- ID:
- ivo://CDS.VizieR/J/A+A/614/A40
- Title:
- Spectral significance for 15 delta Scuti
- Short Name:
- J/A+A/614/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is known that the observed distribution of frequencies in CoRoT and Kepler {delta} Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip such as {delta} Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, just in the range of the pulsational frequency content of the {delta} Scuti stars, is shown to be crucial to determine their oscillation frequencies, the first step to perform asteroseismology of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of {delta} Scuti stars. We select a sample of 15 {delta} Scuti stars observed by the CoRoT satellite, for which ultra-high quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of {delta} Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and data with gaps interpolated using Autoregressive and Moving Average models (ARMA). The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. Therefore, in order to reduce the effect of the spectral window to the minimum it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content, and not only to perform a pre-whitening of the data.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AZh/82/420
- Title:
- Spectral study of 19 radio sources
- Short Name:
- J/AZh/82/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical identifications, classifications, and radio spectra of 19 radio sources from a complete sample in flux-density with the declinations 10{deg}-12{deg}30' (J2000) obtained with the 6-m optical telescope (4000-9000{AA}) and RATAN-600 radio telescope (0.97-21.7GHz) of the Special Astrophysical Observatory. Twelve objects with redshifts from 0.573-2.694 have been classified as quasars, and two objects with featureless spectra as BL Lac objects. Four objects are emission-line radio galaxies with redshifts from 0.204 to 0.311, one object is an absorption-line radio galaxy with redshift 0.214. Radio flux densities have been obtained at six frequencies for all sources except for two extended objects. The radio spectra of five of the sources can be separated into extended and compact components. Three objects display substantial rapid and long-term variability of their flux densities.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/295
- Title:
- Spectral survey of Case emission-line galaxies
- Short Name:
- J/A+AS/131/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of the follow-up spectroscopy of 178 emission-line galaxy (ELG) candidates from the Case objective-prism survey and nine Markarian galaxies with the 6m telescope are described. Only the candidates classified in the Case survey as those with emission lines were observed with the aim to form a statistical sample of blue compact galaxies (BCGs) with strong emission lines in the zone RA: 8h-16h, and DE: =+29deg-+38deg. We present the redshifts, equivalent widths and flux ratios for the strongest lines and the spectrum type for most of the galaxies with detected emission lines. A significant fraction (about 23%) of the observed Case galaxies do not show emission lines in blue. Preliminary analysis of the data is presented and the properties of the observed ELGs are compared with those of other known samples.
- ID:
- ivo://CDS.VizieR/III/40A
- Title:
- Spectral Survey of Southern Milky Way
- Short Name:
- III/40A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectral survey, carried out at the Stockholm Observatory, was initiated by B. Lindblad. The observational material was obtained by L.O. Loden, K. Loden and others in the years 1956-1965, when the Stockholm Observatory took part in a joint enterprise for using the Harvard-Boyden station. The Swedish Natural Science Research Council, the Royal Academy of the Sciences, and the K. and A. Wallenberg Foundation funded the observations, which are based on both direct and objective prism plates. The data were published in three parts, the first having less precise positions than the others. The coordinates for Catalogue I (3033) were later recomputed with the same reduction procedure as Catalogues II (3034) and III (3035), making the present catalogue uniform (Andersen, 1977). The files include star identification, finding chart identification, RA and Dec, galactic longitude and latitude, spectral type, blue magnitude, visual magnitude and remarks. The data concerning the part 2 were revised by Brian Skiff in November 1996 (see the "History" section below)
- ID:
- ivo://CDS.VizieR/J/ApJ/676/286
- Title:
- Spectral templates for galaxies from 0.2 to 10um
- Short Name:
- J/ApJ/676/286
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We built an optimal basis of low-resolution templates for galaxies over the wavelength range from 0.2 to 10um using a variant of the algorithm presented by Budavari and coworkers. We derived them using 11 bands of photometry from the NDWFS, FLAMEX, zBootes, and IRAC Shallow surveys for 16033 galaxies in the NDWFS Bootes field with spectroscopic redshifts measured by the AGN and Galaxy Evolution Survey. We also developed algorithms to accurately determine photometric redshifts, K-corrections, and bolometric luminosities using these templates. Our photometric redshifts have an accuracy of sigma_z_/(1+z)=0.04 when clipped to the best 95%. We used these templates to study the spectral type distribution in the field and to estimate luminosity functions of galaxies as a function of redshift and spectral type. In particular, we note that the 5-8um color distribution of galaxies is bimodal, much like the optical g-r colors.
- ID:
- ivo://CDS.VizieR/III/267
- Title:
- Spectral types from Uppsala Observatory
- Short Name:
- III/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The two papers compiled here contain spectral types for about 2600 stars in two regions near +20 deg and +40 deg galactic latitude at far-northern Declination. The +20 deg latitude region extends from about RA 19h30m to 0h00m; the +40 deg latitude region extends from about RA 10h to 15h45m. Each zone is about 5 deg in width and the faintest stars are about V mag 11. This includes nearly all BD stars plus many fainter ones. A statistical study of these stars was presented in a third paper (1954ArA.....1..483S). The source material consists of objective-prism plates taken between 1934 and 1940 with the Zeiss-Heyde astrograph (15cm aperture f/10 triplet) of the Uppsala Observatory. The 9.7-deg prism gave a dispersion of 1.4mm between H-gamma and H-epsilon, roughly 260A/mm. The stars were classified on the basis of microphotometer tracings of the spectra. For the present list only the spectral types have been preserved, and various magnitudes, line-ratios, and color-equivalents omitted. The coordinates are mainly from Tycho-2. The magnitudes close to standard V are from modern sources including Tycho-2 and the TASS MkIV survey. The Uppsala spectral types are expressed in MK notation, specifically relating to dwarf/giant discrimination via the CN bands for G and K stars, and some luminosity classification via Balmer line-widths for stars between late-B and early-A. In principle, the temperature types are matched to the HD scale. A few "new" metallic-line A-type stars are reported here as well. In addition, two mag 10 stars were identified by Schalen as type 'B'. Examination of Burrell Schmidt objective-prism plates (uv-transparent 10-degree prism, 110A/mm) shows that both are previously unrecognized B subdwarfs (BD+74 435 and BD+77 564 in the latitude +40 zone). The catalogue contains many stars not classified, for instance, in the HD or for the Yale and AGK astrometric catalogues. Similarly, large numbers of BD stars without accurate coordinates are identified here for the first time. Non-BD stars are assigned the acronyms [S48] and [S49]. There are several clerical errors in the published tables such that stars are either not the named BD star or are not recovered near the nominal coordinates. A combination of the spectral types and more recent photometric colors was used to identify candidates within about 10' radius, but a few stars remain lost.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A125
- Title:
- Spectral types of CoRoT stars
- Short Name:
- J/A+A/543/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In here we study the stellar content of the CoRoT-fields IRa01, LRa01 (=LRa06), and LRa02 by determining the spectral types of 11466 stars. Nine planet host stars have already been identified in these fields. The determination of the spectral types of thousands of stars of which CoRoT obtained high-precision light-curves also opens up a large variety of other research projects. For our study, we used spectra obtained with the multi-object spectrograph AAOmega and derived the spectral types by using template spectra with well known parameters. We find that 34.8+/-0.7% of the stars observed by CoRoT in these fields are F-dwarfs, 15.1+/-0.5% G-dwarfs, and 5.0+/-0.3% K-dwarfs. We conclude that the apparent lack of exoplanets of K- and M-stars is explained by the relatively small number of these stars in the observed sample. We also show that the apparently large number of planets orbiting F-stars is also explained by the large number of such stars in these fields. Given the number of F-stars, we would have expected to find even more planet orbiting F-stars. Our study also shows that the difference between the sample of stars that CoRoT observes and a sample of randomly selected stars is relatively small, and that the yield of CoRoT is the detection one hot Jupiter amongst 2100+/-700 stars. We finally conclude that transit search programs can be used in order to study the relation between the frequency of planets and the mass of the host stars, and that the results obtained so far are in general agreement with those of radial velocity programs.
- ID:
- ivo://CDS.VizieR/J/AJ/146/85
- Title:
- Spectral types of 1576 optical stars in ONC
- Short Name:
- J/AJ/146/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new spectral types or spectral classification constraints for over 600 stars in the Orion Nebula Cluster (ONC) based on medium resolution (R{approx}1500-2000) red optical spectra acquired using the Palomar 200" and Kitt Peak 3.5m telescopes. Spectral types were initially estimated for F, G, and early K stars from atomic line indices while for late K and M stars, which constitute the majority of our sample, indices involving TiO and VO bands were used. To ensure proper classification, particularly for reddened, veiled, or nebula-contaminated stars, all spectra were then visually examined for type verification or refinement. We provide an updated spectral type table that supersedes previous work, increasing the percentage of optically visible ONC stars with spectral type information from 68% to 90%. However, for many objects, repeated observations have failed to yield spectral types primarily due to the challenges of adequate sky subtraction against a bright and spatially variable nebular background. The scatter between our new and our previously determined spectral types is approximately two spectral sub-classes. We also compare our grating spectroscopy results with classification based on narrow-band TiO filter photometry, finding similar scatter. While the challenges of working in the ONC may explain much of the spread, we highlight several stars showing significant and unexplained bona fide spectral variations in observations taken several years apart; these and similar cases could be due to a combination of accretion and extinction changes. Finally, nearly 20% of ONC stars exhibit obvious CaII triplet emission indicative of strong accretion.
- ID:
- ivo://CDS.VizieR/III/264
- Title:
- Spectral types of stars in Coalsack region
- Short Name:
- III/264
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/541/A34
- Title:
- Spectral types of stars in CoRoT fields
- Short Name:
- J/A+A/541/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of giant stars indicate that the frequency of giant planets is much higher for intermediate-mass stars than for solar-like stars. Up to now all known planets of giant stars orbit at relatively far distances from their host stars. It is not known whether intermediate-mass stars also had many close-in planets when they were on the main sequence, which were then engulfed when the star became a giant star. To understand the formation and evolution of planets it is therefore important to find out whether main-sequence stars of intermediate-mass have close-in planets or not. A survey for transiting planets of intermediate-mass stars would be ideal to solve this question, because the detection of transiting planets is not affected by the rapid rotation of these stars. With CoRoT it is possible to detect transiting planets around stars up to a spectral type B4V. As a first step for an efficient survey we need to identify intermediate-mass stars in the CoRoT-fields, which can then be used as an input list. To compile the input list we derived the spectral types of essentially all O, B and A stars down to 14.5mag in the CoRoT fields IRa01, LRa01, LRa02 taken with the multi-object spectrograph AAOmega. We determined the spectral types by comparing the spectra with template spectra from a library. In total we identify 1856 A and B stars that have been observed with CoRoT. Using multiple spectra of these stars, we find that the accuracy of the resulting spectral classification is 1.61+/-0.14 sub-classes for A and B stars. Given the number of planets that have been detected in these fields amongst late-type stars, we estimate that there are one to four transiting planets of intermediate-mass stars waiting to be discovered. Our survey not only allows us to carry out a dedicated planet search programme but is also essential for any types of studies of the light curves of early-type stars in the CoRoT database. We also show that it would be possible to extend the survey to all fields that CoRoT has observed using photometrically determined spectral types.