The Mid-Infrared Period-Luminosity Relations for the Small Magellanic Cloud Cepheids Derived from Spitzer Archival Data

TL;DR

This study derives mid-infrared period-luminosity relations for SMC Cepheids using Spitzer data, revealing a break at log(P)=0.4 and showing consistency with LMC and Galactic Cepheid relations.

Contribution

It provides the first detailed mid-infrared P-L relations for SMC Cepheids, including a break at log(P)=0.4, and compares these with LMC and Galactic relations.

Findings

P-L relations show a break at log(P)=0.4 in 3.6 and 4.5 micron bands.

Slopes for log(P)>0.4 are consistent with LMC and Galactic Cepheids.

5.8 and 8.0 micron bands do not show a clear slope change.

Abstract

In this paper we derive the Spitzer IRAC band period-luminosity (P-L) relations for the Small Magellanic Cloud (SMC) Cepheids, by matching the Spitzer archival SAGE-SMC data with the OGLE-III SMC Cepheids. We find that the 3.6micron and 4.5micron band P-L relations can be better described using two P-L relations with a break period at log(P)=0.4: this is consistent with similar results at optical wavelengths for SMC P-L relations. The 5.8micron and 8.0micron band P-L relations do not extend to sufficiently short periods to enable a similar detection of a slope change at log(P)=0.4. The slopes of the SMC P-L relations, for log(P)>0.4, are consistent with their LMC counterparts that were derived from a similar dataset. They are also in agreement with those obtained from a small sample of Galactic Cepheids with parallax measurements.