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Title: On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations

Abstract

We present new theoretical period–luminosity–metallicity (PLZ) relations for RR Lyræ stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent convective hydrodynamical models for a broad range of metal abundances ( Z = 0.0001–0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, μ {sub 0}, and extinction, A {sub V}, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia ’ s first data release. For M4, we find a distance modulus of μ {sub 0} = 11.257 ± 0.035 mag with A {sub V}= 1.45 ± 0.12 mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13 mag.more » However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ∼0.02 mag at mid-infrared wavelengths.« less

Authors:
; ;  [1]; ; ;  [2]; ;  [3]; ;  [4]; ; ;  [5];  [6];  [7];  [8];  [9]
  1. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
  2. Department of Physics, Università di Roma Tor Vergara, via della Ricerca Scientifica 1, I-00133 Roma (Italy)
  3. INAF-Osservatorio Astronomico di Capodimonte, Salita Moiarello 16, I-80131 Napoli (Italy)
  4. Dipartimento di Fisica, Università di Pisa, Lago Bruno Pontecorvo 3, I-56127, Pisa (Italy)
  5. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
  6. Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)
  7. Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
  8. Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)
  9. NRC-Herzberg, Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria BC V9E 2E7 (Canada)
Publication Date:
OSTI Identifier:
22663564
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 841; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; COMPARATIVE EVALUATIONS; DISPERSIONS; DISTANCE; INDICATORS; IRON; LUMINOSITY; METALLICITY; NONLINEAR PROBLEMS; STARS; TIME DEPENDENCE; VISIBLE RADIATION; WAVELENGTHS

Citation Formats

Neeley, Jillian R., Marengo, Massimo, Trueba, Nicolas, Bono, Giuseppe, Braga, Vittorio F., Magurno, Davide, Dall’Ora, Massimo, Marconi, Marcella, Tognelli, Emanuele, Moroni, Pier G. Prada, Beaton, Rachael L., Madore, Barry F., Seibert, Mark, Freedman, Wendy L., Monson, Andrew J., Scowcroft, Victoria, and Stetson, Peter B., E-mail: jrneeley@iastate.edu. On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA713D.
Neeley, Jillian R., Marengo, Massimo, Trueba, Nicolas, Bono, Giuseppe, Braga, Vittorio F., Magurno, Davide, Dall’Ora, Massimo, Marconi, Marcella, Tognelli, Emanuele, Moroni, Pier G. Prada, Beaton, Rachael L., Madore, Barry F., Seibert, Mark, Freedman, Wendy L., Monson, Andrew J., Scowcroft, Victoria, & Stetson, Peter B., E-mail: jrneeley@iastate.edu. On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations. United States. doi:10.3847/1538-4357/AA713D.
Neeley, Jillian R., Marengo, Massimo, Trueba, Nicolas, Bono, Giuseppe, Braga, Vittorio F., Magurno, Davide, Dall’Ora, Massimo, Marconi, Marcella, Tognelli, Emanuele, Moroni, Pier G. Prada, Beaton, Rachael L., Madore, Barry F., Seibert, Mark, Freedman, Wendy L., Monson, Andrew J., Scowcroft, Victoria, and Stetson, Peter B., E-mail: jrneeley@iastate.edu. Thu . "On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations". United States. doi:10.3847/1538-4357/AA713D.
@article{osti_22663564,
title = {On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations},
author = {Neeley, Jillian R. and Marengo, Massimo and Trueba, Nicolas and Bono, Giuseppe and Braga, Vittorio F. and Magurno, Davide and Dall’Ora, Massimo and Marconi, Marcella and Tognelli, Emanuele and Moroni, Pier G. Prada and Beaton, Rachael L. and Madore, Barry F. and Seibert, Mark and Freedman, Wendy L. and Monson, Andrew J. and Scowcroft, Victoria and Stetson, Peter B., E-mail: jrneeley@iastate.edu},
abstractNote = {We present new theoretical period–luminosity–metallicity (PLZ) relations for RR Lyræ stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent convective hydrodynamical models for a broad range of metal abundances ( Z = 0.0001–0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, μ {sub 0}, and extinction, A {sub V}, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia ’ s first data release. For M4, we find a distance modulus of μ {sub 0} = 11.257 ± 0.035 mag with A {sub V}= 1.45 ± 0.12 mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13 mag. However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ∼0.02 mag at mid-infrared wavelengths.},
doi = {10.3847/1538-4357/AA713D},
journal = {Astrophysical Journal},
number = 2,
volume = 841,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}
  • Interstellar dust presents a significant challenge to extending parallax-determined distances of optically observed pulsational variables to larger volumes. Distance ladder work at mid-infrared wavebands, where dust effects are negligible and metallicity correlations are minimized, has been largely focused on few-epoch Cepheid studies. Here we present the first determination of mid-infrared period-luminosity (PL) relations of RR Lyrae stars from phase-resolved imaging using the preliminary data release of the Wide-field Infrared Survey Explorer (WISE). We present a novel statistical framework to predict posterior distances of 76 well observed RR Lyrae that uses the optically constructed prior distance moduli while simultaneously imposing amore » power-law PL relation to WISE-determined mean magnitudes. We find that the absolute magnitude in the bluest WISE filter is M{sub W1} = (- 0.421 {+-} 0.014) - (1.681 {+-} 0.147)log{sub 10}(P/0.50118 day), with no evidence for a correlation with metallicity. Combining the results from the three bluest WISE filters, we find that a typical star in our sample has a distance measurement uncertainty of 0.97% (statistical) plus 1.17% (systematic). We do not fundamentalize the periods of RRc stars to improve their fit to the relations. Taking the Hipparcos-derived mean V-band magnitudes, we use the distance posteriors to determine a new optical metallicity-luminosity relation. The results of this analysis will soon be tested by Hubble Space Telescope parallax measurements and, eventually, with the GAIA astrometric mission.« less
  • We present new distance determinations to the nearby globular M4 (NGC 6121) based on accurate optical and near-infrared (NIR) mean magnitudes for fundamental (FU) and first overtone (FO) RR Lyrae variables (RRLs), and new empirical optical and NIR period-luminosity (PL) and period-Wesenheit (PW) relations. We have found that optical-NIR and NIR PL and PW relations are affected by smaller standard deviations than optical relations. The difference is the consequence of a steady decrease in the intrinsic spread of cluster RRL apparent magnitudes at fixed period as longer wavelengths are considered. The weighted mean visual apparent magnitude of 44 cluster RRLs ismore » =13.329 ± 0.001 (standard error of the mean) ±0.177 (weighted standard deviation) mag. Distances were estimated using RR Lyr itself to fix the zero-point of the empirical PL and PW relations. Using the entire sample (FU+FO) we found weighted mean true distance moduli of 11.35 ± 0.03 ± 0.05 mag and 11.32 ± 0.02 ± 0.07 mag. Distances were also evaluated using predicted metallicity dependent PLZ and PWZ relations. We found weighted mean true distance moduli of 11.283 ± 0.010 ± 0.018 mag (NIR PLZ) and 11.272 ± 0.005 ± 0.019 mag (optical-NIR and NIR PWZ). The above weighted mean true distance moduli agree within 1σ. The same result is found from distances based on PWZ relations in which the color index is independent of the adopted magnitude (11.272 ± 0.004 ± 0.013 mag). These distances agree quite well with the geometric distance provided by Kaluzny et al. based on three eclipsing binaries. The available evidence indicates that this approach can provide distances to globulars hosting RRLs with a precision better than 2%-3%.« less
  • We present new nonlinear, time-dependent convective hydrodynamical models of RR Lyrae stars computed assuming a constant helium-to-metal enrichment ratio and a broad range in metal abundances (Z = 0.0001–0.02). The stellar masses and luminosities adopted to construct the pulsation models were fixed according to detailed central He-burning horizontal-branch evolutionary models. The pulsation models cover a broad range in stellar luminosity and effective temperatures and the modal stability is investigated for both fundamental (FU) and first overtone polsators (FOs). We predict the topology of the instability strip (IS) as a function of the metal content and new analytical relations for themore » edges of the IS in the observational plane. Moreover, a new analytical relation to constrain the pulsation mass of double pulsators as a function of the period ratio and the metal content is provided. We derive new Period–Radius–Metallicity relations for FU and FO pulsators. They agree quite well with similar empirical and theoretical relations in the literature. From the predicted bolometric light curves, transformed into optical (UBVRI) and near-infrared (NIR; JHK) bands, we compute the intensity-averaged mean magnitudes along the entire pulsation cycle and in turn new and homogenous metal-dependent (RIJHK) Period–Luminosity relations. Moreover, we compute new dual and triple-band optical, optical–NIR, and NIR Period–Wesenheit–Metallicity relations. Interestingly, we find that the optical Period-W(V, B–V) is independent of the metal content and that the accuracy of individual distances is a balance between the adopted diagnostics and the precision of photometric and spectroscopic data sets.« less
  • Using time-resolved, mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) and geometric parallaxes from the Hubble Space Telescope for four Galactic RR Lyrae variables, we derive the following Population II period-luminosity (PL) relations for the WISE [W1], [W2], and [W3] bands at 3.4, 4.6, and 12 μm, respectively: The slopes and the scatter around the fits are consistent with a smooth extrapolation of those same quantities from previously published K-band observations at 2.2 μm, where the asymptotic (long-wavelength) behavior is consistent with a period-radius relation with a slope of 0.5. No obvious correlation with metallicity (spanning 0.4 dex inmore » [Fe/H]) is found in the residuals of the four calibrating RR Lyrae stars about the mean PL regression line.« less