Search

Start Over Capability Type Simple Cone Search
2911. Classification of IRS sources in the SMC
ID:
ivo://CDS.VizieR/J/MNRAS/451/3504
Title:
Classification of IRS sources in the SMC
Short Name:
J/MNRAS/451/3504
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Magellanic clouds are uniquely placed to study the stellar contribution to dust emission. Individual stars can be resolved in these systems even in the mid-infrared, and they are close enough to allow detection of infrared excess caused by dust. We have searched the Spitzer Space Telescope data archive for all Infrared Spectrograph (IRS) staring-mode observations of the Small Magellanic Cloud (SMC) and found that 209 Infrared Array Camera (IRAC) point sources within the footprint of the Surveying the Agents of Galaxy Evolution in the Small Magellanic Cloud (SAGE-SMC) Spitzer Legacy programme were targeted, within a total of 311 staring mode observations. We classify these point sources using a decision tree method of object classification, based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information. We find 58 asymptotic giant branch (AGB) stars, 51 young stellar objects (YSOs), 4 post-AGB objects, 22 Red Supergiants (RSGs), 27 stars (of which 23 are dusty OB stars), 24 planetary nebulae (PNe), 10 Wolf-Rayet (WR) stars, 3 HII regions, 3 R Coronae Borealis (R CrB) stars, 1 Blue Supergiant and 6 other objects, including 2 foreground AGB stars. We use these classifications to evaluate the success of photometric classification methods reported in the literature.
2912. Classification of LAMOST DR4 galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/474/1873
Title:
Classification of LAMOST DR4 galaxies
Short Name:
J/MNRAS/474/1873
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the classification and composite spectra of galaxies in the fourth data release (DR4) of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST). We select 40182 spectra of galaxies from LAMOST DR4, which have photometric information but no spectroscopic observations in the Sloan Digital Sky Survey (SDSS). These newly observed spectra are recalibrated and classified into six classes - passive, H{alpha}-weak, star-forming, composite, LINER and Seyfert - using the line intensity (H{beta}, [OIII] 5007, H{alpha} and [NII] 6585). We also study the correlation between spectral class and morphological type through three parameters: concentration index, (u-r) colour and D4000n index. We calculate composite spectra of high signal-to-noise ratio (S/N) for six spectral classes and, using these composites, we pick out some features that can differentiate the classes effectively, including H{beta}, Fe5015, H{gamma}A, HK and the Mg2 band. In addition, we compare our composite spectra with the SDSS ones and analyse their differences. A galaxy catalogue of 40182 newly observed spectra (36601 targets) and the composite spectra of the six classes are available online (http://sciwiki.lamost.org/downloads/wll).
2913. Classification of Late Type Stars
ID:
ivo://CDS.VizieR/J/MNRAS/286/500
Title:
Classification of Late Type Stars
Short Name:
J/MNRAS/286/500
Date:
21 Oct 2021
Publisher:
CDS
Description:
Energy distributions for 33 galactic (super)giants situated mostly in the southern Milky Way in the range from 4800 to 7700 Angstroems with an effective resolution of 10 Angstroems are presented here. The observations and reductions are described in the paper. The errors of the absolute and relative flux calibration are 0.028 and 0.021 mag, respectively. The S/N ratio is at least 80 for each star. Cross references, MK classifications and spectral indices one may find in the paper. Further informations are available at M.O.Oestreicher (mio@astro.ruhr-uni-bochum.de). The data are given in three files: 1) stars.dat A list of the programme stars listing the HD/HDE numbers, MK types and positions related to J2000 2) absolute.dat A list of absolute fluxes for each star observed under photometric conditions (18 stars). The fluxes are given in magnitudes according to the system of Hayes & Latham (1975). A monochromatic magnitude of 0.00 corresponds to a flux of 3.5x10^-20^ erg.cm-2.s-1.Hz-1, (3.5x10^-23^ W/m2/Hz), i.e. the fluxes are related to FREQUENCY INTERVALS. 3) relative.dat A list of relative fluxes for each star observed in nights of low quality (15 stars). The fluxes are normalized to 1 at 5555 Angstr. and are related to WAVELENGTH INTERVALS.
2914. Classification of nearby galaxies
ID:
ivo://CDS.VizieR/J/ApJS/147/1
Title:
Classification of nearby galaxies
Short Name:
J/ApJS/147/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
A major problem in extragalactic astronomy is the inability to distinguish in a robust, physical, and model-independent way how galaxy populations are physically related to each other and to their formation histories. A similar, but distinct, and also long-standing question is whether the structural appearances of galaxies, as seen through their stellar light distributions, contain enough physical information to offer this classification. We argue through the use of 240 images of nearby galaxies that three model-independent parameters measured on a single galaxy image reveal its major ongoing and past formation modes and can be used as a robust classification system. These parameters quantitatively measure: the concentration (C), asymmetry (A), and clumpiness (S) of a galaxy's stellar light distribution. When combined into a three-dimensional "CAS" volume all major classes of galaxies in various phases of evolution are cleanly distinguished. We argue that these three parameters correlate with important modes of galaxy evolution: star formation and major merging activity. This is argued through the strong correlation of H{alpha} equivalent width and broadband colors with the clumpiness parameter S, the uniquely large asymmetries of 66 galaxies undergoing mergers, and the correlation of bulge to total light ratios, and stellar masses, with the concentration index. As an obvious goal is to use this system at high redshifts to trace evolution, we demonstrate that these parameters can be measured, within a reasonable and quantifiable uncertainty with available data out to z~3 using the Hubble Space Telescope GOODS ACS and Hubble Deep Field images.
2915. Classification of nova light curves
ID:
ivo://CDS.VizieR/J/AJ/140/34
Title:
Classification of nova light curves
Short Name:
J/AJ/140/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 93 very-well-observed nova light curves. The light curves were constructed from 229,796 individual measured magnitudes, with the median coverage extending to 8.0mag below peak and 26% of the light curves following the eruption all the way to quiescence. Our time-binned light curves are presented in figures and as complete tabulations. We also calculate and tabulate many properties about the light curves, including peak magnitudes and dates, times to decline by 2, 3, 6, and 9mag from maximum, the time until the brightness returns to quiescence, the quiescent magnitude, power-law indices of the decline rates throughout the eruption, the break times in this decline, plus many more properties specific to each nova class. We present a classification system for nova light curves based on the shape and the time to decline by 3mag from the peak (t3). The designations are "S" for smooth light curves (38% of the novae), "P" for plateaus (21%), "D" for dust dips (18%), "C" for cusp-shaped secondary maxima (1%), "O" for quasi-sinusoidal oscillations superposed on an otherwise smooth decline (4%), "F" for flat-topped light curves (2%), and "J" for jitters or flares superposed on the decline (16%). Our classification consists of this single letter followed by the t3 value in parentheses; so, for example, V1500 Cyg is S(4), GK Per is O(13), DQ Her is D(100), and U Sco is P(3).
2916. Classification of planetary nebulae
ID:
ivo://CDS.VizieR/J/A+A/475/217
Title:
Classification of planetary nebulae
Short Name:
J/A+A/475/217
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we present a re-analysis of the criteria used to characterize the Peimbert classes I, IIa, IIb, III and IV, through a statistical study of a large sample of planetary nebulae previously classified according to these groups. In the original classification, it is usual to find planetary nebulae that cannot be associated with a single type; these most likely have dubious classifications into two or three types. Statistical methods can greatly contribute in providing a better characterization of planetary nebulae groups. We use the Bayes Theorem to calculate the posterior probabilities for an object to be member of each of the types I, IIa, IIb, III and IV. This calculation is particularly important for planetary nebulae that are ambiguously classified in the traditional method. The posterior probabilities are defined from the probability density function of classificatory parameters of a well-defined sample, composed only by planetary nebulae unambiguously fitted into the Peimbert types. Because the probabilities depend on the available observational data, they are conditional probabilities, and, as new observational data are added to the sample, the classification of the nebula can be improved, to take into account this new information. This method differs from the original classificatory scheme, because it provides a quantitative result of the representativity of the object within its group. Also, through the use of marginal distributions it is possible to extend the Peimbert classification even to those objects for which only a few classificatory parameters are known.
2917. Classification of RASS optical counterparts
ID:
ivo://CDS.VizieR/J/AJ/133/2495
Title:
Classification of RASS optical counterparts
Short Name:
J/AJ/133/2495
Date:
21 Oct 2021
Publisher:
CDS
Description:
Previous work (Rutledge et al., 2000ApJS..131..335R) statistically identified 5492 optical counterparts, with >~90% confidence, from among the ~18000 X-ray sources appearing in the ROSAT All-Sky Survey Bright Source Catalog (RASS BSC; Voges et al. 1999, Cat. <IX/10>). Using low-resolution spectra in the wavelength range 3700-7900{AA}, we present spectroscopic classifications for 195 of these counterparts which have not previously been classified. Of these 195, we find 168 individual stars of F, G, K, or M type, 6 individual stars of unknown type, 6 double stars, 6 AGNs or galaxies, and 7 unclassifiable objects; the spectra of the 2 remaining objects were saturated.
2918. Classification of sources from the 2XMMi-DR3 cat.
ID:
ivo://CDS.VizieR/J/ApJ/756/27
Title:
Classification of sources from the 2XMMi-DR3 cat.
Short Name:
J/ApJ/756/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
We carry out classification of 4330 X-ray sources in the 2XMMi-DR3 catalog. They are selected under the requirement of being a point source with multiple XMM-Newton observations and at least one detection with the signal-to-noise ratio larger than 20. For about one-third of them we are able to obtain reliable source types from the literature. They mostly correspond to various types of stars (611), active galactic nuclei (AGNs, 753), and compact object systems (138) containing white dwarfs, neutron stars, and stellar-mass black holes. We find that about 99% of stars can be separated from other source types based on their low X-ray-to-IR flux ratios and frequent X-ray flares. AGNs have remarkably similar X-ray spectra, with the power-law photon index centered around 1.91+/-0.31, and their 0.2-4.5keV flux long-term variation factors have a median of 1.48, with 98.5% being less than 10. In contrast, 70% of compact object systems can be very soft or hard, highly variable in X-rays, and/or have very large X-ray-to-IR flux ratios, separating them from AGNs. Using these results, we derive a source type classification scheme to classify the other sources and find 644 candidate stars, 1376 candidate AGNs, and 202 candidate compact object systems, whose false identification probabilities are estimated to be about 1%, 3%, and 18%, respectively. There are still 320 sources associated with nearby galaxies and 151 in the Galactic plane, which we expect to be mostly compact object systems or background AGNs. We also have 100 candidate ultraluminous X-ray sources. They are found to be much less variable than other accreting compact objects.
2919. Classification of stellar spectra 644-681nm
ID:
ivo://CDS.VizieR/J/A+A/566/A50
Title:
Classification of stellar spectra 644-681nm
Short Name:
J/A+A/566/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of spectral diagnostics available from optical spectra with R=17000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the {gamma} Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the H{alpha} line core and wings, and temperature- and gravity-sensitive sets of lines, each useful as a Teff or logg indicator over a limited range of stellar spectral types. H{alpha} line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global Teff- and logg-sensitive indices {tau} and {gamma}, valid for the entire range of types in the observed sample.
2920. Classification of Swift and XMM-Newton sources
ID:
ivo://CDS.VizieR/J/A+A/657/A138
Title:
Classification of Swift and XMM-Newton sources
Short Name:
J/A+A/657/A138
Date:
22 Feb 2022
Publisher:
CDS
Description:
With the advent of very large X-ray surveys, an automated classification of X-ray sources becomes increasingly valuable. This work proposes a revisited naive Bayes classification of the X-ray sources in the Swift-XRT and XMM- Newton catalogs into four classes - AGN, stars, X-ray binaries (XRBs), and cataclysmic variables (CVs) - based on their spatial, spectral, and timing properties and their multiwavelength counterparts. An outlier measure is used to identify objects of other natures. The classifier is optimized to maximize the classification performance of a chosen class (here XRBs), and it is adapted to data mining purposes. We augmented the X-ray catalogs with multiwavelength data, source class, and variability properties. We then built a reference sample of about 25000 X-ray sources of known nature. From this sample, the distribution of each property was carefully estimated and taken as reference to assign probabilities of belonging to each class. The classification was then performed on the whole catalog, combining the information from each property. Using the algorithm on the Swift reference sample, we retrieved 99%, 98%, 92%, and 34% of AGN, stars, XRBs, and CVs, respectively, and the false positive rates are 3%, 1%, 9%, and 15%. Similar results are obtained on XMM sources. When applied to a carefully selected test sample, representing 55% of the X-ray catalog, the classification gives consistent results in terms of distributions of source properties. A substantial fraction of sources not belonging to any class is efficiently retrieved using the outlier measure, as well as AGN and stars with properties deviating from the bulk of their class. Our algorithm is then compared to a random forest method; the two showed similar performances, but the algorithm presented in this paper improved insight into the grounds of each classification. This robust classification method can be tailored to include additional or different source classes and can be applied to other X-ray catalogs. The transparency of the classification compared to other methods makes it a useful tool in the search for homogeneous populations or rare source types, including multi-messenger events. Such a tool will be increasingly valuable with the development of surveys of unprecedented size, such as LSST, SKA, and Athena, and the search for counterparts of multi-messenger events.

Limit your search

more »

more »

more »

more »

more »

more »