- ID:
- ivo://CDS.VizieR/J/A+AS/139/231
- Title:
- Early-type stars towards the Galactic Centre
- Short Name:
- J/A+AS/139/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have begun a search for early-type stars towards the galactic centre which are potentially young objects situated within the inner few kiloparsecs of the disk. U and V (or I) band photographic photometry from the UK Schmidt Telescope has been obtained to identify the bluest candidates in nineteen Schmidt fields (centred close to the galactic centre). We have spectroscopically observed these targets for three fields with the FLAIR multi-fibre system to determine their spectral types. In particular, ten early B-type stars have been identified and equivalent width measurements of their Balmer and HeI lines have been used to estimate atmospheric parameters. These early-type objects have magnitudes in the range 11.5=<V<=16.0, and our best estimates of their distance (given probable highly variable reddening in this direction together with errors in the plate photometry) suggest that some of them originated close to (i.e R_g_<3kpc), or even beyond the galactic centre. Future high-resolution spectroscopy of these stars will provide reliable atmospheric parameters and element abundances, in order to map the current chemical composition of the inner galaxy.
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- ID:
- ivo://CDS.VizieR/J/A+A/578/A45
- Title:
- E-BOSS. II. Catalogue second release
- Short Name:
- J/A+A/578/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar bow shocks have been studied not only observationally, but also theoretically since the late 1980s. Only a few catalogues of them exist. The bow shocks show emission along all the electromagnetic spectrum, but they are detected more easily in infrared wavelengths. The release of new and high-quality infrared data eases the discovery and subsequent study of new objects. We search stellar bow-shock candidates associated with nearby runaway stars, and gather them together with those found elsewhere, to enlarge the list of the E-BOSS first release. We aim to characterize the bow-shock candidates and provide a database suitable for statistical studies. We investigate the low-frequency radio emission at the position of the bow-shock features, that can contribute to further studies of high-energy emission from these objects. We considered samples from different literature sources and searched for bow-shaped structures associated with stars in the Wide-field Infrared Survey Explorer (WISE) images. We looked for each bow-shock candidate on centimeter radio surveys. We reunited 45 bow-shock candidates and generated composed WISE images to show the emission in different infrared bands. Among them there are new sources, previously studied objects, and bow shocks found serendipitously. Five bow shocks show evidence of radio emission. Stellar bow shocks constitute an active field with open questions and enormous amounts of data to be analyzed. Future research at all wavelengths databases, and use of instruments like Gaia, will provide a more complete picture of these objects. For instance, infrared spectral energy distributions can give information about physical parameters of the bow shock matter. In addition, dedicated high-sensitivity radio observations can help to understand the radio-{gamma} connection.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2815
- Title:
- Eleven new {gamma} Doradus variables
- Short Name:
- J/AJ/129/2815
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new high-dispersion spectroscopic and precise photometric observations to identify 11 new {gamma} Doradus variables. Seven of these new Doradus stars appear to be single, three are primaries of single-lined binaries, and one has two distant visual companions; none are double-lined or close visual binaries. Several of the stars show spectroscopic line-profile and low-amplitude radial velocity variability indicative of pulsation. All 11 stars are photometrically variable with amplitudes between 8 and 93mmag in Johnson B and periods between 0.398 and 2.454 days.
- ID:
- ivo://CDS.VizieR/J/ApJS/126/461
- Title:
- Equivalent Widths in the Spectrum of Sirius
- Short Name:
- J/ApJS/126/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The equivalent widths of total 546 lines (26 elements are included) in the spectrum of the bright Am star Sirius from 380 to 930 nm are tabulated. The high-resolution, high signal-to-noise ratio spectrum was obtained with the Coude Echelle Spectrograph attached to the 2.16 m telescope at Beijing Astronomical Observatory (Xinglong, China). Here we also give the results of the equivalent widths comparison between our measurements and those of Strom et al. (=1966ApJ...146..880S) and Sadakane & Ueta (=1989PASJ...41..279S). Table 1. Observation Journal of Sirius: ---------------------------------------------------------------------------- Spectral Range Exposure Time Geocentric Radial Velocity (nm) Obs. Date (s) (km s-1) ---------------------------------------------------------------------------- 386.5-572.1 1997 Feb 18/19 180 12.75 (0.45) 383.3-661.9 1997 Feb 18/19 40+40+30 12.37 (0.96) 378.9-551.6 1997 Feb 18/19 40+40 12.31 (0.82) 380.7-649.3 1997 Feb 18/19 40+40 12.42 (0.93) 623.8-922.7 1999 Apr 01/02 300+300 15.49 (0.52) 624.8-930.4 1999 Apr 01/02 300+300 15.58 (0.69) ----------------------------------------------------------------------------
- ID:
- ivo://CDS.VizieR/J/A+A/555/A25
- Title:
- Equivalent widths of DIBs
- Short Name:
- J/A+A/555/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar spectroscopic surveys may bring useful statistical information on the links between diffuse interstellar bands (DIBs) and the interstellar environment. DIB databases can also be used as a complementary tool for locating interstellar (IS) clouds. Our goal is to develop fully automated methods of DIB measurements to be applied to extensive data from stellar surveys. We present a method that is appropriate for early-type nearby stars, along with its application to high-resolution spectra of ~130 targets recorded with the ESO FEROS spectrograph and comparisons with other determinations. Using a DIB average profile deduced from the most reddened stars, we performed an automated fitting of a combination of a smooth stellar continuum, the DIB profile, and, when necessary, a synthetic telluric transmission.
- ID:
- ivo://CDS.VizieR/J/A+A/419/1123
- Title:
- Equivalent widths of 3 post-AGB
- Short Name:
- J/A+A/419/1123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present model atmosphere analyses of high resolution Keck and VLT optical spectra for three evolved stars in globular clusters, viz. ZNG-1 in M10, ZNG-1 in M15 and ZNG-1 in NGC6712. The derived atmospheric parameters and chemical compositions confirm the programme stars to be in the post-Asymptotic Giant Branch (post-AGB) evolutionary phase.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A13
- Title:
- Evolutionary models for main-sequence phase
- Short Name:
- J/A+A/647/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification of stellar-mass black-hole mergers with up to 80M_{sun}_ as powerful sources of gravitational wave radiation led to increased interest in the physics of the most massive stars. The largest sample of possible progenitors of such objects, very massive stars (VMS) with masses up to 300M_{sun}_, have been identified in the 30 Dor star-forming region in the Large Magellanic Cloud (LMC). In this young starburst analogue, VMS were found to dominate stellar feedback. Despite their importance, the physics and evolution of VMS is highly uncertain, mainly due to their proximity to the Eddington limit. In this work, we investigate the two most important effects that are thought to occur near the Eddington limit: enhanced mass loss through optically thick winds and the formation of radially inflated stellar envelopes. We compute evolutionary models for VMS at LMC metallicity and perform a population synthesis of the young stellar population in 30 Dor. We adjust the input physics of our models to match the empirical properties of the single-star population in 30 Dor as derived in the framework of the VLT-Flames Tarantula Survey (VFTS). Enhanced mass loss and envelope inflation near the Eddington limit have a dominant effect on the evolution of the most massive stars. While the observed mass-loss properties and the associated surface He-enrichment are well described by our new models, the observed O-star mass-loss rates are found to cover a much larger range than theoretically predicted, with particularly low mass-loss rates for the youngest objects. Also, the (rotational) surface enrichment in the O-star regime appears to not be well understood. The positions of the most massive stars in the Hertzsprung-Russell diagram (HRD) are affected by mass loss and envelope inflation. For instance, the majority of luminous B supergiants in 30 Dor, and the lack thereof at the highest luminosities, can be explained through the combination of envelope inflation and mass loss. Finally, we find that the upper limit for the inferred initial stellar masses in the greater 30 Dor region is significantly lower than in its central cluster, R 136, implying a variable upper limit for the masses of stars. The implementation of mass-loss and envelope physics in stellar evolution models turns out to be essential for the modelling of the observable properties of young stellar populations. While the properties of the most massive stars (>~100M_{sun}_) are well described by our new models, the slightly less massive O stars investigated in this work show a much more diverse behaviour than previously thought, which has potential implications for rotational mixing and angular momentum transport. While the present models are a big step forward in the understanding of stellar evolution in the upper HRD, more work is needed to understand the mechanisms that regulate the mass-loss rates of OB stars and the physics of fast-rotating stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/4364
- Title:
- Extended H2 emission from massive YSOs survey
- Short Name:
- J/MNRAS/450/4364
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a survey, designed to investigate the accretion process of massive young stellar objects (MYSOs) through near infrared narrow band imaging using the H_2_ {nu}=1-0 S(1) transition filter. A sample of 353 Massive Young Stellar Object (MYSO) candidates was selected from the Red MSX Source survey using photometric criteria at longer wavelengths (infrared and submillimeter) and chosen with positions throughout the Galactic Plane. Our survey was carried out at the SOAR Telescope in Chile and CFHT in Hawaii covering both hemispheres.
- ID:
- ivo://CDS.VizieR/J/AN/324/219
- Title:
- Extinction of OB stars
- Short Name:
- J/AN/324/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents an extensive list of the total to selective extinction ratios R calculated from the infrared magnitudes of 597 O and B stars using the extrapolation method. The IR magnitudes of these stars were taken from the literature. The IR colour excesses are determined with the aid of "artificial standards", Wegner (1994MNRAS.270..229W). The individual and mean values of total to selective extinction ratios R differ in most cases from the average value R=3.10+/-0.05, Wegner (1993AcA....43..209W) in different OB associations. The relation between total to selective extinction ratios R determined in this paper and those calculated using the "method of variable extinction" and the Cardelli et al. (1989ApJ...345..245C) formulae is discussed. The R values presented in this paper can be used to determine individual absolute magnitudes of reddened OB stars with known trigonometric parallaxes.
- ID:
- ivo://CDS.VizieR/J/ApJS/96/605
- Title:
- Far UV Stellar Photometry
- Short Name:
- J/ApJS/96/605
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Far-ultraviolet photometry for 741 objects in a field in Sagittarius centered near M8 and 541 objects in a field centered near zeta Scorpii is presented. These data were extracted from electrographic images obtained with two cameras during a shuttle flight in 1991 April/May. The cameras provided band passes with lambda_eff = 1375 A and lambda_eff = 1781 A. Synthetic colors show that these bands are sensitive to effective temperature for hot stars. Our measurements were placed on a quantitative far-ultraviolet magnitude scale by convolving the spectra of stars observed by IUE with our cameras' spectral response functions. Fifty-eight percent of the ultraviolet objects were identified with visible stars using the SIMBAD database while another 40% of the objects are blends of early type stars too close together to separate with our resolution. Our photometry is compared with that from the TD-1, OAO 2, and ANS satellites and the S201 (Apollo 16) far-ultraviolet camera and found to agree at the level of a few tenths of a magnitude. Unlike previous studies, almost half of the identified visual counterparts to the ultraviolet objects are early B stars. A plot of distance modulus against ultraviolet color excess reveals a significant population of stars with strong ultraviolet excesses.
