This is a new reduction of FOCAT-S photographic catalogue of southern stars. This reduction has to replace the preceding one. The differences from previous version are as follows: 1. The new version was sorted according right ascension of stars inside 10-degree declination zone; 2. New proper motions were calculated for all almost stars. New Astrographic Catalogue plate reduction was developed for this aim. The average rms of new FOCAT-S proper motions is 0.002 - 0.003 "/year; 3. The number of the Astrographic Catalogue star positions used for the proper motion calculation is added; 4. The magnitude (mag) and spectral type (Sp) columns were revised significantly: some errors were corrected; stars identified in C.S.I. catalogue have got Mag, Sp from this catalogue as it was in previous version. Other stars have got Mag, Sp from PPM-S catalogue. 5. The list of Durchmusterung star numbers was changed. Now it contains the Cape Photographic Durchmusterung (CPD) numbers for stars in [-90, -23] declination zones; Cordoba Durchmusterung (CoD) star numbers are used only if it was impossible to identify star in BD or CPD. Format of this column was changed also. 6. PPM catalogue star numbers were added.
FON Astrographic Catalogue (FONAC, Version 2.0) containing more then 2.0 million stars (J2000, epoch 1991.25)
Short Name:
FONAC_Version2.0
Date:
20 Feb 2014 21:58:06
Publisher:
Nikolaev Astronomical Observatory
Description:
The FONAC 2.0 is a compiled catalogue of positions, proper motions and photometric data for 2,005,137 stars between declinations of +90° and -2°. The mean epoch of positions is 1988.19. The catalogue was compiled using a new reduction of measurements for more than 1700 plates, which were obtained with the wide-angle astrograph of the Main Astronomical Observatory in Ukraine within the FON project. The acronym FON (Russian, Ukrainian) stands for Photographic Survey of the Northern Sky. The ACT Reference Catalogue as well as the Guide Star and USNO A2.0 catalogues were applied for the reductions of positions and determination of photometric characteristics of stars. Median precision of the FONAC data are ±200 mas, ±3 mas/year and ±0.18 mag in positions, proper motions and magnitudes of stars, respectively.
Four new eclipsing mid M-dwarf systems from MEarth
Short Name:
J/AJ/156/140
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using data from the MEarth-North and MEarth-South transit surveys, we present the detection of eclipses in four mid M-dwarf systems: LP 107-25, LP 261-75, LP 796-24, and LP 991-15. Combining the MEarth photometry with spectroscopic follow-up observations, we show that LP 107-25 and LP 796-24 are short-period (1.388 and 0.523 day, respectively) eclipsing binaries in triple-lined systems with substantial third-light contamination from distant companions. LP 261-75 is a short-period (1.882 day) single-lined system consisting of a mid M-dwarf eclipsed by a probable brown dwarf secondary, with another distant visual brown dwarf companion. LP 991-15 is a long-period (29.3 day) double-lined eclipsing binary on an eccentric orbit with a geometry that produces only primary eclipses. A spectroscopic orbit is given for LP 991-15, and initial orbits for LP 107-25 and LP 261-75.
The FK4 was an attempt to establish a fundamental system of stellar positions and proper motions for the 1950 equinox using as much position data as were available. Most of the stars are brighter than 7.0 mag. To increase the star density in some regions of the sky, positions and proper motions for additional stars were established on the same system. This catalog contains seven data files, six for different equinoxes (1950, 1955, 1960, 1965, 1970, and 1975) and one for the supplemental stars. The 1950 and 1975 files contain the complete FK4 catalog (1535 stars); the others contain only 52 polar stars. In addition to a header record, the primary catalog contains for each star an identification number; the magnitude (maximum for a variable star); a variability flag, the minimum magnitude for a variable or the magnitude of the secondary for a double star; the HD spectral type and the type for the companion or a second type for a variable star; the position and the change and acceleration of the position; the proper motion and its change with time; the mean epoch of the observations for both right ascension and declination; the standard deviations of the position and proper motion; the numbers of the star in the Boss General Catalog, the N30 catalog, and in the Durchmusterungs; and the parallax. The supplement has a flag to indicate duplicity but no information about variability or the second component. It has no information about the temporal change of the position and proper motion and does not list the N30 and Durchmusterung numbers. It also omits the mean epoch for the observations.
We used fractal statistics to quantify the degree of observed substructures in a sample of 50 embedded clusters and more evolved open clusters (<100Myr) found in different galactic regions. The observed fractal parameters were compared with N-body simulations from the literature, which reproduce star-forming regions under different initial conditions and geometries that are related to the cluster' dynamical evolution. Parallax and proper motion from Gaia-DR2 were used to accurately determine cluster membership by using the Bayesian model and cross-entropy technique. The statistical parameters Q, <m> and <s> were used to compare observed cluster structure with simulations. A low level of substructures (Q<0.8) is found for most of the sample that coincides with simulations of regions showing fractal dimension D~2-3. Few clusters (<20 per cent) have uniform distribution with a radial density profile ({alpha}<2). A comparison of Q with mass segregation ({LAMBDA}MSR) and local density as a function of mass ({SIGMA}LDR) shows the clusters coinciding with models that adopt supervirial initial conditions. The age-crossing time plot indicates that our objects are dynamically young, similar to the unbound associations found in the Milky Way. We conclude that this sample may be expanding very slowly. The flat distribution in the Q-age plot and the absence of trends in the distributions of {LAMBDA}MSR and {SIGMA}LDR against age show that in the first 10 Myr the clusters did not change structurally and seem not to have expanded from a much denser region.
Data on the multiplicity of F- and G-type dwarf stars within 67pc of the Sun are presented. This distance-limited sample based on the Hipparcos catalog contains 4847 primary stars (targets) with 0.5<V-I_C_<0.8 and is >90% complete. There are 2196 known stellar pairs; some of them belong to 361 hierarchical systems from triples to quintuples. Models of companion detection by radial velocity, astrometric acceleration, direct resolution, and common proper motion are developed. They serve to compute completeness for each target, using the information on its coverage collected here. About 80% of companions to the primary stars are detected, but the census of subsystems in the secondary components is only about 30%. Masses of binary components are estimated from their absolute magnitudes or by other methods; the periods of wide pairs are evaluated from their projected separations. A third of binaries with periods shorter than ~100yr are spectroscopic and/or astrometric pairs with yet unknown periods and mass ratios. These data are used in the accompanying Paper II to derive unbiased statistics of hierarchical multiple systems.
We use LAMOST DR4 M giants combined with Gaia DR2 proper motions and ALLWISE photometry to obtain an extremely pure sample of Sagittarius (Sgr) stream stars. Using TiO5 and CaH spectral indices as indicators, we selected a large sample of M-giant stars from M-dwarf stars in LAMOST DR4 spectra. Considering the position, distance, proper motion, and angular momentum distribution, we obtained 164 pure Sgr stream stars. We find that the trailing arm has higher energy than the leading arm in the same angular momentum. The trailing arm we detected extends to a heliocentric distance of ~130kpc at {Lambda}_{sun}_~170{deg}, which is consistent with the feature found in RR Lyrae in Sesar+ (2017, J/ApJ/844/L4). Both of these detections of Sgr, in M-giants and in RR Lyrae, imply that the Sgr stream may contain multiple stellar populations with a broad metallicity range.
Based on data from the ESA Gaia Data Release 2 (DR2) and several ground-based, multi-band photometry surveys we have compiled an all-sky catalogue of 39800 hot subluminous star candidates selected in Gaia DR2 by means of colour, absolute magnitude, and reduced proper motion cuts. We expect the majority of the candidates to be hot subdwarf stars of spectral type B and O, followed by blue horizontal branch stars of late B-type (HBB), hot post-AGB stars, and central stars of planetary nebulae. The contamination by cooler stars should be about 10%.
The precise parallax, proper motion, and photometric measurements contained in Gaia Data Release 2 (DR2) offer the opportunity to reexamine the membership and ages of nearby young moving groups (NYMGs), i.e., loose groups of stars of age <~100Myr in the solar vicinity. Here, we analyze the available DR2 data for members and candidate members of the {epsilon}Cha Association ({epsilon}CA) which, at an estimated age of ~3-5Myr, has previously been identified as among the youngest NYMGs. The several dozen confirmed members of {epsilon}CA include MPMus and TCha, two of the nearest stars of roughly solar mass that are known to host primordial protoplanetary disks, and the Herbig Ae/Be star HD104237A. We have used Gaia DR2 data to ascertain the Galactic positions and kinematics and color-magnitude diagram positions of {epsilon}CA members and candidates so as to reassess their membership status and thereby refine estimates of the distance, age, multiplicity, and disk fraction of the group. Our analysis yields 36 bona fide {epsilon}CA members, as well as 20 provisional members, including 3 new members identified here as comoving companions to previously known {epsilon}CA stars. We determine a mean distance to {epsilon}CA of 101.0{+/-}4.6pc and confirm that, at an age of 5_-2_^+3^Myr, {epsilon}CA represents the youngest stellar group within ~100pc of Earth. We identify several new photometric binary candidates, bringing the overall multiplicity fraction (MF) of {epsilon}CA to 40%, intermediate between the MFs of young T associations and the field.
Gaia Data Release 2. Summary of the contents and survey properties: We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on as- trophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the G_BP_ (330-680nm) and G_RP_ (630-1050nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy. The catalogue of radial velocity standard stars (Soubiran et al., 2018A&A...616A...7S) The Radial Velocity Spectrometer (RVS) on board of Gaia having no calibration device, the zero point of radial velocities needs to be calibrated with stars proved to be stable at the level of 300m/s during the Gaia observations. A dataset of about 71000 ground-based radial velocity measurements from five high resolution spectrographs has been compiled. A catalogue of 4813 stars was built by combining these individual measurements. The zero point has been established using asteroids. The resulting catalogue has 7 observations per star on average on a typical time baseline of 6 years, with a median standard deviation of 15m/s. A subset of the most stable stars fulfilling the RVS requirements has been used to establish the zero point of the radial velocities provided in Gaia DR2. The stars not used for calibration are used for the RVS data validation.
