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|Title:||New NIR light-curve templates for classical Cepheids||Authors:||INNO, LAURA
Groenewegen, M. A. T.
Laney, C. D.
Madore, B. F.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||576||First Page:||A30||Abstract:||Aims: We present new near-infrared (NIR) light-curve templates for fundamental (FU, J, H, K<SUB>S</SUB>) and first overtone (FO, J) classical Cepheids. The new templates together with period-luminosity and period-Wesenheit (PW) relations provide Cepheid distances from single-epoch observations with a precision only limited by the intrinsic accuracy of the method adopted. Methods: The templates rely on a very large set of Galactic and Magellanic Cloud Cepheids (FU, ~600; FO, ~200) with well-sampled NIR (IRSF data set) and optical (V, I; OGLE data set) light-curves. To properly trace the change in the shape of the light-curve as a function of pulsation period, we split the sample of calibrating Cepheids into ten different period bins. The templates for the first time cover FO Cepheids and the short-period range of FU Cepheids (P ≤ 5 days). Moreover, the phase zero-point is anchored to the phase of the mean magnitude along the rising branch. The new approach has several advantages in sampling the light-curve of bump Cepheids when compared with the canonical phase of maximum light. We also provide new empirical estimates of the NIR-to-optical amplitude ratios for FU and FO Cepheids. We perform detailed analytical fits using seventh-order Fourier series and multi-Gaussian periodic functions. The latter are characterized by fewer free parameters (nine vs. fifteen). Results: The mean NIR magnitudes based on the new templates are up to 80% more accurate than single-epoch NIR measurements and up to 50% more accurate than the mean magnitudes based on previous NIR templates, with typical associated uncertainties ranging from 0.015 mag (J band) to 0.019 mag (K<SUB>S</SUB> band). Moreover, we find that errors on individual distance estimates for Small Magellanic Cloud Cepheids derived from NIR PW relations are essentially reduced to the intrinsic scatter of the adopted relations. Conclusions: Thus, the new templates are the ultimate tool for estimating precise Cepheid distances from NIR single-epoch observations, which can be safely adopted for future interesting applications, including deriving the 3D structure of the Magellanic Clouds. Full Tables 2 and 4 are available in electronic form at "http://www.aanda.org/10.1051/0004-6361/201424396/olm"||Acknowledgments:||This work was partially supported by PRIN–INAF 2011 “Tracing the formation and evolution of the Galactic halo with VST” (P.I.: M. Marconi) and by PRIN-MIUR (2010LY5N2T) “Chemical and dynamical evolution of the Milky Way and Local Group galaxies” (P.I.: F. Matteucci). One of us (G.B.) thanks The Carnegie Observatories visitor program for support as science visitor. N.M. acknowledges the support by Grants-in-Aid for Scientific Research (Nos. 23684005 and 26287028) from the Japan Society for the Promotion of Science (JSPS). Support from the Polish National Science Center grant MAESTRO 2012/06/A/ST9/00269 is also acknowledged. W.G. gratefully acknowledges support for this work from the BASAL Centro de Astrofísica y Tecnologías Afines (CATA) PFB-06/2007, and from the Chilean Ministry of Economy, Development and Tourism’s Millenium Science Iniciative through grant IC 120009 awarded to the Millenium Institute of Astrophysics (MAS). We also acknowledge G. Fiorentino for many useful discussions concerning the theoretical predictions on NIR period Wesenheit relations. It is also a pleasure to thank an anonymous referee for his/her supportive attitude and insightful suggestions that helped us to improve the readability of the paper.||URI:||http://hdl.handle.net/20.500.12386/24025||URL:||https://www.aanda.org/articles/aa/abs/2015/04/aa24396-14/aa24396-14.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201424396||Bibcode ADS:||2015A&A...576A..30I||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Sep 29, 2020
checked on Sep 29, 2020
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