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841. [alpha/Fe] ratios from LAMOST spectra
ID:
ivo://CDS.VizieR/J/other/RAA/16.G10
Title:
[alpha/Fe] ratios from LAMOST spectra
Short Name:
J/other/RAA/16.G
Date:
21 Oct 2021
Publisher:
CDS
Description:
The [{alpha}/Fe] ratios in stars are good tracers to probe the formation history of stellar populations and the chemical evolution of the Galaxy. The spectroscopic survey of LAMOST provides a good opportunity to determine [{alpha}/Fe] of millions of stars in the Galaxy. We present a method of measuring the [{alpha}/Fe] ratios from LAMOST spectra using the template-matching technique of the LSP3 pipeline. We use three test samples of stars selected from the ELODIE and MILES libraries, as well as the LEGUE survey to validate our method. Based on the test results, we conclude that our method is valid for measuring [{alpha}/Fe] from low-resolution spectra acquired by the LAMOST survey. Within the range of the stellar parameters Teff=[5000, 7500]K, logg=[1.0, 5.0]dex and [Fe/H]=[-1.5, +0.5]dex, our [{alpha}/Fe] measurements are consistent with values derived from high-resolution spectra, and the accuracy of our [{alpha}/Fe] measurements from LAMOST spectra is better than 0.1dex with spectral signal-to-noise higher than 20.
842. alpha Leo spectro-interferometric observation
ID:
ivo://CDS.VizieR/J/MNRAS/511/4724
Title:
alpha Leo spectro-interferometric observation
Short Name:
J/MNRAS/511/4724
Date:
15 Mar 2022 08:32:16
Publisher:
CDS
Description:
Differential Interferometry allows to obtain the differential visibility and phase, in addition to the spectrum. The differential phase contains important information about the structure and motion of stellar photosphere such as stellar spots and non-radial pulsations, and particularly the rotation. Thus, this interferometric observable strongly helps to constrain the stellar fundamental parameters of fast rotators. The spectroastrometry mainly uses the photocentre displacements, which is a first approximation of the differential phase, and is applicable only for unresolved or marginally objects. We study here the sensitivity of relevant stellar parameters to the simulated photocentres using the scirocco code: a semi-analytical algorithm dedicated to fast rotators, applied to two theoretical modelling stars based on Achernar and Regulus, in order to classify the importance of these parameters and their impact on the modelling. We compare our simulations with published VLTI/AMBER data. This work sets the limits of application of photocentre displacements to fast rotators, and under which conditions we can use the photocentres and/or the differential phase, through a pre-established physical criterion. To validate our theoretical study, we apply our method of analysis on observed data of the edge-on fast rotator Regulus. For unresolved targets, with a visibility V~1, the photocentre can constrain the main stellar fundamental parameters of fast rotators, whereas from marginally resolved objects (0.8<=V<1), mainly the rotation axis position angle (PA_rot_) can be directly deduced from the vectorial photocentre displacement, which is very important for young cluster studies.
843. Alpha Per cluster low-mass members. I.
ID:
ivo://CDS.VizieR/J/AN/319/201
Title:
Alpha Per cluster low-mass members. I.
Short Name:
J/AN/319/201
Date:
21 Oct 2021
Publisher:
CDS
Description:
Following the work of Randich et al. (1996A&A...305..785R) involving a ROSAT raster scan survey of the {alpha} Persei open cluster, we present here the results of a photometric/spectroscopic program examining the possible optical counterparts to a group of 73 X-ray sources in the raster survey which were not matched to catalogued stars. Of the 73 sources investigated, ~40 have an optical counterpart with photometry acceptable for cluster membership and ~20 of these also have radial velocities consistent with membership. We discuss the X-ray properties of these potential new members and why they may not have been identified in earlier membership surveys of this cluster.
844. Alpha Per cluster low-mass members. II.
ID:
ivo://CDS.VizieR/J/AN/319/215
Title:
Alpha Per cluster low-mass members. II.
Short Name:
J/AN/319/215
Date:
21 Oct 2021
Publisher:
CDS
Description:
The present investigation examines possible optical counterparts to 130 X-ray sources in the region of the alpha Persei open cluster (d~170pc, age~50Myr) resulting from the analysis of three 22-25ksec ROSAT PSPC pointings. In the same manner as for 73 X-ray sources from a raster survey in alpha Per (Prosser & Randich, 1998, Cat. <J/AN/319/201>), CCD photometry is employed to obtain magnitudes and colors for stars/objects close to the X-ray positions, with additional echelle and low-dispersion Halpha spectra provided for some stars. For almost 60 X-ray sources, an optical counterpart with photometry acceptable for cluster membership is identified, some of which can be excluded from membership on the basis of discrepant radial velocity or X-ray characteristics. On the order of 30 new members or likely members associated with X-ray sources have been identified based on available data. A photometric rotation period has been obtained for one rapid rotator identified in X-rays.
845. {alpha} Per cluster members
ID:
ivo://CDS.VizieR/J/ApJ/752/58
Title:
{alpha} Per cluster members
Short Name:
J/ApJ/752/58
Date:
21 Oct 2021
Publisher:
CDS
Description:
Because of its proximity to the Galactic plane, reliable identification of members of the {alpha} Persei cluster is often problematic. Based primarily on membership evaluations contained in six published papers, we constructed a mostly complete list of high-fidelity members of spectral type G and earlier that lie within 3 arc degrees of the cluster center. {alpha} Persei was the one nearby, rich, young open cluster not surveyed with the Spitzer Space Telescope. We examined the first and final data releases of the Wide-field Infrared Survey Explorer (WISE) and found 11, or perhaps 12, {alpha} Per cluster members that have excess mid-infrared emission above the stellar photosphere attributable to an orbiting dusty debris disk. The most unusual of these is V488 Per, a K-type star with an excess IR luminosity 16% (or more) of the stellar luminosity; this is a larger excess fraction than that of any other known dusty main-sequence star. Much of the dust that orbits V488 Per is at a temperature of ~800 K; if these grains radiate like blackbodies, then they lie only ~0.06 AU from the star. The dust is probably the aftermath of a collision of two planetary embryos or planets with small semimajor axes; such orbital radii are similar to those of many of the transiting planets discovered by the Kepler satellite.
846. alpha Per cluster possible members
ID:
ivo://CDS.VizieR/J/MNRAS/457/1028
Title:
alpha Per cluster possible members
Short Name:
J/MNRAS/457/1028
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained membership probabilities of stars within a field of from the centre of the open cluster alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of alpha Persei shows a turnover at m=0.62M_{sun}_ with low- and high-mass slopes of {alpha}_low_=0.50+/-0.09 (0.1<m/M_{sun}_<0.62) and {alpha}_high_=2.32+/-0.14 (0.62<=m/M_{sun}_<4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 110 to 2.63 outside 22, whereas the mean stellar mass decreases from 0.95 to 0.57M_{sun}_ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour-magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin=34+/-12 per cent for stars with 0.70<m/M_{sun}_<4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of {alpha}_low_=0.89+/-0.11 and {alpha}_high_=2.37+/-0.09 and a total cluster mass of 352M_{sun}_ for alpha Persei.
847. Alpha Per faint stars photometry
ID:
ivo://CDS.VizieR/J/A+A/395/813
Title:
Alpha Per faint stars photometry
Short Name:
J/A+A/395/813
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a deep, wide-field optical survey of the young stellar cluster Alpha Per, in which we have discovered a large population of candidate brown dwarfs. Subsequent infrared photometric follow-up shows that the majority of them are probable or possible members of the cluster, reaching to a minimum mass of 0.035M_{sun}_.
848. Alpha Per High res. spectral atlas at 3810-8100{AA}
ID:
ivo://CDS.VizieR/J/PASP/118/636
Title:
Alpha Per High res. spectral atlas at 3810-8100{AA}
Short Name:
J/PASP/118/636
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a high resolution (R=90000) spectral atlas of the F5Ib star Alpha Per covering the 3810-8100{AA} region. The atlas, based on data obtained with the aid of the echelle spectrograph BOES fed by 1.8-m telescope at Bohyunsan observatory (Korea) is a result of co-addition of a few well-exposed spectra. A final signal-to-noise ratio is ~800 at ~6000{AA}. The atlas is compared with the synthetic spectrum computed using the code based on (Kurucz, 1995, ASP Conf. Ser. 81, 583) software and databases. The adopted model atmosphere parameters are Teff=6240+/-20K, logg=0.58+/-0.04, and Vturb=3.20+/-0.05km/s. We also derived the iron abundance of [Fe/H]=-0.28+/-0.06. The spectral lines of Alpha Per have been identified by matching the synthetic spectrum with the observed one. The atlas is presented in figures and available in digital form at http://www.boao.re.kr/BOES/atlas/hd20902.html along with synthetic spectrum and spectral line identification tables.
849. alpha Persei and Praesepe Clusters
ID:
ivo://CDS.VizieR/J/AJ/123/1570
Title:
alpha Persei and Praesepe Clusters
Short Name:
J/AJ/123/1570
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two hundred forty-two members of the Praesepe and alpha Persei clusters have been surveyed with high angular resolution 2.2{mu}m speckle imaging on the 3m Infrared Telescope Facility, the 5m Hale, and the 10m Keck telescopes, along with direct imaging using the near-infrared camera (NICMOS) aboard the Hubble Space Telescope. The observed stars range in spectral type from B (~5M_{sun}_) to early M (~0.5M_{sun}_), with the majority of the targets more massive than ~0.8M_{sun}_. The one quadruple and 39 binary systems detected encompass separations from 0.053" to 7.28"; 28 of the systems are new detections, and there are nine candidate substellar companions.
850. {alpha} Persei open cluster members
ID:
ivo://CDS.VizieR/J/AJ/131/2967
Title:
{alpha} Persei open cluster members
Short Name:
J/AJ/131/2967
Date:
21 Oct 2021
Publisher:
CDS
Description:
A kinematical study of the nearby open cluster {alpha} Persei is presented based on the astrometric proper motions and positions in the Tycho-2 catalog (Cat. I/259) and Second USNO CCD Astrographic Catalog (UCAC2, Cat. I/289). Using the astrometric data and photometry from the Tycho-2 and ground-based catalogs, 139 probable members of the cluster are selected, 18 of them new.