CDROM/AJ/V108/P0222
Pop. II Variable Stars (Nemec+ 1994)
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Period-Luminosity-Metallicity Relations, Pulsation Modes, Absolute
Magnitudes,
and Distances for Population II Variable Stars
James M. Nemec, Amanda F. Linnell Nemec, Thomas E. Lutz
<1994, AJ, 108, 222>
=1994AJ....108..222N
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Abstract:
Period-luminosity-metallicity (P-L-[Fe/H]) relations are presented for
RR Lyrae stars, Pop. II Cepheids, anomalous Cepheids and SX Phe stars
pulsating in the fundamental (F) and first-overtone (H) modes. The
relations were derived by fitting regression lines to the observed
pulsation periods and mean B, V, and K magnitudes of over 1200 stars in
~40 stellar systems. Analysis of covariance methods, which allow the
simultaneous computation of more than one P-L-[Fe/H] relation, were
used to estimate the slopes and intercepts. Of the 24 possible
P-L-[Fe/H] relations for the four kind of stars, two pulsation modes,
and three passbands considered here, 18 relations have been derived -the others could not be derived because of a lack of photometry in one
or more of the three passbands. The slopes for the F and H pulsators
were tested for departures from equality for all types of stars and
passbands; the results suggest that the observations are consistent
with the assumption that, for each kind of star (except possibly the
Pop. II Cepheids), the P-L-[Fe/H] relations for the F and H pulsation
modes are parallel but vertically offset, with a family of lines
corresponding to a range of metallicities. Pulsation modes and
absolute magnitudes are presented for the non-RR Lyrae variable stars
considered in the analysis, and distances are estimated for the program
clusters. It is well established from previous studies that the P-L
relations for RR Lyrae stars are approximately flat for the B passband,
and have a slope Delta M(K)/Delta log P ~ -2.4 for the K passband. We
recover these slopes, and find that the P-L-[Fe/H] relation in V has an
intermediate slope, Delta M(V)/Delta log P = -0.52 +/- 0.11. A similar
dependence of slope on passband is seen for classical Cepheids [see
Madore & Freedman, PASP, 103, 933 (1991)]. The available B,V
photometry for ~40 of the known globular cluster Cepheids are found to
be consistent with Arp's [AJ, 60, 1 (1955)] assumption that Pop. II
Cepheids pulsate in the F and H modes (and not in the F mode only, as
has often been assumed). The estimated slopes of the corresponding
P-L-[Fe/H] relations are Delta M(B)/Delta log P = -1.69 +/- 0.05 and
Delta M(V)/Delta log P = -1.93 +/- 0.05, with a separation between the
F and H modes of 0.59 mag in B, and 0.45 mag in V. As in the case of
the RR Lyrae stars the redder passband has the steeper slope. We find
that 15 of the 21 short-period BL Her Cepheids (P <= 8 days) appear to
be H pulsators, while 15 of the 19 W Cir Cepheids (12 <= P <= 30 days)
appear to be F pulsators. The period-amplitude (P-A(B)) diagram
suggests that at a given period the first-overtone pulsators have
larger amplitudes than the fundamental mode pulsators. For the
Anomalous Cepheids the estimated P-L-[Fe/H] relations have slopes Delta
M(B)/Delta log P = -3.20 +/- 0.18, and Delta M(V)/Delta log P = -3.13
+/- 0.28. The offsets between the F and H mode relations are 0.68 and
0.66 mag in B and V, respectively. The estimated P-L-[Fe/H] relations
in B and V for the SX Phe stars have slopes Delta M(B)/Delta log P =
-2.66 +/- 0.52 and Delta M(V)/Delta log P = -2.56 +/- 0.54, and the F
and H relations are separated by 0.34 and 0.29 mag in B and V,
respectively. These relations are consistent with the observed period
ratio for the double-mode star SX Phe. In a period-amplitude diagram
the longest period SX Phe stars have the largest amplitudes, with no
dependence on metallicity. The (B-V)0 color range of the SX Phe stars
is from 0.12 to 0.29.
File Summary:
------------------------------------------------------------------------------File Name
Lrecl
Records
Explanations
------------------------------------------------------------------------------table4.dat
137
50
Pop. II Cepheids in galactic globular
clusters
table4.tex
106
315
TeX version of table4.dat
table4.txt
79
167
Plain text version of table4.tex
table5.dat
157
24
Anomalous Cepheids: puls. modes and abs.
mags
table5.tex
89
235
TeX version of table5.dat
table5.txt
80
105
Plain text version of table5.tex
table6.dat
154
21
SX Phe Stars: pulsation modes and abs.
mags
table6.tex
109
239
TeX version of table6.dat
table6.txt
78
103
Plain text version of table6.tex
------------------------------------------------------------------------------Byte-by-byte Description of file: table4.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1-11
A11
--Name
*Star name
12-17
F6.2
--Fe_H
[]? Assumed metal abundance
18-22
F5.2
--E_B-V
[]? Assumed reddening
23-32
F10.6
day
P
[]? Pulsation period
33-40
F8.4
--logP
[]? Log base 10 of P
41
1X
----Blank
42-45
A4
--Type
*Type of Cepheid and pulsation mode
46-50
F5.2
--A_B
Blue amplitude of the Cepheid
51-56
F6.2
mag
B
Assumed mean B magnitude
57-62
F6.2
mag
B0
Dereddened B magnitude
63-68
F6.2
mag
V
[]? Assumed mean V magnitude
69-74
F6.2
mag
V0
[]? Dereddened V magnitude
75-79
F5.2
mag
B-V
[]? B-V color
80-84
F5.2
mag
B-V_0
[]? Dereddened B-V color
85-90
F6.2
mag
o_B0_M15 *Observed M15-normalized apparent B
mag
91-96
F6.2
mag
p_B0_M15 *Predicted M15-normalized apparent B
mag
97-102 F6.2
mag
o_V0_M15 *[]? Observed M15-normalized apparent
V mag
103-108 F6.2
mag
p_V0_M15 *[]? Predicted M15-normalized
apparent V mag
109-114 F6.2
mag
o_M_B
Observed absolute B magnitude
115-120 F6.2
mag
p_M_B
Predicted absolute B magnitude
121-126 F6.2
mag
o_M_V
[]? Observed absolute V magnitude
127-132 F6.2
mag
p_M_V
[]? Predicted absolute V magnitude
133
1X
----Blank
134-137 A4
--Ref
*Reference for source of data
------------------------------------------------------------------------------Notes for file: table4.dat
------------------------------------------------------------------------------Type:
Cepheid Types:
BL=BL Her
WV=W Vir
RV=RV Tau
Pulsation Modes: F = fundamental mode
H = first-overtone mode
o_B0_M15, p_B0_M15, o_V0_M15, p_V0_M15:
Observed and predicted apparent B and V magnitudes after correcting and
normalizing the metallicity and distance to that of M15 (i.e., the
magnitudes
are the values that the stars would have if they were all at the
distance of
M15 and had the metallicity [Fe/H] = -2.15). See equation 5 in the
printed
paper.
Ref:
C88
CS78
D69
DH74
DC67
E72
G93
H85
=
=
=
=
=
=
=
=
K68
L74
PM77
PR77
W86
WS84
WS85
W92
=
=
=
=
=
=
=
=
Clement, Sawyer Hogg & Yee 1988, AJ, 96, 1642
Clement & Sawyer Hogg 1978, AJ, 83, 167
Demers 1969, AJ, 74, 926
Demers & Harris 1974, AJ, 79, 627
Dickens & Carey 1967, Roy. Obs. Bull. no. 129, p. E335
Eggen 1972, ApJ, 172, 639
Gonzalez 1993, Ph.D. thesis, U. of Washington, Seattle, WA
Harris 1985, in Cepheids: Theory and Observations. IAU
Colloquim No. 82, edited by B. F. Madore (Cambridge
University Press, Cambridge), p. 232
Kwee 1968, Bulletin Astron. Inst. Netherlands, 19, 374
Lee 1974, Observatory, 94, 74
Pike & Meston 1977, MNRAS, 180, 613
Pinto & Rosino 1977, A&AS, 28, 427
Wehlau et al. 1986, AJ, 91, 1340
Wehlau & Sawyer Hogg 1984, AJ, 89, 1005
Wehlau & Sawyer Hogg 1985, AJ, 90, 2514
Wehlau 1992, private communication
------------------------------------------------------------------------------Byte-by-byte Description of file: table5.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1-14
A14
--Name
Star name
15-20
F6.2
--Fe_H
Assumed metal abundance
21-25
F5.2
--E_B-V
Assumed reddening
26-34
F9.5
h
Ph
Pulsation period (hours)
35-43
F9.6
day
Pd
Pulsation period (day)
44-51
F8.4
--logP
Log base 10 of P (day)
52
1X
----Blank
53
A1
--Mode
*Pulsation mode
54-59
F6.2
mag
B
Assumed mean B magnitude
60-65
F6.2
mag
B0
Dereddened B magnitude
66-70
F5.2
--A_B
[]? B pulsation amplitude
71-76
F6.2
mag
V
[]? Assumed mean V magnitude
77-82
F6.2
mag
V0
[]? Dereddened V magnitude
83-87
F5.2
--A_V
[]? V pulsation amplitude
88-92
F5.2
mag
B-V
[]? B-V color
93-97
F5.2
mag
B-V_0
[]? Dereddened B-V color
98-103 F6.2
mag
o_B0_M15
Observed M15-normalized apparent B
mag
104-109 F6.2
mag
p_B0_M15
Predicted M15-normalized apparent B
mag
110-115 F6.2
mag
d_B0_M15
Difference between o_B0(M15)p_B0(M15)
116-121 F6.2
mag
o_V0_M15
[]? Observed M15-normalized apparent
V mag
122-127 F6.2
mag
p_V0_M15
[]? Predicted M15-normalized
apparent V mag
128-133 F6.2
mag
d_B0_M15
[]? Difference between o_V0(M15)p_V0(M15)
134-139 F6.2
mag
o_M_B
Observed absolute B magnitude
140-145 F6.2
mag
p_M_B
Predicted absolute B magnitude
146-151 F6.2
mag
o_M_V
[]? Observed absolute V magnitude
152-157 F6.2
mag
p_M_V
[]? Predicted absolute V magnitude
------------------------------------------------------------------------------Notes for file: table5.dat
------------------------------------------------------------------------------Mode:
Pulsation Modes: F = fundamental mode
H = first-overtone mode
------------------------------------------------------------------------------Byte-by-byte Description of file: table6.dat
------------------------------------------------------------------------------Bytes Format Units
Label
Explanations
------------------------------------------------------------------------------1-14
A14
--Name
Star name
15-20
F6.2
--Fe_H
Assumed metal abundance
21
1X
----Blank
22-24
A3
--r_Fe_H
*Source of metal abundance
25-29
F5.2
--E_B-V
Assumed reddening
30
1X
----Blank
31-33
A3
--r_E_B-V
*Source of reddening
34-40
F7.2
min
Pm
Pulsation period (minutes)
41-47
F7.4
day
Pd
Pulsation period (day)
48-54
F7.4
--logP
Log base 10 of P (day)
55
1X
----Blank
56
A1
--Mode
*Pulsation mode
57-62
F6.2
mag
B
Assumed mean B magnitude
63-68
F6.2
mag
B0
Dereddened B magnitude
69-74
F6.2
mag
V
Assumed mean V magnitude
75-80
F6.2
mag
V0
Dereddened V magnitude
81-85
F5.2
--A_V
V pulsation amplitude
86-90
F5.2
mag
B-V
B-V color
91-95
F5.2
mag
B-V_0
Dereddened B-V color
96-101 F6.2
mag
o_B0_M15
Observed M15-normalized apparent B
mag
102-107 F6.2
mag
p_B0_M15
[]? Predicted M15-normalized
apparent B mag
108-113 F6.2
mag
d_B0_M15
[]? Difference between o_B0(M15)p_B0(M15)
114-119 F6.2
mag
o_V0_M15
Observed M15-normalized apparent V
mag
120-125 F6.2
mag
p_V0_M15
[]? Predicted M15-normalized
apparent V mag
126-131 F6.2
mag
d_B0_M15
[]? Difference between o_V0(M15)p_V0(M15)
132-136 F5.2
mag
o_M_B
Observed absolute B magnitude
137-141 F5.2
mag
p_M_B
[]? Predicted absolute B magnitude
142-146 F5.2
mag
o_M_V
Observed absolute V magnitude
147-151 F5.2
mag
p_M_V
[]? Predicted absolute V magnitude
------------------------------------------------------------------------------Notes for file: table6.dat
------------------------------------------------------------------------------r_Fe_H:
ADZ = Armandroff, Demarque & Zinn 1993,
BM = Burki & Meylan 1986, A&A, 159, 261
EI = Eggen & Iben 1989, AJ, 97, 431
GMC = Geisler, Minniti & Claria 1992, AJ, 104, 627
KK = Kaluzny & Krzeminski 1993, MNRAS, 264, 785
MB = McNamara & Budge 1985, PASP, 97, 322
MF = McNamara & Feltz 1980, PASP, 90, 275
ZW
= Zinn & West 1984, ApJS, 55, 45
r_E_B-V:
FRN = Fahlman, Richer & Nemec 1991, ApJ, 380, 124
RF = Richer & Fahlman 1988, ApJ, 325, 218
Z85 = Zinn 1985a, ApJ, 293, 424
Mode:
Pulsation Modes: F = fundamental mode
H = first-overtone mode
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(End)
Lee Brotzman [ADS] 10Oct-1994