- ID:
- ivo://CDS.VizieR/J/A+AS/123/93
- Title:
- Lambda Boo stars consolidated catalogue
- Short Name:
- J/A+AS/123/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper describes the first steps towards the homogenization of the lambda Bootis group, leading to a concise definition of lambda Bootis stars: Population I, hydrogen burning, metal poor (except of C, N, O and S) A to F-type stars. The definition does not depend on phenomenological features, like flux depressions, colour excesses, vsini values, etc. Based on this new homogeneous catalogue with 45 lambda Bootis stars, we discuss classification criteria which can be used for a spectroscopic and photometric all-sky survey for lambda Bootis stars in the field and in clusters of different ages.
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- ID:
- ivo://CDS.VizieR/J/AJ/154/31
- Title:
- {lambda} Bootis stars: the southern survey I.
- Short Name:
- J/AJ/154/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The {lambda} Boo stars are a class of chemically peculiar Population I A-type stars characterized by under-abundances of the refractory elements, but near-solar abundances of carbon, nitrogen, oxygen, and sulfur. There is some evidence that {lambda} Boo stars have higher frequencies of "bright" debris disks than normal A-type stars. The discovery of four exoplanets orbiting HR8799, a {lambda} Boo star with a resolved debris disk, suggests that the {lambda} Boo phenomenon may be related to the presence of a dynamic debris disk, perhaps perturbed by migrating planets. However, only 64 {lambda} Boo stars are known, and those stars were discovered with different techniques, making it problematic to use that sample for statistical purposes, including determining the frequency of debris disks. The purpose of this paper is to derive a new sample of {lambda} Boo stars using a technique that does not lead to biases with respect to the presence of infrared excesses. Through spectroscopic observations in the southern hemisphere, we have discovered 33 {lambda} Boo stars and have confirmed 12 others. As a step toward determining the proportion of {lambda} Boo stars with infrared excesses, we have used WISE data to examine the infrared properties of this sample out to 22{mu}m. On this basis, we cannot conclude that {lambda} Boo stars have a greater tendency than normal A-type stars to show infrared excesses. However, observing this sample at longer wavelengths may change that conclusion, as many {lambda} Boo debris disks are cool and do not radiate strongly at 22{mu}m.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A34
- Title:
- LAMOST DR4 New mercury-manganese stars
- Short Name:
- J/A+A/645/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present work presents our efforts at identifying new mercury-manganese (HgMn/CP3) stars using spectra obtained with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Suitable candidates were searched for among pre-selected early-type spectra from LAMOST DR4 using a modified version of the MKCLASS code that probes several HgII and MnII features. The spectra of the resulting 332 candidates were visually inspected. Using parallax data and photometry from Gaia DR2, we investigated magnitudes, distances from the Sun, and the evolutionary status of our sample stars. We also searched for variable stars using diverse photometric survey sources. We present 99 bona fide CP3 stars, 19 good CP3 star candidates, and seven candidates. Our sample consists of mostly new discoveries and contains, on average, the faintest CP3 stars known (peak distribution 9.5<=G<=13.5mag). All stars are contained within the narrow spectral temperature-type range from B6 to B9.5, in excellent agreement with the expectations and the derived mass estimates (2.4<=M_{sun}_<=4 for most objects). Our sample stars are between 100Myr and 500Myr old and cover the whole age range from zero-age to terminal-age main sequence. They are almost homogeneously distributed at fractional ages on the main sequence <=80%, with an apparent accumulation of objects between fractional ages of 50% to 80%. We find a significant impact of binarity on the mass and age estimates. Eight photometric variables were discovered, most of which show monoperiodic variability in agreement with rotational modulation. Together with the recently published catalogue of APOGEE CP3 stars, our work significantly increases the sample size of known Galactic CP3 stars, paving the way for future in-depth statistical studies.
- ID:
- ivo://CDS.VizieR/J/A+A/364/674
- Title:
- Li-rich giants atomic lines
- Short Name:
- J/A+A/364/674
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed analysis has been carried out for a sample of 16 red giants showing a strong Li I 670.8nm line. Ten of them were detected in a survey by Castilho et al. (1998A&AS..127..139C), and the other 6 stars are Li-rich giants selected from the literature. Element abundances in the sample Li-rich giants are similar to those in normal red giants, differing only by their high Li abundance and infrared excess. This suggests that Li-rich giants may correspond to a phase of stellar evolution of normal red giants, when Li is produced and transported to the atmosphere.
- ID:
- ivo://CDS.VizieR/III/68
- Title:
- List of Early-Type Chemically Peculiar Stars
- Short Name:
- III/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue is a subset of the "CATALOGUE OF STELLAR GROUPS" (CSG, Jaschek M. and Egret D., 1981BICDS..20...36J). It provides a list of identifications, positions, UBV photometry, subgroup and references for chemically peculiar stars corresponding to the following groups: Table 1: Helium abnormal stars Table 2: Ap stars Table 3: Am stars A bibliography file is also included.
- ID:
- ivo://CDS.VizieR/J/ApJS/134/103
- Title:
- Low-mass members of IC 2391
- Short Name:
- J/ApJS/134/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified a large sample of probable low-mass members of the young open cluster IC 2391 based on optical (VRIZ) and infrared (JHKs) photometry. Our sample includes 50 probable members and 82 possible members, both very low-mass stars and brown dwarfs. We also provide accurate positions for these stars and brown dwarf candidates derived from red UK Schmidt plates measured using the microdensitometer SuperCOSMOS. Assuming an age of 53Myr, we estimate that we have reached a mass of 0.025M_{sun}_, if the identified objects are indeed members of IC 2391.
- ID:
- ivo://CDS.VizieR/J/A+A/275/163
- Title:
- Luminous Carbon stars in Galactic Plane
- Short Name:
- J/A+A/275/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of distant (2-10kpc), heavily obscured asymptotic giant branch (AGB) stars were observed for CO emission. Simultaneous observations at the frequencies of the J=1-0 (115.27GHz) and J=2-1 (230.58GHz) transitions of CO were made at the 30m IRAM telescope on Pico Velata, Spain, in September 1989.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/62.244
- Title:
- Magnetic field in CP stars
- Short Name:
- J/other/AstBu/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dependence of the degree of anomaly of parameter Z of Geneva photometry (Z0=Z_CP_-Z_norm_) on the average surface magnetic field Bs is analyzed. The Z0 value is proportional to the degree of anomaly of chemical composition. It was found that Bs-->0 corresponds Z0-->-0.010/-0.015, i.e., part of CP stars are virtually devoid of magnetic field, but exhibit chemical anomalies. This effect may be due to selection whereby only objects with strong chemical anomalies are classified as CP stars, thereby producing a deficit of stars with relatively weak anomalies. Moreover, CP stars have other sources of stabilization of their atmospheres besides the magnetic field, e.g., slow rotation. Formulas relating Z0 to Bs are derived.
- ID:
- ivo://CDS.VizieR/J/ApJ/873/L5
- Title:
- Magnetic field measurements of Ap/Bp stars
- Short Name:
- J/ApJ/873/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on magnetic field measurements of 157 chemically peculiar A/B stars (Ap/Bp) based on resolved, magnetically split absorption lines present in H-band spectra provided by the Sloan Digital Sky Survey (SDSS)/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. These stars represent the extreme magnetic end of a still-growing sample of >900 Ap/Bp stars selected among the APOGEE telluric standard stars as those with CeIII absorption lines and/or literature Ap/Bp classifications. The lines most frequently resolved into their split components for these stars in the H-band pertain primarily pertain to CeIII, CrII, FeI, MnII, SiI, and CaII, in addition to one or more unidentified ions. Using mean magnetic field modulus (<B>) estimates for transitions with known Lande factors, we estimate effective Lande factors for 5 CeIII lines and 15 unknown lines and proceed to measure <B> of 157 stars, only 3 of which have previous literature estimates of <B>. This 183% increase in the number of Ap/Bp stars for which <B> has been measured is a result of the large number of stars observed by SDSS/APOGEE, extension of high-resolution Ap/Bp star observations to fainter magnitudes, and the advantages of long wavelengths for resolving magnetically split lines. With <B>~25kG, the star 2MASS J02563098+4534239 is currently the most magnetic star of the SDSS/APOGEE sample. Effective Lande factors, representative line profiles, and magnetic field moduli are presented. The validity of the results is supported using optical, high-resolution, follow-up spectra for 29 of the stars.
- ID:
- ivo://CDS.VizieR/J/A+A/475/1053
- Title:
- Magnetic fields in Ap/Bp stars
- Short Name:
- J/A+A/475/1053
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated a sample of 28 well-known spectroscopically-identified magnetic Ap/Bp stars, with weak, poorly-determined or previously undetected magnetic fields. The aim of this study is to explore the weak part of the magnetic field distribution of Ap/Bp stars. Using the MuSiCoS and NARVAL spectropolarimeters at Telescope Bernard Lyot (Observatoire du Pic du Midi, France) and the cross-correlation technique Least Squares Deconvolution (LSD), we have obtained 282 LSD Stokes $V$ signatures of our 28 sample stars, in order to detect the magnetic field and to infer its longitudinal component with high precision (median sigma=40G).
