (V-M_V)_0, evolutionary tracks used for given cluster and reference to the source of UBV data. The data in data.dat consists of star serial number, color index, V magnitude, luminosity, effective temperature, and ages and masses of stars.
- ID:
- ivo://CDS.VizieR/J/A+A/329/101
- Title:
- Masses of Pleiades members
- Short Name:
- J/A+A/329/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of the best available member list and duplicity information, we have studied the radial distribution of 270 stars and multiple systems earlier than K0 in the Pleiades. Five new long period spectroscopic binaries have been identified from the CORAVEL observations. We have found a clear mass segregation between binaries and single stars, which is explained by the greater average mass of the multiple systems. The mass function of the single stars and primaries appears to be significantly different. While the central part of the cluster is spherical, the outer part is clearly elliptical, with an ellipticity of 0.17. The various parameters describing the Pleiades are (for a distance of 125pc): core radius r_c_=0.6 deg (1.4pc), tidal radius r_t_=7.4 (16pc), half mass radius r_m/2_=0.88 (1.9pc), harmonic radius r=1.82 (4pc). Low-mass stars (later than K0) probably extend further out and new proper motion and radial velocity surveys over a larger area and to fainter magnitudes would be very important to improve the description of the cluster structure and complete mass function.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/3236
- Title:
- Masses of Praesepe members
- Short Name:
- J/MNRAS/434/3236
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined possible cluster members of the nearby open cluster Praesepe (M44) based on J and K photometry and proper motions from the PPMXL catalogue and z photometry from the Sloan Digital Sky Survey. In total, we identified 893 possible cluster members down to a magnitude of J=15.5mag, corresponding to a mass of about 0.15M_{sun}_ for an assumed cluster distance modulus of (m-M)0=6.30mag (d~182pc), within a radius of 3.5{deg} around the cluster centre. We derive a new cluster centre for Praesepe (RA_centre_=8:39:37, DE_centre_=19:35:02). We also derive a total cluster mass of about 630M_{sun}_, and a 2D half-number and half-mass radius of 4.25 and 3.90pc, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/540/A57
- Title:
- Mass function of Quintuplet cluster
- Short Name:
- J/A+A/540/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar mass function is a probe for a potential dependence of star formation on the environment. Only a few young clusters are known to reside within the central molecular zone and can serve as test-beds for star formation under the extreme conditions in this region. We determine the present-day mass function of the Quintuplet cluster, a young massive cluster in the vicinity of the Galactic centre. We use two epochs of high resolution near infrared imaging data obtained with NAOS/CONICA at the ESO VLT to measure the individual proper motions of stars in the Quintuplet cluster in the cluster reference frame. An unbiased sample of cluster members within a radius of 0.5pc from the cluster centre was established based on their common motion with respect to the field and a subsequent colour-cut. Initial stellar masses were inferred from four isochrones covering ages from 3 to 5Myr and two sets of stellar evolution models. For each isochrone, the present-day mass function of stars was determined for the full sample of main sequence cluster members using an equal number binning scheme. We find the slope of the present-day mass function in the central part of the Quintuplet cluster to be alpha=-1.68^+0.13^_-0.09_ for an approximate mass range from 5 to 40M_{sun}_, which is significantly flatter than the Salpeter slope of alpha=-2.35. The flattening of the present-day mass function may be caused by rapid dynamical evolution of the cluster in the strong Galactic centre tidal field. The derived mass function slope is compared to the values found in other young massive clusters in the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A74
- Title:
- Massive binaries in Cepheus OB2/3 region
- Short Name:
- J/A+A/538/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two different formation scenarios for stars of masses larger than 10M_{sun}_ exist. Although simulations within both scenarios are capable of producing stars up to the highest observed masses, the relevance of the two formation scenarios for massive star-formation is not yet clear. We aim to detect companions to massive stars to constrain the binary parameters of the multiple systems. These findings will help to constrain the formation of massive stars.