- ID:
- ivo://CDS.VizieR/J/ApJ/847/131
- Title:
- KIC 8462852 one-yr obs. from UV to MIR
- Short Name:
- J/ApJ/847/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star over a wide wavelength range from the UV to the mid- infrared from 2015 October through 2016 December, using Swift, Spitzer and AstroLAB IRIS. The star faded in a manner similar to the long-term fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period reported is 22.1+/-9.7mmag/yr in the Swift wavebands, with amounts of 21.0+/-4.5mmag in the ground-based B measurements, 14.0+/-4.5mmag in V, and 13.0+/-4.5 in R, and a rate of 5.0+/-1.2mmag/yr averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at >~3{sigma} by three different observatories operating from the UV to the IR. The presence of long-term secular dimming means that previous spectral energy distribution models of the star based on photometric measurements taken years apart may not be accurate. We find that stellar models with Teff=7000-7100K and A_V_~0.73 best fit the Swift data from UV to optical. These models also show no excess in the near-simultaneous Spitzer photometry at 3.6 and 4.5{mu}m, although a longer wavelength excess from a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of the fading favors a relatively neutral color (i.e., R_V_>~5, but not flat across all the bands) compared with the extinction law for the general interstellar medium (R_V_=3.1), suggesting that the dimming arises from circumstellar material.
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- ID:
- ivo://CDS.VizieR/J/other/PASA/32.36
- Title:
- lambda Boo star membership evaluations
- Short Name:
- J/other/PASA/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The literature on the {lambda} Boo stars has grown to become somewhat heterogenous, as different authors have applied different criteria across the UV, optical and infrared regions to determine the membership status of {lambda} Boo candidates. We aim to clear up the confusion by consulting the literature on 212 objects that have been considered as {lambda} Boo candidates, and subsequently evaluating the evidence in favour of their admission to the {lambda} Boo class. We obtained new spectra of ~90 of these candidates and classified them on the MK system to aid in the membership evaluations. The re-evaluation of the 212 objects resulted in 64 members and 103 non-members of the {lambda} Boo class, with a further 45 stars for which membership status is unclear. We suggest observations for each of the stars in the latter category that will allow them to be confidently included or rejected from the class. Our reclassification facilitates homogeneous analysis on group members, and represents the largest collection of confirmed {lambda} Boo stars known.
- 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.
- 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.
