- ID:
- ivo://CDS.VizieR/J/ApJS/253/22
- Title:
- Ks absolute magnitudes from LAMOST for OB stars
- Short Name:
- J/ApJS/253/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a data-driven method to estimate absolute magnitudes for O- and B-type stars from the LAMOST spectra, which we combine with Gaia DR2 parallaxes to infer distance and binarity. The method applies a neural network model trained on stars with precise Gaia parallax to the spectra and predicts K_s_-band absolute magnitudes M_Ks_ with a precision of 0.25mag, which corresponds to a precision of 12% in spectroscopic distance. For distant stars (e.g., >5kpc), the inclusion of constraints from spectroscopic M_Ks_ significantly improves the distance estimates compared to inferences from Gaia parallax alone. Our method accommodates for emission-line stars by first identifying them via principal component analysis reconstructions and then treating them separately for the M_Ks_ estimation. We also take into account unresolved binary/multiple stars, which we identify through deviations in the spectroscopic M_Ks_ from the geometric M_Ks_ inferred from Gaia parallax. This method of binary identification is particularly efficient for unresolved binaries with near equal-mass components and thus provides a useful supplementary way to identify unresolved binary or multiple-star systems. We present a catalog of spectroscopic M_Ks_, extinction, distance, flags for emission lines, and binary classification for 16002 OB stars from LAMOST DR5. As an illustration, we investigate the M_Ks_ of the enigmatic LB-1 system, which Liu et al. 2019Natur.575..618L had argued consists of a B star and a massive stellar-mass black hole. Our results suggest that LB-1 is a binary system that contains two luminous stars with comparable brightness, and the result is further supported by parallax from the Gaia eDR3.
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- ID:
- ivo://CDS.VizieR/J/A+A/438/377
- Title:
- Kyiv Meridian Axial Circle Catalogue, KMAC1
- Short Name:
- J/A+A/438/377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of astrometric observations of faint V<17mag stars in sky strip areas with ICRF objects obtained with the Kyiv meridian axial circle (D=180mm) equipped with a 1040x1160 CCD micrometer. Observations were carried out in a declination zone of 0+30 degrees. The work resulted in a compilation of a catalogue KMAC1 that presents an extension of the ICRF to faint stars in optical domain. The catalogue was obtained in the two versions: with reduction to the space catalogue Tycho2, <I/259>, (the version KMAC1-T, 159 ICRF fields, 104794 stars) and with reduction to the modern CCD catalogues CMC13 and UCAC2 (<I/289>) which are given also in the ICRF system (the version KMAC1-CU, 192 ICRF fields, 115032 stars). Due to a large number of CMC13 and UCAC2 stars used as reference, the version KMAC1-CU is of slightly better accuracy, though it may inherit local systematic errors of reference catalogues.
- ID:
- ivo://CDS.VizieR/J/AJ/127/213
- Title:
- LALA Bootes field X-ray source catalog
- Short Name:
- J/AJ/127/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of a deep, 172ks Chandra observation of the Large Area Lyman Alpha survey (LALA) Bootes field, obtained with the Advanced CCD Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This is one of the deepest Chandra images of the extragalactic sky; only the 2Ms Chandra Deep Field North (CDF-N) and 1Ms Chandra Deep Field South (CDF-S) are substantially deeper. In this paper we present the X-ray source catalog obtained from this image, along with an analysis of source counts and optical identifications. The X-ray image is composed of two individual observations obtained in 2002 and reaches 0.5-2.0 and 2.0-10.0keV flux limits of 1.5x10^-16^ and 1.0x10^-15^ergs/cm^2^/s, respectively, for point sources near the aim point. A total of 168 X-ray sources were detected: 160 in the 0.5-7.0keV band, 132 in the 0.5-2.0keV band, and 111 in the 2.0-7.0keV band. Our primary optical data are R-band imaging from the NOAO Deep Wide-Field Survey (NDWFS), with a limiting magnitude of R=25.7 (Vega, 3{sigma}, and 4" diameter aperture).
- ID:
- ivo://CDS.VizieR/J/A+AS/123/93
- Title:
- Lambda Boo stars consolidated catalogue
- Short Name:
- J/A+AS/123/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper describes the first steps towards the homogenization of the lambda Bootis group, leading to a concise definition of lambda Bootis stars: Population I, hydrogen burning, metal poor (except of C, N, O and S) A to F-type stars. The definition does not depend on phenomenological features, like flux depressions, colour excesses, vsini values, etc. Based on this new homogeneous catalogue with 45 lambda Bootis stars, we discuss classification criteria which can be used for a spectroscopic and photometric all-sky survey for lambda Bootis stars in the field and in clusters of different ages.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A34
- Title:
- LAMOST DR4 New mercury-manganese stars
- Short Name:
- J/A+A/645/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present work presents our efforts at identifying new mercury-manganese (HgMn/CP3) stars using spectra obtained with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Suitable candidates were searched for among pre-selected early-type spectra from LAMOST DR4 using a modified version of the MKCLASS code that probes several HgII and MnII features. The spectra of the resulting 332 candidates were visually inspected. Using parallax data and photometry from Gaia DR2, we investigated magnitudes, distances from the Sun, and the evolutionary status of our sample stars. We also searched for variable stars using diverse photometric survey sources. We present 99 bona fide CP3 stars, 19 good CP3 star candidates, and seven candidates. Our sample consists of mostly new discoveries and contains, on average, the faintest CP3 stars known (peak distribution 9.5<=G<=13.5mag). All stars are contained within the narrow spectral temperature-type range from B6 to B9.5, in excellent agreement with the expectations and the derived mass estimates (2.4<=M_{sun}_<=4 for most objects). Our sample stars are between 100Myr and 500Myr old and cover the whole age range from zero-age to terminal-age main sequence. They are almost homogeneously distributed at fractional ages on the main sequence <=80%, with an apparent accumulation of objects between fractional ages of 50% to 80%. We find a significant impact of binarity on the mass and age estimates. Eight photometric variables were discovered, most of which show monoperiodic variability in agreement with rotational modulation. Together with the recently published catalogue of APOGEE CP3 stars, our work significantly increases the sample size of known Galactic CP3 stars, paving the way for future in-depth statistical studies.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A140
- Title:
- Large Quasar Astrometric Catalogue 4, LQAC-4
- Short Name:
- J/A+A/614/A140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From an astrometric point of view, quasars constitute the best and almost ideal reference objects in the celestial sphere, with a priori no significant proper motion. Since the third release of the Large Quasar Astrometric Catalogue (LQAC-3, Cat. J/A+A/583/A75), a large number of quasars have been discovered, in particular those coming from the DR12Q release of the SDSS (Paris et al., 2017, Cat. VII/279). Moreover, for cross-matched objects, we have taken advantage of the very accurate determinations of the quasars identified within the recent Gaia DR1 catalogue (2018, Cat. I/345). Following the same procedure as in the three previous releases of the LQAC, our aim is to compile the large majority of all the quasars recorded so far. Our goal is to record their best coordinates and substantial information concerning their physical properties such as the redshift as well as multi-bands apparent and absolute magnitudes. Emphasis is given to the results of the cross-matches with the Gaia DR1 catalogue. New quasars coming from the DR12Q release were cross-matched with the precedent LQAC-3 compilation with a 1" search radius, in order to add the objects without counterpart to the LQAC-4 compilation. A similar cross-match was done with Gaia DR1 to identify the known quasars detected by Gaia. This enables one to improve significantly the positioning of these objects, and in parallel to study the astrometric performance of the individual catalogues of the LQAC-4 compilation. Finally, a new method was used to determine absolute magnitudes. Our final catalogue, called LQAC-4, contains 443 725 objects. This is roughly 37.82% more than the number of objects recorded in the LQAC-3. Among them, 249071 were found in common with the Gaia DR1, with a 1" search radius. That corresponds to 56.13% of the whole population in the compilation. The LQAC-4 delivers to the astronomical community a nearly complete catalogue of spectroscopically confirmed quasars (including a small proportion of compact AGNs), with the aim of giving their best equatorial coordinates with respect to the ICRF2 and with exhaustive additional information. For more than 50% of the sample, these coordinates come from the very recent Gaia DR1.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/55
- Title:
- Large-scale structure of M31 halo. II. PAndAS
- Short Name:
- J/ApJ/868/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Pan-Andromeda Archaeological Survey is a survey of >400deg^2^ centered on the Andromeda (M31) and Triangulum (M33) galaxies that has provided the most extensive panorama of an L* galaxy group to large projected galactocentric radii. Here, we collate and summarize the current status of our knowledge of the substructures in the stellar halo of M31, and discuss connections between these features. We estimate that the 13 most distinctive substructures were produced by at least 5 different accretion events, all in the last 3 or 4Gyr. We suggest that a few of the substructures farthest from M31 may be shells from a single accretion event. We calculate the luminosities of some prominent substructures for which previous estimates were not available, and we estimate the stellar mass budget of the outer halo of M31. We revisit the problem of quantifying the properties of a highly structured data set; specifically, we use the OPTICS clustering algorithm to quantify the hierarchical structure of M31's stellar halo and identify three new faint structures. M31's halo, in projection, appears to be dominated by two "mega-structures", which can be considered as the two most significant branches of a merger tree produced by breaking M31's stellar halo into increasingly smaller structures based on the stellar spatial clustering. We conclude that OPTICS is a powerful algorithm that could be used in any astronomical application involving the hierarchical clustering of points.
- ID:
- ivo://CDS.VizieR/J/AJ/83/1090
- Title:
- Late-type M dwarfs towards the SGP
- Short Name:
- J/AJ/83/1090
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog, including finding charts, is presented which contains 282 faint stars of spectral type M3 and later, located in an area of 173 square degrees near the South Galactic Pole. The catalog is based on a spectroscopic survey undertaken with the Curtis Schmidt at CTIO and provides a finding list of M stars free of any possible kinematic bias. The majority of these stars are expected to be dwarfs. To the same limiting magnitude, the observed surface density is comparable to that of the faint M stars in the direction of the North Galactic Pole, named 273 over 190 square degrees.
- ID:
- ivo://CDS.VizieR/I/200
- Title:
- Lick Northern Proper Motion: NPM1 Ref. Galaxies
- Short Name:
- I/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Lick Northern Proper Motion (NPM) program measured proper motions, positions, and photographic photometry for some 149,000 stars (NPM1 Catalog) covering the sky outside the Milky Way north of declination 23 degrees. The NPM1 proper motions were measured with respect to an absolute reference frame defined by some 50,000 faint galaxies (mostly 16 < B < 18 mag). The rms position errors for the NPM1 reference galaxies average 0.2 arcsec. The rms errors for the B magnitudes average 0.25 mag. More complete descriptive information is available in the ASCII or LaTeX documentation written by R.B. Hanson (UCO/Lick Obs.).
- ID:
- ivo://CDS.VizieR/I/199A
- Title:
- Lick Northern Proper Motion Program: NPM1 Catalog
- Short Name:
- I/199A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The NPM1 catalog is the first part of the Lick Northern Proper Motion (NPM) program to measure absolute proper motions, on an inertial system defined by some 50,000 faint galaxies, for some 300,000 stars over a blue apparent magnitude range from 8 to 18. There are 1246 6-degree by 6-degree fields in the NPM survey (to declination -23 degrees). The NPM1 catalog covers the 72% of the northern sky lying outside the Milky Way and contains some 149,000 stars from measures in 899 of the 1246 NPM fields. A second catalog (NPM2) will cover the NPM Milky Way fields. The Yale Southern Proper Motion (SPM) program will complete the southern sky. Each NPM field was photographed at two epochs between 1947 and 1988. The mean first and second epochs are 1950 and 1977; the average epoch difference is 27 years. The first-epoch plates were taken in the blue only; both blue and yellow plates were taken at the second epoch. Some 94000 stars were chosen anonymously for the NPM astrometric reductions and for statistical studies of stellar motions. In addition, the NPM1 catalog contains some 28000 positional reference stars, and some 27000 stars were chosen from the Lick Input Catalog of Special Stars (ICSS). The previous version of the NPM1 Catalog (I/199) deposited with the data centers (ADC and CDS) gives positions for equinox B1950 and computed epoch 1950, and is in one data file (148,940 lines) concatenating the 114 one-degree declination zones from +90 degrees to -23 degrees. Each star has an NPM1 "name" reflecting the declination zone and a running number in right ascension order within the zone. The present J2000 version gives the NPM1 positions transformed into the J2000 system and updated to the epoch 2000 using the NPM1 proper motions. The proper motions have been rotated into the J2000 coordinate system. The J2000 NPM1 Catalog is ordered in zones from +90 degrees to -23 degrees, and within each zone, the stars are sorted in right ascension order. To avoid "renaming" stars, the B1950 NPM1 "names" were retained, but the user must note that these no longer strictly reflect the declination zone and right ascension order in the J2000 NPM1 Catalog. The J2000 NPM1 Catalog is also available as 114 separate files, one for each declination zone from +90 degrees (z+90j) to -23 degrees (z-23j), from http://www.ucolick.org/~npm/NPM1/zones/ Each star's entry includes the absolute proper motion and blue magnitude. For 97% of the stars the color is also given. Other data given for each star are: the original mean epoch, a stellar class code, the number of NPM fields measured, and discrepancy flags for position, proper motion, and photometry. Finally, as an additional identification, the AGK3 (north) or SAO (south) number (if any) is given. The rms errors of the NPM absolute proper motions are about 0.5"/cent in each coordinate. The rms position errors at the catalog epoch 1950 average about 0.15" in each coordinate. The rms errors for the NPM photographic photometry average about 0.2 mag in B, and 0.15 mag in B-V. More complete information is available in the PostScript documentation for the 1993 (B1950) NPM1 Catalog (npm1b.ps), written by R.B. Hanson. We thank the National Science Foundation for its continued support of the NPM program. Recent work was supported by NSF grant AST-9530632. Current work is supported by NSF grant AST-9988105.
