Catalogue Of Stars Research Articles

High-Accuracy Guide Star Catalogue Generation with a Machine Learning Classification Algorithm.

In order to detect gravitational waves and characterise their sources, three laser links were constructed with three identical satellites, such that interferometric measurements for scientific experiments can be carried out. The attitude of the spacecraft in the initial phase of laser link docking is provided by a star sensor (SSR) onboard the satellite. If the attitude measurement capacity of the SSR is improved, the efficiency of establishing laser linking can be elevated. An important technology for satellite attitude determination using SSRs is star identification. At present, a guide star catalogue (GSC) is the only basis for realising this. Hence, a method for improving the GSC, in terms of storage, completeness, and uniformity, is studied in this paper. First, the relationship between star numbers in the field of view (FOV) of a staring SSR, together with the noise equivalent angle (NEA) of the SSR—which determines the accuracy of the SSR—is discussed. Then, according to the relationship between the number of stars (NOS) in the FOV, the brightness of the stars, and the size of the FOV, two constraints are used to select stars in the SAO GSC. Finally, the performance of the GSCs generated by Decision Trees (DC), K-Nearest Neighbours (KNN), Support Vector Machine (SVM), the Magnitude Filter Method (MFM), Gradient Boosting (GB), a Neural Network (NN), Random Forest (RF), and Stochastic Gradient Descent (SGD) is assessed. The results show that the GSC generated by the KNN method is better than those of other methods, in terms of storage, uniformity, and completeness. The KNN-generated GSC is suitable for high-accuracy spacecraft applications, such as gravitational detection satellites.

The Alma catalogue of OB stars – II. A cross-match with Gaia DR2 and an updated map of the solar neighbourhood

ABSTRACT We cross-match the Alma catalogue of OB stars with Gaia DR2 astrometry and photometry as a first step towards producing a clean sample of massive stars in the solar neighbourhood with a high degree of completeness. We analyse the resulting colour–absolute magnitude diagram to divide our sample into categories and compare extinction estimates from two sources, finding problems with both of them. The distances obtained with three different priors are found to have few differences among them, indicating that Gaia DR2 distances are robust. An analysis of the 3D distribution of massive stars in the solar neighbourhood is presented. We show that a kinematically distinct structure we dub the Cepheus spur extends from the Orion–Cygnus spiral arm towards the Perseus arm and is located above the Galactic mid-plane, likely being related to the recently discovered Radcliffe wave. We propose that this corrugation pattern in the Galactic disc may be responsible for the recent enhanced star formation at its crests and troughs. We also discuss our plans to extend this work in the immediate future.

VVV survey near-infrared colour catalogue of known variable stars

Context. The Vista Variables in the Via Lactea (VVV) near-infrared variability survey explores some of the most complex regions of the Milky Way bulge and disk in terms of high extinction and high crowding. Aims. We add a new wavelength dimension to the optical information available at the American Association of Variable Star Observers International Variable Star Index (VSX-AAVSO) catalogue to test the VVV survey near-infrared photometry to better characterise these objects. Methods. We cross-matched the VVV and the VSX-AAVSO catalogues along with Gaia Data Release 2 photometry and parallax. Results. We present a catalogue that includes accurate individual coordinates, near-infrared magnitudes (ZYJHKs), extinctions AKs, and distances based on Gaia parallaxes. We also show the near-infrared CMDs and spatial distributions for the different VSX types of variable stars, including important distance indicators, such as RR Lyrae, Cepheids, and Miras. By analysing the photometric flags in our catalogue, we found that about 20% of the stars with measured and verified variability are flagged as non-stellar sources, even when they are outside of the saturation and/or noise regimes. Additionally, we pair-matched our sample with the VIVA catalogue and found that more than half of our sources are missing from the VVV variability list, mostly due to observations with low signal-to-noise ratio or photometric problems with a low percentage due to failures in the selection process. Conclusions. Our results suggest that the current knowledge of the variability in the Galaxy is biased to nearby stars with low extinction. The present catalogue also provides the groundwork for characterising the results of future large variability surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time in the highly crowded and reddened regions of the Galactic plane, as well as follow-up campaigns for characterising specific types of variables. The analysis of the incorrectly flagged stars can be used to improve the photometric classification of the VVV data, allowing us to expand the amount of data considered useful for science purposes. In addition, we provide a list of stars that are missed by the VIVA procedures for which the observations are good and which were missed due to some failure in the VIVA selection process.

A spectroscopically confirmed Gaia-selected sample of 318 new young stars within ∼200 pc

ABSTRACT In the Gaia era, the majority of stars in the Solar neighbourhood have parallaxes and proper motions precisely determined while spectroscopic age indicators are still missing for a large fraction of low-mass young stars. In this work, we select 756 overluminous late K and early M young star candidates in the southern sky and observe them over 64 nights with the ANU 2.3-m Telescope at Siding Spring Observatory using the Echelle (R = 24 000) and Wide Field spectrographs (WiFeS, R = 3000–7000). Our selection is kinematically unbiased to minimize the preference against low-mass members of stellar associations that dissipate first and to include potential members of diffuse components. We provide measurements of Hα and calcium H&K emission, as well as of Li i 6708 Å in absorption. This enables identification of stars as young as 10–30 Myr – a typical age range for stellar associations. We report on 346 stars showing detectable lithium absorption, 318 of which are not included in existing catalogues of young stars. We also report 125 additional stars in our sample presenting signs of stellar activity indicating youth but with no detectable lithium. Radial velocities are determined for WiFeS spectra with a precision of 3.2 km s−1 and 1.5 km s−1 for the Echelle sample.

The JPL Planetary and Lunar Ephemerides DE440 and DE441

Abstract The planetary and lunar ephemerides called DE440 and DE441 have been generated by fitting numerically integrated orbits to ground-based and space-based observations. Compared to the previous general-purpose ephemerides DE430, seven years of new data have been added to compute DE440 and DE441, with improved dynamical models and data calibration. The orbit of Jupiter has improved substantially by fitting to the Juno radio range and Very Long Baseline Array (VLBA) data of the Juno spacecraft. The orbit of Saturn has been improved by radio range and VLBA data of the Cassini spacecraft, with improved estimation of the spacecraft orbit. The orbit of Pluto has been improved from use of stellar occultation data reduced against the Gaia star catalog. The ephemerides DE440 and DE441 are fit to the same data set, but DE441 assumes no damping between the lunar liquid core and the solid mantle, which avoids a divergence when integrated backward in time. Therefore, DE441 is less accurate than DE440 for the current century, but covers a much longer duration of years −13,200 to +17,191, compared to DE440 covering years 1550–2650.

Algol anomaly or careful observations of its brightness? The values recorded for the magnitude of Algol in the medieval astronomical corpus

The historical evidence from the past two millennia show two problems concerning the star Algol (β Per): First, a critical variation in its brightness from a magnitude m ~ 2 in (1) Ptolemy’s Almagest (2nd century AD) and reported by (2) al-Ṣūfī (10th ct.) through its diminution to m = 4 in (3) the star catalog prepared by the Persian astronomers in service of the Yuan dynasty of China in the 13th ct. to becoming brighter, m = 3, as reported by (4) Ibn al-Shāṭir (14th ct.) and (5) Tycho Brahe (16th ct.). In the early modern period, it returned back to m ~ 2, as reported, for example, by Hevelius and Flamsteed (17th ct.), before the discovery of its periodic variability in 1783. Second, al-Ṣūfī reports it as a red star. We present detailed analyses of the sources (3) and (4) for the test of their accuracy and reliability. Our conservative hypothesis concerning the first problem is that the past astronomers observed the star at various phases of its 3-day period of variability. We reject the reddening to have arisen from the extinction due to either the Earth’s atmosphere or an interstellar medium. For resolving both problems, we instead speculate on astrophysical explanations for the observations. These are: copious dust produced as a result of arrested coronal mass ejections or pulverized planetary debris that resides close to the central binary before being dispersed; and a much-enhanced accretion rate that lead Algol into a W Ser-like state in which the primary was enveloped in an inflated accretion disk. We draw an analogy between the dimming of Algol and the recent dimming of Betelgeuse in order to highlight the value of historical observations for understanding astrophysical phenomena.

Assessment of the accuracy of measures in the 1829 southern double star catalogue of James Dunlop

ABSTRACT In 1829 James Dunlop published the first southern double star catalogue of some 253 double stars. The accuracy of this catalogue has been determined by using Aladin to cross-match them with Gaia DR2 and estimate their positional (right ascension, declination, position angle, and separation) and magnitude accuracy. Seven per cent could not be identified using Aladin and 14 were single stars. We found 13 double stars (5 per cent) not currently listed in the Washington Double Star Catalog. The catalogue equinox was determined as B1826.0. Overall, 1σ uncertainties in right ascension were within 1 sidereal minute and declinations within 10 arcmin. We also identified and corrected a number of Quadrant errors in the position angles and quantified the separations. Apparent visual magnitude estimates were generally within 1 mag. Dunlop’s overall uncertainties were larger than those of his contemporaries, nevertheless the little known catalogue remains valuable as the earliest source of over 200 double star astrometric and visual magnitude estimates.

Future of the General Catalogue of Variable Stars from the Experience of Recent Name-lists

Abstract We briefly outline the history of the General Catalogue of Variable Stars (GCVS) and the New Catalogue of Suspected Variable Stars (NSV catalogue). Recently, we have completed a revision of the NSV catalogue. Positional information was checked for all its stars and, in many cases, new photometric data were added. As a result, one third of all NSV stars have been transferred to the GCVS. Having determined equatorial coordinates for variable stars in globular star clusters, we began to add them to the GCVS. Two Name-lists published so far contain more than 1700 variable stars in 36 globular clusters; an additional Name-list (about 900 variable stars in 27 globular clusters) will be published before the end of 2021. We discuss problem cases in the literature and in the Catalogue of Variable Stars in Galactic Globular Clusters revealed during our preparation of the Name-lists. The future of traditional catalogues of variable stars (GCVS; AAVSO Variable-star Data Index VSX) is discussed.

Achievements of Space Astrometry

Astrometry is the basis for astronomical observations and measurements of coordinates and time. Its main task is to implement a reference frame—the one mentioned in Newton’s first law. Since ancient times, astronomers have created star catalogs for this purpose. Work on them led to the discovery of the precession and nutation of the Earth’s axis, proper motions and parallaxes of stars, and the orbital motion of binary stars. The modern International Celestial Reference Frame (ICRF) is based on observations in the radio and optical range of very distant objects—quasars. It is to them that the GPS or GLONASS system is tied in the navigation device. The 21st century, with its computational capabilities, has led to the creation of star catalogs of unprecedented power, containing over a billion objects. However, the main breakthrough, even a revolution in astrometry, has happened in space observations. Two spacecraft have already created star catalogs of fantastic accuracy, which makes it possible to approach the solution of problems even the setting of which was unthinkable a few years ago. This article is dedicated to an overview of the achievements of astrometry over the past two millennia, massive star catalogs, and space astrometric projects.

Research on Partitioning Algorithm Based on Dynamic Star Simulator Guide Star Catalog

The simulated star map generated by the dynamic star simulator cannot meet the current demand for calibration of the star map recognition rate of the star sensor due to the huge amount of guide star catalog data and the slow retrieval process. This paper proposes the guide star equipartition method, which makes the constant number of each sub-region of the guide star catalog basically the same. This method first divides the declination at equal intervals through the field of view of the dynamic star simulator, and then determines the interval of the right ascension by the average number of stars with magnitude Mv that can be photographed in the field of view of the star sensor. The SAO (Smithsonian Astrophysical Observatory) catalog containing 5103 stars in the whole celestial sphere is divided into 452 sub-areas by the average number of guide stars. After the division, the guide star retrieval time is about 8ms, and the refresh rate of the simulated star map is increased by more than three times. The real-time requirements of the dynamic star simulator have been improved. Based on this, a star map simulation software is designed, which can realize the division of star catalogs with different fields of view and different magnitude thresholds.

New precise positions in 2013–2019 and a catalog of ground-based astrometric observations of 11 Neptunian satellites (1847–2019) based on Gaia-DR2

Context. Developing high-precision ephemerides for Neptunian satellites requires not only the continuation of observing campaigns but also the collection and improvement of existing observations. So far, no complete catalogs of observations of Neptunian satellites are available. Aims. We aim to provide new, precise positions, and to compile a catalog including all available ground-based astrometric observations of Neptunian satellites. The observations are tabulated in a single and consistent format and given in the same timescale, the Terrestrial Time (TT), and reference system, the International Celestial Reference System (ICRS), including necessary changes and corrections. Methods. New CCD observations of Triton and Nereid were made at Lijiang 2.4-m and Yaoan 0.8-m telescopes in 2013–2019, and then reduced based on Gaia-DR2. Furthermore, a catalog called OCNS2019 (Observational Catalog of Neptunian Satellites (2019 version)) was compiled, after recognizing and correcting errors and omissions. Furthermore, in addition to what was considered for the COSS08 catalog for eight main Saturnian satellites, all observed absolute and relative coordinates were converted to the ICRS with corrections for star catalog biases with respect to Gaia-DR2. New debiasing tables for both the modern and old star catalogs, which were previously not provided based on Gaia-DR2, are developed and applied. Treatment of missing positions of comparison bodies in conversions of observed relative coordinates are proposed. Results. OCNS2019 and the new debiasing tables are publicly available online. OCNS2019 includes 24996 observed coordinates of 11 Neptunian satellites obtained over 3741 nights from 1847 to 2019. All observations are given in TT and ICRS. The star catalog biases are removed, which are significant for Nereid and outer satellites. We obtained 880 (5% of total now available) new coordinates for Triton over 41 nights (1% of total observation nights so far), and 790 (14%) for Nereid over 47 nights (10%). The dispersions of these new positions are about 0.″03 for Triton and 0.″06 for Nereid. Conclusions. OCNS2019 should be useful in improving ephemerides for the above-mentioned objects.

An approach of target photometric measuring for theodolite visible light imaging

Photoelectric theodolite is important optical measurement equipment in pelagic aerospace TT&C systems. The visible light imaging method helps capture significant information of the observed target, photometric information is one of them. To achieve expediently and quickly target photometric measuring, it studies and realizes a measuring method, by using stars in the same field of view as the observed target in this paper. Firstly, it calculates the gray values for target and star by image processing algorithm in the image captured by theodolite. Then magnitude information of the star is obtained by using a star catalogue. Lastly, magnitude of the target is calculated by antitheses method. The approach is implemented to investigate the measuring performance and an experiment is carried out by using images containing at least two stars. The result shows good performance of the proposed method.

New mercury-manganese stars and candidates from LAMOST DR4

Aims.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).Methods.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 Hg IIand Mn IIfeatures. The spectra of the resulting 332 candidates were visually inspected. Using parallax data and photometry fromGaiaDR2, 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.Results.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≤ 13.5 mag). 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⊙≤ 4 for most objects). Our sample stars are between 100 Myr and 500 Myr 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.Conclusions.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.

Guide star catalog generation of star sensors for interstellar navigation

In interstellar travel, parallax and stellar aberration have a non-negligible influence on the star identification of star sensors. Through the analysis of the working principle of star sensors, only the guide star catalog generation can solve this problem. The influence mechanism of parallax and stellar aberration is synthetically analyzed by four-dimensional time-space diagrams, and a generation algorithm of the guide star catalog for the interstellar star identification is presented. The update cycle of the catalog is studied, and a block update method based on the distance distribution is given. The Hipparcos catalog is adopted as the fundamental catalog. On the premise of meeting the accuracy requirement of star identification, the maximum travel distance supported by the catalog is about 0.3 light-years. In order to balance the star identification and the influence of parallax, eliminating 30% to 40% of the nearby guide stars is an optimal criterion for the guide star selection. The analysis of the catalog distribution shows that the parallax and the stellar aberration have opposite effects on the distribution of guide stars. The methods and conclusions provide a theoretical basis for interstellar celestial navigation.

Ephemeris error correction in celestial navigation system considering Earth’s precession-nutation

Navigation systems are crucial space detector components. Advancements in optical equipment have made the Celestial Navigation System (CNS) continually more accessible. Ephemeris error, however, limits the CNS navigation accuracy. This paper proposes an autonomous CNS equipped with an ephemeris error correction model. The model provides the navigation stars’ high-accuracy ephemeris information for navigation stars based on the coupled effects of the Earth’s nutation and precession; this allows for effective positioning and attitude determination of space detector. The navigation star ephemeris errors under the proposed method are significantly improved compared to the traditional Smithsonian Astrophysical Observatory (SAO) star catalog recorded on January 1, 2000. The proposed method also shows more accurate space detector attitude and positioning estimations compared to another existing ephemeris error correction method. The proposed method can be effectively applied to high-accuracy attitude and position estimation.

The determination of Hipparchus' phenomena and their consistency with the Almagest star catalog

AbstractThe derivation of the phenomena in Hipparchus' Commentary on the phenomena of Aratus and Eudoxus from the star positions of his presumed star catalog is investigated under the assumption of their determination by a star globe. As most of Hipparchus' star coordinates are not available, they are reconstructed from the star catalog in Ptolemy's Almagest. Data consistent with the assumed determination of the phenomena are identified by a statistical method for the elimination of erroneous data; the parameters underlying this determination and the data accuracy are estimated by adjustment theory. The results indicate that, for the majority of the data under investigation, an accurate determination by a globe can be assumed. The estimated values of the parameters, the obliquity of the ecliptic and the observer's latitude, agree with information from historical sources and with values found in previous investigations of Hipparchus' data. Moreover, in most instances, the conducted analysis substantiates a strong relation between Ptolemy's and Hipparchus' star data under investigation.

Pairing function of visual binary stars

ABSTRACTAn all-sky sample of 1227 visual binaries based on Washington Double Star catalogue is constructed to infer the initial mass function (IMF), mass ratio, and projected distance distribution with a dedicated population synthesis model. Parallaxes from Gaia DR2 and Hipparcos are used to verify the distance distribution. The model is validated on the single-star Tycho-2 sample and successfully reproduces the observed magnitudes and angular separations. The projected separation distribution follows f(s) ∼ s−1.2 in 102–2 × 103 au range for 1–4.5 m⊙ primary stars. Several algorithms are explored as pairing functions. Random pairing is confidently rejected. Primary-constrained pairing (PCP) and split-core pairing (SCP), the scenarios adopting primary component’s or total system’s mass as fundamental, are considered. The preferred IMF slope is α ∼ 2.8 either way. A simple power-law mass ratio distribution is unlikely, but the introduction of a twin excess provides a favourable result. PCP with f(q) ∼ q−1 is preferred with a tiny twin fraction, models with f(q) ∼ q−1.5 are acceptable when a larger twin excess is allowed. SCP is similar to PCP when a larger slope of the power law is adopted: f(q) ∼ qβ + 0.7.

The distances of 61 PGCCs in the second galactic quadrant

ABSTRACT Determining the distances to the Planck Galactic cold clumps (PGCCs) is crucial for the measurement of their physical parameters and the study of their Galactic distribution. Based on two large catalogues of stars with robust distances and reddening estimates from the literature, we have estimated accurate distances to 61 PGCCs in the second Galactic quadrant. For this purpose, we have selected stars along the sightlines overlapping with the cores of the sample clumps and fitted the reddening profiles with a simple reddening model. The typical uncertainties of the resultant distances of these PGCCs are less than 8 per cent. The new estimates differ significantly from the kinematic values, well known to suffer from large errors. With the new distances, we have updated the physical properties including the radii, masses, and virial parameters of the cores of the PGCCs.

Estimating camera parameters from starry night photographs

We propose an efficient, specific method for estimating camera parameters from a single starry night image. Such an image consists of a collection of disks representing stars, so traditional estimation methods for common pictures do not work. Our method uses a database, a star catalog, that stores the positions of stars on the celestial sphere. Our method computes magnitudes (i.e., brightnesses) of stars in the input image and uses them to find the corresponding stars in the star catalog. Camera parameters can then be estimated by a simple geometric calculation. Our method is over ten times faster and more accurate than a previous method.

A Distance Determination to the Small Magellanic Cloud with an Accuracy of Better than Two Percent Based on Late-type Eclipsing Binary Stars

Abstract We present a new study of late-type eclipsing binary stars in the Small Magellanic Cloud (SMC) undertaken with the aim of improving the distance determination to this important galaxy. A sample of 10 new detached, double-lined eclipsing binaries identified from the OGLE variable star catalogs and consisting of F- and G-type giant components has been analyzed. The absolute physical parameters of the individual components have been measured with a typical accuracy of better than 3%. All but one of the systems consist of young and intermediate population stars with masses in the range of 1.4 to 3.8 M ☉. This new sample has been combined with five SMC eclipsing binaries previously published by our team. Distances to the binary systems were calculated using a surface brightness—color calibration. The targets form an elongated structure, highly inclined to the plane of the sky. The distance difference between the nearest and most-distant system amounts to 10 kpc with the line-of-sight depth reaching 7 kpc. We find tentative evidence of the existence of a spherical stellar substructure (core) in the SMC coinciding with its stellar center, containing about 40% of the young and intermediate age stars in the galaxy. The radial extension of this substructure is ∼1.5 kpc. We derive a distance to the SMC center of D SMC = 62.44 ± 0.47 (stat.) ± 0.81 (syst.) kpc corresponding to a distance modulus (m − M)SMC = 18.977 ± 0.016 ± 0.028 mag, representing an accuracy of better than 2%.