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Gaia Data Release 1: Testing parallaxes with local Cepheids and RR Lyrae stars

Clementini, G and Eyer, L and Ripepi, V and Marconi, M and Muraveva, T and Garofalo, A and Sarro, LM and Palmer, M and Luri, X and Molinaro, R and Rimoldini, L and Szabados, L and Musella, I and Anderson, RI and Prusti, T and De Bruijne, JHJ and Brown, AGA and Vallenari, A and Babusiaux, C and Bailer-Jones, CAL and Bastian, U and Biermann, M and Evans, DW and Jansen, F and Jordi, C and Klioner, SA and Lammers, U and Lindegren, L and Mignard, F and Panem, C and Pourbaix, D and Randich, S and Sartoretti, P and Siddiqui, HI and Soubiran, C and Valette, V and Van Leeuwen, F and Walton, NA and Aerts, C and Arenou, F and Cropper, M and Drimmel, R and Høg, E and Katz, D and Lattanzi, MG and O'Mullane, W and Grebel, EK and Holland, AD and Huc, C and Passot, X and Perryman, M and Bramante, L and Cacciari, C and Castañeda, J and Chaoul, L and Cheek, N and De Angeli, F and Fabricius, C and Guerra, R and Hernández, J and Jean-Antoine-Piccolo, A and Masana, E and Messineo, R and Mowlavi, N and Nienartowicz, K and Ordóñez-Blanco, D and Panuzzo, P and Portell, J and Richards, PJ and Riello, M and Seabroke, GM and Tanga, P and Thévenin, F and Torra, J and Els, SG and Gracia-Abril, G and Comoretto, G and Garcia-Reinaldos, M and Lock, T and Mercier, E and Altmann, M and Andrae, R and Astraatmadja, TL and Bellas-Velidis, I and Benson, K and Berthier, J and Blomme, R and Busso, G and Carry, B and Cellino, A and Cowell, S and Steele, IA and Marchant, JM (2017) Gaia Data Release 1: Testing parallaxes with local Cepheids and RR Lyrae stars. Astronomy and Astrophysics, 605. ISSN 0004-6361

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Abstract

Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (M V -[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. Methods. Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σ Ω /Ω < 0.5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with σ Ω /Ω < 0.5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with σ Ω /Ω < 0.5). The new relations were computed using multi-band (V,I,J,K s ) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL,PW,PLZ, and M V - [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods. Results. Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the Hipparcos measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive. Conclusions. TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018. © ESO, 2017.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: EDP Sciences
Date Deposited: 13 Oct 2017 09:37
Last Modified: 13 Oct 2017 09:37
DOI or Identification number: 10.1051/0004-6361/201629925
URI: http://researchonline.ljmu.ac.uk/id/eprint/7340

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