V/80 Low-Mass Stars' Membership in Alpha Persei Cluster (Prosser 1992)
Membership of Low-Mass Stars in the Open Cluster Alpha Persei Prosser C.F. <Astron. J. 103, 488 (1992)> =1992AJ....103..488P
ADC_Keywords: Clusters, open; Stars, masses; Proper motions; Spectroscopy; Description: This catalog contains the tabulated results of a combined astrometric, photometric, and spectroscopic search for low-mass members in the intermediate-age open cluster Alpha Persei. It contains information on 132 new members and likely members, and 16 uncertain members of Alpha Per. The new membership information suggested to the author a revised age of the cluster to approximately 8x10+7yr. Tabulated data include AP number, VBI photometry, 1950 coordinates, relative proper motions with errors, H-alpha equivalent widths, and spectral type. Included are the individual membership determinations, based on H-alpha emission, spectral type, and echelle spectra data. The photometric data were obtained with the Lick Obs. 1-m Nickel Telescope using a TI 500x500 pixel CCD in B, V, and I bands. Low dispersion CCD spectra centered on H-alpha for candidates whose V-I photometry indicated likely membership using the Lick 1-m Nickel and 3-m Shane telescopes. High-dispersion echelle spectra were obtained for many bright candidates using the Hamilton echelle spectrographic with the Shane and Coude auxiliary telescopes. Introduction: van den Bergh & Sher (1960) found from studying several open clusters that in general the faint end of the cluster luminosity function decreased or remained constant down to the level of observation. If true, the observed cluster luminosity functions are unable to account for the luminosity function of nearby field stars which increases to faint magnitudes. One possible solution is that additional unidentified low-mass stars exist in most (or all) open clusters. Recent studies in the Hyades (Weis & Hanson 1988AJ.....96..148W, Griffin et al. 1988AJ.....96..172G, Stauffer 1982AJ.....87..899S), Pleiades (Stauffer et al. 1991AJ....101..980S, Prosser et al. 1991AJ....101.1361P), and Praesepe (Mermilliod et al. 1990A&A...235..114M, Jones & Stauffer 1991AJ....102.1080J) have identified faint candidate members. It is the aim of this study to determine the existence, and some of the properties, of the low-mass membership in the open cluster Alpha Persei. Alpha Per was chosen for study because of the limited information on low-mass membership, because it is nearby (which enables both proper motion analysis and observation of low-mass candidates), because no other clusters of the same relatively youthful age have been studied completely, and because of the existence of the photographic plate material needed for the proper motion analysis. After a brief review of the history and previous work in this cluster, the proper motion survey of this study is described. This is accompanied by a description of the CCD photometry and spectroscopy programs employed to aid in identifying cluster members. A review of current information on previous members and possible members is also given, followed by a section presenting the new members and candidate members found in this study. An analysis of some cluster properties including luminosity function, age, spatial distribution of members, reddening, H-alpha emission strengths, and rotational velocity distribution is presented. Finally, the last section provides a general review of the results found in Alpha Per. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table4.dat 121 187 Table 4: HE candidates (Heckmann et al. 1956AN....283..109H) table6.dat 100 58 Table 6: Fresneau's suggested HE members table10.dat 106 148 Table 10: New AP membership information table11.dat 72 33 Table 11: Velocities of new AP stars refs.txt 74 74 References from the source publication prosser.tex 95 1554 LaTeX Document (in lyxtex) lyxtex.tex 68 27 Lyxtex macros based on Psizzl fontdefs.lyx 76 365 Lyxtex support file letter.lyx 73 213 Lyxtex support file lists.lyx 72 113 Lyxtex support file macros.lyx 73 89 Lyxtex support file memo.lyx 65 79 Lyxtex support file misc.lyx 75 138 Lyxtex support file output.lyx 71 203 Lyxtex support file
See also: I/68 : Positions and Proper Motions in alpha Per cluster (Fresneau 1980) Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 4 I4 --- HE Star identification 6 A1 --- HEn *[N ] 8- 12 F5.2 mag Vmag *V magnitude 13 A1 --- u_Vmag *[: ]V magnitude uncertainty flag 15- 19 F5.3 mag B-V *B-V color index 22- 28 A7 --- BD BD (Cat. I/122) designation 30 I1 h RAh *Right ascension (1950) 33- 34 I2 min RAm Right ascension (1950) 37- 40 F4.1 s RAs Right ascension (1950) 42 A1 --- DE- *Declination (1950) sign 43- 44 I2 deg DEd *Declination (1950) 47- 48 I2 arcmin DEm Declination (1950) 50- 52 F3.0 arcsec DEs Declination (1950) 54- 58 F5.1 km/s RVKr ?Radial velocity from Kraft 60- 64 A5 km/s RVo [0-9 . :±] Other radial velocity 66- 69 F4.1 km/s e_RVo ?Error in other radial velocity 71- 72 A2 --- l_Vrot [>≤ ] Limit indication for rot. velocity 73- 75 I3 km/s Vrot *?Rotational velocity from echelle spectra 76 A1 --- u_Vrot [: ]Rotational velocity uncertainty flag 78 I1 --- ref_1 *?Reference 1 80 I1 --- ref_2 *?Reference 2 82- 83 A2 --- mphot [YN? ] HE membership from photometry 85- 86 A2 --- mesche [YN? ] HE membership from echelle spectra 88- 89 A2 --- mli [YWK? ] HE membership from LI 91- 92 A2 --- mfinal [YN? ] Final HE membership determination 94-121 A28 --- notes Notes
Note on RAh, DE-, DEd: Coordinates determined from the x,y coordinates in arcsec given by Heckmann et al. (1956AN....283..109H). Note on HEn: Heckmann's star identification numbers, followed by an "N" if it is a non-member. Note on Vmag, u_Vmag, B-V: Photometry from Mitchell (1960ApJ...132...68M). Identification of nonmembers in table 4 was usually based on star's photometry and radial velocity. Note on Vrot: Radial and rotational velocities in table 4 are from a variety of sources, rather than from this study. Note on ref_1, ref_2: 1). Petrie and Heard (1970) (1969PDAO...13..329P) 2). Stauffer et al. (1985ApJ...289..247S). 3). Stauffer et al. (1989ApJ...346..160S). 4). Kraft (1967a, 1967ApJ...148..129K). 5). This study, Hamilton spectrograph. 6). Abt et al. (1990ApJS...74..551A). 7). Morse et al. (1991AJ....101.1495M). 8). Morrell and Abt (1991 preprint, 1992ApJ...393..666M). 9). HE 441 = HD 20510. 10). HE 601: V0-MV=14.4, Crawford and Barnes (1974AJ.....79..687C). 11). Mermilliod (1991, priv. comm.).
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 4 I4 --- HE Star identification 6- 10 F5.2 mag Vmag V magnitude 11- 15 F5.2 mag B-V B-V color index 17- 21 F5.2 mag V-I V-I color index 23 I1 --- v Number of V observations 25 I1 --- b Number of B observations 27 I1 --- i Number of I observations 29- 34 A6 --- BD BD designation (Cat. I/122) 36 I1 h RAh *Right ascension (1950) 38- 39 I2 min RAm Right ascension (1950) 41- 44 F4.1 s RAs Right ascension (1950) 45 A1 --- DE- *Declination (1950) sign 46- 47 I2 deg DEd *Declination (1950) 49- 50 I2 arcmin DEm Declination (1950) 52- 53 I2 arcsec DEs Declination (1950) 55- 58 F4.2 --- Fprob *Fresneau's membership probability 60- 61 A2 --- mBVI *[YN? ] Membership based on BVI 63- 64 A2 --- muvby *[YNPM? ] Membership based on uvby-beta photometry by Trullols et al. (1989A&AS...81...47T) 66- 70 F5.1 km/s RV *?Radial velocity from echelle spectra 73- 76 F4.1 km/s e_RV ?Error in radial velocity 79 A1 --- l_Vrot [>< ] Limit indication for rot. velocity 80- 82 I3 km/s Vrot *?Rotational velocity from echelle spectra 83 A1 --- u_Vrot [: ] Rotational velocity uncertainty 85- 86 A2 --- mfinal [YN? ] Final HE membership determination 88-100 A13 --- notes Notes
Note on RAh, DE-, DEd: Coordinates from Heckmann et al. (1956AN....283..109H). Note on Fprob: Probability of membership in Alpha Persei cluster from Fresneau (1980AJ.....85...66F). Note on mBVI: Fresneau's membership status based on BVI photometry. Note on muvby: Trullols et al. (1989A&AS...81...47T) obtained uvby-beta photometry for a number of these stars and assigned this membership status for them. Note on RV, Vrot: Velocity information in Table 6 is mostly from the echelle spectra obtained in this study.
Byte-by-byte Description of file: table10.dat
Bytes Format Units Label Explanations
1- 3 I3 --- AP *AP number 6- 10 F5.2 mag Vmag *V magnitude 12- 15 F4.2 mag B-V *?B-V color index 17- 20 F4.2 mag V-I *V-I color index 23 I1 --- v Number of V obs. 25 I1 --- b Number of B obs. 27 I1 --- i Number of I obs. 30 I1 h RAh Right ascension (1950) 32- 33 I2 min RAm Right ascension (1950) 35- 38 F4.1 s RAs Right ascension (1950) 40 A1 --- DE- Declination sign 41- 42 I2 deg DEd Declination (1950) 44- 45 I2 arcmin DEm Declination (1950) 47- 49 F3.0 arcsec DEs Declination (1950) 52- 55 F4.2 arcsec/yr pmX Relative proper motion in X direction 57- 61 F5.2 arcsec/yr pmY Relative proper motion in Y direction 63- 66 F4.2 10mas/yr e_pmX Proper motion error in X direction 68- 71 F4.2 10mas/yr e_pmY Proper motion error in Y direction 74- 77 A4 0.1nm EW [0-9 .-]? H-alpha equiv. width (angstroms) 80- 84 A5 --- Sp ?MK Spectral Type 87- 88 A2 --- mphot *[YN? ] phot. membership determination 90- 91 A2 --- mhalph *[YNWAF? ]? H-alpha membership determination 93- 94 A2 --- mspect *[YN? ]? Spectral membership determination 97- 98 A2 --- mesche *[YN? ]? Echelle spect. determination 101-102 A2 --- mfinal [Y? ] Final membership determination 104-106 A3 --- notes *Notes
Note on AP: To avoid confusion, the author has given new cluster members and candidate cluster members the designation of AP stars numbered consecutively to follow the lists of Stauffer et al. (1985ApJ...289..247S, 1989ApJ...346..160S). Note on Vmag, B-V, V-I: The photometric data were obtained with the Lick Obs. 1-m Nickel Telescope using a TI 500x500 pixel CCD in B, V, and I bands. Note on mphot: The author has used the V-I color to separate cluster stars from the background field. The determination was based on plotting V-I vs. V. Note on mhalph: Low dispersion CCD spectra centered on H-alpha for candidates whose V-I photometry indicated likely membership were obtained using the Lick 1-m Nickel and 3-m Shane telescopes. Stars showing definite emission at low dispersion form a well defined sequence in a plot of V vs. pMK. Stars falling below this sequence have spectral types too early for their apparent magnitudes. Many of the stars falling below the cluster sequence are late-type (K, early M) stars, with weak H alpha absorption. Some stars along the sequence are H alpha filled, and may be stars having weaker H alpha emission that is not strong enough to result in a noticeable emission feature at this resolution. Y = emission, F = filled, WA = weak absorption, N = no emission Note on mspect: (See note on mhalph). The presence or absence of H alpha emission alone is not adequate for membership determination. The spectral type is an aid based on the V vs. pMK sequence and the H alpha observations are a confirming or secondary aid. Note on mesche: A large fraction of the bright candidates were observed using the Hamilton echelle spectrograph on the 3m Shane and Coude Auxilliary telescopes. These were used to measure radial and rotational velocities. Slow rotators (Vrot ≤ 20 km/s) with radial velocities within approx. 2 km/s of the cluster mean were considered to be members. Note on notes: Additional notes related to the final cluster membership determination. MMT means that a low-dispersion MMT spectrum at H alpha was obtained.
Byte-by-byte Description of file: table11.dat
Bytes Format Units Label Explanations
1- 3 I3 --- AP *AP number 6- 10 F5.2 mag Vmag *V magnitude 12- 15 F4.2 mag B-V *?B-V color index 17- 20 F4.2 mag V-I *V-I color index 23- 27 F5.1 km/s RV ?Heliocentric radial velocity 29- 32 F4.1 km/s e_RV ?Error in radial velocity 34- 38 A5 km/s Vrot [0-9>←: ] Rotational velocity (Vsini) 41- 43 A3 --- Li *[STRYWK?- ] Presence of Li 6707 line 46- 47 A2 --- mesche *Membership based on echelle spectra 50- 70 A21 --- Notes ?Notes on binary status, spectrum, velocity
Note on AP: To avoid confusion, the author has given new cluster members and candidate cluster members the designation of AP stars numbered consecutively to follow the lists of Stauffer et al. (1985ApJ...289..247S, 1989ApJ...346..160S). Note on Vmag, B-V, V-I: The photometric data were obtained with the Lick Obs. 1-m Nickel Telescope using a TI 500x500 pixel CCD in B, V, and I bands. See source reference for details of the photometric reduction. Note on Li: Indicates presence (and/or relative strength) of Li 6707 absorption line for the new AP stars from the high-dispersion spectra. This is considered a supporting piece of evidence for cluster membership. Note on mesche: Indicates whether or not radial velocity and rotational velocity from echelle spectra suggest cluster membership. (See note on mesche for table 10 above).
References: References can be found in the file "refs.txt". Modifications: [ADC] 4-Jun-1997: The tables were extracted from the lyxtex files provided by the author. This necessitated reformatting to align columns and replace some non-ASCII characters. The parentheses around velocity error values in table 6 were removed. [ADC] 4-Jun-1997: Coordinates in table 4 were computed by author from x,y coordinates of Heckmann et al. (1956). ADC changed two entries as follows: HE 756 Dec changed from 48d 05' 60." to 48d 06' 00." HE 861N Dec changed from 46d 45' 60." to 46d 46' 00." [CDS] 13-Jul-2001: added bibcodes in the documentation.
(End) James E. Gass [ADC/SSDOO] 4-Jun-1997
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