- ID:
- ivo://CDS.VizieR/J/A+A/538/A100
- Title:
- Abundances red giants in Carina dSph
- Short Name:
- J/A+A/538/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ages of individual Red Giant Branch stars can range from 1Gyr old to the age of the Universe, and it is believed that the abundances of most chemical elements in their photospheres remain unchanged with time (those that are not affected by the first dredge-up). This means that they trace the interstellar medium in the galaxy at the time the star formed, and hence the chemical enrichment history of the galaxy. Colour-Magnitude Diagram analysis has shown the Carina dwarf spheroidal to have had an unusually episodic star formation history and this is expected to be reflected in the abundances of different chemical elements.
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- ID:
- ivo://CDS.VizieR/J/ApJ/836/168
- Title:
- Abundances & RVs for stars near (or in) NGC6273
- Short Name:
- J/ApJ/836/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent observations have shown that a growing number of the most massive Galactic globular clusters contain multiple populations of stars with different [Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been recognized as a member of this "iron-complex" cluster class, and we provide here a chemical and kinematic analysis of >300 red giant branch and asymptotic giant branch member stars using high-resolution spectra obtained with the Magellan-M2FS and VLT-FLAMES instruments. Multiple lines of evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that ranges from about [Fe/H]=-2 to -1 dex, and may include at least three populations with different [Fe/H] values. The three populations identified here contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars, but a Mg-Al anti-correlation may only be present in stars with [Fe/H]>~-1.65. The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process must have dominated the heavy element enrichment at higher metallicities. A small group of stars with low [{alpha}/Fe] is identified and may have been accreted from a former surrounding field star population. The cluster's large abundance variations are coupled with a complex, extended, and multimodal blue horizontal branch (HB). The HB morphology and chemical abundances suggest that NGC 6273 may have an origin that is similar to {omega} Cen and M54.
- ID:
- ivo://CDS.VizieR/J/AJ/154/69
- Title:
- ACRONYM II. The {beta} Pictoris Moving Group
- Short Name:
- J/AJ/154/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We confirm 66 low-mass stellar and brown dwarf systems (K7-M9) plus 19 visual or spectroscopic companions of the {beta} Pictoris moving group (BPMG). Of these, 41 are new discoveries, increasing the known low-mass members by 45%. We also add four objects to the 14 known with masses predicted to be less than 0.07 M_{sun}_. Our efficient photometric + kinematic selection process identified 104 low-mass candidates, which we observed with ground-based spectroscopy. We collected infrared observations of the latest spectral types (>M5) to search for low-gravity objects. These and all <M5 candidates were observed with high-resolution optical spectrographs to measure the radial velocities and youth indicators, such as lithium absorption and H{alpha} emission, needed to confirm BPMG membership, achieving a 63% confirmation rate. We also compiled the most complete census of BPMG membership, with which we tested the efficiency and false-membership assignments using our selection and confirmation criteria. Using the new census, we assess a group age of 22+/-6 Myr, consistent with past estimates. With the now-densely sampled lithium depletion boundary, we resolve the broadening of the boundary by either an age spread or astrophysical influences on lithium-burning rates. We find that 69% of the now-known members with AFGKM primaries are M stars, nearing the expected value of 75%. However, the new initial mass function for the BPMG shows a deficit of 0.2-0.3 M_{sun}_ stars by a factor of ~2. We expect that the AFGK census of the BPMG is also incomplete, probably due to biases of searches toward the nearest stars.
- ID:
- ivo://CDS.VizieR/J/other/Ap/62.147
- Title:
- Activity types of ROSAT/SDSS galaxies
- Short Name:
- J/other/Ap/62.14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study we carry out detailed spectral classification of 173 AGN candidates from the Joint HRC/BHRC sample, which is a combination of HRC (Hamburg-ROSAT Catalogue) and BHRC (Byurakan-Hamburg-ROSAT Catalogue). These objects were revealed as optical counterparts for ROSAT X-ray sources, however spectra for 173 of them are given in SDSS without definite spectral classification. We studied these 173 objects using the SDSS spectra and revealed the detailed activity types for them. Three diagnostic diagrams and direct examination of the spectra were used to have more confident classification. We also made identification of these sources in other wavelength ranges and calculated some of their parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/156/61
- Title:
- A study of the H{alpha} variability of Be stars
- Short Name:
- J/AJ/156/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of 4 years of high-resolution spectral observations of 69 emission-line stars, 54 of them being newly discovered sources. We classified the stars on the basis of their position in the two-color IR diagram and some additional criteria: shape and width of the H{alpha} profile, presence of He lines, proper motion and parallax, membership to open cluster and associations. Sixty of our targets turned out to be Be stars. We also found four late giants, four pre-MS stars, and one late dwarf. The H{alpha} emission profiles of our Be stars range from single peaked to typical shell profiles that can also be highly asymmetric or single-peaked profiles with a narrow absorption core. The emission profiles appear almost constant with time or highly variable in intensity and in their V/R ratio. The detected long-term variability of the H{alpha} emission is important for investigating the on/off switch phenomenon of Be stars. Our study led to an increase of the number of the emission-line stars of 16 open clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/153/95
- Title:
- Catalog of Suspected Nearby Young Stars
- Short Name:
- J/AJ/153/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new nearby young moving group (NYMG) kinematic membership analysis code, LocAting Constituent mEmbers In Nearby Groups (LACEwING), a new Catalog of Suspected Nearby Young Stars, a new list of bona fide members of moving groups, and a kinematic traceback code. LACEwING is a convergence-style algorithm with carefully vetted membership statistics based on a large numerical simulation of the Solar Neighborhood. Given spatial and kinematic information on stars, LACEwING calculates membership probabilities in 13 NYMGs and three open clusters within 100 pc. In addition to describing the inputs, methods, and products of the code, we provide comparisons of LACEwING to other popular kinematic moving group membership identification codes. As a proof of concept, we use LACEwING to reconsider the membership of 930 stellar systems in the Solar Neighborhood (within 100 pc) that have reported measurable lithium equivalent widths. We quantify the evidence in support of a population of young stars not attached to any NYMGs, which is a possible sign of new as-yet-undiscovered groups or of a field population of young stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/102
- Title:
- Equivalent widths of 9 RGB in Carina dSph
- Short Name:
- J/ApJ/751/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detailed abundances of 23 chemical elements in nine bright red giant branch stars in the Carina dwarf spheroidal galaxy are presented based on high-resolution spectra gathered at the Very Large Telescope (VLT) and Magellan telescopes. A spherical model atmospheres analysis is applied using standard methods (local thermodynamic equilibrium and plane-parallel radiative transfer) to spectra ranging from 380 to 680nm. Stellar parameters are found to be consistent between photometric and spectroscopic analyses, both at moderate and high resolution. The stars in this analysis range in metallicity from -2.9<[Fe/H]<-1.3, and adopting the ages determined by Lemasle et al. (Cat. J/A+A/538/A100), we are able to examine the chemical evolution of Carina's old and intermediate-aged populations.
- ID:
- ivo://CDS.VizieR/J/A+A/384/491
- Title:
- Fast-rotating nearby solar-type stars. I.
- Short Name:
- J/A+A/384/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of high-resolution spectroscopic and high-precision photometric observations on a sample of 129 late-F and G-type nearby stars selected on the basis of their large rotational velocity. Using also data from the Hipparcos satellite, CORAVEL and from the ROSAT satellite database, we infer spectral types, compute radial velocities, vsini, Li abundances and X-ray luminosities and investigate the single or binary nature of the sample stars. Such a careful analysis of our sample shows a large fraction of binaries (~62%) and of young single disk stars. In particular, at least 9 stars can be considered bona-fide PMS or ZAMS objects, and 30 stars are identified as SBs for the first time. Information on the presence of Ca II K emission and on optical variability is given for some of the stars of the sample. The photometry has been obtained at the European Southern Observatory (ESO-La silla, Chile) during several observing runs (19/11-03/12 1993, 24/11-04/12 1994, 15-28/01/1995 and 1-12/10/1995), by using the 50cm ESO telescope. The figures were published in paper II.
- ID:
- ivo://CDS.VizieR/J/AJ/153/99
- Title:
- Galactic outer disk: a field toward Tombaugh 1
- Short Name:
- J/AJ/153/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ optical photometry and high-resolution spectroscopy to study a field toward the open cluster Tombaugh 1, where we identify a complex population mixture that we describe in terms of young and old Galactic thin disks. Of particular interest is the spatial distribution of the young population, which consists of dwarfs with spectral types as early as B6 and is distributed in a blue plume feature in the color-magnitude diagram. For the first time, we confirm spectroscopically that most of these stars are early-type stars and not blue stragglers or halo/thick-disk subdwarfs. Moreover, they are not evenly distributed along the line of sight but crowd at heliocentric distances between 6.6 and 8.2 kpc. We compare these results with present-day understanding of the spiral structure of the Galaxy and suggest that they trace the outer arm. This range of distances challenges current Galactic models adopting a disk cutoff at 14 kpc from the Galactic center. The young dwarfs overlap in space with an older component, which is identified as an old Galactic thin disk. Both young and old populations are confined in space since the disk is warped at the latitude and longitude of Tombaugh 1. The main effects of the warp are that the line of sight intersects the disk and entirely crosses it at the outer arm distance and that there are no traces of the closer Perseus arm, which would then be either unimportant in this sector or located much closer to the formal Galactic plane. Finally, we analyze a group of giant stars, which turn out to be located at very different distances and to possess very different chemical properties, with no obvious relation to the other populations.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A101
- Title:
- Galaxy population of Abell 1367
- Short Name:
- J/A+A/527/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic and photometric data of the galaxy population of the galaxy cluster Abell 1367, over a field of 34'x90', covering the cluster centre out to a radius of ~2.2Mpc, are presented as the first stage of a study of their stellar population and star formation properties. Spectroscopic catalogue contains new detection data of emission and/or absorption lines for 84 galaxies in our survey regions. Photometric data give optical and near-infrared isophotal magnitudes for 303 galaxies, determined within R_24_ isophotal diameters. H{alpha} emission catalogue reports equivalent widths and fluxes of 72 galaxies, confirmed as cluster members of Abell 1367.
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