The Araucaria Project: The distance to the Small Magellanic Cloud from near infrared photometry of Type~II Cepheids

TL;DR

This study uses near-infrared observations of Type II Cepheids in the Small Magellanic Cloud to derive period-luminosity relations and estimate the galaxy's distance, confirming previous measurements with improved infrared data.

Contribution

It provides new near-infrared P-L relations for Type II Cepheids in the SMC and refines the galaxy's distance measurement using these relations.

Findings

Derived P-L relations in J and Ks bands consistent with previous studies.

Estimated SMC distance modulus as 18.85, aligning with other methods.

Confirmed the reliability of near-infrared Cepheid observations for distance measurements.

Abstract

We have obtained deep near infrared J- and K-band observations of 14 BL Herculis and 5 W Virginis SMC stars from the OGLE III survey with the ESO New Technology Telescope equipped with the SOFI infrared camera. From these observations, period-luminosity (P-L) relations in the J and Ks 2MASS bands were derived. The slopes of the K and J band relations of -2.15 +- 0.19 and -1.95 +- 0.24, respectively, agree very well with the corresponding slopes derived previously for population II Cepheids in globular clusters, Galactic bulge and in the Large Magellanic Cloud. The distance modulus to the SMC obtained from our data using P-L relation derived for globular cluster Cepheids equals 18.85 +- 0.07 (statistical) +- 0.07 (systematic without including potential metallicity effect), which within the uncertainties agrees well with the results obtained with other methods.