Alpha Persei Research Articles

Rotational velocities of newly discovered, low-mass members of the Alpha Persei cluster

About 30 new, low-mass members of the young open cluster Alpha Persei are identified via a proper-motion study and subsequent photometric and spectroscopic observations. Membership in the cluster is confirmed for a number of the fainter proper-motion candidates from Heckman, Dieckvoss, and Kox (1956). Coordinates, finding charts, BVRI photometry, and rotational velocities are provided for most of the stars. At least two of the stars show peculiar H-alpha emission profiles, with weak but very broad emission wings, and relatively narrow absorption reversals. The rotational velocity distribution for low-mass stars in the Alpha Per cluster are compared with recently derived rotational velocity distributions for T Tauri stars, placing strong constraints on the mechanisms for angular momentum loss during pre-main-sequence evolution.

Lithium abundances among solar-type pre-main-sequence stars

Measurements of Li I 6707 A line strengths were carried out for two samples of pre-main-sequence (PMS) stars (L 1641 and Taurus-Auriga), and the Li abundances estimated for PMS stars are compared with those deduced from observations of Li line strengths for main-sequence stars in the Alpha Persei cluster. It was found that the maximum Li abundances among the PMS stars with solar mass values greater than 1.0 exceed the maximum abundances for Alpha Per stars by at least 0.3 dex. Some PMS stars, including few apparently young stars, showed large (greater than 1.0 dex) Li depletion, and some apparently old PMS stars showed little or no depletion. 26 refs.

Lithium Abundances among Solar Type Pre Main Sequence Stars

Measurements of Li I 6707 A line strengths were carried out for two samples of pre-main-sequence (PMS) stars (L 1641 and Taurus-Auriga), and the Li abundances estimated for PMS stars are compared with those deduced from observations of Li line strengths for main-sequence stars in the Alpha Persei cluster. It was found that the maximum Li abundances among the PMS stars with solar mass values greater than 1.0 exceed the maximum abundances for Alpha Per stars by at least 0.3 dex. Some PMS stars, including few apparently young stars, showed large (greater than 1.0 dex) Li depletion, and some apparently old PMS stars showed little or no depletion.

Lithium in lower-main-sequence stars of the Alpha Persei cluster

Lithium abundances are presented for main-sequence stars of spectral types F, G, and K in the young open cluster Alpha Per. For 46 cluster members, a correlation between Li abundance and projected rotational velocity v sin i is found: all of the Li-poor stars are slow rotators. Two explanations are proposed to account for the correlation: (1) that the Li depletion is introduced following a rapid spin-down phase experienced by young low-mass stars, and that this episode of Li depletion may be the dominant one determining the spread of Li abundances among young low-mass main-sequence stars, and (2) that star formation has occurred over a finite period such that the older stars have undergone a spin-down and depletion of Li by a means that may or may not depend on rotation. The Li abundance in the warm and rapidly rotating stars appears to be undepleted, as is predicted by recent models of pre-main-sequence stars. The depletion observed in the cool stars exceeds the level predicted by these models.

Effects of rotation on the colours and line indices of stars 1. The alpha Persei cluster

Analysis of the available observational data for the α-Persei cluster members shows that rotation effects on the intermediate-band indices c1 and (u-b) are considerable. In c1, rotation produces a reddening of 0.040 magnitudes per 100 km s-1 In (u-b) the effect for B stars is found to be 0.06 magnitudes per 100 km s-1 ofV sin i.

Rotational properties of composite polytrope models

view Abstract Citations (30) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rotational Properties of Composite Polytrope Models Rucinski, S. M. Abstract Factional radii of gyration for both the convective envelope and the radiative core have been determined using the composite-polytrope model of Rappaport et al. (1983) which describes low-mass stars by appropriately matched polytropes n(outer) = 3/2 and n(inner) = 3. Radii of gyration computed for ZAMS stars with masses of 0.4-1.2 solar masses are used to obtain ZAMS angular momenta for low-mass rapidly rotating stars in the Pleiades and Alpha Persei clusters. Results indicate that there is little chance of observing single young early G and late F type stars in rapid rotation because of the very short timescales for braking of their thin convective envelopes. Publication: The Astronomical Journal Pub Date: June 1988 DOI: 10.1086/114784 Bibcode: 1988AJ.....95.1895R Keywords: Early Stars; Polytropic Processes; Stellar Interiors; Stellar Mass; Stellar Models; Stellar Rotation; Angular Momentum; Density Distribution; F Stars; G Stars; Astrophysics; STARS: EVOLUTION full text sources ADS | data products SIMBAD (2)

Lithium in the Pleiades and Alpha Persei clusters

view Abstract Citations (115) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Lithium in the Pleiades and alpha Persei Clusters Boesgaard, Ann Merchant ; Budge, Kent G. ; Ramsay, Mary Elizabeth Abstract The authors have made observations of the Li region in 23 F dwarfs of the Pleiades and α Per clusters. All 21 of the stars in the temperature region 6100 - 7300K show strong Li I lines with values of log N(Li) near 3.0 [where log N(H) = 12.0]. There is no apparent Li dip in the Pleiades Li-temperature profile, although a decrease to log N(Li) ≡ 2.85 near 6500K cannot be excluded. The dramatic decline in surface Li, possibly caused by diffusion or differential rotation, apparently occurs for cluster stars between the ages of ≡5×107 and ≡5×108yr. The authors have determined the [Fe/H] abundances for each of their Pleiades and α Per stars. The mean [Fe/H] for the Pleiades is 0.00±0.05 and for α Per is +0.01±0.07. Publication: The Astrophysical Journal Pub Date: April 1988 DOI: 10.1086/166201 Bibcode: 1988ApJ...327..389B Keywords: Abundance; Dwarf Stars; Lithium; Star Clusters; Stellar Spectrophotometry; Stellar Temperature; Charge Coupled Devices; Pre-Main Sequence Stars; Signal To Noise Ratios; Stellar Atmospheres; Stellar Spectra; Astrophysics; CLUSTERS: OPEN; STARS: ABUNDANCES full text sources ADS | data products SIMBAD (27)

PHOTOMETRIC LIGHT CURVES FOR SEVEN RAPIDLY-ROTATING K DWARFS IN THE PLEIADES AND ALPHA PERSEI CLUSTERS.

ABSTRACT Light curves and period estimates were obtained for several Pleiades and Alpha Persei cluster K dwarfs which were identified as rapid rotators in earlier spectroscopic studies. A few of the stars have previously-published light curves, making it possible to study the long-term variability of the light-curve shapes. The general cause of the photometric variability observed for these stars is an asymmetric distribution of photospheric inhomogeneities (starspots). The presence of these inhomogeneities combined with the rotation of the star lead to the light curves observed. The photometric periods derived are thus identified with the rotation period of the star, making it possible to estimate equatorial rotational velocities for these K dwarfs. These data are of particular importance because the clusters are sufficiently young that stars of this mass should have just arrived on the main sequence. These data could be used to estimate the temperatures and sizes of the spot groups necessary to produce the observed light curves for these stars.

Evolution of low-mass stars in the Alpha Persei cluster

view Abstract Citations (167) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolution of low-mass stars in the alpha Persei cluster. Stauffer, J. R. ; Hartmann, L. W. ; Burnham, J. N. ; Jones, B. F. Abstract The results of a photometric and spectroscopic survey of the Alpha Per cluster are presented in tables, graphs, and diagrams and discussed. From relative-proper-motion determinations on about 4000 stars of V magnitude brighter than about 16 in a 1.2 x 1.2-deg area, 88 probable cluster members are selected for BVRI photometry with the 0.9-m and 1.3-m KPNO telescopes and H-alpha and 519.7-nm observations with echelle spectrographs on the 1.5-m telescope and MMT at Mount Hopkins. An apparent premain sequence is seen, and the positions of the faint cluster members on the V/(V-I) diagram correspond to the 50-Myr isochrone proposed by VandenBerg et al. (1983). The light variations observed in six G and K dwarf members are shown in graphs and attributed to surface spots in rotation. Over 50 percent of the stars of types later than G2 are found to have v sin i = 25-150 km/sec (velocities attributed to spin-up during contraction to the main sequence), and comparison with Hyades K dwarfs suggests spin-down to v sin i less than 10 km/sec over a few times 10 Myr. Publication: The Astrophysical Journal Pub Date: February 1985 DOI: 10.1086/162885 Bibcode: 1985ApJ...289..247S Keywords: Astronomical Photometry; Star Clusters; Stellar Evolution; Stellar Motions; Stellar Spectra; Dwarf Stars; G Stars; K Stars; Late Stars; Pre-Main Sequence Stars; Stellar Rotation; Variable Stars; Astronomy full text sources ADS | data products SIMBAD (88) GCPD (1)

Concentrations in the Local Association – II. The northern concentrations including the α Persei, Pleiades, M34 and δ Lyrae clusters

Concentrations in the Local Association – II. The northern concentrations including the α Persei, Pleiades, M34 and δ Lyrae clusters

The VELA star cloud. I - NGC 2547, TR 10, the Gamma Velorum system, and bright stars

view Abstract Citations (54) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The VELA star cloud. I. NGC 2547, TR 10, the GAM Vel system, and bright stars. Eggen, O. J. Abstract The first results of an intermediate-band, large-scale photometric survey of the Vela star cloud are discussed. Attention is given to the luminosity and reddening, as well as the apparent or proper motions of all the CPD stars near NGC 2547, the brightest stars in Trumpler 10, a random selection of stars in the region of Gamma Velorum, and the HR stars. The similarity of the Alpha Persei cluster with the clusters in the Vela sheet is shown, and it is found that the Vela sheet, at least over the region surveyed, is nearly perpendicular to the line of sight. The probability is demonstrated that a thin sheet of coeval (2.5 x 10 to the 7th yr) stars, some 425 pc distant and with a similar metal abundance, lies in front of a dense dark cloud. Publication: The Astrophysical Journal Pub Date: June 1980 DOI: 10.1086/158020 Bibcode: 1980ApJ...238..627E Keywords: Galactic Clusters; Star Clusters; Stellar Evolution; Stellar Spectrophotometry; Brightness; Stellar Luminosity; Stellar Motions; Astrophysics full text sources ADS | data products SIMBAD (171) GCPD (1) Related Materials (2) Part 2: 1982ApJS...50..199E Part 3: 1986AJ.....92.1074E

The main sequence of NGC 6231

view Abstract Citations (38) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The main sequence of NGC 6231. Garrison, R. F. ; Schild, R. E. Abstract New MK spectral classifications (30 stars) and UBV photoelectric photometry (27 stars) are presented for stars in the central region of the rich young cluster NGC 6231, which is the nucleus of the association I Sco. A distance modulus of 11.6 is derived by comparison with the main sequences of II Sco, the Alpha Persei cluster, and the Hyades, assuming a distance modulus of 3.3 for the Hyades. Publication: The Astronomical Journal Pub Date: July 1979 DOI: 10.1086/112506 Bibcode: 1979AJ.....84.1020G Keywords: Electrophotometry; Main Sequence Stars; Star Clusters; Stellar Spectrophotometry; Ubv Spectra; Astronomical Spectroscopy; B Stars; Hertzsprung-Russell Diagram; Astronomy; Main-Sequence Stars:Open Clusters; Open Clusters:Spectral Classification; Open Clusters:UBV Photometry full text sources ADS | data products SIMBAD (31) GCPD (1)

Energy distributions in main-sequence A and F stars

view Abstract Citations (12) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Energy distribution in main-sequence A and F stars. Boehm-Vitense, E. Abstract Scanner observations of A and F main-sequence stars are examined in order to check whether the observed continuum energy distributions match scaled Bilderberg models and whether some influence of rotation on convection can be detected. The continuum energy distributions of A and F field stars and of stars in different clusters with different rotational velocities are compared; the clusters include the Hyades, Praesepe, Coma, Alpha Persei, and the Pleiades. A comparison with radiative-equilibrium model-atmosphere computations reveals some UV flux reduction for many stars with B-V greater than 0.14 and a strong UV flux reduction for all stars with B-V greater than 0.22, regardless of rotational velocity. The energy distributions are found to match the scaled Bilderberg models, and this is attributed to a reduced temperature gradient in convectively unstable layers. It is shown that rotation does not impede convection, but even seems to enhance it, contrary to expectations. Publication: The Astrophysical Journal Pub Date: July 1978 DOI: 10.1086/156285 Bibcode: 1978ApJ...223..509B Keywords: Early Stars; F Stars; Hot Stars; Main Sequence Stars; Spectral Energy Distribution; Ultraviolet Astronomy; A Stars; Atmospheric Models; Continuous Spectra; Interstellar Extinction; Pleiades Cluster; Stellar Rotation; Astrophysics; Convection:Stellar Atmospheres; Main-Sequence Stars: Energy Distribution full text sources ADS | data products SIMBAD (45)

OAO 2 observations of the Alpha Persei cluster

UV photometry of the Alpha Persei cluster obtained with the OAO 2 satellite is analyzed. The data are used together with ground-based coude spectra to examine 20 stars ranging in spectral type from B3 to A3 for rotation effects as predicted by the models of Collins (1974) and of Collins and Sonneborn (1977). Values of v sin i are estimated on the recalibrated system of Slettebak et al. (1975), and an H-R diagram is plotted for the program stars. The distribution of the stars on the diagram is compared with the ZAMS for a chemical composition of X = 0.7 and Y = 0.02 as well as with two isochrones for logarithmic nuclear ages (in years) of 7.5 and 7.7. It is found that there is a seemingly narrow band of early-type stars lying a magnitude or so above the ZAMS on the plot, while the later types form a looser collection straddling the ZAMS. The data for Alpha Persei itself yield an upper limit of 7.4 to the logarithmic age. The analysis for rotation effects reveals one late-type star that does not conform to the model predictions and one 'weak helium' star. Evidence is discussed that these stars are not pole-on rapid rotators. It is concluded that there is a photometric effect for stars earlier than about B6 whereby these stars are displaced redward in color-magnitude diagrams.

A photometric survey of the Alpha Persei cluster for Delta Scuti variables

view Abstract Citations (21) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A photometric survey of the alpha Persei cluster for delta Scuti variables. Slovak, M. H. Abstract To investigate the incidence of Delta Scuti variables in the Alpha Persei cluster, a program of differential photometry was undertaken which included 24 A- and F-type stars (V no more than 9.48) in or near the Delta Scuti instability strip. All stars in the sample were determined to have a high probability of cluster membership on the basis of multiple criteria, including proper motions, radial velocities, and extensive photometric data. Three variables were detected (BD +48 deg 894, BD +48 deg 905, and BD +47 deg 842). These are located in the region of the instability strip and have periods close to those predicted from the period-color-luminosity relation. The relative incidence of Delta Scuti variables in the cluster is approximately 25%. As in the Pleiades cluster, the main-sequence variables may be slower rotators than the nonvariables in the instability strip. The exclusion of pulsation among main-sequence Am stars in the cluster is also confirmed. Publication: The Astrophysical Journal Pub Date: July 1978 DOI: 10.1086/156250 Bibcode: 1978ApJ...223..192S Keywords: Star Clusters; Stellar Evolution; Stellar Spectrophotometry; Variable Stars; A Stars; F Stars; Main Sequence Stars; Pleiades Cluster; Radial Velocity; Stellar Motions; Astronomy; Delta Scuti Stars:Open Clusters full text sources ADS | data products SIMBAD (23)

Experience with a Simple Plate Overlap Reduction Method in a Field Around Alpha Persei

Some years ago at Bergedorf we studied the field around Alpha Persei (Heckmann, O. et alt., 1956). In an area of 5° x 5° more than 100 cluster members were found from an analysis of proper motions (p.m.) of 1453 stars. Meanwhile the field was studied photo metric ally (e.g. Mitchell, R. I., 1960). The age of the group seems to be comparable to that of the Pleiades (cp. e.g. Dachs, J., 1970), of the order of magnitude 108 years.

Studies of Stellar Rotation.IV. a Comparison of Rotational Velocities in the Alpha Persei Cluster and the Pleiades

Studies of Stellar Rotation.IV. a Comparison of Rotational Velocities in the Alpha Persei Cluster and the Pleiades

Spectrophotometry of the F Stars Alpha Canis Minoris and Alpha Persei. III.

view Abstract Citations (6) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometry of the F Stars Alpha Canis Minoris and Alpha Persei. III. Greenstein, Jesse L. ; Hiltner, W. A. Abstract Measurements of line intensities in the P/tot oinet nc Atlas of Stellar Spectra have been used to obtain curves of growth of a CMi and a Per. Remeasurements with a normal transmission-type microphotometer were made to check the intensities; line contours of a few strong lines were also obtained. Curves of growth are given in Figures 1-6; line contours are given in Figures 7 and 8. The line contours are predicted theoret- icallywith the aid of data from the curves of growth. The correction forinstrumental broadening is applied, and the final predicted contours are compared with the observed ones. It is found that in a CMi the damping wings of the lines have been lost because of of the complexity of the spectrum; the K line is also shown to be badly affected by the blending with H~ and H~. The contours of lines in a Per are found to be shallower and broader than those predicted. Either rotation, large-scale turbulence, or an extended atmosphere would produce this shallowness Publication: The Astrophysical Journal Pub Date: March 1949 DOI: 10.1086/145128 Bibcode: 1949ApJ...109..265G full text sources ADS |

Curves of growth of neutral and ionized atoms in the spectrum of alpha Persei.

Intensities of one thousand lines in the spectrum of a Persei have been determined recently from high dispersion spectra, 4 to 7 A7mm, using the Observatory intensitometer. Curves of growth, which relate the intensity of a line to the number of atoms which produce it, have been obtained for a number of atoms by plotting the stellar line intensities against solar f-values. It was found that the shape of the curves for neutral atoms is different from that for ionized atoms. The observations were fitted to theoretical curves given by Menzel and by Unso~ld, and the variable parameters of excitation temperature, damping factor and turbulent velocity were calculated for each atom. Values for a few atoms are given in the accompanying table. r - V No. of Atom km/sec Lioes Fe 1 49505K 1.3 X 106 5.0 325 Ti 1 5600 3.9 53 Cr 1 5350 1.6 4.6 29 Fe II 4500 0.2 7.5 60 Ti II 5350 0.1 6.1 62 Cr II 5400 - 8.3 25 When lines produced by neutral and ionized atoms of the same element are compared it appears that, for the neutral atom, I. the excitation temperature is somewhat higher; 2. the damping factor is greater, i.e., the pressure is greater; 3. the turbulent velocity is less. Though the observations and the method are such that these conclusions cannot be considered final, they suggest that there is appreciable stratification in the atmosphere of this supergiant star, with the mean position of the ionized atoms lying above that of the neutral atoms. Dominion Astrophysical Observatory, Victoria, B. C.

Predicted lines of CrII in the spectra of the Sun and of alpha Persei.

Predicted lines of CrII in the spectra of the Sun and of alpha Persei.