- ID:
- ivo://CDS.VizieR/J/AJ/126/1455
- Title:
- 2MASS photometry of hot subdwarf stars
- Short Name:
- J/AJ/126/1455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Utilizing the Two Micron All Sky Survey (2MASS) Second Incremental Data Release Catalog, we have retrieved near-IR magnitudes for several hundred hot subdwarfs (sdO and sdB stars) drawn from the Catalogue of Spectroscopically Identified Hot Subdwarfs by Kilkenny et al. (1988SAAOC..12....1K). This sample size greatly exceeds that of previous studies of hot subdwarfs. Examining 2MASS photometry alone or in combination with visual photometry (Johnson BV or Stroemgren uvby) available in the literature, we show that it is possible to identify hot subdwarf stars that exhibit atypically red IR colors, which can be attributed to the presence of an unresolved late-type companion. Utilizing this large sample, we attempt for the first time to define an approximately volume-limited sample of hot subdwarfs. We discuss the considerations, biases, and difficulties in defining such a sample. We find that, of the hot subdwarfs in Kilkenny et al. (1988SAAOC..12....1K), about 40% in a magnitude-limited sample have colors that are consistent with the presence of an unresolved late-type companion. Binary stars are overrepresented in a magnitude-limited sample. In an approximately volume-limited sample the fraction of composite-color binaries is about 30%.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/404/689
- Title:
- Metallicities of Slowly Pulsating B stars
- Short Name:
- J/A+A/404/689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derived the stellar parameters (angular diameters, effective temperatures, metallicities) and interstellar reddenings for 20 Slowly Pulsating B (SPB) and 34 reference stars observed during the IUE satellite mission. The parameters were derived by means of an algorithmic procedure of fitting theoretical flux distributions to the low-resolution IUE spectra and optical spectrophotometric observations. Since the metallicity [m/H] has a special importance for pulsating B type stars, we focused our attention on that parameter. We found that the mean value of the metallicity of the considered SPB and reference stars amounts to [m/H]~-0.20. The results only slightly depend on the reduction procedure used for the IUE images (NEWSIPS and INES). The metal abundances obtained in this paper are in accordance with the average value of -0.2dex for stars in the solar neighborhood recently reported by other investigators.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1793
- Title:
- Metallicity calibrations for UBV photometry
- Short Name:
- J/MNRAS/371/1793
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Calibrations are presented here for metallicity ([Fe/H]) in terms of the ultraviolet excess, [{Delta}(U-B) at B-V=0.6, hereafter D0.6], and also for the absolute visual magnitude (M_V_) and its difference with respect to the Hyades ({Delta}M^H^_V_) in terms of D0.6 and (B-V), making use of high-resolution spectroscopic abundances from the literature and Hipparcos parallaxes.
- ID:
- ivo://CDS.VizieR/J/AJ/106/1839
- Title:
- Metal-rich halo A stars
- Short Name:
- J/AJ/106/1839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of spectrophotometry of the Ca II K and Balmer lines and radial velocity measurements for stars earlier than type F0, with 10<V<15.5 in fields at (l;b)=(90deg, 270deg; -45deg) are reported. Slit spectroscopy of 320 stars shows that in this magnitude range there are ~80 stars with [Fe/H]>-0.5. The metal-rich population has a vertical scale height of ~600pc and a space density at the Sun equal to 1/225 of the young thin disk A star population. The metal-rich A stars have V_rot_=210+/-60km/s with decreasing angular momentum as a function of distance from the Galactic plane. The line-of-sight velocity dispersion is 40+/-3km/s indicating an anomalous relation between structure and kinematics. There is strong evidence that these stars are identical in properties to the metal-rich extended populations found by Perry [1969AJ.....74..139P] at the NGP and Rodgers [1971ApJ...165..581R] at the SGP.
- ID:
- ivo://CDS.VizieR/J/AJ/139/59
- Title:
- Milky Way halo velocity dispersion profile
- Short Name:
- J/AJ/139/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic sample of 910 distant halo stars from the Hypervelocity Star survey from which we derive the velocity dispersion profile of the Milky Way halo. The sample is a mix of 74% evolved horizontal branch stars and 26% blue stragglers. We estimate distances to the stars using observed colors, metallicities, and stellar evolution tracks. Our sample contains twice as many objects with R>50kpc as previous surveys. We compute the velocity dispersion profile in two ways: with a parametric method based on a Milky Way potential model and with a non-parametric method based on the caustic technique originally developed to measure galaxy cluster mass profiles. The resulting velocity dispersion profiles are remarkably consistent with those found by two independent surveys based on other stellar populations: the Milky Way halo exhibits a mean decline in radial velocity dispersion of -0.38+/-0.12km/s/kpc over 15<R<75kpc. This measurement is a useful basis for calculating the total mass and mass distribution of the Milky Way halo.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/2432
- Title:
- MiMeS magnetic analysis of O-type stars
- Short Name:
- J/MNRAS/465/2432
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis performed on spectropolarimetric data of 97 O-type targets included in the framework of the Magnetism in Massive Stars (MiMeS) Survey. Mean least-squares deconvolved Stokes I and V line profiles were extracted for each observation, from which we measured the radial velocity, rotational and non-rotational broadening velocities, and longitudinal magnetic field B_l_. The investigation of the Stokes I profiles led to the discovery of two new multiline spectroscopic systems (HD 46106, HD 204827) and confirmed the presence of a suspected companion in HD 37041. We present a modified strategy of the least-squares deconvolution technique aimed at optimizing the detection of magnetic signatures while minimizing the detection of spurious signatures in Stokes V. Using this analysis, we confirm the detection of a magnetic field in six targets previously reported as magnetic by the MiMeS collaboration (HD 108, HD 47129A2, HD 57682, HD 148937, CPD-28 2561, and NGC 1624-2), as well as report the presence of signal in Stokes V in three new magnetic candidates (HD 36486, HD 162978, and HD 199579). Overall, we find a magnetic incidence rate of 7+/-3 per cent, for 108 individual O stars (including all O-type components part of multiline systems), with a median uncertainty of the B_l_ measurements of about 50G. An inspection of the data reveals no obvious biases affecting the incidence rate or the preference for detecting magnetic signatures in the magnetic stars. Similar to A- and B-type stars, we find no link between the stars' physical properties (e.g. T_eff_, mass, and age) and the presence of a magnetic field. However, the Of?p stars represent a distinct class of magnetic O-type stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/2
- Title:
- MiMeS survey of magnetism in massive stars
- Short Name:
- J/MNRAS/456/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The MiMeS (Magnetism in Massive Stars) project is a large-scale, high-resolution, sensitive spectropolarimetric investigation of the magnetic properties of O- and early B-type stars. Initiated in 2008 and completed in 2013, the project was supported by three Large Program allocations, as well as various programmes initiated by independent principal investigators, and archival resources. Ultimately, over 4800 circularly polarized spectra of 560 O and B stars were collected with the instruments ESPaDOnS (Echelle SpectroPolarimetric Device for the Observation of Stars) at the Canada-France-Hawaii Telescope, Narval at the Telescope Bernard Lyot and HARPSpol at the European Southern Observatory La Silla 3.6m telescope, making MiMeS by far the largest systematic investigation of massive star magnetism ever undertaken. In this paper, the first in a series reporting the general results of the survey, we introduce the scientific motivation and goals, describe the sample of targets, review the instrumentation and observational techniques used, explain the exposure time calculation designed to provide sensitivity to surface dipole fields above approximately 100G, discuss the polarimetric performance, stability and uncertainty of the instrumentation, and summarize the previous and forthcoming publications.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A93
- Title:
- Multiwavelength fluxes of RCW120
- Short Name:
- J/A+A/600/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The expansion of HII regions can trigger the formation of stars. An overdensity of young stellar objects (YSOs) is observed at the edges of HII regions but the mechanisms that give rise to this phenomenon are not clearly identified. Moreover, it is difficult to establish a causal link between HII-region expansion and the star formation observed at the edges of these regions. A clear age gradient observed in the spatial distribution of young sources in the surrounding might be a strong argument in favor of triggering. We have observed the Galactic HII region RCW120 with Herschel PACS and SPIRE photometers at 70, 100, 160, 250, 350 and 500um. We produced temperature and H_2_ column density maps and use the getsources algorithm to detect compact sources and measure their fluxes at Herschel wavelengths. We have complemented these fluxes with existing infrared data. Fitting their spectral energy distributions (SEDs) with a modified blackbody model, we derived their envelope dust temperature and envelope mass. We computed their bolometric luminosities and discuss their evolutionary stages. The Herschel data, with their unique sampling of the far infrared domain, have allowed us to characterize the properties of compact sources observed towards RCW120 for the first time. We have also been able to determine the envelope temperature, envelope mass and evolutionary stage of these sources. Using these properties we have shown that the density of the condensations that host star formation is a key parameter of the star-formation history, irrespective of their projected distance to the ionizing stars.
- ID:
- ivo://CDS.VizieR/II/26A
- Title:
- Narrow-band photometry of early-type stars
- Short Name:
- II/26A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A compilation of the photoelectric measurements in the Barbier-Morguleff system is presented for 773 stars of spectral types O8 to F6. 706 stars have been measured at least twice. The passbands (in Angstroems) and the mean photometric errors of the indexes C(j)-C(2) (in magnitudes) are: ----------------------- Band Interval m.e. ----------------------- C(1) 6000-5900 0.0318 C(2) 5000-4900 --- C(3) 4905-4815 0.0073 C(4) 4380-4310 0.0100 C(5) 4070-4010 0.0102 C(6) 3965-3925 0.0201 C(7) 3780-3720 0.0195 C(8) 3650-3575 0.0189 ----------------------- Regarding the catalog Pass Bands Morguleff and Gerbaldi (1975) note the following: These spectral intervals permit the determination of certain physical characteristics .... The pass bands 1 and 5 lead us to calculate red and blue gradients. The equivalent widths of the H(beta), H(gamma) lines of hydrogen and the K lines of Ca II are derived from band 3, 4, and 6. Bands 7 and 8 measure the Balmer jump. Listed in the catalog file are the normalized magnitudes corresponding to the above pass bands. The normalized magnitude of a pass band, C(j), is defined as the color index of the magnitude in the band minus the magnitude of the second band, C(2). See Morguleff and Gerbaldi (1975) for a brief discussion of conservation of the system and mean errors across all stars.
- ID:
- ivo://CDS.VizieR/J/A+A/487/307
- Title:
- Nearby B-type stars abundances
- Short Name:
- J/A+A/487/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent downward revision of the solar photospheric abundances now leads to severe inconsistencies between the theoretical predictions for the internal structure of the Sun and the results of helioseismology. There have been claims that the solar neon abundance may be underestimated and that an increase in this poorly-known quantity could alleviate (or even completely solve) this problem. Early-type stars in the solar neighbourhood are well-suited to testing this hypothesis because they are the only stellar objects whose absolute neon abundance can be derived from the direct analysis of photospheric lines. Here we present a fully homogeneous NLTE abundance study of the optical Ne I and Ne II lines in a sample of 18 nearby, early B-type stars, which suggests log[epsilon(Ne)]=7.97+/-0.07dex (on the scale in which log[epsilon(H)=12)]) for the present-day neon abundance of the local ISM. Chemical evolution models of the Galaxy only predict a very small enrichment of the nearby interstellar gas in neon over the past 4.6Gyr, implying that our estimate should be representative of the Sun at birth. Although higher by about 35% than the new recommended solar abundance, such a value appears insufficient by itself to restore the past agreement between the solar models and the helioseismological constraints.
