J/AJ/108/222 J/AJ/108/222 Pop. II variable stars J M Nemec A F Linnell-Nemec T E Lutz Astron. J. 108 222 1994 1994AJ....108..222N Clusters, globular Stars, population II Stars, variable 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 DeltaM(K)/DeltalogP~-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)/DeltalogP=-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 DeltaM(V)/DeltalogP=-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<=8days) appear to be H pulsators, while 15 of the 19 W Cir Cepheids (12<=P<=30days) 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 DeltaM(B)/DeltalogP=-3.20+/-0.18, and DeltaM(V)/DeltalogP=-3.13+/-0.28. The offsets between the F and H mode relations are 0.68 and 0.66mag in B and V, respectively. The estimated P-L-[Fe/H] relations in B and V for the SX Phe stars have slopes DeltaM(B)/DeltalogP=-2.66+/-0.52 and DeltaM(V)/DeltalogP=-2.56+/-0.54, and the F and H relations are separated by 0.34 and 0.29mag 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.

Name Star name --- [Fe/H] Assumed metal abundance --- E(B-V) Assumed reddening --- P Pulsation period d logP Log base 10 of P d Type Type of Cepheid and pulsation mode number=1 Cepheid Types: BL=BL Her WV=W Vir RV=RV Tau Pulsation Modes: F = fundamental mode H = first-overtone mode --- AB Blue amplitude of the Cepheid mag Bmag Assumed mean B magnitude mag B0 Dereddened B magnitude mag Vmag Assumed mean V magnitude mag V0 Dereddened V magnitude mag B-V B-V color mag (B-V)0 Dereddened B-V color mag B0obs Observed M15-normalized apparent B mag number=2 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. mag B0pred Predicted M15-normalized apparent B mag number=2 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. mag V0obs Observed M15-normalized apparent V mag number=2 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. mag V0pred Predicted M15-normalized apparent V mag number=2 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. mag MBobs Observed absolute B magnitude mag MBpred Predicted absolute B magnitude mag MVobs Observed absolute V magnitude mag MVpred Predicted absolute V magnitude mag Ref Reference for source of data number=3 References: C88 = Clement, Sawyer Hogg & Yee 1988, AJ, 96, 1642 CS78 = Clement & Sawyer Hogg 1978, AJ, 83, 167 D69 = Demers 1969, AJ, 74, 926 DH74 = Demers & Harris 1974, AJ, 79, 627 DC67 = Dickens & Carey 1967, Roy. Obs. Bull. no. 129, p. E335 E72 = Eggen 1972, ApJ, 172, 639 G93 = Gonzalez 1993, Ph.D. thesis, U. of Washington, Seattle, WA H85 = Harris 1985, in Cepheids: Theory and Observations. IAU Colloquim No. 82, edited by B. F. Madore (Cambridge University Press, Cambridge), p. 232 K68 = Kwee 1968, Bulletin Astron. Inst. Netherlands, 19, 374 L74 = Lee 1974, Observatory, 94, 74 PM77 = Pike & Meston 1977, MNRAS, 180, 613 PR77 = Pinto & Rosino 1977, A&AS, 28, 427 W86 = Wehlau et al. 1986, AJ, 91, 1340 WS84 = Wehlau & Sawyer Hogg 1984, AJ, 89, 1005 WS85 = Wehlau & Sawyer Hogg 1985, AJ, 90, 2514 W92 = Wehlau 1992, private communication --- Name Star name --- [Fe/H] Assumed metal abundance --- E(B-V) Assumed reddening --- Ph Pulsation period h Pd Pulsation period d logP Log base 10 of P d Mode Pulsation mode number=1 Pulsation Modes: F = fundamental mode H = first-overtone mode --- Bmag Assumed mean B magnitude mag B0 Dereddened B magnitude mag AB B pulsation amplitude mag Vmag Assumed mean V magnitude mag V0 Dereddened V magnitude mag AV V pulsation amplitude mag B-V B-V color mag (B-V)0 Dereddened B-V color mag B0obs Observed M15-normalized apparent B mag mag B0pred Predicted M15-normalized apparent B mag mag dB0 Difference between B0obs-B0pred mag V0obs Observed M15-normalized apparent V mag mag V0pred Predicted M15-normalized apparent V mag mag dV0 Difference between V0obs-V0pred mag MBobs Observed absolute B magnitude mag MBpred Predicted absolute B magnitude mag MVobs Observed absolute V magnitude mag MVpred Predicted absolute V magnitude mag Name Star name --- [Fe/H] Assumed metal abundance --- r_[Fe/H] Source of metal abundance number=1 References for [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 --- E(B-V) Assumed reddening --- r_E(B-V) Source of reddening number=2 References for B-V FRN = Fahlman, Richer & Nemec 1991, ApJ, 380, 124 RF = Richer & Fahlman 1988, ApJ, 325, 218 Z85 = Zinn 1985a, ApJ, 293, 424 --- Pm Pulsation period min Pd Pulsation period d logP Log base 10 of P --- Mode Pulsation mode number=3 Pulsation Modes: F = fundamental mode H = first-overtone mode --- B Assumed mean B magnitude mag B0 Dereddened B magnitude mag V Assumed mean V magnitude mag V0 Dereddened V magnitude mag AV V pulsation amplitude mag B-V B-V color mag (B-V)0 Dereddened B-V color mag B0obs Observed M15-normalized apparent B mag mag B0pred Predicted M15-normalized apparent B mag mag dB0 Difference between B0obs-B0pred mag V0obs Observed M15-normalized apparent V mag mag V0pred Predicted M15-normalized apparent V mag mag dB0 Difference between V0obs-V0pred mag MBobs Observed absolute B magnitude mag MBpred Predicted absolute B magnitude mag MVobs Observed absolute V magnitude mag MVpred Predicted absolute V magnitude mag table4.texTeX version of table4.dat table5.texTeX version of table5.dat table6.texTeX version of table6.dat Lee Brotzman ADS 1994, Patricia Bauer [CDS] 16-Feb-1995Oct10Nemec J.M. nemec@das.nrc.ca Department of Astronomy, University of Washington, Seattle, Washington 98195 and Program in Astronomy, Washington State University, Pullman, Washington 99164 Linnell Nemec A.F. anemec@galaxy.gov.bc.ca International Statistics & Research Corporation, Brentwood Bay, British Columbia, Canada V8M 1R3 Lutz T.E. tlutz@beta.math.wsu.edu Program in Astronomy, Washington State University, Pullman, Washington 99164 AAS CD-ROM series, Volume 3, 1995 J_AJ_108_222.xml