- ID:
- ivo://CDS.VizieR/J/A+AS/123/135
- Title:
- Spectral classifications of 180 IR stars
- Short Name:
- J/A+AS/123/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 180 supposedly composite-spectrum stars has been studied on the basis of spectra obtained in the near infrared (8370-8780{AA}) at a dispersion of 33{AA}/mm. The objective was to study the cooler components of the systems. Of our sample, 120 are true composite spectra, 35 are hot spectra of types B, F and 25 are Am stars. We find a strong concentration of the cooler components of the composite spectra around G8III. In view of the difficulty of classifying composite spectra, because of the superposition of an early type dwarf and a late type giant or supergiant spectrum, we have made several tests to control the classification based upon the infrared region. Since all tests gave positive results, we conclude that our classifications can be considered as being both reliable and homogeneous.
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Search Results
- 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/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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/1925
- Title:
- Spectrocopic Binarity of O and B type stars
- Short Name:
- J/MNRAS/424/1925
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation of stars above about 20M_{sun}_ and their apparently high multiplicity remain heavily debated subjects in astrophysics. We have performed a vast high-resolution radial velocity spectroscopic survey of about 250 O- and 540 B-type stars in the southern Milky Way which indicates that the majority of stars (>82%) with masses above 16M_{sun}_ form close binary systems while this fraction rapidly drops to 20% for stars of 3M_{sun}_. The binary fractions of O-type stars among different environment classes are: clusters (72+/-13%), associations (73+/-8%), field (43+/-13%) and runaways (69+/-11%). The high frequency of close pairs with components of similar mass argues in favour of a multiplicity originating from the formation process rather than from a tidal capture in a dense cluster. The high binary frequency of runaway O stars that we found in our survey (69% compared to 19-26% in previous surveys) points to the importance of ejection from young star clusters and thus supports the competitive accretion scenario.
- ID:
- ivo://CDS.VizieR/J/A+A/442/211
- Title:
- Spectroscopic distances of 322 NLTT stars
- Short Name:
- J/A+A/442/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distance estimates based on low-resolution spectroscopy and Two Micron All Sky Survey (2MASS, Cat. <II/246>) J magnitudes are presented for 322 nearby candidates from Luyten's NLTT catalogue (<I/98>). Mainly relatively bright (typically 7<Ks<11) and red high proper motion stars have been selected according to their 2MASS magnitudes and optical-to-infrared colours (+1<R-Ks<+7). Some LHS stars previously lacking spectroscopy have also been included. We have classified the majority of the objects as early-M dwarfs (M2-M5). More than 70% of our targets turned out to lie within the 25pc horizon of the catalogue of nearby stars, with 50 objects placed within 15pc and 8 objects being closer than 10pc. Three objects in the 10pc sample have no previously published spectral type: LP 876-10 (M4), LP 870-65 (M4.5), and LP 869-26 (M5). A large fraction of the objects in our sample (57%) ave independent distance estimates, mainly by the recent efforts of Reid and collaborators. Our distance determinations are generally in good agreement with theirs. 11 rather distant (d>100pc) objects have also been identified, including a probable halo, but relatively hot (Teff=13000K) white dwarf (LHS 1200) and 10 red dwarfs with extremely large tangential velocities (250<v_t_<1150km/s). Altogether, there are 11 red dwarfs (including one within 70pc) with tangential velocities larger than about 250km/s. All these objects are suspected to be in fact subdwarfs, if so, their distances would be only about half of our original estimates. The three most extreme objects in that respect are the K and early M dwarfs LP 323-168, LHS 5343 and LP 552-21 with corrected distances between 180pc and 400pc and resulting tangential velocities still larger than about 400km/s.
- ID:
- ivo://CDS.VizieR/III/53
- Title:
- Stars classified from S2/68 UV line features
- Short Name:
- III/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog provides the spectral classifications of 1900 stars from the papers listed in References. The classifications were made from spectra obtained by the S2/68 sky survey telescope experiment aboard the TD1 satellite.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A104
- Title:
- Stellar parameters of OB stars in SMC wing
- Short Name:
- J/A+A/625/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars which start their lives with spectral types O and early-B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of 320 massive stars of spectral types O (23 stars) and B (297 stars) in the Wing of the Small Magellanic Cloud (SMC). The spectra, which we obtained with the ESO Very Large Telescope, were analyzed using state-of-the-art stellar atmosphere models, and the stellar parameters were determined. We find that the stellar winds of our sample stars are generally much weaker than theoretically expected. The stellar rotation rates show broad, tentatively bi-modal distribution. The upper Hertzsprung-Russell diagram (HRD) is well populated by the stars of our sample from a specific field in the SMC Wing. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additionally massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggest a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below ~30M_{sun}_ seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, stars with initially more than ~30M_{sun}_ol appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measure the key parameters of stellar feedback and establish the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments the stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of stochastic mode of massive star-formation, where the resulting stellar population is fully capable of producing large scale structures like the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long time scales.
- ID:
- ivo://CDS.VizieR/III/18B
- Title:
- Stellar Spectra Classified in Morgan-Keenan System
- Short Name:
- III/18B
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of this catalog is to provide bibliographic references to spectral classifications of stars in the Morgan-Keenan system published in the literature prior to January 1963. The catalog includes, with few exceptions, only objects contained in the Durchmusterungen: BD, SD, CD, and CPD. Objects belonging to stellar clusters and extragalactic nebulae were excluded from the catalog if they are not listed in the Durchmusterungen. The catalog includes sequential numbers, HD and DM numbers, right ascension and declination (B1900.0), magnitudes, spectral classifications, and bibliographic references. This machine-readable version was modified and corrected with errata at the Astronomical Data Center/Goddard Space Flight Center, NASA/Goddard Space Flight Center.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/38.129
- Title:
- Stellar Spectral Classification. II.
- Short Name:
- J/other/RMxAA/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The method developed by Stock & Stock (1999RMxAA..35..143S) for stars of spectral types A to K to derive absolute magnitudes and intrinsic colors from the equivalent widths of absorption lines in stellar spectra is extended to B-type stars. Spectra of this type of stars for which the Hipparcos catalogue gives parallaxes with an error of less than 20% were observed with the CIDA 1-meter reflector equipped with a Richardson spectrograph with a Thompson 576x384 CCD detector. The dispersion is 1.753{AA}/pixel using a 600 lines/mm grating in the first order. In order to cover the spectral range 3850{AA} to 5750{AA} the grating had to be used in two different positions, with an overlap in the region from 4800{AA} to 4900{AA}. A total of 116 stars was observed, but not all with both grating positions. A total of 12 measurable absorption lines were identified in the spectra and their equivalent widths were measured. These were related to the absolute magnitudes derived from the Hipparcos catalogue and to the intrinsic colors (deduced from the MK spectral types) using linear and second order polynomials and two or three lines as independent variables. The best solutions were obtained with polynomials of three lines, reproducing the absolute magnitudes with an average residual of about 0.40 magnitudes and the intrinsic colors with an average residual of 0.016 magnitudes.
- ID:
- ivo://CDS.VizieR/III/147
- Title:
- Studies of LMC stellar content
- Short Name:
- III/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectral survey has been made during the period 1971 to 1975 with the ESO 40cm astrograph at La Silla, equipped with its normal prism, giving an intermediate dispersion of 95Angstroem/mm at 4026Angstroem. Long exposure plates taken directly or with an interference filter enabled us to obtain spectral types for nearly 1600 stars. In parallel, a V photographic survey has been carried out during the same period with the same astrograph and has led to the determination of V magnitudes for more that 700 stars having no previous photometric data. New spectroscopic and photometric results as well as previous photoelectric UBV values are given in the catalogue together with additional remarks concerning peculiarities of spectra, V magnitudes, and details on double and multiple systems.
