New LZ and PW(Z) relations of RR Lyrae stars calibrated with Gaia EDR3 parallaxes

Abstract

We present new luminosity-metallicity (LZ; M V − [Fe/H] and M G − [Fe/H]) relations and, for the first time, empirical, Gaia three-band (G, G BP , G RP ) period-Wesenheitmetallicity (P W Z) relations of RR Lyrae stars (RRLs) derived using a hierarchical Bayesian approach and new accurate parallaxes published for these variables in the Gaia Early Data Release 3 (EDR3). In a previous study we obtained Bayesian hierarchically-derived LZ relations from a sample of about four hundred Milky Way field RRLs with G-band light curves and trigonometric parallaxes published in the Gaia Data Release 2 (DR2), using V mean magnitudes, metallicities, absorptions and pulsation periods available in the literature. We now extend that study in two directions. Firstly, we update our previous results using trigonometric parallaxes from Gaia EDR3 and incorporate the Bayesian analysis of a first empirical P W Z relation derived using those field RRLs with G, G BP and G RP time-series photometry available in Gaia DR2. Secondly, we use Bayesian inference to derive LZ relations and empirical PW Gaia three-band relations from 385 RRLs belonging to 15 Milky Way globular clusters (GC) with literature-compiled spectroscopic metallicities ranging from −0.36 to −2.39 dex and prior distances extending from 2.2 to 41.2 kpc. From the samples of RRLs analysed in this paper we infer a mean Gaia EDR3 zero-point offset of −0.028 mas with median values ranging from −0.033 (LZ and P W Z models for field stars) to −0.024 mas (LZ model in the V -band for GC RRLs).

Proper Motions, Orbits, and Tidal Influences of Milky Way Dwarf Spheroidal Galaxies

“…For the proper motions, we assume uncertainties based on 10 years of Gaia data (DR5). For the distances, we assume a 2% error which is an obtainable projection given current systematics in the period-Wesenheit-metallicity relations of RR Lyrae stars (e.g., Nagarajan et al 2021;Garofalo et al 2022). We leave the uncertainties in the Milky Way potential and LMC potential at their present-day uncertainties to assess whether these need to be improved to make use of upcoming data.…”

Revisiting bright delta Scuti stars and their period-luminosity relation with TESS and Gaia DR3

“…Figure 2 shows our updated period-luminosity relation, colourcoded by pulsation amplitude. The red crosses show RR Lyrae variables, which have their own P-L relation (McNamara 2011;Sneden et al 2018;Molnár et al 2022;Garofalo et al 2022). Indeed, when accurate parallaxes are available, the P-L diagram is a useful way to distinguish between HADS and short-period RR Lyr variables (socalled RRc stars, which pulsate in the first overtone), whose light curves look very similar.…”