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 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 1988AJ.....96..148W,
Griffin et al. 1988AJ.....96..172G 1988AJ.....96..172G, Stauffer 1982AJ.....87..899S 1982AJ.....87..899S),
Pleiades (Stauffer et al. 1991AJ....101..980S 1991AJ....101..980S, Prosser et al.
1991AJ....101.1361P 1991AJ....101.1361P), and Praesepe (Mermilliod et al.
1990A&A...235..114M 1990A&A...235..114M, Jones & Stauffer 1991AJ....102.1080J 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 121 187 Table 4: HE candidates (Heckmann et al.
1956AN....283..109H 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
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See also:
I/68 : Positions and Proper Motions in alpha Per cluster (Fresneau 1980)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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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
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Note on RAh, DE-, DEd:
Coordinates determined from the x,y coordinates in arcsec given by
Heckmann et al. (1956AN....283..109H 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 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 1969PDAO...13..329P)
2). Stauffer et al. (1985ApJ...289..247S 1985ApJ...289..247S).
3). Stauffer et al. (1989ApJ...346..160S 1989ApJ...346..160S).
4). Kraft (1967a, 1967ApJ...148..129K 1967ApJ...148..129K).
5). This study, Hamilton spectrograph.
6). Abt et al. (1990ApJS...74..551A 1990ApJS...74..551A).
7). Morse et al. (1991AJ....101.1495M 1991AJ....101.1495M).
8). Morrell and Abt (1991 preprint, 1992ApJ...393..666M 1992ApJ...393..666M).
9). HE 441 = HD 20510.
10). HE 601: V0-MV=14.4, Crawford and Barnes (1974AJ.....79..687C 1974AJ.....79..687C).
11). Mermilliod (1991, priv. comm.).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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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 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
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Note on RAh, DE-, DEd:
Coordinates from Heckmann et al. (1956AN....283..109H 1956AN....283..109H).
Note on Fprob:
Probability of membership in Alpha Persei cluster from Fresneau
(1980AJ.....85...66F 1980AJ.....85...66F).
Note on mBVI:
Fresneau's membership status based on BVI photometry.
Note on muvby:
Trullols et al. (1989A&AS...81...47T 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.
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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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- 23 I1 --- v Number of V obs.
25- 25 I1 --- b Number of B obs.
27- 27 I1 --- i Number of I obs.
30- 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
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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 1985ApJ...289..247S, 1989ApJ...346..160S 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.
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Byte-by-byte Description of file: table11.dat
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Bytes Format Units Label Explanations
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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
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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 1985ApJ...289..247S, 1989ApJ...346..160S 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).
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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