Testing the nonlinearity of the BVIcJHKs period-luminosity relations for the Large Magellanic Cloud Cepheids

Aims. 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. Therefore, the aim of this Research Note is to test the linearity/nonlinearity of the PL relations for the LMC Cepheids in BV IcJHKs 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, lea ds to a strictly larger error rate than applying rigorous stati stical 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 cri terion (SIC) method. Results. The results from these statistical tests strongly suggest t hat the LMC PL relation is nonlinear in BV IcJH 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.

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