Search

Start Over Subject a stars Rights public
1. A and F stars abundances in the Hyades
ID:
ivo://CDS.VizieR/J/A+A/523/A71
Title:
A and F stars abundances in the Hyades
Short Name:
J/A+A/523/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
Abundances of 15 chemical elements have been derived for 28 F and 16 A stars members of the Hyades open cluster in order to set constraints on self-consistent evolutionary models that include radiative and turbulent diffusion A spectral synthesis, iterative procedure was applied to derive the abundances from selected high-quality lines in high-resolution, high-signal-to-noise spectra obtained with SOPHIE and AURELIE at the Observatoire de Haute Provence.
2. Absorption lines in 21 Lyn A-type star
ID:
ivo://CDS.VizieR/J/ApJS/239/19
Title:
Absorption lines in 21 Lyn A-type star
Short Name:
J/ApJS/239/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of absorption lines in the z', Y, and J bands that we identified in 21 Lyn, a slowly rotating A0.5V star. We detected 155 absorption features in the high-resolution (0.90-1.35um, R=28000) spectrum obtained with the WINERED spectrograph after the telluric absorption was carefully removed using a spectrum of a B-type star as a telluric standard. With a visual comparison with synthetic spectra, we compiled a catalog of 219 atomic lines for the 155 features, some of which are composed of multiple fine structure lines. The high-quality WINERED spectrum enabled us to detect a large number of weak lines down to ~1% in depth, which are identified for an A-type star for the first time. The catalog includes the lines of H, C, N, O, Mg, Al, Si, S, Ca, Fe, and Sr. These new lines are expected to be useful for spectral classification and chemical abundance analyses, while the line catalog is useful for observers who plan to use A-type stars as telluric standards because it is necessary to distinguish between stellar lines and telluric absorption lines in high-resolution spectra. ASCII versions of the spectra are available in the online version of the journal.
3. Abundances of A-F stars
ID:
ivo://CDS.VizieR/J/A+A/398/1121
Title:
Abundances of A-F stars
Short Name:
J/A+A/398/1121
Date:
21 Oct 2021
Publisher:
CDS
Description:
Fundamental parameters and abundances of 140 A and F-type stars are presented. The barycentric Julian dates and signal-to-noise ratios are also given.
4. Abundances of 3 supergiants in Sextans A
ID:
ivo://CDS.VizieR/J/AJ/127/2723
Title:
Abundances of 3 supergiants in Sextans A
Short Name:
J/AJ/127/2723
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the abundance analyses of three isolated A-type supergiant stars in the dwarf irregular galaxy Sextans A (=DDO 75) from high-resolution spectra obtained with the Ultraviolet-Visual Echelle Spectrograph (UVES) on the Kueyen telescope (UT2) of the ESO Very Large Telescope (VLT). Detailed model atmosphere analyses have been used to determine the stellar atmospheric parameters and the elemental abundances of the stars.
5. Activity in A-type stars from Kepler
ID:
ivo://CDS.VizieR/J/MNRAS/431/2240
Title:
Activity in A-type stars from Kepler
Short Name:
J/MNRAS/431/2240
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two years of Kepler data are used to investigate low-frequency variations in A-type stars. In about 875 (40%) A-type stars, the periodogram shows a simple peak and its harmonic. If we assume that the photometric period is the period of rotation, we can derive the equatorial rotational velocity from a suitable radius estimate. It turns out that the distribution of equatorial velocities derived in this way is similar to the distribution of equatorial velocities of A-type main-sequence stars in the general field derived from spectroscopic line broadening, verifying our initial assumption. We suggest that the light variation is due to rotational modulation caused by starspots or some other corotating structure. In many stars the rotation peak in the periodogram has a characteristic shape which is not understood. The light amplitudes are highly variable. We deduce from the amplitude distribution that the sizes of starspots in A-type stars are similar to the largest sunspots. From the widths of the peaks in the periodogram we deduce that differential rotation in these stars is similar to that in the Sun. We find that the period-colour relationship used for gyrochronology in late-type stars extends to early F-type and probably late A-type stars as well. Flares in A-type stars have been recently detected. We add 13 additional A-type flare stars to this sample, which means that about 1.5% of A-type stars in the Kepler field show flares. We conclude that A-type stars are active and, like cooler stars, have starspots and flares.
6. A-F type variable stars from Kepler
ID:
ivo://CDS.VizieR/J/AJ/149/68
Title:
A-F type variable stars from Kepler
Short Name:
J/AJ/149/68
Date:
03 Dec 2021 00:36:02
Publisher:
CDS
Description:
The light curves of 2768 stars with effective temperatures and surface gravities placing them near the gamma Doradus ({gamma} Dor)/delta Scuti ({delta} Sct) instability region were observed as part of the Kepler Guest Observer program from Cycles 1 through 5. The light curves were analyzed in a uniform manner to search for {gamma} Dor, {delta} Sct, and hybrid star pulsations. The {gamma} Dor, {delta} Sct, and hybrid star pulsations extend asteroseismology to stars slightly more massive (1.4-2.5M_{sun}_) than our Sun. We find 207 {gamma} Dor, 84 {delta} Sct, and 32 hybrid candidate stars. Many of these stars are cooler than the red edge of the {gamma} Dor instability strip as determined from ground-based observations made before Kepler. A few of our {gamma} Dor candidate stars lie on the hot side of the ground-based {gamma} Dor instability strip. The hybrid candidate stars cover the entire region between 6200K and the blue edge of the ground-based {delta} Sct instability strip. None of our candidate stars are hotter than the hot edge of the ground-based {delta} Sct instability strip. Our discoveries, coupled with the work of others, show that Kepler has discovered over 2000 {gamma} Dor, {delta} Sct, and hybrid star candidates in the 116 square degree Kepler field of view. We found relatively few variable stars fainter than magnitude 15, which may be because they are far enough away to lie between spiral arms in our Galaxy, where there would be fewer stars.
7. Ages of A-K type stars in DEBRIS survey
ID:
ivo://CDS.VizieR/J/AJ/143/135
Title:
Ages of A-K type stars in DEBRIS survey
Short Name:
J/AJ/143/135
Date:
21 Oct 2021
Publisher:
CDS
Description:
DEBRIS is a flux-limited survey of nearby stars (spectral types A-M) for evidence of debris disks with the Herschel Space Observatory. One goal of the survey is to determine disk incidence as a function of various stellar parameters. Understanding debris disk evolution depends on knowledge of the precise age of stars around which these debris disks are found. However, finding ages for field stars is notoriously difficult. Furthermore, in an unbiased sample like DEBRIS, one is working with stars across many spectral types. This requires a multi-method approach to age determination. In this paper, we outline several methods of age determination broken down by spectral type, including some strengths and limitations of each method. In total, we were able to calculate ages for 263 of 274 F-, G-, and K-type stars, and all 83 A-type stars in the DEBRIS sample.
8. Analysis of B6-A9 stars from INES UV spectra
ID:
ivo://CDS.VizieR/J/AJ/143/28
Title:
Analysis of B6-A9 stars from INES UV spectra
Short Name:
J/AJ/143/28
Date:
21 Oct 2021
Publisher:
CDS
Description:
Main-sequence (MS) and giant late-B and early-A type stars are the best targets for searching for nearby interstellar (IS) SiIV and CIV resonance lines because they are not able to produce them, either in atmospheric layers or in their circumstellar environment, and because many stars of these spectral types are nearby and located in the local interstellar medium (LISM). In addition, the use of certain stars hotter than B6 can lead to misinterpretations (e.g., alpha Arae). This work analyzes the reliable Short-Wavelength Prime (SWP) high-resolution UV spectra of 558 B6-A9 type stars observed by the International Ultraviolet Explorer at distances lower than 400pc from the Sun. For the first time, this work utilizes the entire INES database to extract stellar and IS information in a systematic way from homogeneous data. Stars were classified into seven groups: normal (MS and subgiant), giant, peculiar, emission line, Algols, pre-main sequence or Herbig Ae/Be, and shell stars. Only 10 normal stars, located beyond 90pc, show weak SiIV and CIV absorptions and are clustered around the direction of Sco-Cen, while 85 located closer than 90pc, as well as another 89 beyond 90pc, do not show any absorptions at all.
9. beta Pic BRITE, bRing, SMEI light curves
ID:
ivo://CDS.VizieR/J/A+A/627/A28
Title:
beta Pic BRITE, bRing, SMEI light curves
Short Name:
J/A+A/627/A28
Date:
21 Oct 2021
Publisher:
CDS
Description:
Exoplanet properties crucially depend on the parameters of their host stars: more accurate stellar parameters yield more accurate exoplanet characteristics. When the exoplanet host star shows pulsations, asteroseismology can be used for an improved description of the stellar parameters. We aim to revisit the pulsational properties of {beta} Pic and identify its pulsation modes from normalized amplitudes in five different passbands. We also investigate the potential presence of a magnetic field. We conducted a frequency analysis using three seasons of BRITE-Constellation observations in the two BRITE filters, the about 620-day-long bRing light curve, and the nearly 8-year-long SMEI photometric time series. We calculated normalized amplitudes using all passbands and including previously published values obtained from ASTEP observations. We investigated the magnetic properties of {beta} Pic using spectropolarimetric observations conducted with the HARPSpol instrument. Using 2D rotating models, we fit the normalized amplitudes and frequencies through Monte Carlo Markov chains. We identify 15 pulsation frequencies in the range from 34 to 55d^-1^, where two, F13 at 53.6917d^-1^ and F11 at 50.4921d^-1^, display clear amplitude variability. We use the normalized amplitudes in up to five passbands to identify the modes as three l=1, six l=2, and six l=3 modes. {beta} Pic is shown to be non-magnetic with an upper limit of the possible undetected dipolar field of 300 Gauss. Multiple fits to the frequencies and normalized amplitudes are obtained, including one with a near equator-on inclination for {beta} Pic, which corresponds to our expectations based on the orbital inclination of {beta} Pic b and the orientation of the circumstellar disk. This solution leads to a rotation rate of 27% of the Keplerian breakup velocity, a radius of 1.497+/-0.025R_{sun}_, and a mass of 1.797+/-0.035M_{sun}_. The ~2% errors in radius and mass do not account for uncertainties in the models and a potentially erroneous mode-identification.
10. beta Pictoris debris disk image
ID:
ivo://CDS.VizieR/J/A+A/646/A132
Title:
beta Pictoris debris disk image
Short Name:
J/A+A/646/A132
Date:
21 Oct 2021
Publisher:
CDS
Description:
The nearby young star beta Pictoris hosts a rich and complex planetary system, with at least two giant planets and a nearly edge-on debris disk that contains several dynamical subpopulations of planetesimals. While the inner ranges of the debris disk have been studied extensively, less information is known about the outer, fainter parts of the disk. Here we present an analysis of archival FORS V-band imaging data from 2003-2004, which have previously not been explored scientifically because the halo substructure of the bright stellar point spread function is complex. Here we present the deepest imaging yet for the outer range of the beta Pic disk.

Limit your search