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321. Luyten's White Dwarf Catalogues
ID:
ivo://CDS.VizieR/III/70
Title:
Luyten's White Dwarf Catalogues
Short Name:
III/70
Date:
21 Oct 2021
Publisher:
CDS
Description:
The catalogue includes all probable white dwarf and degenerate stars found in the Proper Motion and Faint Blue Star Surveys conducted by W.J. Luyten. The catalogue was originally published in two booklets, one in 1970 (3035 entries), and the part II in 1977 (3511 entries). As a guideline for the inclusion of stars into this catalogue, the author has used stars which present minimal values of the combined proper motions - magnitude quantity H defined by H = m + 5 + 5 log {mu} ({mu} is the proper motion in arcsec/yr) which show the minimal H values according to the color class: b 13.5 f 15.5 g-k 17.7 a 14.4 g 17.0 k 18.3 with the following exceptions: a) evidence from photoelectric colors or spectra indicate the object is a degenerate star (e.g. LB 3303) or b) the object is close to the antapex (which is the case for many stars at alpha=21h and delta =+42{deg}, plate 234). The bluest stars (color classes b or a) will probably prove to be genuine white dwarfs; probably no more than 40% of the yellower objects (color class k) will prove to be genuine degenerates.
322. Machine-learning investigation of the open cluster M67
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.
323. Masses of Praesepe members
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.
324. Mass function of Quintuplet cluster
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.
325. 2MASS J18212815+1414010 field stars
ID:
ivo://CDS.VizieR/J/MNRAS/455/357
Title:
2MASS J18212815+1414010 field stars
Short Name:
J/MNRAS/455/357
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used the OSIRIS camera at the 10.4m Gran Telescopio Canarias (GTC) to monitor the astrometric motion of the L4.5 dwarf 2M1821+14 over 17 months. The astrometric residuals of 11 epochs have an rms dispersion of 0.4mas, which is larger than the average precision of 0.23mas per epoch and hints towards an additional signal or excess noise. Comparison of the point-spread functions in OSIRIS and FORS2/VLT images reveals no differences critical for high-precision astrometry, despite the GTC's segmented primary mirror. We attribute the excess noise to an unknown effect that may be uncovered with additional data. For 2M1821+14, we measured a relative parallax of 10^6.15^+/-0.18mas and determined a correction of 0.50+/-0.05mas to absolute parallax, leading to a distance of 9.38+/-0.03pc. We excluded at 3{sigma} confidence the presence of a companion to 2M1821+14 down to a mass ratio of 0.1 (~5M_Jupiter_) with a period of 50-1000d and a separation of 0.1-0.7au. The accurate parallax allowed us to estimate the age and mass of 2M1821+14 of 120-700Myr and 0.049^+0.014^_-0.024_M_{sun}_, thus confirming its intermediate age and substellar mass. We complement our study with a parallax and proper motion catalogue of 587 stars (i'=~15.5-22) close to 2M1821+14, used as astrometric references. This study demonstrates submas astrometry with the GTC, a capability applicable for a variety of science cases including the search for extrasolar planets and relevant for future astrometric observations with E-ELT and TMT.
326. MC structure and properties
ID:
ivo://CDS.VizieR/J/A+A/649/A7
Title:
MC structure and properties
Short Name:
J/A+A/649/A7
Date:
22 Feb 2022
Publisher:
CDS
Description:
This work is part of the Gaia Data Processing and Analysis Consortium papers published with the Gaia Early Data Release 3 (EDR3). It is one of the demonstration papers aiming to highlight the improvements and quality of the newly published data by applying them to a scientific case. We use the Gaia EDR3 data to study the structure and kinematics of the Magellanic Clouds. The large distance to the Clouds is a challenge for the Gaia astrometry. The Clouds lie at the very limits of the usability of the Gaia data, which makes the Clouds an excellent case study for evaluating the quality and properties of the Gaia data. The basis of our work are two samples selected to provide a representation as clean as possible of the stars of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The selection used criteria based on position, parallax, and proper motions to remove foreground contamination from the Milky Way, and allowed the separation of the stars of both Clouds. From these two samples we defined a series of subsamples based on cuts in the colour-magnitude diagram; these subsamples were used to select stars in a common evolutionary phase and can also be used as approximate proxies of a selection by age. We compared the Gaia Data Release 2 (DR2) and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insights into features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones.
327. M dwarfs at high spectral-resolution in Y band
ID:
ivo://CDS.VizieR/J/AJ/159/52
Title:
M dwarfs at high spectral-resolution in Y band
Short Name:
J/AJ/159/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
In young Sun-like stars and field M-dwarf stars, chromospheric and coronal magnetic activity indicators such as H{alpha}, X-ray, and radio emission are known to saturate with low Rossby number (Ro<~0.1), defined as the ratio of rotation period to convective turnover time. The mechanism for the saturation is unclear. In this paper, we use photospheric TiI and CaI absorption lines in the Y band to investigate magnetic field strength in M dwarfs for Rossby numbers between 0.01 and 1.0. The equivalent widths of the lines are magnetically enhanced by photospheric spots, a global field, or a combination of the two. The equivalent widths behave qualitatively similar to the chromospheric and coronal indicators: we see increasing equivalent widths (increasing absorption) with decreasing Ro and saturation of the equivalent widths for Ro<~0.1. The majority of M dwarfs in this study are fully convective. The results add to mounting evidence that the magnetic saturation mechanism occurs at or beneath the stellar photosphere.
328. M dwarf-white dwarf binary systems
ID:
ivo://CDS.VizieR/J/AJ/129/2428
Title:
M dwarf-white dwarf binary systems
Short Name:
J/AJ/129/2428
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. We present the measured radial velocities and complete space motions for 161 white dwarf stars in wide binaries.
329. Mean Positions and proper motions of 995 FK4Sup stars
ID:
ivo://CDS.VizieR/I/210
Title:
Mean Positions and proper motions of 995 FK4Sup stars
Short Name:
I/210
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalogue lists improved mean positions and proper motions for the 995 stars in the FK4 Supplement (Veroeff. Astron. Rechen-Inst. Heidelberg No 11, 1963) which were not included in the Fifth Fundamental Catalogue (Part I: "The Basic FK5", Fricke et al., 1988, Veroeff. Astron. Rechen-Inst. Heidelberg No 32, Catalogue I/149/; Part II: "The FK5 Extension", Fricke et al., 1991, Veroeff. Astron. Rechen-Inst. Heidelberg No 33, Catalogue I/175/). The main purpose of the FK4 Supplement was to stimulate further observations within absolute and differential programs of the stars listed in that catalogue with the aim of their inclusion as new fundamental stars into a future fundamental catalogue. The new fundamental stars should increase the star density without extending the magnitude limit to fainter magnitudes. Since the publication of the "Supplement-Katalog des FK3" (published in Astron-Geodaet. Jahrbuch 1954 and Astron-Geodaet. Jahrbuch 1956) these stars were included in many observing programs. Within work on deriving the FK5 Extension all stars in the FK4 Supplement had been treated in exactly the same way and improved mean positions and proper motions had thus been obtained for all FK4 Sup stars. For more details reference is made to the introduction of the FK5 Extension. FK4 Sup stars with the best astrometric data were included in the FK5 Extension for achieving a homogeneous distribution in magnitude and taking simultaneously into account an even distribution on the sky. This selection process included 992 of the 1987 FK4 Sup stars into the FK5 Extension. Although the astrometric precision of the stars given in the present catalogue is inferior to that of the FK4 Supplement stars included in the FK5 Extension, they deserve being published because a considerable number of observations has been obtained for these stars since about 1955, stimulated by the publication of the FK3 Supplement. The average mean epoch of observation of the stars given is therefore shifted to comparatively modern epochs (see the table in Section 2 of the publication). The astrometric precision of the stars presented here is better than for most other published star positions and proper motions, and the positions and proper motions are the best which could be derived from the available observations. These observations are published in the same catalogues as listed in the FK5, Part II on pages 139 ff. The apparent visual magnitudes are between 3.6 and 7.7 with a concentration around the mean value of 5.94. They are thus within the magnitude limit of the Basic FK5.
330. MEarth mid-to-late M dwarfs rotation & kinematics
ID:
ivo://CDS.VizieR/J/ApJ/812/3
Title:
MEarth mid-to-late M dwarfs rotation & kinematics
Short Name:
J/ApJ/812/3
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H{alpha} emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that v sin i measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, late-type, slowly rotating stars present in our sample. Additionally, we find that all M dwarfs with rotation periods shorter than 26 days (early-type; M1-M4) and 86 days (late-type; M5-M8) are magnetically active. This potential mismatch suggests that the physical mechanisms that connect stellar rotation to chromospheric heating may be different in fully convective stars. A kinematic analysis suggests that the magnetically active, rapidly rotating stars are consistent with a kinematically young population, while slow-rotators are less active or inactive and appear to belong to an older, dynamically heated stellar population.