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J/A+AS/121/213 BV photometry of Blanco 1 stars (Panagi+, 1997)
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Spectroscopy of the open cluster Blanco 1. II.
Halpha emission as an indicator of relative age
Panagi P.M., O'Dell M.A.
<Astron. Astrophys. Suppl. Ser. 121, 213 (1997)>
=1997A&AS..121..213P (SIMBAD/NED BibCode)
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ADC_Keywords: Clusters, open ; Photometry
Keywords: Galaxy: open clusters and associations: Blanco 1 - stars: activity -
stars: chromospheres - stars: late-type
Abstract:
We present the results of H{alpha}(6562A) and Li I(6708A)
observations of 114 low-mass stars of the young open cluster Blanco 1.
We also present observations of 30 stars in Ca II(K). This work
extends the first Blanco 1 spectroscopic study of Panagi et al.
(1994A&A...285..233D). From a sample of four well-studied clusters,
including Blanco 1, we find that the fraction of H{alpha}
emission-line stars amongst K dwarfs is a good indicator of relative
age, with a smaller fraction indicative of older age. Blanco 1 shows
a relatively small fraction of emitters, inconsistent with previous
age estimates for the cluster. We estimate the cluster age to to be
90+/-25Myr, slightly older than the Pleiades. The method is shown to
be more sensitive to age than lithium and a useful alternative to
other age measurement techniques. The variation of H{alpha} with (B-V)
is similar to that observed in the older solar neighbourhood dwarfs,
suggesting that, at least for the absorption-line stars, the
contribution of stellar rotation to the equivalent width is unclear.
We combine both spectroscopy and photometry to revise cluster
membership and give accurate positions for all these stars.
Objects:
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RA (2000) DE Designation(s)
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00 04.3 -29 56 Blanco 1 = C 0001-302 = zeta Scl cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1 64 210 APM positions of proposed members of the
open-cluster Blanco 1.
tablea2 52 57 Positions of stars/objects classified as
non-members.
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Byte-by-byte Description of file: tablea1
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Bytes Format Units Label Explanations
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1- 3 I3 --- ZS ? ZS number (de Epstein & Epstein (1985))
4 A1 --- m_ZS Multyiplicity index on ZS
6- 7 A2 --- n_ZS Note on ZS (1)
11- 12 I2 h RAh Right ascension 1950.0
14- 15 I2 min RAm Right ascension 1950.0
17- 21 F5.2 s RAs Right ascension 1950.0
23 A1 --- DE- Declination sign
24- 25 I2 deg DEd Declination 1950.0
27- 28 I2 arcmin DEm Declination 1950.0
30- 33 F4.1 arcsec DEs Declination 1950.0
35- 39 F5.2 mag Vmag V magnitude
41- 46 F6.3 mag B-V B-V color index
49- 68 A20 --- Name Other designations (2)
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Note (1): ** = binary
+ = possible error in position.
# = close pair/group, target in doubt or unresolved by the APM.
~ = not recovered by the APM.
Note (2): W = Star No. assigned by Westerlund et al. (1988, <J/A+AS/76/101>)
E = Star No. assigned by Epstein (1968AJ.....73..556E)
HD = Henry Draper Catalogue number
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Byte-by-byte Description of file: tablea2
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Bytes Format Units Label Explanations
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1- 3 I3 --- ZS ZS number (de Epstein & Epstein, 1985)
5- 7 I3 --- West ? Westerlund number (Westerlund et al. (1988))
9- 10 I2 h RAh Right ascension 1950.0
12- 13 I2 min RAm Right ascension 1950.0
15- 19 F5.2 s RAs Right ascension 1950.0
21 A1 --- DE- Declination sign
22- 23 I2 deg DEd Declination 1950.0
25- 26 I2 arcmin DEm Declination 1950.0
28- 31 F4.1 arcsec DEs Declination 1950.0
33- 37 F5.2 mag Vmag V magnitude
39- 43 F5.3 mag B-V B-V color index
46- 52 A7 --- Rem Remarks (1)
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Note (1): The publication/source where non-membership status was first given,
P78 = Perry, Walter & Crawford (1978PASP...90...81P)
A85 = Abraham de Epstein & Epstein (1985AJ.....90.1211D)
W88 = Westerlund et al (1988A&AS...76..101W, Cat. <J/A+AS/76/101>)
P94 = Panagi et al (1994A&A...285..233D)
P96 = this paper.
and criterion, where:
pm = proper motion studies.
ph = photometry.
sp = spectroscopy.
ns = non-stellar object
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References:
de Epstein & Epstein, 1985, AJ, 90, 1211 =1985AJ.....90.1211D
Epstein I., 1968, AJ, 73, 556 =1968AJ.....73..556E
Panagi P.M. et al. 1994, A&A, 292, 439 (Paper I) =1994A&A...285..233D
Perry C.L. et al., 1978, PASP, 90, 81 =1978PASP...90...81P
Westerlund B.E. et al., 1988, A&AS, 76, 101 =Catalogue <J/A+AS/76/101>
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(End) Patricia Bauer [CDS] 03-Jun-1996