Testing the nonlinearity of the BVIcJHKs period-luminosity relations for the Large Magellanic Cloud Cepheids
Department of Astronomy, University of Illinois, Urbana, IL 61801, USA e-mail: firstname.lastname@example.org
2 Department of Physics, State University of New York at Oswego, Oswego, NY 13126, USA e-mail: email@example.com
3 Department of Mathematics, State University of New York at Oswego, Oswego, NY 13126, USA e-mail: firstname.lastname@example.org
Accepted: 24 October 2007
Context.A number of recent works have suggested that the period-luminosity (PL) relation for the Large Magellanic Cloud (LMC) Cepheids exhibits a controversial nonlinear feature with a break period at 10 days.
Aims.We aim to test the linearity/nonlinearity of the PL relations in this Research Note for the LMC Cepheids in BVIcJHKs band, as well as in the Wesenheit functions.
Methods.We show that simply comparing the long and short period slopes, together with their associated standard deviations, leads to a strictly larger error rate than applying rigorous statistical tests such as the F-test. We applied various statistical tests to the current published LMC Cepheid data. These statistical tests include the F-test, the testimator test, and the Schwarz information criterion (SIC) method.
Results.The results from these statistical tests strongly suggest that the LMC PL relation is nonlinear in BVIcJH band but linear in the Ks band and in the Wesenheit functions. Using the properties of period-color relations at maximum light and multi-phase relations, we believe that the nonlinear PL relation is not caused by extinction errors.
Key words: stars: variables: Cepheids / cosmology: distance scale / methods: statistical / stars: oscillations
© ESO, 2007